Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. ·...

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Hindawi Publishing Corporation Journal of Spectroscopy Volume 2013, Article ID 171735, 18 pages http://dx.doi.org/10.1155/2013/171735 Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational Analysis of O-Anisic Acid and Anisic Acid Based on DFT Calculations R. Mathammal, 1 N. Jayamani, 2 and N. Geetha 3 1 Department of Physics, Sri Sarada College for Women (Autonomous), Salem 636016, India 2 Department of Physics, Vivekanandha College of Arts and Sciences (W), Namakkal 637205, India 3 Department of Physics, Bharathiyar Arts & Science College (W), Salem 636112, India Correspondence should be addressed to N. Jayamani; [email protected] Received 1 May 2013; Accepted 14 July 2013 Academic Editor: Renata Diniz Copyright © 2013 R. Mathammal et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. is work deals with the vibrational spectroscopy of O-Anisic acid (OAA) and Anisic acid (AA). e fundamental vibrational frequencies and intensity of vibrational bands were evaluated using density functional theory (DFT) with standard B3LYP/6-31G ∗∗ method and basis set combinations. e vibrational spectra were interpreted, with the aid of normal coordinate analysis based on a scaled quantum mechanical force field. e infrared and Raman spectra were also predicted from the calculated intensities. e effects of carbonyl and methyl substitutions on the structure and vibrational frequencies have been investigated. Comparison of simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes. e 13 C and 1 H NMR chemical shiſts of the DFA and CA molecules were calculated using the gauge-invariant-atomic orbital (GIAO) method in DMSO solution using IEF-PCM model and compared with experimental data. 1. Introduction Aromatic acids have all the properties characteristic of the carboxylic acids of the aromatic series. In medicine, aromatic acids are employed as weak antiseptics, and their salts as carriers of specific cations [1]. Benzoic acid derivatives substituted by hydroxyl group or ether containing oxygen atom have active bacteriostatic and fragrant properties. ey are typically used in pharmaceutical and perfumery industry. Anisic acid or methoxy benzoic acid is an organic com- pound which is a carboxylic acid. Anisic acid is a part of cresol class antiseptic compounds. It is also used as an insect repel- lent. Anisic acid and its derivatives are also widely used in chemical reaction as intermediates to obtain target materials such as dyes, pharmaceuticals, perfumes, photoinitiators, and agrochemicals. O-Anisic acid is used in organic synthesis and antiseptic disinfectant [2]. e vibrational assignments of the compounds can be proposed on the basis of the wavenumber agreement between the computed harmonics and the observed fundamentals. Quantum chemical computational methods have proven to be an essential tool for interpretations and prediction of vibrational spectra [3, 4]. A significant advent in this area was made by the scaled quantum mechanical (SQM) force field method [58]. In the SQM approach, the systematic errors of the computed harmonic force field are corrected by a few scale factors which were found to be well transferable between chemically related molecules [4, 911]. In this study, we recorded FTIR and FT-Raman spec- tra and calculated the vibrational frequencies of O-Anisic acid and Anisic acid in the ground state to distinguish fundamentals from experimental vibrational frequencies and geometric parameters using DFT/B3LYP (Becke3-Lee-yang- Parr) method. Natural bond orbital (NBO) analysis of the title molecules was also carried out. In addition, the gauge- invariant-atomic orbital (GIAO) 13 C and 1 H chemical shiſts calculations of the title compounds were calculated by using B3LYP/6-31G ∗∗ basis set [12]. e calculated quantum chem- ical parameters are HOMO , LUMO , Δ, and those parameters that give valuable information about the reactive behavior

Transcript of Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. ·...

Page 1: Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. · Molecular Structure, NMR, HOMO, LUMO, ... ects of carbonyl and methyl substitutions

Hindawi Publishing CorporationJournal of SpectroscopyVolume 2013 Article ID 171735 18 pageshttpdxdoiorg1011552013171735

Research ArticleMolecular Structure NMR HOMO LUMOand Vibrational Analysis of O-Anisic Acid andAnisic Acid Based on DFT Calculations

R Mathammal1 N Jayamani2 and N Geetha3

1 Department of Physics Sri Sarada College for Women (Autonomous) Salem 636016 India2Department of Physics Vivekanandha College of Arts and Sciences (W) Namakkal 637205 India3 Department of Physics Bharathiyar Arts amp Science College (W) Salem 636112 India

Correspondence should be addressed to N Jayamani njayamaniraviyahoocoin

Received 1 May 2013 Accepted 14 July 2013

Academic Editor Renata Diniz

Copyright copy 2013 R Mathammal et alThis is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

This work deals with the vibrational spectroscopy of O-Anisic acid (OAA) and Anisic acid (AA) The fundamental vibrationalfrequencies and intensity of vibrational bands were evaluated using density functional theory (DFT) with standard B3LYP6-31Glowastlowastmethod and basis set combinations The vibrational spectra were interpreted with the aid of normal coordinate analysis based ona scaled quantum mechanical force field The infrared and Raman spectra were also predicted from the calculated intensities Theeffects of carbonyl and methyl substitutions on the structure and vibrational frequencies have been investigated Comparison ofsimulated spectra with the experimental spectra provides important information about the ability of the computational methodto describe the vibrational modes The 13C and 1H NMR chemical shifts of the DFA and CA molecules were calculated using thegauge-invariant-atomic orbital (GIAO) method in DMSO solution using IEF-PCMmodel and compared with experimental data

1 Introduction

Aromatic acids have all the properties characteristic of thecarboxylic acids of the aromatic series In medicine aromaticacids are employed as weak antiseptics and their saltsas carriers of specific cations [1] Benzoic acid derivativessubstituted by hydroxyl group or ether containing oxygenatom have active bacteriostatic and fragrant properties Theyare typically used in pharmaceutical and perfumery industry

Anisic acid or methoxy benzoic acid is an organic com-poundwhich is a carboxylic acid Anisic acid is a part of cresolclass antiseptic compounds It is also used as an insect repel-lent Anisic acid and its derivatives are also widely used inchemical reaction as intermediates to obtain target materialssuch as dyes pharmaceuticals perfumes photoinitiators andagrochemicals O-Anisic acid is used in organic synthesis andantiseptic disinfectant [2]

The vibrational assignments of the compounds can beproposed on the basis of the wavenumber agreement betweenthe computed harmonics and the observed fundamentals

Quantum chemical computational methods have proven tobe an essential tool for interpretations and prediction ofvibrational spectra [3 4] A significant advent in this area wasmade by the scaled quantum mechanical (SQM) force fieldmethod [5ndash8] In the SQM approach the systematic errorsof the computed harmonic force field are corrected by a fewscale factorswhichwere found to bewell transferable betweenchemically related molecules [4 9ndash11]

In this study we recorded FTIR and FT-Raman spec-tra and calculated the vibrational frequencies of O-Anisicacid and Anisic acid in the ground state to distinguishfundamentals from experimental vibrational frequencies andgeometric parameters using DFTB3LYP (Becke3-Lee-yang-Parr) method Natural bond orbital (NBO) analysis of thetitle molecules was also carried out In addition the gauge-invariant-atomic orbital (GIAO) 13C and 1H chemical shiftscalculations of the title compounds were calculated by usingB3LYP6-31Glowastlowast basis set [12]The calculated quantum chem-ical parameters are 119864HOMO 119864LUMOΔ119864 and those parametersthat give valuable information about the reactive behavior

2 Journal of Spectroscopy

such as chemical potential (119875119894) global hardness (120578) and the

softness (120590) [13] A detailed quantum chemical study willaid in making definite assignments to fundamental normalmodes of OAA and AA to clarify the experimental data forthese important molecules

2 Experimental

The pure crystalline samples of OAA and AA were obtainedfrom Lanchester chemical company UK and used withoutfurther purification for the spectral measurements Theroom-temperature Fourier-transform (FT) infrared spectraof the title compounds were measured in the region 4000ndash400 cmminus1 at a resolution of plusmn1 cmminus1 using BRUKER IFS-66V Fourier-transform spectrometer equippedwith anMCTdetector a KBr beam splitter and a globar source The FT-Raman spectra were recorded on the same instrument withan FRA-106 Raman accessory in the region 4000ndash50 cmminus1The 1064-nm line of a NdYAG laser was used as excitationsource and the laser power was set to 200mw

The 1H and 13C NMR spectra were taken in CDCl3 and

DMSO-1198896solution and all signals were referenced to TMS

on a BRUKER FT-NMR spectrometer All NMR spectra weremeasured at room temperature

3 Computational Details

All the calculations were performed by using Gaussian 03program [14] package on the personal computer The Beckersquosthree-parameter hybrid density functional B3LYP was usedto calculate both harmonic and anharmonic vibrationalwavenumbers with 6-31Glowastlowast basis set It is well known in thequantum chemical literature that the B3LYP functional yieldsa good description of harmonic vibrational wavenumbers forsmall andmedium sized moleculesThe optimized structuralparameters were used in the vibrational frequency calcula-tions at the DFT levels to characterize all stationary points asminimaThe Cartesian representation of the theoretical forceconstants has been computed at the fully optimized geometryby assuming119862

119904point group symmetry respectively for OAA

and AA The theoretical DFT force field was transformedfrom Cartesian coordinates into the local coordinates andthen scaled empirically according to the SQM procedure [5]

119865Scaled119894119895

= (119862119894119862119895)12

119865B3LYP119894119895

(1)

where 119862119894is the scale factor of coordinate 119894 119865B3LYP

119894119895is the

B3LYP6-31Glowastlowast force constant in local coordinate and119865Scaled119894119895

is the scaled force constantThe prediction of Raman intensities was carried out by

following the procedure outlined belowTheRaman activities(119878119894) calculated by the Gaussian 03 program and adjusted

during the scaling procedure with the MOLVIB programwere converted to relative Raman intensities (119868

119894) using

the following relationship derived from the basic theory ofRaman scattering [15ndash17]

119868119894=

119891(120592119900minus 120592119894)4

119878119894

120592119894[1 minus exp (minusℎ119888120592

119894119870119879)]

(2)

where 1205920is the exciting frequency (in cmminus1 units) 120592

119894the

vibrational wavenumber of the 119894th normal mode ℎ 119888 and 119896

are the fundamental constants and 119891 is the suitably chosencommon normalization factor for all the peak intensities

The calculated quantum chemical parameters such asthe highest occupied molecular orbital energy (119864HOMO) thelowest unoccupied molecular orbital energy (119864LUMO) energygap (Δ119864) chemical potential (119875

119894) global hardness (120578) and the

softness (120590) were calculatedThe concept of these parametersis related to each other [18ndash21] where

119875119894= minus120594

119875119894=(119864HOMO + 119864LUMO)

2

120578 =(119864LUMO minus 119864HOMO)

2

(3)

The inverse values of the global hardness are designatedas the softness 120590 as follows

120590 =1

120578 (4)

For NMR calculations the title molecules are firstlyoptimized and after optimization 1H and 13CNMR chemicalshifts (H and C) were calculated using the GIAO methodin CDCl

3at B3LYP method with 6-31Glowastlowast basis set [22 23]

Absolute isotropic magnetic shielding was transformed intochemical shifts by referring to the shielding of a standardcompound (TMS) computed at the same level It has beenshown that B3LYP applications were successful in shieldingcalculations on carbon and hydrogen atoms [23]

4 Results and Discussion

41 Molecular Geometry The molecular structures of OAAand AA with 119862

119904symmetry are shown in Figures 1(a) and

1(b) respectively The optimized bond lengths and anglesfor OAA and AA using DFT methods are given in Table 1The global minimum energies obtained by the DFT structureoptimization for OAA and AA are calculated as minus5353530and minus5353627 Hartrees respectively The substitution ofOCH3with COOH group in the OAA andAA leads to strong

intermolecular hydrogen bonding and +I effect respectively

42 Vibrational Force Constants Quantum mechanical cal-culations contain the force constant matrix in Cartesiancoordinates and in HartreeBohr2 units These force con-stants were transformed to the force fields in internallocal-symmetry coordinates The local-symmetry coordi-nates defined in terms of the internal valence coordinates

Journal of Spectroscopy 3

(a) (b)

Figure 1 (a) Molecular structure of O-Anisic acid along with numbering of atoms (b) Molecular structure of Anisic acid along withnumbering of atoms

Table 1 Optimized geometrical parameters O-Anisic acid (OAA) and Anisic acid (AA) obtained by B3LYP6-31Glowastlowast density functional cal-culations

Bond lengtha Value ( A) Bond anglea Value (∘)OAA AA OAA AA

C1ndashC2 139 139 C1ndashC2ndashC3 11999 11999C2ndashC3 139 139 C2ndashC3ndashC4 11999 11999C3ndashC4 139 139 C3ndashC4ndashC5 12000 12000C4ndashC5 139 139 C4ndashC5ndashC6 11999 11999C5ndashC6 139 139 C2ndashC1ndashC7 12001 12001C1ndashC7 154 154 C1ndashC7ndashO8 13007 13007C7ndashO8 123 123 C1ndashC7ndashO9 11229 11229O9ndashC7 135 135 C7ndashO9ndashH10 11060 11060O9ndashH10 097 094 C3ndashC2ndashO11(H11) 11998 11998C2ndashO11(H11) 143 109 C2ndashO11ndashC12 (C4ndashC3ndashH12) 10950 12001C11ndashC12 (H12ndashC2) 143 100 O11ndashC12ndashH13 (C5ndashC4ndashO13) 10947 11998C12ndashH13 (O13ndashC3) 107 143 O11ndashC12ndashH14 (C4ndashO13ndashC14) 10947 10950C12ndashH14 (C14ndashO13) 107 143 O11(O13)ndashC12(C14)ndashH15 10947 10947C12(C14)ndashH15 107 107 C4(O13)ndashC3(C14)ndashH16 12001 10947C3(C14)ndashH16 109 107 C5(O13)ndashC4(C14)ndashH17 11998 10947C4(C14)ndashH17 109 107 C6ndashC5ndashH18 12000 12000C5ndashH18 109 109 C1ndashC6ndashH19 11999 11999C6ndashH19 109 109aThe atoms indicated in the parenthesis belongs to AAFor numbering of atoms refer to Figures 1(a) and 1(b)

following the IUPAC recommendations [24 25] are given inTables 4 and 5 for the title compounds

The bonding properties of OAA and AA are influencedby their rearrangements of electrons during substitutionsand addition reactions The stretching force constants ofC1ndashC7 in OAA and AA are found to be lower than the valuesof stretching force constant of other CndashC atoms The force

constant of C1ndashC7 in OAA is found to be greater than AAdue to steric effect (ie bulky groups in OAA) The mostimportant diagonal force constants (stretching only) of OAAand AA are listed in Table 6

43 Assignment of Fundamentals The molecules OAA andAA are disubstituted aromatic system The vibrational bands

4 Journal of Spectroscopy

Table 2 Definition of internal coordinates of O-Anisic acid (OAA)

No (i) Symbol Type DefinitionStretching

1ndash4 119903119894

CndashH C3ndashH16 C4ndashH17 C5ndashH18 C6ndashH195ndash11 119903

119894CndashC C1ndashC2 C2ndashC3 C3ndashC4 C4ndashC5 C5ndashC6 C6ndashC1 C1ndashC7

12ndash14 119903119894

CndashO C7ndashO8 C7ndashO9 C2ndashO1115 119903

119894OndashC O11ndashC12

16 119903119894

OndashH O9ndashH1017ndash19 119903

119894CndashH(methyl) C12ndashH13 C12ndashH14 C12ndashH15

Bending20-21 120573

119894CndashCndashC C2ndashC1ndashC7 C6ndashC1ndashC7

22ndash29 120573119894

CndashCndashH C2ndashC3ndashH16 C4ndashC3ndashH16 C3ndashC4ndashH17 C5ndashC4ndashH17C4ndashC5ndashH18 C6ndashC5ndashH18 C5ndashC6ndashH19 C1ndashC6ndashH19

30ndash32 120573119894

CndashCndashH(methyl) O11ndashC12ndashH13 O11ndashC12ndashH14 O11ndashC12ndashH1533ndash35 120573

119894HndashCndashH H13ndashC12ndashH14 H13ndashC12ndashH15 H14ndashC12ndashH15

36-37 120573119894

CndashCndashO C1ndashC7ndashO8 C1ndashC7ndashO938 120573

119894CndashOndashH C7ndashO9ndashH10

39-40 120573119894

CndashCndashO C1ndashC2ndashO11 C3ndashC2ndashO1141 120573

119894CndashOndashC C2ndashO11ndashC12

42ndash47 120573119894

CndashCndashC (Ring) C1ndashC2ndashC3 C2ndashC3ndashC4 C3ndashC4ndashC5 C4ndashC5ndashC6C5ndashC6ndashC1 C6ndashC1ndashC2

Out-of-plane bending

48ndash51 120596119894

CndashH H16ndashC3ndashC2ndashC4 H17ndashC4ndashC5ndashC3 H18ndashC5ndashC6ndashC4H19ndashC6ndashC1ndashC5

52 120596119894

CndashC C7ndashC1ndashC6ndashC253 120596

119894CndashO O11ndashC2ndashC1ndashC3

Torsion54-55 120591

119894CndashO C2ndashC1ndashC7ndashO8 C2ndashC1ndashC7ndashO9

56-57 120591119894

CndashOndashC C1ndashC2ndashO11ndashC12 C3ndashC2ndashO11ndashC12

58ndash60 120591119894

CndashH(methyl) C2ndashO11ndashC12ndashH13 C2ndashO11ndashC12ndashH14C2ndashO11ndashC12ndashH15

61 120591119894

OndashH C1ndashC7ndashO9ndashH10

62ndash67 120591119894

tring C1ndashC2ndashC3ndashC4 C2ndashC3ndashC4ndashC5 C3ndashC4ndashC5ndashC6C4ndashC5ndashC6ndashC1 C5ndashC6ndashC1ndashC2 C6ndashC1ndashC2ndashC3

For numbering of atoms refer to Figure 1(a)

observed in the IR region are very sharp broad and lessintense The title compounds belong to 119862

119904point group The

19 atoms present in OAA and AA molecular structure eachhas 51 fundamental modes of vibrations For molecules of119862119904symmetry group theory analysis indicates that the 51

fundamental vibrations are distributed among the symmetryspecies as

Γvib = 35A1015840 (in-plane) + 16A10158401015840 (out-of-plane) (5)

for bothOAA andAA respectively From the structural pointof view of the molecules OAA and AA have 18 stretchingvibrations 33 bending vibrations respectively All the vibra-tions were found to be active both in Raman scattering andinfrared absorption

The observed and calculated wave numbers calculatedIR and Raman intensities and normal mode descriptions(characterized by potential energy distribution (PED)) for

the fundamental vibrations of OAA and AA are depictedin Tables 7 and 8 For visual comparison the observed andsimulated FTIR and FT-Raman spectra of the compoundsare presented in Figures 2 3 4 and 5 which help to under-stand the observed spectral features The root mean square(RMS) error of the observed and calculated wavenumbers(unscaledB3LYP6-31Glowastlowast) of OAA and AA was found to be843 cmminus1 and 891 cmminus1 respectively This is understandablesince the mechanical force fields usually differ appreciablyfrom the observed ones This is partly due to the neglectof anharmonicity and partly due to the approximate natureof the quantum mechanical methods However for reliableinformation on the vibrational properties the use of selectivescaling is necessary The calculated wavenumbers are scaledusing the set of transferable scale factors recommended byFogarasi and Pulay [7]The SQM treatment has resulted in anRMS deviation of 967 cmminus1 and 113 cmminus1 for OAA and AA

Journal of Spectroscopy 5

Table 3 Definition of internal coordinates of Anisic acid (AA)

No (i) Symbol Type DefinitionStretching

1ndash4 119903119894

CndashH C2ndashH11 C3ndashH12 C5ndashH18 C6ndashH195ndash10 119903

119894CndashC C1ndashC2 C2ndashC3 C3ndashC4 C4ndashC5 C5ndashC6C6ndashC1

11 119903119894

CndashCfn C1ndashC712ndash14 119903

119894CndashO C7ndashO8 C7ndashO9 C4ndashO13

15 119903119894

OndashC O13ndashC1416 119903

119894OndashH O9ndashH10

17ndash19 119903119894

CndashH(methyl) C14ndashH15 C14ndashH16 C14ndashH17Bending

20-21 120573119894

CndashC C2ndashC1ndashC7 C6ndashC1ndashC7

22ndash29 120573119894

CndashCndashHC1ndashC2ndashH11 C3ndashC2ndashH11C2ndashC3ndashH12 C4ndashC3ndashH12C4ndashC5ndashH18 C6ndashC5ndashH18C5ndashC6ndashH19 C1ndashC6ndashH19

30ndash35 120573119894

CndashCndashH(methyl) O13ndashC14ndashH15 O13ndashC14ndashH16 O13ndashC14ndashH17H17ndashC14ndashH15 H15ndashC14ndashH16 H17ndashC14ndashH16

36-37 120573119894

CndashCndashO C3ndashC4ndashO13 C5ndashC4ndashO1338 120573

119894CndashOndashH C7ndashO9ndashH10

39-40 120573119894

CndashCndashO C1ndashC7ndashO8 C1ndashC7ndashO941 120573

119894CndashOndashC C4ndashO13ndashC14

42ndash47 120573119894

CndashCndashC (Ring) C1ndashC2ndashC3 C2ndashC3ndashC4 C3ndashC4ndashC5 C4ndashC5ndashC6C5ndashC6ndashC1 C6ndashC1ndashC2

Out-of-plane bending

48ndash51 120596119894

CndashH H11ndashC2ndashC3ndashC1 H12ndashC3ndashC4ndashC2 H18ndashC5ndashC6ndashC4H19ndashC6ndashC1ndashC5

52 120596119894

CndashC C7ndashC1ndashC6ndashC253 120596

119894CndashO O13ndashC4ndashC5ndashC3

Torsion54ndash55 120591

119894CndashO C2ndashC1ndashC7ndashO8 C2ndashC1ndashC7ndashO9

56-57 120591119894

CndashOndashC C3ndashC4ndashO13ndashC14 C5ndashC4ndashO13ndashC14

58ndash60 120591119894

CndashH(methyl) C4ndashO13ndashC14ndashH15 C4ndashO13ndashC14ndashH16C4ndashO13ndashC14ndashH16

61 120591119894

OndashH C1ndashC7ndashO9ndashH10

62ndash67 120591119894

tring C1ndashC2ndashC3ndashC4 C2ndashC3ndashC4ndashC5 C3ndashC4ndashC5ndashC6C4ndashC5ndashC6ndashC1 C5ndashC6ndashC1ndashC2 C6ndashC1ndashC2ndashC3

For numbering of atoms refer to Figure 1(b)

respectively The RMS values of wavenumbers were obtainedin this study using the following expression

RMS = radic1

119899 minus 1

119899

sum

119894

(120592calc119894

minus 120592exp119894

)2

(6)

431 CH Vibrations Aromatic compounds commonly ex-hibit multiple weak bands in the region 3100ndash3000 cmminus1 [26]due to aromatic CndashH stretching vibrations According to thePED analysis the bands observed in experimental spectrumat 3098 3083 3069 3020 cmminus1 in OAA and 3085 3034 3029and 3002 cmminus1 inAAwere assigned to stretching vibrations of

CndashH bond According to these studies all the CndashH stretchingvibrations are not mixed with other types of vibrations

The CndashH in-plane deformation vibrations are assigned inthe region 1100ndash1400 cmminus1 [27] The in-plane deformationsof CndashH groups are noticed on PED analysis at 1494 14391288 and 1182 in OAA and 1518 1301 1181 and 1131 cmminus1 inAAThere is slight increase in the CndashH in-plane deformationfrequency because of steric effect in OAA and inductive effect(+I) in AAThese values of calculated frequencies are typicaland in very good agreement with experimental data The in-plane CndashH deformation vibrations are slightly mixed in bothOAA and AA

The CndashH out-of-plane deformation vibrations areassigned in the region 900ndash600 cmminus1 [26] The bands

6 Journal of Spectroscopy

Table 4 Definition of natural internal coordinates of O-Anisic acid (OAA)

No (i) Symbola Definitionb

1ndash4 CndashH stretch 1199031 1199032 1199033 1199034

5ndash11 CndashC stretch 1199035 1199036 1199037 1199038 1199039 11990310 11990311

12ndash14 CndashO stretch 11990312 11990313 11990314

15 OndashC stretch 11990315

16 OndashH stretch 11990316

17 CH3 ss (11990317+ 11990318+ 11990319) radic3

18 CH3 ips (211990317minus 11990318minus 11990319) radic6

19 CH3 ops (11990318minus 11990319) radic2

20 bCndashCndashC (12057320minus 12057321) radic2

21ndash24 bCndashCndashH (12057322minus 12057323) radic2 (120573

24minus 12057325) radic2 (120573

26minus 12057327) radic2 (120573

28minus 12057329) radic2

25 CH3 sb (minus12057330minus 12057331minus 12057332+ 12057333+ 12057334+ 12057335) radic6

26 CH3 ipb (minus12057333minus 12057334minus 212057335)radic6

27 CH3 opb (12057333minus 12057334) radic2

28 CH3 ipr (212057330minus 12057331minus 12057332)radic6

29 CH3 opr (12057331minus 12057332)radic2

30 bCndashCndashO (12057336minus 12057337) radic2

31 bCndashOndashH 12057338

32-33 bCndashCndashO 12057339 12057340

34 bCndashOndashC 12057341

35 Rtrigd (12057342minus 12057343+ 12057344minus 12057345+ 12057346minus 12057347) radic6

36 Rsymd (minus12057342minus 12057343+ 12057344minus 12057345minus 12057346+ 212057347)radic12

37 Rasymd (12057342minus 12057343+ 12057345minus 12057346) 2

38ndash41 120596CndashH 12059648 12059649 12059650 12059651

42 120596CndashC 12059652

43 120596CndashO 12059653

44-45 tCndashO 12059154 12059155

46 tCndashOndashC 12 (12059156+ 12059157)

47 tCH3 13 (12059158+ 12059159+ 12059160)

48 tOndashH 12059161

49 Ttrigd (12059162minus 12059163+ 12059164minus 12059165+ 12059166minus 12059167) radic6

50 Tsymd (12059162minus 12059163+ 12059165+ 12059166) 2

51 Tasymd (minus12059162+ 212059163minus 12059164minus 12059165+ 12059166minus 12059167) radic12

aThese symbols are used for description of the normal modes by PED in Table 7bThe internal coordinates used here are defined in Table 2

appearing at 960 937 865 and 755 cmminus1 in OAA and929 854 846 and 774 cmminus1 in AA were assigned toout-of-plane deformation type of vibration (120596) of CndashHgroups There is slight increase in the CndashH out-of-planedeformation frequency because of strong intermolecularhydrogen bonding in OAA In these bands the pronouncedparticipation of other types of vibrations is observed Theseare also supported by the literature

432 Carboxylic Acid Vibrations Due to the presence ofstrong intermolecular hydrogen bonding the FT-IR spectraexhibits spectra exhibit a broad band due to the OndashHstretching vibrations and a strong banddue toC=Ostretchingvibrations The carboxylic acid dimers display a very broadand intenseOndashH stretching absorption in the region of 3300ndash2500 cmminus1 [28] The title molecules both exhibit intermolec-ular hydrogen bonding In our case the bands at 3390 cmminus1

in OAA and 3435 cmminus1 in AA are assigned as OndashH stretchingvibrations There is a slight increase in the OndashH frequencybecause of steric effect in OAA and +I effect in AA The OndashH out-of-plane bending vibration occurs near the region of920 cmminus1 [27] The bands appearing at 595 cmminus1 in OAA and505 cmminus1 in AA are assigned to OndashH out-of-plane bendingvibrationThe OndashH out-of-plane bending vibrations in OAAand AA decrease due to intermolecular hydrogen bonding

The carbonyl stretching vibrations are expected in theregion 1720 cmminus1ndash1680 cmminus1 [28] The IR band at 1670 cmminus1in OAA and FT-Raman band at 1688 cmminus1 in AA are assignedasC=O stretching vibrationsTheCndashObond appears stronglyin the 1320ndash1210 cmminus1 region [29] The bands observed at1049 and 795 cmminus1 in OAA and 1267 and 1100 cmminus1 in AAare assigned to CndashO stretching mode The CndashO stretchingvibrational frequency is lower than general range In thecase of carboxylic acid dimers like OAA and AA the OH

Journal of Spectroscopy 7

Table 5 Definition of natural internal coordinates of Anisic acid (AA)

No (i) Symbola Definitionb

1ndash4 CndashH stretch 1199031 1199032 1199033 1199034

5ndash10 CndashC stretch 1199035 1199036 1199037 1199038 1199039 11990310

11 CndashCfn stretch 11990311

12ndash14 CndashO stretch 11990312 11990313 11990314

15 OndashC stretch 11990315

16 OndashH stretch 11990316

17 CH3 ss (11990317+ 11990318+ 11990319) radic3

18 CH3 ips (211990317minus 11990318minus 11990319) radic6

19 CH3 ops (11990318minus 11990319) radic2

20 bCndashCndashC (12057320minus 12057321) radic2

21ndash24 bCndashCndashH (12057322minus 12057323) radic2 (120573

24minus 12057325) radic2 (120573

26minus 12057327) radic2 (120573

28minus 12057329) radic2

25 CH3 sb (minus12057330minus 12057331minus 12057332+ 12057333+ 12057334+ 12057335) radic6

26 CH3 ipb (minus12057333minus 12057334minus 212057335)radic6

27 CH3 opb (12057333minus 12057334) radic2

28 CH3 ipr (212057330minus 12057331minus 12057332) radic6

29 CH3 opr (12057331minus 12057332) radic2

30 bCndashCndashO (12057335minus 12057336) radic2

31 bCndashOndashH 12057338

32-33 bCndashCndashO 12057339 12057340

34 bCndashOndashC 12057341

35 Rtrigd (12057342minus 12057343+ 12057344minus 12057345+ 12057346minus 12057347) radic6

36 Rsymd (minus12057342minus 12057343+ 12057344minus 12057345minus 12057346+ 212057347) radic12

37 Rasymd (12057342minus 12057343+ 12057345minus 12057346) 2

38ndash41 120596CndashH 12059648 12059649 12059650 12059651

42 120596CndashC 12059652

43 120596CndashO 12059653

44-45 tCndashO 12059154 12059155

46 tCndashOndashC 12 (12059156+ 12059157)

47 tCH3 13 (12059158+ 12059159+ 12059160)

48 tOndashH 12059161

49 Ttrigd (12059162minus 12059163+ 12059164minus 12059165+ 12059166minus 12059167) radic6

50 Tsymd (12059162minus 12059163+ 12059165+ 12059166)2

51 Tasymd (minus12059162+ 212059163minus 12059164minus 12059165+ 12059166minus 12059167) radic12

aThese symbols are used for description of the normal modes by PED in Table 8bThe internal coordinates used here are defined in Table 3

in-plane bending and CndashO stretching bands involve someinteraction between them they are referred to as coupledOH in-plane bending and CndashO stretching vibrations [26]The CndashO bending vibration occurs in the region of 580ndash340 cmminus1 [30] The band observed at 380 cmminus1 in OAA and440 cmminus1 in AA are assigned to CndashO bending mode Thepresent assignments agree very well with the values availablein the literature

433 Methyl Group Vibrations The title molecules OAAand AA under consideration possess one CH

3group For

the assignments of CH3group one can expect that 9 fun-

damentals can be associated with each CH3group namely

the symmetrical stretching (CH3symmetric stretch) and

asymmetrical stretching (CH3asymmetric stretch) in-plane

stretching modes (ie in-plane hydrogen stretching modes)

and the symmetrical (CH3symmetric deform) and asym-

metrical (CH3asymmetric deform) deformation modes in-

plane rocking (CH3ipr) out-of-plane rocking (CH

3opr) and

twisting (tCH3) bending modes

For the methyl group compounds the asymmetricstretching mode appeared in the range 2965ndash3005 cmminus1 andthe symmetric stretching mode appeared in the range of2815ndash2860 cmminus1 [30] The FT-Raman band at 2983 cmminus1 forOAA and IR band at 2941 cmminus1 for AA are symmetricstretching The symmetric stretching vibrational frequencyis higher in OAA and AA due to steric effect and +I effectThe asymmetric methyl stretching band appeared at 30033018 cmminus1 in OAA and 2990 2956 cmminus1 in AA respectivelyThe asymmetric deformation mode appeared in the range1445ndash1485 cmminus1 and symmetric deformation mode appearedin the range of 1420ndash1460 cmminus1 [30] The IR band at 1466

8 Journal of Spectroscopy

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 2 FTIR spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Table 6 Diagonal force constants (102 Nmminus1) of O-Anisic acid(OAA) and Anisic acid (AA)

Descriptiona Force constantsb

OAA AAC1ndashC2 621 630C2ndashC3 633 696C3ndashC4 677 626C4ndashC5 675 628C5ndashC6 682 663C6ndashC1 644 648C1ndashC7 465 222C7ndashO8 532 522C7ndashO9 1030 1128C2ndashO11(C4ndashO13) 449 576O11ndashC12(O13ndashC14) 413 499O9ndashH10 644 661C12ndashH13(C14ndashH15) 498 508C12ndashH14(C14ndashH16) 526 470C12ndashH15(C14ndashH17) 498 507C3ndashH16(C2ndashH11) 514 498C4ndashH17(C3ndashH12) 501 496C5ndashH18 505 500C6ndashH19 532 522aThe atoms indicated in the parenthesis belong to AAbStretching force constants are given in mdyn A

minus1

For numbering of atoms refer to Figures 1(a) and 1(b)

and 1435 cmminus1 in OAA and 1468 and 1461 cmminus1 in AA areassigned as asymmetric deformation vibrations The IR bandat 1411 cmminus1 for OAA and 1429 cmminus1 for AA are symmet-ric deformation mode The CH

3deformation absorption

occurs at 1466 cmminus1 and 1429 cmminus1 this vibration is knownas umbrella mode that overlaps with CC ring stretchingvibrations for the title compounds These are also supportedby the literature

The tensional modes appeared in the range of 265ndash185 cmminus1 [30] This modes are strongly coupled with other

vibrations that are observed at 280 cmminus1 inOAAand 165 cmminus1in AAwhich are in agreement with the calculated results also

434 Ring Vibrations The ring CndashC stretching vibrationsoccur in the region of 1600ndash1400 cmminus1 [29]The bands appearat 1600 1579 1312 1184 1153 1062 and 698 cmminus1 in OAAand 1608 1580 1416 1307 1107 1028 and 825 cmminus1 in AAwere assigned to CndashC stretching vibrations The shift in thefrequency of CndashC vibrations towards lower wave numbermay be due to the COOH and OCH

3groups Many ring

modes are affected by the substitutions in the aromatic ringThe bands at 180 cmminus1 and 285 cmminus1 for OAA and AA wereassigned to CndashC bending vibrationsThe out-of-plane and in-plane deformations of the phenyl ring are observed below1000 cmminus1 and these modes are sensitive by the additionof functional groups The out-of-plane bending vibrationswere observed at 170 cmminus1 and 111 cmminus1 for OAA and AASmall changes in the wavenumbers were observed due tothe presence of +I effect in AA and steric effect in OAAThe computed wavenumbers are in good agreement withexperimental data

5 Electronic Properties

Atomic charges on the various atoms of OAA and AAobtained by Mulliken population analysis [31] are given inTable 9 From the listed atomic charge values the oxygen[O8 O9] and O11 in OAA and O13 in AA atoms had a largenegative charge and behaved as electron acceptor It was alsoobserved that there is a large accumulation of charge on O11inOAAO13 in AAmoleculesTherefore C7 andO11 inOAAand C7 and O13 in AA had a greater ionic character

Natural bond orbital analysis provides an efficientmethod for studying steric effect and intermolecular bondingand interaction among bonds and also provides a convenientbasis for investigating charge transfer or conjugative interac-tion in molecular systems Natural charge analysis is givenin Table 10 for the title compounds The results show thatsubstitution of COOH and CH

3group in OAA and AA leads

to a redistribution of electron density The C7 atom in OAAand AA is more positive charge (+08091 +08139) In the

Journal of Spectroscopy 9Ta

ble7Detailedassig

nmento

ffun

damentalvibratio

nsof

O-Anisic

acid

(OAA)b

yno

rmalmod

eanalysis

basedon

SQM

forcefi

eldcalculations

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

1A1015840

3390

mdash3771

3390

72652

155385

120592OH(100)

2A1015840

mdash3098

3273

3098

1612

499564

120592CH

(99)

3A1015840

mdash3083

3233

3083

1700

135114

120592CH

(99)

4A1015840

3069

mdash3207

3069

10674

70382

120592CH

(99)

5A1015840

mdash3020

3186

3024

17253

1372

01120592CH

(99)

6A1015840

3018

mdash3157

3018

38987

58202

120592CH

3(99)

7A10158401015840

3003

mdash3085

3003

5946

78409

120592CH

3(99)

8A1015840

mdash2983

3020

2983

52626

120657

120592CH

3(99)

9A1015840

1670

mdash1822

1670

358567

54628

120592CO

(53)120592CC

(14)bC

CO(14

)bC

OH(12)

10A1015840

1600

mdash1656

1600

15061

16343

120592CC

(60)bCH

(20)R

asym

d(10)

11A1015840

1579

mdash1630

1579

61364

48880

120592CC

(69)bCH

(19)

12A1015840

1494

mdash1539

1494

58214

10686

bCH(48)120592CC

(37)

13A1015840

1466

mdash1513

1466

6534

6058

bCH

3(43)bCH

(25)120592CC

(16)

14A1015840

mdash1439

1506

1439

22318

5639

bCH(39)bCH

3(37)120592CC

(17)

15A10158401015840

1435

mdash1500

1435

3652

510814

bCH

3(88)

16A1015840

1411

mdash1475

1411

11849

19713

bCH

3(74)

17A1015840

1382

1367

4497

1268

bCOH(35)120592CO

(32)bCC

O(13)120592CC

(11)

18A1015840

mdash1312

1350

1312

2182

8877

120592CC

(67)

19A1015840

1288

mdash1320

1288

6319

416

48bC

H(33)R

trigd(20)120592CO

(13)120592CC

(12)

20A1015840

mdash1287

1302

1287

19694

044

9Rtrig

d(26)120592CC

(25)bCH

(20)120592CO

(12)

21A1015840

mdash1184

1210

1184

228252

32980

120592CC

(31)bCH

(19)bC

H3(17)120592CO

(17)

22A1015840

1182

mdash1201

1182

162989

2713

6bC

H(42)120592CC

(34)bCH

3(10)

23A1015840

1170

mdash119

3117

015

764576

bCH

3(57)bCH

(24)

24A1015840

mdash117

3117

31153

7419

1097

120592CC

(31)bCH

(29)bCH

3(25)

25A1015840

1140

mdash1168

1140

0662

4253

bCH

3(96)

26A1015840

1049

mdash1087

1050

1073

0478

09120592CO

(29)120592CC

(27)R

trigd(12)

27A1015840

-1062

1077

1060

104848

21650

120592CC

(41)120592CO

(22)bCH

(12)

28A10158401015840

960

-1060

960

060

90057

120596CH

(91)

29A1015840

mdash974

989

974

2078

710836

120592OC(62)120592CC

(12)120592CO

(11)

30A10158401015840

937

mdash965

935

1244

1294

120596CH

(91)

31A10158401015840

mdash865

869

865

3148

3432

120596CH

(64)ttrigd(19)

32A1015840

mdash795

830

795

12200

4238

120592CO

(29)R

symd(21)120592OC(15)120592CC

(15)

33A10158401015840

761

mdash795

761

1002

0207

tCO(32)ttrigd(28)120596

CH(23)120596

CC(11)

34A10158401015840

mdash755

770

755

41473

1456

120596CH

(51)ttrigd(27)120596

CO(14

)35

A10158401015840

695

mdash747

698

64512

0469

ttrigd(52)120596

CH(23)tCO

(15)

36A1015840

mdash698

712

695

10016

17946

120592CC

(33)120592CO

(23)bCC

O(21)

37A1015840

mdash602

639

602

13503

2683

Rasymd(36)bCC

O(15)

120592CC

(12)R

symd(11)

38A10158401015840

mdash595

594

595

74804

8168

tOH(79)

39A1015840

mdash565

588

565

21902

1740

bCCO

(28)120592CC

(17)bCO

(15)R

symd(14

)bC

CO(13)

10 Journal of Spectroscopy

Table7Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

540

mdash548

540

5598

4848

bCCO

(40)bCC

(16)120592CC

(13)R

asym

d(10)

41A10158401015840

480

mdash540

480

0946

0860

120596CO

(40)120596

CH(16)ttrigd(14

)tsy

m(14

)42

A10158401015840

mdash40

1435

401

3585

0792

tsym

(14)120596CC

(15)

43A1015840

mdash380

388

380

4805

4133

bCO(64)bCC

O(16)

44A1015840

mdash303

383

303

1180

4980

Rsym

d(59)bCO

C(17)120592CC

(15)

45A10158401015840

mdash280

283

280

0092

0016

tCH

3(79)

46A1015840

mdash240

280

240

0927

0935

bCOC(40)bCC

(30)bCC

O(18)

47A10158401015840

mdash180

229

180

0018

2096

120596CC

(30)tCO

(20)tsym

(18)

tasym

(11)120596CH

(10)

48A1015840

mdash170

190

170

3092

0715

bCC(42)bCO

C(29)bCO

(12)

49A10158401015840

mdash115

119115

4502

0508

tCOC(47)tsym

(15)tCH

3(12)

50A10158401015840

mdash110

9696

0922

3779

tsym

(35)tCO

(25)

tCOC(21)tCH

3(13)

51A10158401015840

mdashmdash

1730

1260

0037

tCO(99)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 11Ta

ble8Detailedassig

nmento

ffun

damentalvibratio

nsof

Anisic

acid

(AA)b

yno

rmalmod

eanalysis

basedon

SQM

forcefi

eldcalculations

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

1A1015840

3435

mdash3768

3435

7952

3164209

120592OH(100)

2A1015840

mdash3085

3232

3085

21438

120058

120592CH

(89)

3A1015840

mdash3034

3224

3034

7547

126718

120592CH

(99)

4A1015840

3029

mdash3218

3029

3520

99229

120592CH

(99)

5A1015840

3002

mdash3209

3002

5141

52552

120592CH

(99)

6A1015840

2990

mdash3155

2990

2423

53071

120592CH

ops(99)

7A10158401015840

2956

mdash3087

2956

45319

94074

120592CH

ips(51)120592CH

ss(36)120592CH

ops(12)

8A1015840

2941

mdash3022

2941

42847

91231

120592CH

ss(56)120592CH

ips(44

)9

A1015840

1688

mdash1813

1688

302139

74665

120592CO

(72)bCC

O(17)

10A1015840

1608

mdash1666

1608

216104

153242

120592CC

(62)bCH

(22)R

symd(11)

11A1015840

1580

mdash1624

1580

34785

12359

120592CC

(66)bCH

(14)

12A1015840

1518

mdash1559

1518

41495

8422

bCH(52)120592CC

(30)

13A1015840

1468

mdash1516

1468

37550

10673

bCHsb

(77)

14A10158401015840

1461

mdash1504

1461

14058

1218

3bC

Hop

b(83)

15A1015840

1429

mdash1486

1429

5851

19586

bCHipb(70)120592CC

(10)bCH

(10)

16A1015840

1416

mdash1465

1416

14835

9149

120592CC

(39)bCH

(35)bCH

ipb(18)

17A1015840

1324

mdash1391

1324

31290

5311

bCOH(27)120592CO

(22)bCC

O(21)120592CC

(13)

18A1015840

1307

mdash1371

1307

806

814

44120592CC

ar(65)bCH

(20)

19A1015840

1301

mdash1331

1301

40408

7073

bCH(43)120592CC

(33)

20A1015840

1267

mdash1304

1267

245222

3723

120592CO

(37)R

trigd(20)120592CC

(16)

21A1015840

1181

mdash1221

1181

5734

6023

bCH(61)120592CC

(21)

22A1015840

1172

mdash1209

1172

5690

5161

bCHop

r(61)bC

H(13)

23A1015840

mdash1137

1189

1137

0662

4334

bCHipr(78)bC

Hop

r(14)

24A1015840

1131

mdash117

61131

190946

42508

bCH(35)120592CC

(21)

25A1015840

1107

mdash1139

1107

245972

63024

120592CC

fn(25)R

trigd(23)bCH

(16)120592OC(13)

26A1015840

mdash1100

1114

1100

318070

20809

120592CO

(40)bCO

H(22)bCC

O(11)

27A1015840

1028

mdash1069

1028

0786

11056

120592CC

(58)bCH

(16)

28A1015840

mdash1010

1026

1010

29566

2343

120592OC(51)120592CC

(28)

29A10158401015840

929

mdash991

929

0010

046

4120596CH

(89)

30A10158401015840

854

mdash966

854

1379

1924

120596CH

(82)ttrigd(12)

31A10158401015840

846

mdash863

846

3652

212

44120596CH

(39)120596

CO(32)ttrigd(20)

32A1015840

825

mdash834

825

24090

2237

3120592CC

ar(32)R

symd(27)120592OC(22)

33A10158401015840

774

mdash830

774

0365

4928

120596CH

(84)

34A10158401015840

mdash755

775

755

1082

0243

ttrigd(51)120596

CC(15)120596

CH(14

)tCO(11)

35A1015840

698

mdash725

698

3553

93075

bCCO

(44)120592CO

(25)bCO

H(25)

36A10158401015840

634

mdash710

634

76887

0059

tCO(57)120596

CH(20)ttrigd(12)

37A1015840

617

mdash647

617

0592

644

1Ra

symd(81)

38A1015840

550

mdash603

550

14566

0968

Rsym

d(32)120592CC

fn(13)120592CO

(11)bCC

O(11)bCO

C(10)

39A10158401015840

545

mdash601

545

27876

4847

120596CO

(42)tOH(14

)120596CH

(11)120596

CC(11)

12 Journal of Spectroscopy

Table8Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

525

mdash511

525

12735

1849

bCCO

(82)

41A1015840

505

mdash511

505

50036

5698

tOH(24)ttrigd(23)120596

CO(19)120596

CH(14

)42

A1015840

440

mdash481

440

3190

2294

bCO(35)bCO

C(29)

43A10158401015840

mdash375

427

375

0415

0023

tsym

(60)120596

CH(19

)tasym

(17)

44A1015840

mdash310

335

310

3569

0577

Rsym

d(48)120592CC

fn(25)

45A10158401015840

mdash285

304

285

4416

0596

120596CC

(33)tasym

(24)tCO

(16)

46A1015840

mdash220

267

220

3713

2509

bCOC(29)bCO

(17)

47A10158401015840

mdash165

226

165

0047

0429

tCH

3(85)

48A1015840

mdash111

165

111

0211

0159

bCC(80)

49A10158401015840

mdash98

132

982323

0292

Tasym

(30)tCO

C(30)120596

CC(11)120596

CH(10)tsym

(10)

50A10158401015840

mdash70

7870

1302

1199

tCO(95)

51A10158401015840

mdash60

6560

0898

0216

tCOC(48)tCO

(31)tCH

3(12)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 13

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 3 FT-Raman spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 4 FTIR spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 5 FT-Raman spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

title molecules all the hydrogen atoms have a net positivecharge in particular the hydrogen atoms H(10) that havecharge of 05047 and 05050 respectively The presence oflarge amounts of negative charge on oxygen and net positivecharge on H(10) atoms may suggest the presence of inter-molecular hydrogen bonding in the crystalline phase

Highest occupied molecular orbital and lowest unoc-cupied molecular orbital are very important parametersfor quantum chemistry This is also used by the frontierelectron density for predicting the most reactive position in120587-electron systems and also explains several types of reactionin conjugated system [32] The conjugated molecules are

characterized by a small highest occupied molecular orbitalndashlowest unoccupied molecular orbital (HOMO-LUMO) sep-aration which is the result of a significant degree of inter-molecular charge transfer from the end-capping electron-donating groups to the efficient electron-acceptor groupsthrough 120587 conjugated path [33] Both the highest occupiedmolecular orbital and lowest unoccupied molecular orbitalare the main orbitals that take part in chemical stability[34] Energy difference betweenHOMOand LUMOorbital iscalled energy gap that is an important stability for structureswhich are given in Table 11 We performed an analysis ofall the molecular orbitals involved taking into consideration

14 Journal of Spectroscopy

Table 9 Atomic charges for optimized geometry of O-Anisic acid(OAA) and Anisic acid (AA) obtained by B3LYP6-31Glowastlowast densityfunctional calculations

Atomsa MullikenOAA AA

C1 00018 00373C2 03297 minus01002

C3 minus01368 minus01219

C4 minus00836 03612

C5 minus00943 minus01394

C6 minus01061 minus01118

C7 05570 05445O8 minus04650 minus04848

O9 minus05104 minus05064

H10 03198 03217O11 (H11) minus04841 01203C12 (H12) minus00837 01021H13 (O13) 01064 minus05111

H14 (C14) 01352 minus00831

H15 01211 01099H16 00913 01302H17 00929 01246H18 00886 00913H19 01200 01155aThe atoms indicated in the parenthesis belong to AA

Table 10Natural atomic charges ofO-Anisic acid (OAA) andAnisicacid (AA) calculations performed at the B3LYP6-31Glowastlowast level oftheory

Atomsa OAA AAC1 minus02176 minus02053

C2 03724 minus01746

C3 minus03284 minus02801

C4 minus01952 03443

C5 minus02720 minus03289

C6 minus01806 minus01748

C7 08091 08139O8 minus05861 minus06102

O9 minus07295 minus07217

H10 05047 05050O11 (H11) minus04921 02634C12 (H12) minus03307 02544H13 (O13) 02070 minus05119

H14 (C14) 02390 minus03300

H15 02070 02090H16 02443 02352H17 02426 02090H18 02439 02449H19 02621 02585aThe atoms indicated in the parenthesis belong to AAFor numbering of atoms refer to Figures 1(a) and 1(b)

that orbital 40 is the HOMO and orbital 41 is the LUMO forOAA and AA respectively

Many organic molecules that contain conjugated 120587 elec-trons are characterized as hyperpolarisabilities and are ana-lyzed by means of vibrational spectroscopy The analysis

Table 11 Calculated quantum chemical parameters ofO-Anisic acid(OAA) and Anisic acid (AA) derivatives

Parameters OAA AA119864HOMO minus0227 minus0231

119864LUMO minus0041 minus0036

Δ119864 0186 0195120594 0134 0133Η 0093 0097Σ 10752 10256

Table 12 Calculated 13C NMR chemical shifts (ppm) of O-Anisicacid (OAA) and Anisic acid (AA)

Carbona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAC1 11782 12315 10447 12620C2 15848 13146 14696 13936C3 11204 11384 9681 12272C4 13517 16297 11926 17125C5 12191 11384 10447 11047C6 13347 13146 12019 13751C7 16634 16714 14609 17174C12 (C14) 5674 5544 4322 5549aThe atoms indicated in the parenthesis belong to AA

Table 13 Experimental and calculated 1H NMR chemical shifts(ppm) of O-Anisic acid (OAA) and Anisic acid (AA)

Protona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAH10 1030 13 11 11H13 H14 H15 (H11) 4066 7914 3932 8405H16 (H12) 708 7027 6831 7147H17 (H15 H16 H17) 756 3836 7570 3824H18 710 7027 7069 6673H19 813 7914 3932 8217aThe atoms indicated in the parenthesis belong to AA

of the wave function indicates that the electron absorptioncorresponds to the transition from the ground state to thefirst excited state and is mainly described by the one-electronexcitation from the HOMO to the LUMO The HOMO of 120587nature (ie aromatic ring) is delocalized over the whole CndashC bond By contrast the LUMO is located over the aromaticring Consequently the HOMO-LUMO transition implies anelectron density transfer toCOOHandOCH

3group from the

aromatic ringThe theoretical basis for the new quantities lies in the

density functional formalism [35] Since molecular orbital(MO) theory is by far the most widely used by chemistsit is important to place 120594 and 120578 in a MO framework Ithas already been shown [36] that the MO theory of thechemical bond contains the values of 120594 and 120578 for the bondingfragments Hard molecules have a large HOMO-LUMO gapand soft molecules have a small HOMO-LUMO gap A small

Journal of Spectroscopy 15

HOMO

(a)

LUMO

(b)

Figure 6 Contour surfaces of frontier molecular orbitals of O-Anisic acid

HOMO

(a)

LUMO

(b)

Figure 7 Contour surfaces of frontier molecular orbitals of Anisic acid

HOMO-LUMO gap automatically means small excitationenergies to the manifold of excited states Therefore softmolecules with a small gap will be more polarizable thanhard molecules High polarizability was the most character-istic property attributed to soft acids and bases Energy gapsshould be small for best bonding or bothmolecules should besoft

In the present study the title compound AA is dynam-ically more stable due to the large energy gap OAA is asoft molecule due to small energy gap The Contour surfacesof the frontier molecular orbitals are sketched in Figures 6and 7

51 NMR Spectra DFT methods treat the electronic energyas a function of the electron density of all electrons simul-taneously and thus include electron correlation effect [37]In this study molecular structure of the OAA and AA wasoptimized by using B3LYP method in conjunction with 6-31Glowastlowast 13C and 1H chemical shift calculations of the titlecompounds have been made by using GIAO method andsame basis set The isotropic shielding values were usedto calculate the isotropic chemical shifts 120575 with respect totetramethylsilane (TMS) The isotropic chemical shifts arefrequently used as an aid in identification of reactive ionicspecies The B3LYP method allows calculating the shielding

16 Journal of Spectroscopy

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 150

140

130

120

110

100

90110 120 130 140 150 160 170

(a)

70 75 80 85 90 95 100 1056

7

8

9

10

11

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

(b)

Figure 8 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for O-Anisic acid

constants with the proper accuracy and the GIAOmethod isone of the most common approaches for calculating nuclearmagnetic shielding tensors

Theoretical and experimental chemical shifts of OAA andAA in 1H and 13C NMR spectra are gathered in Tables 12and 13 The range of the 13C NMR chemical shifts for atypical organic molecules usually is gt100 ppm [38 39] andthe accuracy ensures reliable interpretation of spectroscopicparameters In the present study the 13C NMR chemicalshifts in the ring are gt100 ppm as they would be expectedThe 13C chemical shifts carbonyl carbons vary from 150 to220 ppm This depends on the decrease in electron donatingor shielding ability of the attached atoms [40] The C=Ogroups of carboxylic acids and derivatives are in the range of150ndash185 ppm [29]

Hydrogens bonded to an aromatic ring are stronglydeshielded and absorb downfieldWhen the120587-electrons enterthe magnetic field they circulate around the ring to generatea ring current This produces a small induced magnetic fieldthat reinforces the applied field outside the ring resultingin aromatic protons being deshielded [41] A related effectis observed for carboxylic acids For these compoundscirculation of electrons in the double bonds produces inducedmagnetic field These are responsible for the high chemicalshift values of acid protons (H10) Carboxylic acids asstable hydrogen-bonded dimers in nonpolar solvents even athigh dilution The carboxylic proton therefore absorbs in acharacteristically narrow range 132 to 100 and is affectedonly slightly by concentration [29]

In a methyl group a proton is covalently bonded tocarbon oxygen or other atoms by a sigma bond Whenplaced in a strong magnetic field the electrons of the sigmabond circulate to generate a small magnetic field whichopposes the applied field A nearby electronegative atomwithdraws electron density from the neighbourhood of theproton so that a smaller applied field is needed to cause thespin state of the proton to flip The signal for a deshielded

Table 14 Theoretically computed energies (au) zero-point vibra-tional energies (kcalmolminus1) rotational constants (GHz) entropies(calmolminus1 Kminus1) nuclear repulsion energy (Hartrees) and dipolemoment (Debye) for OAA and AA

Parameters B3LYP6-31Glowastlowast

OAA AAZero-point energy 9306056 9314966

Rotational constants139942 344405114384 056752063193 048875

EntropyTotal 99243 97126Translational 40967 40967Rotational 30142 30199Vibrational 28134 25960Dipole moment 24181 35822Nuclear repulsion energy 592968293 573992628

proton (1 surrounded by less electron density) is observed tobe more downfield than the signals for protons that are notdeshielded by electronegative atoms [40] The chemical shiftvalue of C7 (OAA and AA) has bigger value than the othercarbons due to the electronegative property of oxygen atom

The linear correlations between calculated and experi-mental data of 13CNMRand 1HNMRspectra are determinedas 09 and 10 for OAA and 09 and 09 for AA respectivelyThere is an excellent linear relationship between experimentaland computed results which are shown in Figures 8 and 9

6 Thermodynamic Properties

Several calculated thermodynamical parameters are pre-sented in Table 14 for OAA andAA respectively Scale factorshave been recommended [42] for an accurate prediction in

Journal of Spectroscopy 17

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 180

170

160

150

140

130

120

110110

120 130 140 150 160 170

(a)

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

11

10

9

8

7

7 8 9 10 11 12 13

(b)

Figure 9 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for Anisic acid

determining the zero-point vibration energies (ZPVE) andthe entropy 119878vib(119879) The total energies and the change inthe total entropy at room temperature using B3LYP6-31Glowastlowastmethod are presented

7 Conclusion

Attempts have been made in the present work for the molec-ular parameters and frequency assignments for the com-pounds OAA and AA from the FTIR and FT-Raman spectraThe equilibrium geometries and harmonic and anharmonicfrequencies for the title compounds were determined andanalyzed at DFT level of theory utilizing 6-31Glowastlowast basis setThe assignments of most of the fundamentals of the titlecompounds provided in this work are quite comparableThe excellent agreement of the calculated and observedvibrational spectra reveals the advantages of a smaller basisset for quantum chemical calculations HOMO and LUMOenergy gap explains the eventual charge transfer interactionstaking place within the molecule The experimental andtheoretical investigation of the title compounds have beenperformed successfully by using 1H and 13C NMR Thevarious modes of vibrations were unambiguously assignedon the basis of the result of the PED output obtainedfrom normal coordinate analysis These studies confirm thepresence of COOH and OCH

3group Dimeric molecules are

held together by hydrogen bridges between carbonyl groupsThe obtained data and simulations both show the way to thecharacterization of the molecules and help in spectra studiesin the future

References

[1] GMelentyeva and LAntonovaPharmaceutical ChemistryMirPublishers Moscow Russia 1988

[2] ldquoo-Anisic acid(579-75-9) catalog of chemical suppliersrdquo httpwwwchemexpercomchemicalssuppliercas579-75-9html

[3] B A Hess Jr L J Schaad P Carsky and R Zaharaduick ldquoAbinitio calculations of vibrational spectra and their use in theidentification of unusual moleculesrdquo Chemical Reviews vol 86no 4 pp 709ndash730 1986

[4] P Pulay X Zhou and G Forgarasi in Recent Experimental andComputational Advances in Molecular Spectroscopy R Faustoand R Fransto Eds vol 406 ofNATOASI Series p 99 KluwerDordrecht Netherlands 1993

[5] P Pulay G Fogarasi G Pongor J E Boggs and A VarghaldquoCombination of theoretical ab initio and experimental infor-mation to obtain reliable harmonic force constants ScaledQuantum Mechanical (SQM) force fields for glyoxal acroleinbutadiene formaldehyde and ethylenerdquo Journal of the Ameri-can Chemical Society vol 105 no 24 pp 7037ndash7047 1983

[6] C E Blom and C Altona ldquoApplication of self-consistent-fieldab initio calculations to organic moleculesrdquo Molecular Physicsvol 31 no 5 pp 1377ndash1391 1976

[7] G Fogarasi and P Pulay in Vibrational Spectra and Structure JR Durig Ed vol 14 Elsevier Amsterdam Netherlands 1985

[8] G Fogarasi ldquoRecent developments in the method of SQM forcefields with application to 1-methyladeninerdquo Spectrochimica ActaA vol 53 no 8 pp 1211ndash1224 1997

[9] G R deMare N Yu Panchenko andW Ch Bock ldquoAnMP26-31GlowastMP26-31Glowast vibrational analysis of s-trans- and s-cis-acryloyl fluoride CH2=CH-CF=Ordquo The Journal of PhysicalChemistry vol 98 no 5 pp 1416ndash1420 1994

[10] G Pongor P Pulay G Fogarasi and J E Boggs ldquoTheoreticalprediction of vibrational spectra 1 The in-plane force fieldand vibrational spectra of pyridinerdquo Journal of the AmericanChemical Society vol 106 no 10 pp 2765ndash2769 1984

[11] Y Yamakitu and M Tasumi ldquoVibrational analyses of p-benzoquinodimethane and p-benzoquinone based on ab initioHartree-Fock and second-order Moller-Plesset calculationsrdquoThe Journal of Physical Chemistry vol 99 no 21 pp 8524ndash85341995

18 Journal of Spectroscopy

[12] M Karabacak A Coruh and M Kurt ldquoFT-IR FT-RamanNMR spectra and molecular structure investigation of 23-dibromo-N-methylmaleimide a combined experimental andtheoretical studyrdquo Journal of Molecular Structure vol 892 no1ndash3 pp 125ndash131 2008

[13] M S Masoud M K Awad M A Shaker and M M T El-Tahawy ldquoThe role of structural chemistry in the inhibitiveperformance of some aminopyrimidines on the corrosion ofsteelrdquo Corrosion Science vol 52 no 7 pp 2387ndash2396 2010

[14] M J Frisch G W Trucks H B Schlegel et al Gaussian 03Revision B4 Gaussian Inc Pittsburgh Pa USA 2003

[15] P L Polavarapu ldquoAb initio vibrational Raman and Ramanoptical activity spectrardquo Journal of Physical Chemistry vol 94no 21 pp 8106ndash8112 1990

[16] G Keresztury S Holly J Varga G Besenyei A Wang andJ R Durig ldquoVibrational spectra of monothiocarbamates-IIIR and Raman spectra vibrational assignment conforma-tional analysis and ab initio calculations of S-methyl-NN-dimethylthiocarbamaterdquo Spectrochimica Acta A vol 49 no 13-14 pp 2007ndash2017 1993

[17] G Keresztury ldquoRaman spectroscopy theoryrdquo in Handbook ofVibrational Spectroscopy J M Chalmers and P R Griffths Edsvol 1 p 71 John Wiley and Sons 2002

[18] R G Parr R A Donnelly M Levy and W E Palke ldquoElec-tronegativity the density functional viewpointrdquo The Journal ofChemical Physics vol 68 no 8 pp 3801ndash3807 1977

[19] R G Parr and R G Pearson ldquoAbsolute hardness companionparameter to absolute electronegativityrdquo Journal of theAmericanChemical Society vol 105 no 26 pp 7512ndash7516 1983

[20] R G Pearson ldquoAbsolute electronegativity and hardness appli-cation to inorganic chemistryrdquo Inorganic Chemistry vol 27 no4 pp 734ndash740 1988

[21] P Geerlings F De Proft and W Langenaeker ldquoConceptualdensity functional theoryrdquo Chemical Reviews vol 103 no 5 pp1793ndash1873 2003

[22] R Ditchfield ldquoMolecular orbital theory of magnetic shieldingand magnetic susceptibilityrdquo Journal of Physical Chemistry vol56 no 11 article 5688 4 pages 1972

[23] KWolinski J F Hilton and P Pulay ldquoEfficient implementationof the gauge-independent atomic orbital method for NMRchemical shift calculationsrdquo Journal of the American ChemicalSociety vol 112 no 23 pp 8251ndash8260 1990

[24] M Kurt M Yurdakul and S Yurdakul ldquoMolecular structureand vibrational spectra of 3-chloro-4-methyl aniline by densityfunctional theory and ab initio Hartree-Fock calculationsrdquoJournal of Molecular Structure vol 711 no 1ndash3 pp 25ndash32 2004

[25] D Steele and D H Whiffen ldquoThe vibration frequencies ofpentafluorobenzenerdquo Spectrochimica Acta vol 16 no 3 pp368ndash375 1960

[26] D N Sathyanarayanan Vibrational Spectroscopy Theory andApplication New Age International publishers New DelhiIndia 1996

[27] L D S YadavOrganic Spectroscopy Springer NewDelhi India2004

[28] J Mohan Organic Spectroscopy Principles and ApplicationsNarosa Publishing House New Delhi 2nd edition 2009

[29] R M Silverstein G C Bassler and T C Morrill SpectrometricIdentification of Organic Compounds John Wiley amp Sons NewYork NY USA 1981

[30] G Socrates Infrared Characteristic Group Frequencies WileyNew York NY USA 1980

[31] R S Mulliken ldquoElectronic population analysis on LCAO-MOmolecular wave functionsrdquoThe Journal of Chemical Physics vol23 no 10 pp 1833ndash1840 1955

[32] K Fukuli T Yonezawa and H Shingu ldquoA molecular orbitaltheory of reactivity in aromatic hydrocarbonsrdquo Journal ofPhysical Chemistry vol 20 no 4 article 722 4 pages 1952

[33] C H Choi and M Kertesz ldquoConformational information fromvibrational spectra of styrene trans-stilbene and cis-stilbenerdquoJournal of Physical Chemistry A vol 101 no 20 pp 3823ndash38311997

[34] S Gunasekaran R Arun Balaji S Kumaresan G Anandand S Srinivasan ldquoExperimental and theoretical investigationsof spectroscopic properties of N-acetyl-5-methoxytryptaminerdquoCanadian Journal of Analytical Sciences and Spectroscopy vol53 no 4 pp 149ndash162 2008

[35] P Hohenberg and W Kohn ldquoInhomogeneous electron gasrdquoPhysical Review vol 136 no 3 pp B864ndashB871 1964

[36] R G Pearson ldquoAbsolute electronegativity and absolute hard-ness of Lewis acids and basesrdquo Journal of the American ChemicalSociety vol 107 no 24 pp 6801ndash6806 1985

[37] D Avci Y Atalay M Sekerci and M Dincer ldquoMolecular struc-ture and vibrational and chemical shift assignments of 3-(2-Hydroxyphenyl)-4-phenyl-1H-124-triazole-5-(4H)-thione byDFT and ab initio HF calculationsrdquo Spectrochimica Acta A vol73 no 1 pp 212ndash217 2009

[38] H O Kalinowski S Berger and S Braun Carbon13 NMRSpectroscopy John Wiley amp Sons Chichester UK 1988

[39] K Pihlaja and E Kleinpeter Carbon-13 NMR Chemical Shiftsin Structural and Sterochemical Analysis VCH PublishersDeerfield Beach Fla USA 1994

[40] P S Kalsi Spectroscopy of Organic Compounds New AgeInternational 2004

[41] A F Parsons Keynotes in Organic Chemistry Blackwell Pub-lishing Oxford UK 2003

[42] M A Palafox ldquoScaling factors for the prediction of vibrationalspectra I benzenemoleculerdquo International Journal of QuantumChemistry vol 77 no 3 pp 661ndash684 2000

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

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Carbohydrate Chemistry

International Journal of

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Journal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

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Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

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The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

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Quantum Chemistry

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CatalystsJournal of

Page 2: Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. · Molecular Structure, NMR, HOMO, LUMO, ... ects of carbonyl and methyl substitutions

2 Journal of Spectroscopy

such as chemical potential (119875119894) global hardness (120578) and the

softness (120590) [13] A detailed quantum chemical study willaid in making definite assignments to fundamental normalmodes of OAA and AA to clarify the experimental data forthese important molecules

2 Experimental

The pure crystalline samples of OAA and AA were obtainedfrom Lanchester chemical company UK and used withoutfurther purification for the spectral measurements Theroom-temperature Fourier-transform (FT) infrared spectraof the title compounds were measured in the region 4000ndash400 cmminus1 at a resolution of plusmn1 cmminus1 using BRUKER IFS-66V Fourier-transform spectrometer equippedwith anMCTdetector a KBr beam splitter and a globar source The FT-Raman spectra were recorded on the same instrument withan FRA-106 Raman accessory in the region 4000ndash50 cmminus1The 1064-nm line of a NdYAG laser was used as excitationsource and the laser power was set to 200mw

The 1H and 13C NMR spectra were taken in CDCl3 and

DMSO-1198896solution and all signals were referenced to TMS

on a BRUKER FT-NMR spectrometer All NMR spectra weremeasured at room temperature

3 Computational Details

All the calculations were performed by using Gaussian 03program [14] package on the personal computer The Beckersquosthree-parameter hybrid density functional B3LYP was usedto calculate both harmonic and anharmonic vibrationalwavenumbers with 6-31Glowastlowast basis set It is well known in thequantum chemical literature that the B3LYP functional yieldsa good description of harmonic vibrational wavenumbers forsmall andmedium sized moleculesThe optimized structuralparameters were used in the vibrational frequency calcula-tions at the DFT levels to characterize all stationary points asminimaThe Cartesian representation of the theoretical forceconstants has been computed at the fully optimized geometryby assuming119862

119904point group symmetry respectively for OAA

and AA The theoretical DFT force field was transformedfrom Cartesian coordinates into the local coordinates andthen scaled empirically according to the SQM procedure [5]

119865Scaled119894119895

= (119862119894119862119895)12

119865B3LYP119894119895

(1)

where 119862119894is the scale factor of coordinate 119894 119865B3LYP

119894119895is the

B3LYP6-31Glowastlowast force constant in local coordinate and119865Scaled119894119895

is the scaled force constantThe prediction of Raman intensities was carried out by

following the procedure outlined belowTheRaman activities(119878119894) calculated by the Gaussian 03 program and adjusted

during the scaling procedure with the MOLVIB programwere converted to relative Raman intensities (119868

119894) using

the following relationship derived from the basic theory ofRaman scattering [15ndash17]

119868119894=

119891(120592119900minus 120592119894)4

119878119894

120592119894[1 minus exp (minusℎ119888120592

119894119870119879)]

(2)

where 1205920is the exciting frequency (in cmminus1 units) 120592

119894the

vibrational wavenumber of the 119894th normal mode ℎ 119888 and 119896

are the fundamental constants and 119891 is the suitably chosencommon normalization factor for all the peak intensities

The calculated quantum chemical parameters such asthe highest occupied molecular orbital energy (119864HOMO) thelowest unoccupied molecular orbital energy (119864LUMO) energygap (Δ119864) chemical potential (119875

119894) global hardness (120578) and the

softness (120590) were calculatedThe concept of these parametersis related to each other [18ndash21] where

119875119894= minus120594

119875119894=(119864HOMO + 119864LUMO)

2

120578 =(119864LUMO minus 119864HOMO)

2

(3)

The inverse values of the global hardness are designatedas the softness 120590 as follows

120590 =1

120578 (4)

For NMR calculations the title molecules are firstlyoptimized and after optimization 1H and 13CNMR chemicalshifts (H and C) were calculated using the GIAO methodin CDCl

3at B3LYP method with 6-31Glowastlowast basis set [22 23]

Absolute isotropic magnetic shielding was transformed intochemical shifts by referring to the shielding of a standardcompound (TMS) computed at the same level It has beenshown that B3LYP applications were successful in shieldingcalculations on carbon and hydrogen atoms [23]

4 Results and Discussion

41 Molecular Geometry The molecular structures of OAAand AA with 119862

119904symmetry are shown in Figures 1(a) and

1(b) respectively The optimized bond lengths and anglesfor OAA and AA using DFT methods are given in Table 1The global minimum energies obtained by the DFT structureoptimization for OAA and AA are calculated as minus5353530and minus5353627 Hartrees respectively The substitution ofOCH3with COOH group in the OAA andAA leads to strong

intermolecular hydrogen bonding and +I effect respectively

42 Vibrational Force Constants Quantum mechanical cal-culations contain the force constant matrix in Cartesiancoordinates and in HartreeBohr2 units These force con-stants were transformed to the force fields in internallocal-symmetry coordinates The local-symmetry coordi-nates defined in terms of the internal valence coordinates

Journal of Spectroscopy 3

(a) (b)

Figure 1 (a) Molecular structure of O-Anisic acid along with numbering of atoms (b) Molecular structure of Anisic acid along withnumbering of atoms

Table 1 Optimized geometrical parameters O-Anisic acid (OAA) and Anisic acid (AA) obtained by B3LYP6-31Glowastlowast density functional cal-culations

Bond lengtha Value ( A) Bond anglea Value (∘)OAA AA OAA AA

C1ndashC2 139 139 C1ndashC2ndashC3 11999 11999C2ndashC3 139 139 C2ndashC3ndashC4 11999 11999C3ndashC4 139 139 C3ndashC4ndashC5 12000 12000C4ndashC5 139 139 C4ndashC5ndashC6 11999 11999C5ndashC6 139 139 C2ndashC1ndashC7 12001 12001C1ndashC7 154 154 C1ndashC7ndashO8 13007 13007C7ndashO8 123 123 C1ndashC7ndashO9 11229 11229O9ndashC7 135 135 C7ndashO9ndashH10 11060 11060O9ndashH10 097 094 C3ndashC2ndashO11(H11) 11998 11998C2ndashO11(H11) 143 109 C2ndashO11ndashC12 (C4ndashC3ndashH12) 10950 12001C11ndashC12 (H12ndashC2) 143 100 O11ndashC12ndashH13 (C5ndashC4ndashO13) 10947 11998C12ndashH13 (O13ndashC3) 107 143 O11ndashC12ndashH14 (C4ndashO13ndashC14) 10947 10950C12ndashH14 (C14ndashO13) 107 143 O11(O13)ndashC12(C14)ndashH15 10947 10947C12(C14)ndashH15 107 107 C4(O13)ndashC3(C14)ndashH16 12001 10947C3(C14)ndashH16 109 107 C5(O13)ndashC4(C14)ndashH17 11998 10947C4(C14)ndashH17 109 107 C6ndashC5ndashH18 12000 12000C5ndashH18 109 109 C1ndashC6ndashH19 11999 11999C6ndashH19 109 109aThe atoms indicated in the parenthesis belongs to AAFor numbering of atoms refer to Figures 1(a) and 1(b)

following the IUPAC recommendations [24 25] are given inTables 4 and 5 for the title compounds

The bonding properties of OAA and AA are influencedby their rearrangements of electrons during substitutionsand addition reactions The stretching force constants ofC1ndashC7 in OAA and AA are found to be lower than the valuesof stretching force constant of other CndashC atoms The force

constant of C1ndashC7 in OAA is found to be greater than AAdue to steric effect (ie bulky groups in OAA) The mostimportant diagonal force constants (stretching only) of OAAand AA are listed in Table 6

43 Assignment of Fundamentals The molecules OAA andAA are disubstituted aromatic system The vibrational bands

4 Journal of Spectroscopy

Table 2 Definition of internal coordinates of O-Anisic acid (OAA)

No (i) Symbol Type DefinitionStretching

1ndash4 119903119894

CndashH C3ndashH16 C4ndashH17 C5ndashH18 C6ndashH195ndash11 119903

119894CndashC C1ndashC2 C2ndashC3 C3ndashC4 C4ndashC5 C5ndashC6 C6ndashC1 C1ndashC7

12ndash14 119903119894

CndashO C7ndashO8 C7ndashO9 C2ndashO1115 119903

119894OndashC O11ndashC12

16 119903119894

OndashH O9ndashH1017ndash19 119903

119894CndashH(methyl) C12ndashH13 C12ndashH14 C12ndashH15

Bending20-21 120573

119894CndashCndashC C2ndashC1ndashC7 C6ndashC1ndashC7

22ndash29 120573119894

CndashCndashH C2ndashC3ndashH16 C4ndashC3ndashH16 C3ndashC4ndashH17 C5ndashC4ndashH17C4ndashC5ndashH18 C6ndashC5ndashH18 C5ndashC6ndashH19 C1ndashC6ndashH19

30ndash32 120573119894

CndashCndashH(methyl) O11ndashC12ndashH13 O11ndashC12ndashH14 O11ndashC12ndashH1533ndash35 120573

119894HndashCndashH H13ndashC12ndashH14 H13ndashC12ndashH15 H14ndashC12ndashH15

36-37 120573119894

CndashCndashO C1ndashC7ndashO8 C1ndashC7ndashO938 120573

119894CndashOndashH C7ndashO9ndashH10

39-40 120573119894

CndashCndashO C1ndashC2ndashO11 C3ndashC2ndashO1141 120573

119894CndashOndashC C2ndashO11ndashC12

42ndash47 120573119894

CndashCndashC (Ring) C1ndashC2ndashC3 C2ndashC3ndashC4 C3ndashC4ndashC5 C4ndashC5ndashC6C5ndashC6ndashC1 C6ndashC1ndashC2

Out-of-plane bending

48ndash51 120596119894

CndashH H16ndashC3ndashC2ndashC4 H17ndashC4ndashC5ndashC3 H18ndashC5ndashC6ndashC4H19ndashC6ndashC1ndashC5

52 120596119894

CndashC C7ndashC1ndashC6ndashC253 120596

119894CndashO O11ndashC2ndashC1ndashC3

Torsion54-55 120591

119894CndashO C2ndashC1ndashC7ndashO8 C2ndashC1ndashC7ndashO9

56-57 120591119894

CndashOndashC C1ndashC2ndashO11ndashC12 C3ndashC2ndashO11ndashC12

58ndash60 120591119894

CndashH(methyl) C2ndashO11ndashC12ndashH13 C2ndashO11ndashC12ndashH14C2ndashO11ndashC12ndashH15

61 120591119894

OndashH C1ndashC7ndashO9ndashH10

62ndash67 120591119894

tring C1ndashC2ndashC3ndashC4 C2ndashC3ndashC4ndashC5 C3ndashC4ndashC5ndashC6C4ndashC5ndashC6ndashC1 C5ndashC6ndashC1ndashC2 C6ndashC1ndashC2ndashC3

For numbering of atoms refer to Figure 1(a)

observed in the IR region are very sharp broad and lessintense The title compounds belong to 119862

119904point group The

19 atoms present in OAA and AA molecular structure eachhas 51 fundamental modes of vibrations For molecules of119862119904symmetry group theory analysis indicates that the 51

fundamental vibrations are distributed among the symmetryspecies as

Γvib = 35A1015840 (in-plane) + 16A10158401015840 (out-of-plane) (5)

for bothOAA andAA respectively From the structural pointof view of the molecules OAA and AA have 18 stretchingvibrations 33 bending vibrations respectively All the vibra-tions were found to be active both in Raman scattering andinfrared absorption

The observed and calculated wave numbers calculatedIR and Raman intensities and normal mode descriptions(characterized by potential energy distribution (PED)) for

the fundamental vibrations of OAA and AA are depictedin Tables 7 and 8 For visual comparison the observed andsimulated FTIR and FT-Raman spectra of the compoundsare presented in Figures 2 3 4 and 5 which help to under-stand the observed spectral features The root mean square(RMS) error of the observed and calculated wavenumbers(unscaledB3LYP6-31Glowastlowast) of OAA and AA was found to be843 cmminus1 and 891 cmminus1 respectively This is understandablesince the mechanical force fields usually differ appreciablyfrom the observed ones This is partly due to the neglectof anharmonicity and partly due to the approximate natureof the quantum mechanical methods However for reliableinformation on the vibrational properties the use of selectivescaling is necessary The calculated wavenumbers are scaledusing the set of transferable scale factors recommended byFogarasi and Pulay [7]The SQM treatment has resulted in anRMS deviation of 967 cmminus1 and 113 cmminus1 for OAA and AA

Journal of Spectroscopy 5

Table 3 Definition of internal coordinates of Anisic acid (AA)

No (i) Symbol Type DefinitionStretching

1ndash4 119903119894

CndashH C2ndashH11 C3ndashH12 C5ndashH18 C6ndashH195ndash10 119903

119894CndashC C1ndashC2 C2ndashC3 C3ndashC4 C4ndashC5 C5ndashC6C6ndashC1

11 119903119894

CndashCfn C1ndashC712ndash14 119903

119894CndashO C7ndashO8 C7ndashO9 C4ndashO13

15 119903119894

OndashC O13ndashC1416 119903

119894OndashH O9ndashH10

17ndash19 119903119894

CndashH(methyl) C14ndashH15 C14ndashH16 C14ndashH17Bending

20-21 120573119894

CndashC C2ndashC1ndashC7 C6ndashC1ndashC7

22ndash29 120573119894

CndashCndashHC1ndashC2ndashH11 C3ndashC2ndashH11C2ndashC3ndashH12 C4ndashC3ndashH12C4ndashC5ndashH18 C6ndashC5ndashH18C5ndashC6ndashH19 C1ndashC6ndashH19

30ndash35 120573119894

CndashCndashH(methyl) O13ndashC14ndashH15 O13ndashC14ndashH16 O13ndashC14ndashH17H17ndashC14ndashH15 H15ndashC14ndashH16 H17ndashC14ndashH16

36-37 120573119894

CndashCndashO C3ndashC4ndashO13 C5ndashC4ndashO1338 120573

119894CndashOndashH C7ndashO9ndashH10

39-40 120573119894

CndashCndashO C1ndashC7ndashO8 C1ndashC7ndashO941 120573

119894CndashOndashC C4ndashO13ndashC14

42ndash47 120573119894

CndashCndashC (Ring) C1ndashC2ndashC3 C2ndashC3ndashC4 C3ndashC4ndashC5 C4ndashC5ndashC6C5ndashC6ndashC1 C6ndashC1ndashC2

Out-of-plane bending

48ndash51 120596119894

CndashH H11ndashC2ndashC3ndashC1 H12ndashC3ndashC4ndashC2 H18ndashC5ndashC6ndashC4H19ndashC6ndashC1ndashC5

52 120596119894

CndashC C7ndashC1ndashC6ndashC253 120596

119894CndashO O13ndashC4ndashC5ndashC3

Torsion54ndash55 120591

119894CndashO C2ndashC1ndashC7ndashO8 C2ndashC1ndashC7ndashO9

56-57 120591119894

CndashOndashC C3ndashC4ndashO13ndashC14 C5ndashC4ndashO13ndashC14

58ndash60 120591119894

CndashH(methyl) C4ndashO13ndashC14ndashH15 C4ndashO13ndashC14ndashH16C4ndashO13ndashC14ndashH16

61 120591119894

OndashH C1ndashC7ndashO9ndashH10

62ndash67 120591119894

tring C1ndashC2ndashC3ndashC4 C2ndashC3ndashC4ndashC5 C3ndashC4ndashC5ndashC6C4ndashC5ndashC6ndashC1 C5ndashC6ndashC1ndashC2 C6ndashC1ndashC2ndashC3

For numbering of atoms refer to Figure 1(b)

respectively The RMS values of wavenumbers were obtainedin this study using the following expression

RMS = radic1

119899 minus 1

119899

sum

119894

(120592calc119894

minus 120592exp119894

)2

(6)

431 CH Vibrations Aromatic compounds commonly ex-hibit multiple weak bands in the region 3100ndash3000 cmminus1 [26]due to aromatic CndashH stretching vibrations According to thePED analysis the bands observed in experimental spectrumat 3098 3083 3069 3020 cmminus1 in OAA and 3085 3034 3029and 3002 cmminus1 inAAwere assigned to stretching vibrations of

CndashH bond According to these studies all the CndashH stretchingvibrations are not mixed with other types of vibrations

The CndashH in-plane deformation vibrations are assigned inthe region 1100ndash1400 cmminus1 [27] The in-plane deformationsof CndashH groups are noticed on PED analysis at 1494 14391288 and 1182 in OAA and 1518 1301 1181 and 1131 cmminus1 inAAThere is slight increase in the CndashH in-plane deformationfrequency because of steric effect in OAA and inductive effect(+I) in AAThese values of calculated frequencies are typicaland in very good agreement with experimental data The in-plane CndashH deformation vibrations are slightly mixed in bothOAA and AA

The CndashH out-of-plane deformation vibrations areassigned in the region 900ndash600 cmminus1 [26] The bands

6 Journal of Spectroscopy

Table 4 Definition of natural internal coordinates of O-Anisic acid (OAA)

No (i) Symbola Definitionb

1ndash4 CndashH stretch 1199031 1199032 1199033 1199034

5ndash11 CndashC stretch 1199035 1199036 1199037 1199038 1199039 11990310 11990311

12ndash14 CndashO stretch 11990312 11990313 11990314

15 OndashC stretch 11990315

16 OndashH stretch 11990316

17 CH3 ss (11990317+ 11990318+ 11990319) radic3

18 CH3 ips (211990317minus 11990318minus 11990319) radic6

19 CH3 ops (11990318minus 11990319) radic2

20 bCndashCndashC (12057320minus 12057321) radic2

21ndash24 bCndashCndashH (12057322minus 12057323) radic2 (120573

24minus 12057325) radic2 (120573

26minus 12057327) radic2 (120573

28minus 12057329) radic2

25 CH3 sb (minus12057330minus 12057331minus 12057332+ 12057333+ 12057334+ 12057335) radic6

26 CH3 ipb (minus12057333minus 12057334minus 212057335)radic6

27 CH3 opb (12057333minus 12057334) radic2

28 CH3 ipr (212057330minus 12057331minus 12057332)radic6

29 CH3 opr (12057331minus 12057332)radic2

30 bCndashCndashO (12057336minus 12057337) radic2

31 bCndashOndashH 12057338

32-33 bCndashCndashO 12057339 12057340

34 bCndashOndashC 12057341

35 Rtrigd (12057342minus 12057343+ 12057344minus 12057345+ 12057346minus 12057347) radic6

36 Rsymd (minus12057342minus 12057343+ 12057344minus 12057345minus 12057346+ 212057347)radic12

37 Rasymd (12057342minus 12057343+ 12057345minus 12057346) 2

38ndash41 120596CndashH 12059648 12059649 12059650 12059651

42 120596CndashC 12059652

43 120596CndashO 12059653

44-45 tCndashO 12059154 12059155

46 tCndashOndashC 12 (12059156+ 12059157)

47 tCH3 13 (12059158+ 12059159+ 12059160)

48 tOndashH 12059161

49 Ttrigd (12059162minus 12059163+ 12059164minus 12059165+ 12059166minus 12059167) radic6

50 Tsymd (12059162minus 12059163+ 12059165+ 12059166) 2

51 Tasymd (minus12059162+ 212059163minus 12059164minus 12059165+ 12059166minus 12059167) radic12

aThese symbols are used for description of the normal modes by PED in Table 7bThe internal coordinates used here are defined in Table 2

appearing at 960 937 865 and 755 cmminus1 in OAA and929 854 846 and 774 cmminus1 in AA were assigned toout-of-plane deformation type of vibration (120596) of CndashHgroups There is slight increase in the CndashH out-of-planedeformation frequency because of strong intermolecularhydrogen bonding in OAA In these bands the pronouncedparticipation of other types of vibrations is observed Theseare also supported by the literature

432 Carboxylic Acid Vibrations Due to the presence ofstrong intermolecular hydrogen bonding the FT-IR spectraexhibits spectra exhibit a broad band due to the OndashHstretching vibrations and a strong banddue toC=Ostretchingvibrations The carboxylic acid dimers display a very broadand intenseOndashH stretching absorption in the region of 3300ndash2500 cmminus1 [28] The title molecules both exhibit intermolec-ular hydrogen bonding In our case the bands at 3390 cmminus1

in OAA and 3435 cmminus1 in AA are assigned as OndashH stretchingvibrations There is a slight increase in the OndashH frequencybecause of steric effect in OAA and +I effect in AA The OndashH out-of-plane bending vibration occurs near the region of920 cmminus1 [27] The bands appearing at 595 cmminus1 in OAA and505 cmminus1 in AA are assigned to OndashH out-of-plane bendingvibrationThe OndashH out-of-plane bending vibrations in OAAand AA decrease due to intermolecular hydrogen bonding

The carbonyl stretching vibrations are expected in theregion 1720 cmminus1ndash1680 cmminus1 [28] The IR band at 1670 cmminus1in OAA and FT-Raman band at 1688 cmminus1 in AA are assignedasC=O stretching vibrationsTheCndashObond appears stronglyin the 1320ndash1210 cmminus1 region [29] The bands observed at1049 and 795 cmminus1 in OAA and 1267 and 1100 cmminus1 in AAare assigned to CndashO stretching mode The CndashO stretchingvibrational frequency is lower than general range In thecase of carboxylic acid dimers like OAA and AA the OH

Journal of Spectroscopy 7

Table 5 Definition of natural internal coordinates of Anisic acid (AA)

No (i) Symbola Definitionb

1ndash4 CndashH stretch 1199031 1199032 1199033 1199034

5ndash10 CndashC stretch 1199035 1199036 1199037 1199038 1199039 11990310

11 CndashCfn stretch 11990311

12ndash14 CndashO stretch 11990312 11990313 11990314

15 OndashC stretch 11990315

16 OndashH stretch 11990316

17 CH3 ss (11990317+ 11990318+ 11990319) radic3

18 CH3 ips (211990317minus 11990318minus 11990319) radic6

19 CH3 ops (11990318minus 11990319) radic2

20 bCndashCndashC (12057320minus 12057321) radic2

21ndash24 bCndashCndashH (12057322minus 12057323) radic2 (120573

24minus 12057325) radic2 (120573

26minus 12057327) radic2 (120573

28minus 12057329) radic2

25 CH3 sb (minus12057330minus 12057331minus 12057332+ 12057333+ 12057334+ 12057335) radic6

26 CH3 ipb (minus12057333minus 12057334minus 212057335)radic6

27 CH3 opb (12057333minus 12057334) radic2

28 CH3 ipr (212057330minus 12057331minus 12057332) radic6

29 CH3 opr (12057331minus 12057332) radic2

30 bCndashCndashO (12057335minus 12057336) radic2

31 bCndashOndashH 12057338

32-33 bCndashCndashO 12057339 12057340

34 bCndashOndashC 12057341

35 Rtrigd (12057342minus 12057343+ 12057344minus 12057345+ 12057346minus 12057347) radic6

36 Rsymd (minus12057342minus 12057343+ 12057344minus 12057345minus 12057346+ 212057347) radic12

37 Rasymd (12057342minus 12057343+ 12057345minus 12057346) 2

38ndash41 120596CndashH 12059648 12059649 12059650 12059651

42 120596CndashC 12059652

43 120596CndashO 12059653

44-45 tCndashO 12059154 12059155

46 tCndashOndashC 12 (12059156+ 12059157)

47 tCH3 13 (12059158+ 12059159+ 12059160)

48 tOndashH 12059161

49 Ttrigd (12059162minus 12059163+ 12059164minus 12059165+ 12059166minus 12059167) radic6

50 Tsymd (12059162minus 12059163+ 12059165+ 12059166)2

51 Tasymd (minus12059162+ 212059163minus 12059164minus 12059165+ 12059166minus 12059167) radic12

aThese symbols are used for description of the normal modes by PED in Table 8bThe internal coordinates used here are defined in Table 3

in-plane bending and CndashO stretching bands involve someinteraction between them they are referred to as coupledOH in-plane bending and CndashO stretching vibrations [26]The CndashO bending vibration occurs in the region of 580ndash340 cmminus1 [30] The band observed at 380 cmminus1 in OAA and440 cmminus1 in AA are assigned to CndashO bending mode Thepresent assignments agree very well with the values availablein the literature

433 Methyl Group Vibrations The title molecules OAAand AA under consideration possess one CH

3group For

the assignments of CH3group one can expect that 9 fun-

damentals can be associated with each CH3group namely

the symmetrical stretching (CH3symmetric stretch) and

asymmetrical stretching (CH3asymmetric stretch) in-plane

stretching modes (ie in-plane hydrogen stretching modes)

and the symmetrical (CH3symmetric deform) and asym-

metrical (CH3asymmetric deform) deformation modes in-

plane rocking (CH3ipr) out-of-plane rocking (CH

3opr) and

twisting (tCH3) bending modes

For the methyl group compounds the asymmetricstretching mode appeared in the range 2965ndash3005 cmminus1 andthe symmetric stretching mode appeared in the range of2815ndash2860 cmminus1 [30] The FT-Raman band at 2983 cmminus1 forOAA and IR band at 2941 cmminus1 for AA are symmetricstretching The symmetric stretching vibrational frequencyis higher in OAA and AA due to steric effect and +I effectThe asymmetric methyl stretching band appeared at 30033018 cmminus1 in OAA and 2990 2956 cmminus1 in AA respectivelyThe asymmetric deformation mode appeared in the range1445ndash1485 cmminus1 and symmetric deformation mode appearedin the range of 1420ndash1460 cmminus1 [30] The IR band at 1466

8 Journal of Spectroscopy

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 2 FTIR spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Table 6 Diagonal force constants (102 Nmminus1) of O-Anisic acid(OAA) and Anisic acid (AA)

Descriptiona Force constantsb

OAA AAC1ndashC2 621 630C2ndashC3 633 696C3ndashC4 677 626C4ndashC5 675 628C5ndashC6 682 663C6ndashC1 644 648C1ndashC7 465 222C7ndashO8 532 522C7ndashO9 1030 1128C2ndashO11(C4ndashO13) 449 576O11ndashC12(O13ndashC14) 413 499O9ndashH10 644 661C12ndashH13(C14ndashH15) 498 508C12ndashH14(C14ndashH16) 526 470C12ndashH15(C14ndashH17) 498 507C3ndashH16(C2ndashH11) 514 498C4ndashH17(C3ndashH12) 501 496C5ndashH18 505 500C6ndashH19 532 522aThe atoms indicated in the parenthesis belong to AAbStretching force constants are given in mdyn A

minus1

For numbering of atoms refer to Figures 1(a) and 1(b)

and 1435 cmminus1 in OAA and 1468 and 1461 cmminus1 in AA areassigned as asymmetric deformation vibrations The IR bandat 1411 cmminus1 for OAA and 1429 cmminus1 for AA are symmet-ric deformation mode The CH

3deformation absorption

occurs at 1466 cmminus1 and 1429 cmminus1 this vibration is knownas umbrella mode that overlaps with CC ring stretchingvibrations for the title compounds These are also supportedby the literature

The tensional modes appeared in the range of 265ndash185 cmminus1 [30] This modes are strongly coupled with other

vibrations that are observed at 280 cmminus1 inOAAand 165 cmminus1in AAwhich are in agreement with the calculated results also

434 Ring Vibrations The ring CndashC stretching vibrationsoccur in the region of 1600ndash1400 cmminus1 [29]The bands appearat 1600 1579 1312 1184 1153 1062 and 698 cmminus1 in OAAand 1608 1580 1416 1307 1107 1028 and 825 cmminus1 in AAwere assigned to CndashC stretching vibrations The shift in thefrequency of CndashC vibrations towards lower wave numbermay be due to the COOH and OCH

3groups Many ring

modes are affected by the substitutions in the aromatic ringThe bands at 180 cmminus1 and 285 cmminus1 for OAA and AA wereassigned to CndashC bending vibrationsThe out-of-plane and in-plane deformations of the phenyl ring are observed below1000 cmminus1 and these modes are sensitive by the additionof functional groups The out-of-plane bending vibrationswere observed at 170 cmminus1 and 111 cmminus1 for OAA and AASmall changes in the wavenumbers were observed due tothe presence of +I effect in AA and steric effect in OAAThe computed wavenumbers are in good agreement withexperimental data

5 Electronic Properties

Atomic charges on the various atoms of OAA and AAobtained by Mulliken population analysis [31] are given inTable 9 From the listed atomic charge values the oxygen[O8 O9] and O11 in OAA and O13 in AA atoms had a largenegative charge and behaved as electron acceptor It was alsoobserved that there is a large accumulation of charge on O11inOAAO13 in AAmoleculesTherefore C7 andO11 inOAAand C7 and O13 in AA had a greater ionic character

Natural bond orbital analysis provides an efficientmethod for studying steric effect and intermolecular bondingand interaction among bonds and also provides a convenientbasis for investigating charge transfer or conjugative interac-tion in molecular systems Natural charge analysis is givenin Table 10 for the title compounds The results show thatsubstitution of COOH and CH

3group in OAA and AA leads

to a redistribution of electron density The C7 atom in OAAand AA is more positive charge (+08091 +08139) In the

Journal of Spectroscopy 9Ta

ble7Detailedassig

nmento

ffun

damentalvibratio

nsof

O-Anisic

acid

(OAA)b

yno

rmalmod

eanalysis

basedon

SQM

forcefi

eldcalculations

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

1A1015840

3390

mdash3771

3390

72652

155385

120592OH(100)

2A1015840

mdash3098

3273

3098

1612

499564

120592CH

(99)

3A1015840

mdash3083

3233

3083

1700

135114

120592CH

(99)

4A1015840

3069

mdash3207

3069

10674

70382

120592CH

(99)

5A1015840

mdash3020

3186

3024

17253

1372

01120592CH

(99)

6A1015840

3018

mdash3157

3018

38987

58202

120592CH

3(99)

7A10158401015840

3003

mdash3085

3003

5946

78409

120592CH

3(99)

8A1015840

mdash2983

3020

2983

52626

120657

120592CH

3(99)

9A1015840

1670

mdash1822

1670

358567

54628

120592CO

(53)120592CC

(14)bC

CO(14

)bC

OH(12)

10A1015840

1600

mdash1656

1600

15061

16343

120592CC

(60)bCH

(20)R

asym

d(10)

11A1015840

1579

mdash1630

1579

61364

48880

120592CC

(69)bCH

(19)

12A1015840

1494

mdash1539

1494

58214

10686

bCH(48)120592CC

(37)

13A1015840

1466

mdash1513

1466

6534

6058

bCH

3(43)bCH

(25)120592CC

(16)

14A1015840

mdash1439

1506

1439

22318

5639

bCH(39)bCH

3(37)120592CC

(17)

15A10158401015840

1435

mdash1500

1435

3652

510814

bCH

3(88)

16A1015840

1411

mdash1475

1411

11849

19713

bCH

3(74)

17A1015840

1382

1367

4497

1268

bCOH(35)120592CO

(32)bCC

O(13)120592CC

(11)

18A1015840

mdash1312

1350

1312

2182

8877

120592CC

(67)

19A1015840

1288

mdash1320

1288

6319

416

48bC

H(33)R

trigd(20)120592CO

(13)120592CC

(12)

20A1015840

mdash1287

1302

1287

19694

044

9Rtrig

d(26)120592CC

(25)bCH

(20)120592CO

(12)

21A1015840

mdash1184

1210

1184

228252

32980

120592CC

(31)bCH

(19)bC

H3(17)120592CO

(17)

22A1015840

1182

mdash1201

1182

162989

2713

6bC

H(42)120592CC

(34)bCH

3(10)

23A1015840

1170

mdash119

3117

015

764576

bCH

3(57)bCH

(24)

24A1015840

mdash117

3117

31153

7419

1097

120592CC

(31)bCH

(29)bCH

3(25)

25A1015840

1140

mdash1168

1140

0662

4253

bCH

3(96)

26A1015840

1049

mdash1087

1050

1073

0478

09120592CO

(29)120592CC

(27)R

trigd(12)

27A1015840

-1062

1077

1060

104848

21650

120592CC

(41)120592CO

(22)bCH

(12)

28A10158401015840

960

-1060

960

060

90057

120596CH

(91)

29A1015840

mdash974

989

974

2078

710836

120592OC(62)120592CC

(12)120592CO

(11)

30A10158401015840

937

mdash965

935

1244

1294

120596CH

(91)

31A10158401015840

mdash865

869

865

3148

3432

120596CH

(64)ttrigd(19)

32A1015840

mdash795

830

795

12200

4238

120592CO

(29)R

symd(21)120592OC(15)120592CC

(15)

33A10158401015840

761

mdash795

761

1002

0207

tCO(32)ttrigd(28)120596

CH(23)120596

CC(11)

34A10158401015840

mdash755

770

755

41473

1456

120596CH

(51)ttrigd(27)120596

CO(14

)35

A10158401015840

695

mdash747

698

64512

0469

ttrigd(52)120596

CH(23)tCO

(15)

36A1015840

mdash698

712

695

10016

17946

120592CC

(33)120592CO

(23)bCC

O(21)

37A1015840

mdash602

639

602

13503

2683

Rasymd(36)bCC

O(15)

120592CC

(12)R

symd(11)

38A10158401015840

mdash595

594

595

74804

8168

tOH(79)

39A1015840

mdash565

588

565

21902

1740

bCCO

(28)120592CC

(17)bCO

(15)R

symd(14

)bC

CO(13)

10 Journal of Spectroscopy

Table7Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

540

mdash548

540

5598

4848

bCCO

(40)bCC

(16)120592CC

(13)R

asym

d(10)

41A10158401015840

480

mdash540

480

0946

0860

120596CO

(40)120596

CH(16)ttrigd(14

)tsy

m(14

)42

A10158401015840

mdash40

1435

401

3585

0792

tsym

(14)120596CC

(15)

43A1015840

mdash380

388

380

4805

4133

bCO(64)bCC

O(16)

44A1015840

mdash303

383

303

1180

4980

Rsym

d(59)bCO

C(17)120592CC

(15)

45A10158401015840

mdash280

283

280

0092

0016

tCH

3(79)

46A1015840

mdash240

280

240

0927

0935

bCOC(40)bCC

(30)bCC

O(18)

47A10158401015840

mdash180

229

180

0018

2096

120596CC

(30)tCO

(20)tsym

(18)

tasym

(11)120596CH

(10)

48A1015840

mdash170

190

170

3092

0715

bCC(42)bCO

C(29)bCO

(12)

49A10158401015840

mdash115

119115

4502

0508

tCOC(47)tsym

(15)tCH

3(12)

50A10158401015840

mdash110

9696

0922

3779

tsym

(35)tCO

(25)

tCOC(21)tCH

3(13)

51A10158401015840

mdashmdash

1730

1260

0037

tCO(99)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 11Ta

ble8Detailedassig

nmento

ffun

damentalvibratio

nsof

Anisic

acid

(AA)b

yno

rmalmod

eanalysis

basedon

SQM

forcefi

eldcalculations

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

1A1015840

3435

mdash3768

3435

7952

3164209

120592OH(100)

2A1015840

mdash3085

3232

3085

21438

120058

120592CH

(89)

3A1015840

mdash3034

3224

3034

7547

126718

120592CH

(99)

4A1015840

3029

mdash3218

3029

3520

99229

120592CH

(99)

5A1015840

3002

mdash3209

3002

5141

52552

120592CH

(99)

6A1015840

2990

mdash3155

2990

2423

53071

120592CH

ops(99)

7A10158401015840

2956

mdash3087

2956

45319

94074

120592CH

ips(51)120592CH

ss(36)120592CH

ops(12)

8A1015840

2941

mdash3022

2941

42847

91231

120592CH

ss(56)120592CH

ips(44

)9

A1015840

1688

mdash1813

1688

302139

74665

120592CO

(72)bCC

O(17)

10A1015840

1608

mdash1666

1608

216104

153242

120592CC

(62)bCH

(22)R

symd(11)

11A1015840

1580

mdash1624

1580

34785

12359

120592CC

(66)bCH

(14)

12A1015840

1518

mdash1559

1518

41495

8422

bCH(52)120592CC

(30)

13A1015840

1468

mdash1516

1468

37550

10673

bCHsb

(77)

14A10158401015840

1461

mdash1504

1461

14058

1218

3bC

Hop

b(83)

15A1015840

1429

mdash1486

1429

5851

19586

bCHipb(70)120592CC

(10)bCH

(10)

16A1015840

1416

mdash1465

1416

14835

9149

120592CC

(39)bCH

(35)bCH

ipb(18)

17A1015840

1324

mdash1391

1324

31290

5311

bCOH(27)120592CO

(22)bCC

O(21)120592CC

(13)

18A1015840

1307

mdash1371

1307

806

814

44120592CC

ar(65)bCH

(20)

19A1015840

1301

mdash1331

1301

40408

7073

bCH(43)120592CC

(33)

20A1015840

1267

mdash1304

1267

245222

3723

120592CO

(37)R

trigd(20)120592CC

(16)

21A1015840

1181

mdash1221

1181

5734

6023

bCH(61)120592CC

(21)

22A1015840

1172

mdash1209

1172

5690

5161

bCHop

r(61)bC

H(13)

23A1015840

mdash1137

1189

1137

0662

4334

bCHipr(78)bC

Hop

r(14)

24A1015840

1131

mdash117

61131

190946

42508

bCH(35)120592CC

(21)

25A1015840

1107

mdash1139

1107

245972

63024

120592CC

fn(25)R

trigd(23)bCH

(16)120592OC(13)

26A1015840

mdash1100

1114

1100

318070

20809

120592CO

(40)bCO

H(22)bCC

O(11)

27A1015840

1028

mdash1069

1028

0786

11056

120592CC

(58)bCH

(16)

28A1015840

mdash1010

1026

1010

29566

2343

120592OC(51)120592CC

(28)

29A10158401015840

929

mdash991

929

0010

046

4120596CH

(89)

30A10158401015840

854

mdash966

854

1379

1924

120596CH

(82)ttrigd(12)

31A10158401015840

846

mdash863

846

3652

212

44120596CH

(39)120596

CO(32)ttrigd(20)

32A1015840

825

mdash834

825

24090

2237

3120592CC

ar(32)R

symd(27)120592OC(22)

33A10158401015840

774

mdash830

774

0365

4928

120596CH

(84)

34A10158401015840

mdash755

775

755

1082

0243

ttrigd(51)120596

CC(15)120596

CH(14

)tCO(11)

35A1015840

698

mdash725

698

3553

93075

bCCO

(44)120592CO

(25)bCO

H(25)

36A10158401015840

634

mdash710

634

76887

0059

tCO(57)120596

CH(20)ttrigd(12)

37A1015840

617

mdash647

617

0592

644

1Ra

symd(81)

38A1015840

550

mdash603

550

14566

0968

Rsym

d(32)120592CC

fn(13)120592CO

(11)bCC

O(11)bCO

C(10)

39A10158401015840

545

mdash601

545

27876

4847

120596CO

(42)tOH(14

)120596CH

(11)120596

CC(11)

12 Journal of Spectroscopy

Table8Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

525

mdash511

525

12735

1849

bCCO

(82)

41A1015840

505

mdash511

505

50036

5698

tOH(24)ttrigd(23)120596

CO(19)120596

CH(14

)42

A1015840

440

mdash481

440

3190

2294

bCO(35)bCO

C(29)

43A10158401015840

mdash375

427

375

0415

0023

tsym

(60)120596

CH(19

)tasym

(17)

44A1015840

mdash310

335

310

3569

0577

Rsym

d(48)120592CC

fn(25)

45A10158401015840

mdash285

304

285

4416

0596

120596CC

(33)tasym

(24)tCO

(16)

46A1015840

mdash220

267

220

3713

2509

bCOC(29)bCO

(17)

47A10158401015840

mdash165

226

165

0047

0429

tCH

3(85)

48A1015840

mdash111

165

111

0211

0159

bCC(80)

49A10158401015840

mdash98

132

982323

0292

Tasym

(30)tCO

C(30)120596

CC(11)120596

CH(10)tsym

(10)

50A10158401015840

mdash70

7870

1302

1199

tCO(95)

51A10158401015840

mdash60

6560

0898

0216

tCOC(48)tCO

(31)tCH

3(12)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 13

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 3 FT-Raman spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 4 FTIR spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 5 FT-Raman spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

title molecules all the hydrogen atoms have a net positivecharge in particular the hydrogen atoms H(10) that havecharge of 05047 and 05050 respectively The presence oflarge amounts of negative charge on oxygen and net positivecharge on H(10) atoms may suggest the presence of inter-molecular hydrogen bonding in the crystalline phase

Highest occupied molecular orbital and lowest unoc-cupied molecular orbital are very important parametersfor quantum chemistry This is also used by the frontierelectron density for predicting the most reactive position in120587-electron systems and also explains several types of reactionin conjugated system [32] The conjugated molecules are

characterized by a small highest occupied molecular orbitalndashlowest unoccupied molecular orbital (HOMO-LUMO) sep-aration which is the result of a significant degree of inter-molecular charge transfer from the end-capping electron-donating groups to the efficient electron-acceptor groupsthrough 120587 conjugated path [33] Both the highest occupiedmolecular orbital and lowest unoccupied molecular orbitalare the main orbitals that take part in chemical stability[34] Energy difference betweenHOMOand LUMOorbital iscalled energy gap that is an important stability for structureswhich are given in Table 11 We performed an analysis ofall the molecular orbitals involved taking into consideration

14 Journal of Spectroscopy

Table 9 Atomic charges for optimized geometry of O-Anisic acid(OAA) and Anisic acid (AA) obtained by B3LYP6-31Glowastlowast densityfunctional calculations

Atomsa MullikenOAA AA

C1 00018 00373C2 03297 minus01002

C3 minus01368 minus01219

C4 minus00836 03612

C5 minus00943 minus01394

C6 minus01061 minus01118

C7 05570 05445O8 minus04650 minus04848

O9 minus05104 minus05064

H10 03198 03217O11 (H11) minus04841 01203C12 (H12) minus00837 01021H13 (O13) 01064 minus05111

H14 (C14) 01352 minus00831

H15 01211 01099H16 00913 01302H17 00929 01246H18 00886 00913H19 01200 01155aThe atoms indicated in the parenthesis belong to AA

Table 10Natural atomic charges ofO-Anisic acid (OAA) andAnisicacid (AA) calculations performed at the B3LYP6-31Glowastlowast level oftheory

Atomsa OAA AAC1 minus02176 minus02053

C2 03724 minus01746

C3 minus03284 minus02801

C4 minus01952 03443

C5 minus02720 minus03289

C6 minus01806 minus01748

C7 08091 08139O8 minus05861 minus06102

O9 minus07295 minus07217

H10 05047 05050O11 (H11) minus04921 02634C12 (H12) minus03307 02544H13 (O13) 02070 minus05119

H14 (C14) 02390 minus03300

H15 02070 02090H16 02443 02352H17 02426 02090H18 02439 02449H19 02621 02585aThe atoms indicated in the parenthesis belong to AAFor numbering of atoms refer to Figures 1(a) and 1(b)

that orbital 40 is the HOMO and orbital 41 is the LUMO forOAA and AA respectively

Many organic molecules that contain conjugated 120587 elec-trons are characterized as hyperpolarisabilities and are ana-lyzed by means of vibrational spectroscopy The analysis

Table 11 Calculated quantum chemical parameters ofO-Anisic acid(OAA) and Anisic acid (AA) derivatives

Parameters OAA AA119864HOMO minus0227 minus0231

119864LUMO minus0041 minus0036

Δ119864 0186 0195120594 0134 0133Η 0093 0097Σ 10752 10256

Table 12 Calculated 13C NMR chemical shifts (ppm) of O-Anisicacid (OAA) and Anisic acid (AA)

Carbona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAC1 11782 12315 10447 12620C2 15848 13146 14696 13936C3 11204 11384 9681 12272C4 13517 16297 11926 17125C5 12191 11384 10447 11047C6 13347 13146 12019 13751C7 16634 16714 14609 17174C12 (C14) 5674 5544 4322 5549aThe atoms indicated in the parenthesis belong to AA

Table 13 Experimental and calculated 1H NMR chemical shifts(ppm) of O-Anisic acid (OAA) and Anisic acid (AA)

Protona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAH10 1030 13 11 11H13 H14 H15 (H11) 4066 7914 3932 8405H16 (H12) 708 7027 6831 7147H17 (H15 H16 H17) 756 3836 7570 3824H18 710 7027 7069 6673H19 813 7914 3932 8217aThe atoms indicated in the parenthesis belong to AA

of the wave function indicates that the electron absorptioncorresponds to the transition from the ground state to thefirst excited state and is mainly described by the one-electronexcitation from the HOMO to the LUMO The HOMO of 120587nature (ie aromatic ring) is delocalized over the whole CndashC bond By contrast the LUMO is located over the aromaticring Consequently the HOMO-LUMO transition implies anelectron density transfer toCOOHandOCH

3group from the

aromatic ringThe theoretical basis for the new quantities lies in the

density functional formalism [35] Since molecular orbital(MO) theory is by far the most widely used by chemistsit is important to place 120594 and 120578 in a MO framework Ithas already been shown [36] that the MO theory of thechemical bond contains the values of 120594 and 120578 for the bondingfragments Hard molecules have a large HOMO-LUMO gapand soft molecules have a small HOMO-LUMO gap A small

Journal of Spectroscopy 15

HOMO

(a)

LUMO

(b)

Figure 6 Contour surfaces of frontier molecular orbitals of O-Anisic acid

HOMO

(a)

LUMO

(b)

Figure 7 Contour surfaces of frontier molecular orbitals of Anisic acid

HOMO-LUMO gap automatically means small excitationenergies to the manifold of excited states Therefore softmolecules with a small gap will be more polarizable thanhard molecules High polarizability was the most character-istic property attributed to soft acids and bases Energy gapsshould be small for best bonding or bothmolecules should besoft

In the present study the title compound AA is dynam-ically more stable due to the large energy gap OAA is asoft molecule due to small energy gap The Contour surfacesof the frontier molecular orbitals are sketched in Figures 6and 7

51 NMR Spectra DFT methods treat the electronic energyas a function of the electron density of all electrons simul-taneously and thus include electron correlation effect [37]In this study molecular structure of the OAA and AA wasoptimized by using B3LYP method in conjunction with 6-31Glowastlowast 13C and 1H chemical shift calculations of the titlecompounds have been made by using GIAO method andsame basis set The isotropic shielding values were usedto calculate the isotropic chemical shifts 120575 with respect totetramethylsilane (TMS) The isotropic chemical shifts arefrequently used as an aid in identification of reactive ionicspecies The B3LYP method allows calculating the shielding

16 Journal of Spectroscopy

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 150

140

130

120

110

100

90110 120 130 140 150 160 170

(a)

70 75 80 85 90 95 100 1056

7

8

9

10

11

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

(b)

Figure 8 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for O-Anisic acid

constants with the proper accuracy and the GIAOmethod isone of the most common approaches for calculating nuclearmagnetic shielding tensors

Theoretical and experimental chemical shifts of OAA andAA in 1H and 13C NMR spectra are gathered in Tables 12and 13 The range of the 13C NMR chemical shifts for atypical organic molecules usually is gt100 ppm [38 39] andthe accuracy ensures reliable interpretation of spectroscopicparameters In the present study the 13C NMR chemicalshifts in the ring are gt100 ppm as they would be expectedThe 13C chemical shifts carbonyl carbons vary from 150 to220 ppm This depends on the decrease in electron donatingor shielding ability of the attached atoms [40] The C=Ogroups of carboxylic acids and derivatives are in the range of150ndash185 ppm [29]

Hydrogens bonded to an aromatic ring are stronglydeshielded and absorb downfieldWhen the120587-electrons enterthe magnetic field they circulate around the ring to generatea ring current This produces a small induced magnetic fieldthat reinforces the applied field outside the ring resultingin aromatic protons being deshielded [41] A related effectis observed for carboxylic acids For these compoundscirculation of electrons in the double bonds produces inducedmagnetic field These are responsible for the high chemicalshift values of acid protons (H10) Carboxylic acids asstable hydrogen-bonded dimers in nonpolar solvents even athigh dilution The carboxylic proton therefore absorbs in acharacteristically narrow range 132 to 100 and is affectedonly slightly by concentration [29]

In a methyl group a proton is covalently bonded tocarbon oxygen or other atoms by a sigma bond Whenplaced in a strong magnetic field the electrons of the sigmabond circulate to generate a small magnetic field whichopposes the applied field A nearby electronegative atomwithdraws electron density from the neighbourhood of theproton so that a smaller applied field is needed to cause thespin state of the proton to flip The signal for a deshielded

Table 14 Theoretically computed energies (au) zero-point vibra-tional energies (kcalmolminus1) rotational constants (GHz) entropies(calmolminus1 Kminus1) nuclear repulsion energy (Hartrees) and dipolemoment (Debye) for OAA and AA

Parameters B3LYP6-31Glowastlowast

OAA AAZero-point energy 9306056 9314966

Rotational constants139942 344405114384 056752063193 048875

EntropyTotal 99243 97126Translational 40967 40967Rotational 30142 30199Vibrational 28134 25960Dipole moment 24181 35822Nuclear repulsion energy 592968293 573992628

proton (1 surrounded by less electron density) is observed tobe more downfield than the signals for protons that are notdeshielded by electronegative atoms [40] The chemical shiftvalue of C7 (OAA and AA) has bigger value than the othercarbons due to the electronegative property of oxygen atom

The linear correlations between calculated and experi-mental data of 13CNMRand 1HNMRspectra are determinedas 09 and 10 for OAA and 09 and 09 for AA respectivelyThere is an excellent linear relationship between experimentaland computed results which are shown in Figures 8 and 9

6 Thermodynamic Properties

Several calculated thermodynamical parameters are pre-sented in Table 14 for OAA andAA respectively Scale factorshave been recommended [42] for an accurate prediction in

Journal of Spectroscopy 17

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 180

170

160

150

140

130

120

110110

120 130 140 150 160 170

(a)

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

11

10

9

8

7

7 8 9 10 11 12 13

(b)

Figure 9 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for Anisic acid

determining the zero-point vibration energies (ZPVE) andthe entropy 119878vib(119879) The total energies and the change inthe total entropy at room temperature using B3LYP6-31Glowastlowastmethod are presented

7 Conclusion

Attempts have been made in the present work for the molec-ular parameters and frequency assignments for the com-pounds OAA and AA from the FTIR and FT-Raman spectraThe equilibrium geometries and harmonic and anharmonicfrequencies for the title compounds were determined andanalyzed at DFT level of theory utilizing 6-31Glowastlowast basis setThe assignments of most of the fundamentals of the titlecompounds provided in this work are quite comparableThe excellent agreement of the calculated and observedvibrational spectra reveals the advantages of a smaller basisset for quantum chemical calculations HOMO and LUMOenergy gap explains the eventual charge transfer interactionstaking place within the molecule The experimental andtheoretical investigation of the title compounds have beenperformed successfully by using 1H and 13C NMR Thevarious modes of vibrations were unambiguously assignedon the basis of the result of the PED output obtainedfrom normal coordinate analysis These studies confirm thepresence of COOH and OCH

3group Dimeric molecules are

held together by hydrogen bridges between carbonyl groupsThe obtained data and simulations both show the way to thecharacterization of the molecules and help in spectra studiesin the future

References

[1] GMelentyeva and LAntonovaPharmaceutical ChemistryMirPublishers Moscow Russia 1988

[2] ldquoo-Anisic acid(579-75-9) catalog of chemical suppliersrdquo httpwwwchemexpercomchemicalssuppliercas579-75-9html

[3] B A Hess Jr L J Schaad P Carsky and R Zaharaduick ldquoAbinitio calculations of vibrational spectra and their use in theidentification of unusual moleculesrdquo Chemical Reviews vol 86no 4 pp 709ndash730 1986

[4] P Pulay X Zhou and G Forgarasi in Recent Experimental andComputational Advances in Molecular Spectroscopy R Faustoand R Fransto Eds vol 406 ofNATOASI Series p 99 KluwerDordrecht Netherlands 1993

[5] P Pulay G Fogarasi G Pongor J E Boggs and A VarghaldquoCombination of theoretical ab initio and experimental infor-mation to obtain reliable harmonic force constants ScaledQuantum Mechanical (SQM) force fields for glyoxal acroleinbutadiene formaldehyde and ethylenerdquo Journal of the Ameri-can Chemical Society vol 105 no 24 pp 7037ndash7047 1983

[6] C E Blom and C Altona ldquoApplication of self-consistent-fieldab initio calculations to organic moleculesrdquo Molecular Physicsvol 31 no 5 pp 1377ndash1391 1976

[7] G Fogarasi and P Pulay in Vibrational Spectra and Structure JR Durig Ed vol 14 Elsevier Amsterdam Netherlands 1985

[8] G Fogarasi ldquoRecent developments in the method of SQM forcefields with application to 1-methyladeninerdquo Spectrochimica ActaA vol 53 no 8 pp 1211ndash1224 1997

[9] G R deMare N Yu Panchenko andW Ch Bock ldquoAnMP26-31GlowastMP26-31Glowast vibrational analysis of s-trans- and s-cis-acryloyl fluoride CH2=CH-CF=Ordquo The Journal of PhysicalChemistry vol 98 no 5 pp 1416ndash1420 1994

[10] G Pongor P Pulay G Fogarasi and J E Boggs ldquoTheoreticalprediction of vibrational spectra 1 The in-plane force fieldand vibrational spectra of pyridinerdquo Journal of the AmericanChemical Society vol 106 no 10 pp 2765ndash2769 1984

[11] Y Yamakitu and M Tasumi ldquoVibrational analyses of p-benzoquinodimethane and p-benzoquinone based on ab initioHartree-Fock and second-order Moller-Plesset calculationsrdquoThe Journal of Physical Chemistry vol 99 no 21 pp 8524ndash85341995

18 Journal of Spectroscopy

[12] M Karabacak A Coruh and M Kurt ldquoFT-IR FT-RamanNMR spectra and molecular structure investigation of 23-dibromo-N-methylmaleimide a combined experimental andtheoretical studyrdquo Journal of Molecular Structure vol 892 no1ndash3 pp 125ndash131 2008

[13] M S Masoud M K Awad M A Shaker and M M T El-Tahawy ldquoThe role of structural chemistry in the inhibitiveperformance of some aminopyrimidines on the corrosion ofsteelrdquo Corrosion Science vol 52 no 7 pp 2387ndash2396 2010

[14] M J Frisch G W Trucks H B Schlegel et al Gaussian 03Revision B4 Gaussian Inc Pittsburgh Pa USA 2003

[15] P L Polavarapu ldquoAb initio vibrational Raman and Ramanoptical activity spectrardquo Journal of Physical Chemistry vol 94no 21 pp 8106ndash8112 1990

[16] G Keresztury S Holly J Varga G Besenyei A Wang andJ R Durig ldquoVibrational spectra of monothiocarbamates-IIIR and Raman spectra vibrational assignment conforma-tional analysis and ab initio calculations of S-methyl-NN-dimethylthiocarbamaterdquo Spectrochimica Acta A vol 49 no 13-14 pp 2007ndash2017 1993

[17] G Keresztury ldquoRaman spectroscopy theoryrdquo in Handbook ofVibrational Spectroscopy J M Chalmers and P R Griffths Edsvol 1 p 71 John Wiley and Sons 2002

[18] R G Parr R A Donnelly M Levy and W E Palke ldquoElec-tronegativity the density functional viewpointrdquo The Journal ofChemical Physics vol 68 no 8 pp 3801ndash3807 1977

[19] R G Parr and R G Pearson ldquoAbsolute hardness companionparameter to absolute electronegativityrdquo Journal of theAmericanChemical Society vol 105 no 26 pp 7512ndash7516 1983

[20] R G Pearson ldquoAbsolute electronegativity and hardness appli-cation to inorganic chemistryrdquo Inorganic Chemistry vol 27 no4 pp 734ndash740 1988

[21] P Geerlings F De Proft and W Langenaeker ldquoConceptualdensity functional theoryrdquo Chemical Reviews vol 103 no 5 pp1793ndash1873 2003

[22] R Ditchfield ldquoMolecular orbital theory of magnetic shieldingand magnetic susceptibilityrdquo Journal of Physical Chemistry vol56 no 11 article 5688 4 pages 1972

[23] KWolinski J F Hilton and P Pulay ldquoEfficient implementationof the gauge-independent atomic orbital method for NMRchemical shift calculationsrdquo Journal of the American ChemicalSociety vol 112 no 23 pp 8251ndash8260 1990

[24] M Kurt M Yurdakul and S Yurdakul ldquoMolecular structureand vibrational spectra of 3-chloro-4-methyl aniline by densityfunctional theory and ab initio Hartree-Fock calculationsrdquoJournal of Molecular Structure vol 711 no 1ndash3 pp 25ndash32 2004

[25] D Steele and D H Whiffen ldquoThe vibration frequencies ofpentafluorobenzenerdquo Spectrochimica Acta vol 16 no 3 pp368ndash375 1960

[26] D N Sathyanarayanan Vibrational Spectroscopy Theory andApplication New Age International publishers New DelhiIndia 1996

[27] L D S YadavOrganic Spectroscopy Springer NewDelhi India2004

[28] J Mohan Organic Spectroscopy Principles and ApplicationsNarosa Publishing House New Delhi 2nd edition 2009

[29] R M Silverstein G C Bassler and T C Morrill SpectrometricIdentification of Organic Compounds John Wiley amp Sons NewYork NY USA 1981

[30] G Socrates Infrared Characteristic Group Frequencies WileyNew York NY USA 1980

[31] R S Mulliken ldquoElectronic population analysis on LCAO-MOmolecular wave functionsrdquoThe Journal of Chemical Physics vol23 no 10 pp 1833ndash1840 1955

[32] K Fukuli T Yonezawa and H Shingu ldquoA molecular orbitaltheory of reactivity in aromatic hydrocarbonsrdquo Journal ofPhysical Chemistry vol 20 no 4 article 722 4 pages 1952

[33] C H Choi and M Kertesz ldquoConformational information fromvibrational spectra of styrene trans-stilbene and cis-stilbenerdquoJournal of Physical Chemistry A vol 101 no 20 pp 3823ndash38311997

[34] S Gunasekaran R Arun Balaji S Kumaresan G Anandand S Srinivasan ldquoExperimental and theoretical investigationsof spectroscopic properties of N-acetyl-5-methoxytryptaminerdquoCanadian Journal of Analytical Sciences and Spectroscopy vol53 no 4 pp 149ndash162 2008

[35] P Hohenberg and W Kohn ldquoInhomogeneous electron gasrdquoPhysical Review vol 136 no 3 pp B864ndashB871 1964

[36] R G Pearson ldquoAbsolute electronegativity and absolute hard-ness of Lewis acids and basesrdquo Journal of the American ChemicalSociety vol 107 no 24 pp 6801ndash6806 1985

[37] D Avci Y Atalay M Sekerci and M Dincer ldquoMolecular struc-ture and vibrational and chemical shift assignments of 3-(2-Hydroxyphenyl)-4-phenyl-1H-124-triazole-5-(4H)-thione byDFT and ab initio HF calculationsrdquo Spectrochimica Acta A vol73 no 1 pp 212ndash217 2009

[38] H O Kalinowski S Berger and S Braun Carbon13 NMRSpectroscopy John Wiley amp Sons Chichester UK 1988

[39] K Pihlaja and E Kleinpeter Carbon-13 NMR Chemical Shiftsin Structural and Sterochemical Analysis VCH PublishersDeerfield Beach Fla USA 1994

[40] P S Kalsi Spectroscopy of Organic Compounds New AgeInternational 2004

[41] A F Parsons Keynotes in Organic Chemistry Blackwell Pub-lishing Oxford UK 2003

[42] M A Palafox ldquoScaling factors for the prediction of vibrationalspectra I benzenemoleculerdquo International Journal of QuantumChemistry vol 77 no 3 pp 661ndash684 2000

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

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CatalystsJournal of

Page 3: Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. · Molecular Structure, NMR, HOMO, LUMO, ... ects of carbonyl and methyl substitutions

Journal of Spectroscopy 3

(a) (b)

Figure 1 (a) Molecular structure of O-Anisic acid along with numbering of atoms (b) Molecular structure of Anisic acid along withnumbering of atoms

Table 1 Optimized geometrical parameters O-Anisic acid (OAA) and Anisic acid (AA) obtained by B3LYP6-31Glowastlowast density functional cal-culations

Bond lengtha Value ( A) Bond anglea Value (∘)OAA AA OAA AA

C1ndashC2 139 139 C1ndashC2ndashC3 11999 11999C2ndashC3 139 139 C2ndashC3ndashC4 11999 11999C3ndashC4 139 139 C3ndashC4ndashC5 12000 12000C4ndashC5 139 139 C4ndashC5ndashC6 11999 11999C5ndashC6 139 139 C2ndashC1ndashC7 12001 12001C1ndashC7 154 154 C1ndashC7ndashO8 13007 13007C7ndashO8 123 123 C1ndashC7ndashO9 11229 11229O9ndashC7 135 135 C7ndashO9ndashH10 11060 11060O9ndashH10 097 094 C3ndashC2ndashO11(H11) 11998 11998C2ndashO11(H11) 143 109 C2ndashO11ndashC12 (C4ndashC3ndashH12) 10950 12001C11ndashC12 (H12ndashC2) 143 100 O11ndashC12ndashH13 (C5ndashC4ndashO13) 10947 11998C12ndashH13 (O13ndashC3) 107 143 O11ndashC12ndashH14 (C4ndashO13ndashC14) 10947 10950C12ndashH14 (C14ndashO13) 107 143 O11(O13)ndashC12(C14)ndashH15 10947 10947C12(C14)ndashH15 107 107 C4(O13)ndashC3(C14)ndashH16 12001 10947C3(C14)ndashH16 109 107 C5(O13)ndashC4(C14)ndashH17 11998 10947C4(C14)ndashH17 109 107 C6ndashC5ndashH18 12000 12000C5ndashH18 109 109 C1ndashC6ndashH19 11999 11999C6ndashH19 109 109aThe atoms indicated in the parenthesis belongs to AAFor numbering of atoms refer to Figures 1(a) and 1(b)

following the IUPAC recommendations [24 25] are given inTables 4 and 5 for the title compounds

The bonding properties of OAA and AA are influencedby their rearrangements of electrons during substitutionsand addition reactions The stretching force constants ofC1ndashC7 in OAA and AA are found to be lower than the valuesof stretching force constant of other CndashC atoms The force

constant of C1ndashC7 in OAA is found to be greater than AAdue to steric effect (ie bulky groups in OAA) The mostimportant diagonal force constants (stretching only) of OAAand AA are listed in Table 6

43 Assignment of Fundamentals The molecules OAA andAA are disubstituted aromatic system The vibrational bands

4 Journal of Spectroscopy

Table 2 Definition of internal coordinates of O-Anisic acid (OAA)

No (i) Symbol Type DefinitionStretching

1ndash4 119903119894

CndashH C3ndashH16 C4ndashH17 C5ndashH18 C6ndashH195ndash11 119903

119894CndashC C1ndashC2 C2ndashC3 C3ndashC4 C4ndashC5 C5ndashC6 C6ndashC1 C1ndashC7

12ndash14 119903119894

CndashO C7ndashO8 C7ndashO9 C2ndashO1115 119903

119894OndashC O11ndashC12

16 119903119894

OndashH O9ndashH1017ndash19 119903

119894CndashH(methyl) C12ndashH13 C12ndashH14 C12ndashH15

Bending20-21 120573

119894CndashCndashC C2ndashC1ndashC7 C6ndashC1ndashC7

22ndash29 120573119894

CndashCndashH C2ndashC3ndashH16 C4ndashC3ndashH16 C3ndashC4ndashH17 C5ndashC4ndashH17C4ndashC5ndashH18 C6ndashC5ndashH18 C5ndashC6ndashH19 C1ndashC6ndashH19

30ndash32 120573119894

CndashCndashH(methyl) O11ndashC12ndashH13 O11ndashC12ndashH14 O11ndashC12ndashH1533ndash35 120573

119894HndashCndashH H13ndashC12ndashH14 H13ndashC12ndashH15 H14ndashC12ndashH15

36-37 120573119894

CndashCndashO C1ndashC7ndashO8 C1ndashC7ndashO938 120573

119894CndashOndashH C7ndashO9ndashH10

39-40 120573119894

CndashCndashO C1ndashC2ndashO11 C3ndashC2ndashO1141 120573

119894CndashOndashC C2ndashO11ndashC12

42ndash47 120573119894

CndashCndashC (Ring) C1ndashC2ndashC3 C2ndashC3ndashC4 C3ndashC4ndashC5 C4ndashC5ndashC6C5ndashC6ndashC1 C6ndashC1ndashC2

Out-of-plane bending

48ndash51 120596119894

CndashH H16ndashC3ndashC2ndashC4 H17ndashC4ndashC5ndashC3 H18ndashC5ndashC6ndashC4H19ndashC6ndashC1ndashC5

52 120596119894

CndashC C7ndashC1ndashC6ndashC253 120596

119894CndashO O11ndashC2ndashC1ndashC3

Torsion54-55 120591

119894CndashO C2ndashC1ndashC7ndashO8 C2ndashC1ndashC7ndashO9

56-57 120591119894

CndashOndashC C1ndashC2ndashO11ndashC12 C3ndashC2ndashO11ndashC12

58ndash60 120591119894

CndashH(methyl) C2ndashO11ndashC12ndashH13 C2ndashO11ndashC12ndashH14C2ndashO11ndashC12ndashH15

61 120591119894

OndashH C1ndashC7ndashO9ndashH10

62ndash67 120591119894

tring C1ndashC2ndashC3ndashC4 C2ndashC3ndashC4ndashC5 C3ndashC4ndashC5ndashC6C4ndashC5ndashC6ndashC1 C5ndashC6ndashC1ndashC2 C6ndashC1ndashC2ndashC3

For numbering of atoms refer to Figure 1(a)

observed in the IR region are very sharp broad and lessintense The title compounds belong to 119862

119904point group The

19 atoms present in OAA and AA molecular structure eachhas 51 fundamental modes of vibrations For molecules of119862119904symmetry group theory analysis indicates that the 51

fundamental vibrations are distributed among the symmetryspecies as

Γvib = 35A1015840 (in-plane) + 16A10158401015840 (out-of-plane) (5)

for bothOAA andAA respectively From the structural pointof view of the molecules OAA and AA have 18 stretchingvibrations 33 bending vibrations respectively All the vibra-tions were found to be active both in Raman scattering andinfrared absorption

The observed and calculated wave numbers calculatedIR and Raman intensities and normal mode descriptions(characterized by potential energy distribution (PED)) for

the fundamental vibrations of OAA and AA are depictedin Tables 7 and 8 For visual comparison the observed andsimulated FTIR and FT-Raman spectra of the compoundsare presented in Figures 2 3 4 and 5 which help to under-stand the observed spectral features The root mean square(RMS) error of the observed and calculated wavenumbers(unscaledB3LYP6-31Glowastlowast) of OAA and AA was found to be843 cmminus1 and 891 cmminus1 respectively This is understandablesince the mechanical force fields usually differ appreciablyfrom the observed ones This is partly due to the neglectof anharmonicity and partly due to the approximate natureof the quantum mechanical methods However for reliableinformation on the vibrational properties the use of selectivescaling is necessary The calculated wavenumbers are scaledusing the set of transferable scale factors recommended byFogarasi and Pulay [7]The SQM treatment has resulted in anRMS deviation of 967 cmminus1 and 113 cmminus1 for OAA and AA

Journal of Spectroscopy 5

Table 3 Definition of internal coordinates of Anisic acid (AA)

No (i) Symbol Type DefinitionStretching

1ndash4 119903119894

CndashH C2ndashH11 C3ndashH12 C5ndashH18 C6ndashH195ndash10 119903

119894CndashC C1ndashC2 C2ndashC3 C3ndashC4 C4ndashC5 C5ndashC6C6ndashC1

11 119903119894

CndashCfn C1ndashC712ndash14 119903

119894CndashO C7ndashO8 C7ndashO9 C4ndashO13

15 119903119894

OndashC O13ndashC1416 119903

119894OndashH O9ndashH10

17ndash19 119903119894

CndashH(methyl) C14ndashH15 C14ndashH16 C14ndashH17Bending

20-21 120573119894

CndashC C2ndashC1ndashC7 C6ndashC1ndashC7

22ndash29 120573119894

CndashCndashHC1ndashC2ndashH11 C3ndashC2ndashH11C2ndashC3ndashH12 C4ndashC3ndashH12C4ndashC5ndashH18 C6ndashC5ndashH18C5ndashC6ndashH19 C1ndashC6ndashH19

30ndash35 120573119894

CndashCndashH(methyl) O13ndashC14ndashH15 O13ndashC14ndashH16 O13ndashC14ndashH17H17ndashC14ndashH15 H15ndashC14ndashH16 H17ndashC14ndashH16

36-37 120573119894

CndashCndashO C3ndashC4ndashO13 C5ndashC4ndashO1338 120573

119894CndashOndashH C7ndashO9ndashH10

39-40 120573119894

CndashCndashO C1ndashC7ndashO8 C1ndashC7ndashO941 120573

119894CndashOndashC C4ndashO13ndashC14

42ndash47 120573119894

CndashCndashC (Ring) C1ndashC2ndashC3 C2ndashC3ndashC4 C3ndashC4ndashC5 C4ndashC5ndashC6C5ndashC6ndashC1 C6ndashC1ndashC2

Out-of-plane bending

48ndash51 120596119894

CndashH H11ndashC2ndashC3ndashC1 H12ndashC3ndashC4ndashC2 H18ndashC5ndashC6ndashC4H19ndashC6ndashC1ndashC5

52 120596119894

CndashC C7ndashC1ndashC6ndashC253 120596

119894CndashO O13ndashC4ndashC5ndashC3

Torsion54ndash55 120591

119894CndashO C2ndashC1ndashC7ndashO8 C2ndashC1ndashC7ndashO9

56-57 120591119894

CndashOndashC C3ndashC4ndashO13ndashC14 C5ndashC4ndashO13ndashC14

58ndash60 120591119894

CndashH(methyl) C4ndashO13ndashC14ndashH15 C4ndashO13ndashC14ndashH16C4ndashO13ndashC14ndashH16

61 120591119894

OndashH C1ndashC7ndashO9ndashH10

62ndash67 120591119894

tring C1ndashC2ndashC3ndashC4 C2ndashC3ndashC4ndashC5 C3ndashC4ndashC5ndashC6C4ndashC5ndashC6ndashC1 C5ndashC6ndashC1ndashC2 C6ndashC1ndashC2ndashC3

For numbering of atoms refer to Figure 1(b)

respectively The RMS values of wavenumbers were obtainedin this study using the following expression

RMS = radic1

119899 minus 1

119899

sum

119894

(120592calc119894

minus 120592exp119894

)2

(6)

431 CH Vibrations Aromatic compounds commonly ex-hibit multiple weak bands in the region 3100ndash3000 cmminus1 [26]due to aromatic CndashH stretching vibrations According to thePED analysis the bands observed in experimental spectrumat 3098 3083 3069 3020 cmminus1 in OAA and 3085 3034 3029and 3002 cmminus1 inAAwere assigned to stretching vibrations of

CndashH bond According to these studies all the CndashH stretchingvibrations are not mixed with other types of vibrations

The CndashH in-plane deformation vibrations are assigned inthe region 1100ndash1400 cmminus1 [27] The in-plane deformationsof CndashH groups are noticed on PED analysis at 1494 14391288 and 1182 in OAA and 1518 1301 1181 and 1131 cmminus1 inAAThere is slight increase in the CndashH in-plane deformationfrequency because of steric effect in OAA and inductive effect(+I) in AAThese values of calculated frequencies are typicaland in very good agreement with experimental data The in-plane CndashH deformation vibrations are slightly mixed in bothOAA and AA

The CndashH out-of-plane deformation vibrations areassigned in the region 900ndash600 cmminus1 [26] The bands

6 Journal of Spectroscopy

Table 4 Definition of natural internal coordinates of O-Anisic acid (OAA)

No (i) Symbola Definitionb

1ndash4 CndashH stretch 1199031 1199032 1199033 1199034

5ndash11 CndashC stretch 1199035 1199036 1199037 1199038 1199039 11990310 11990311

12ndash14 CndashO stretch 11990312 11990313 11990314

15 OndashC stretch 11990315

16 OndashH stretch 11990316

17 CH3 ss (11990317+ 11990318+ 11990319) radic3

18 CH3 ips (211990317minus 11990318minus 11990319) radic6

19 CH3 ops (11990318minus 11990319) radic2

20 bCndashCndashC (12057320minus 12057321) radic2

21ndash24 bCndashCndashH (12057322minus 12057323) radic2 (120573

24minus 12057325) radic2 (120573

26minus 12057327) radic2 (120573

28minus 12057329) radic2

25 CH3 sb (minus12057330minus 12057331minus 12057332+ 12057333+ 12057334+ 12057335) radic6

26 CH3 ipb (minus12057333minus 12057334minus 212057335)radic6

27 CH3 opb (12057333minus 12057334) radic2

28 CH3 ipr (212057330minus 12057331minus 12057332)radic6

29 CH3 opr (12057331minus 12057332)radic2

30 bCndashCndashO (12057336minus 12057337) radic2

31 bCndashOndashH 12057338

32-33 bCndashCndashO 12057339 12057340

34 bCndashOndashC 12057341

35 Rtrigd (12057342minus 12057343+ 12057344minus 12057345+ 12057346minus 12057347) radic6

36 Rsymd (minus12057342minus 12057343+ 12057344minus 12057345minus 12057346+ 212057347)radic12

37 Rasymd (12057342minus 12057343+ 12057345minus 12057346) 2

38ndash41 120596CndashH 12059648 12059649 12059650 12059651

42 120596CndashC 12059652

43 120596CndashO 12059653

44-45 tCndashO 12059154 12059155

46 tCndashOndashC 12 (12059156+ 12059157)

47 tCH3 13 (12059158+ 12059159+ 12059160)

48 tOndashH 12059161

49 Ttrigd (12059162minus 12059163+ 12059164minus 12059165+ 12059166minus 12059167) radic6

50 Tsymd (12059162minus 12059163+ 12059165+ 12059166) 2

51 Tasymd (minus12059162+ 212059163minus 12059164minus 12059165+ 12059166minus 12059167) radic12

aThese symbols are used for description of the normal modes by PED in Table 7bThe internal coordinates used here are defined in Table 2

appearing at 960 937 865 and 755 cmminus1 in OAA and929 854 846 and 774 cmminus1 in AA were assigned toout-of-plane deformation type of vibration (120596) of CndashHgroups There is slight increase in the CndashH out-of-planedeformation frequency because of strong intermolecularhydrogen bonding in OAA In these bands the pronouncedparticipation of other types of vibrations is observed Theseare also supported by the literature

432 Carboxylic Acid Vibrations Due to the presence ofstrong intermolecular hydrogen bonding the FT-IR spectraexhibits spectra exhibit a broad band due to the OndashHstretching vibrations and a strong banddue toC=Ostretchingvibrations The carboxylic acid dimers display a very broadand intenseOndashH stretching absorption in the region of 3300ndash2500 cmminus1 [28] The title molecules both exhibit intermolec-ular hydrogen bonding In our case the bands at 3390 cmminus1

in OAA and 3435 cmminus1 in AA are assigned as OndashH stretchingvibrations There is a slight increase in the OndashH frequencybecause of steric effect in OAA and +I effect in AA The OndashH out-of-plane bending vibration occurs near the region of920 cmminus1 [27] The bands appearing at 595 cmminus1 in OAA and505 cmminus1 in AA are assigned to OndashH out-of-plane bendingvibrationThe OndashH out-of-plane bending vibrations in OAAand AA decrease due to intermolecular hydrogen bonding

The carbonyl stretching vibrations are expected in theregion 1720 cmminus1ndash1680 cmminus1 [28] The IR band at 1670 cmminus1in OAA and FT-Raman band at 1688 cmminus1 in AA are assignedasC=O stretching vibrationsTheCndashObond appears stronglyin the 1320ndash1210 cmminus1 region [29] The bands observed at1049 and 795 cmminus1 in OAA and 1267 and 1100 cmminus1 in AAare assigned to CndashO stretching mode The CndashO stretchingvibrational frequency is lower than general range In thecase of carboxylic acid dimers like OAA and AA the OH

Journal of Spectroscopy 7

Table 5 Definition of natural internal coordinates of Anisic acid (AA)

No (i) Symbola Definitionb

1ndash4 CndashH stretch 1199031 1199032 1199033 1199034

5ndash10 CndashC stretch 1199035 1199036 1199037 1199038 1199039 11990310

11 CndashCfn stretch 11990311

12ndash14 CndashO stretch 11990312 11990313 11990314

15 OndashC stretch 11990315

16 OndashH stretch 11990316

17 CH3 ss (11990317+ 11990318+ 11990319) radic3

18 CH3 ips (211990317minus 11990318minus 11990319) radic6

19 CH3 ops (11990318minus 11990319) radic2

20 bCndashCndashC (12057320minus 12057321) radic2

21ndash24 bCndashCndashH (12057322minus 12057323) radic2 (120573

24minus 12057325) radic2 (120573

26minus 12057327) radic2 (120573

28minus 12057329) radic2

25 CH3 sb (minus12057330minus 12057331minus 12057332+ 12057333+ 12057334+ 12057335) radic6

26 CH3 ipb (minus12057333minus 12057334minus 212057335)radic6

27 CH3 opb (12057333minus 12057334) radic2

28 CH3 ipr (212057330minus 12057331minus 12057332) radic6

29 CH3 opr (12057331minus 12057332) radic2

30 bCndashCndashO (12057335minus 12057336) radic2

31 bCndashOndashH 12057338

32-33 bCndashCndashO 12057339 12057340

34 bCndashOndashC 12057341

35 Rtrigd (12057342minus 12057343+ 12057344minus 12057345+ 12057346minus 12057347) radic6

36 Rsymd (minus12057342minus 12057343+ 12057344minus 12057345minus 12057346+ 212057347) radic12

37 Rasymd (12057342minus 12057343+ 12057345minus 12057346) 2

38ndash41 120596CndashH 12059648 12059649 12059650 12059651

42 120596CndashC 12059652

43 120596CndashO 12059653

44-45 tCndashO 12059154 12059155

46 tCndashOndashC 12 (12059156+ 12059157)

47 tCH3 13 (12059158+ 12059159+ 12059160)

48 tOndashH 12059161

49 Ttrigd (12059162minus 12059163+ 12059164minus 12059165+ 12059166minus 12059167) radic6

50 Tsymd (12059162minus 12059163+ 12059165+ 12059166)2

51 Tasymd (minus12059162+ 212059163minus 12059164minus 12059165+ 12059166minus 12059167) radic12

aThese symbols are used for description of the normal modes by PED in Table 8bThe internal coordinates used here are defined in Table 3

in-plane bending and CndashO stretching bands involve someinteraction between them they are referred to as coupledOH in-plane bending and CndashO stretching vibrations [26]The CndashO bending vibration occurs in the region of 580ndash340 cmminus1 [30] The band observed at 380 cmminus1 in OAA and440 cmminus1 in AA are assigned to CndashO bending mode Thepresent assignments agree very well with the values availablein the literature

433 Methyl Group Vibrations The title molecules OAAand AA under consideration possess one CH

3group For

the assignments of CH3group one can expect that 9 fun-

damentals can be associated with each CH3group namely

the symmetrical stretching (CH3symmetric stretch) and

asymmetrical stretching (CH3asymmetric stretch) in-plane

stretching modes (ie in-plane hydrogen stretching modes)

and the symmetrical (CH3symmetric deform) and asym-

metrical (CH3asymmetric deform) deformation modes in-

plane rocking (CH3ipr) out-of-plane rocking (CH

3opr) and

twisting (tCH3) bending modes

For the methyl group compounds the asymmetricstretching mode appeared in the range 2965ndash3005 cmminus1 andthe symmetric stretching mode appeared in the range of2815ndash2860 cmminus1 [30] The FT-Raman band at 2983 cmminus1 forOAA and IR band at 2941 cmminus1 for AA are symmetricstretching The symmetric stretching vibrational frequencyis higher in OAA and AA due to steric effect and +I effectThe asymmetric methyl stretching band appeared at 30033018 cmminus1 in OAA and 2990 2956 cmminus1 in AA respectivelyThe asymmetric deformation mode appeared in the range1445ndash1485 cmminus1 and symmetric deformation mode appearedin the range of 1420ndash1460 cmminus1 [30] The IR band at 1466

8 Journal of Spectroscopy

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 2 FTIR spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Table 6 Diagonal force constants (102 Nmminus1) of O-Anisic acid(OAA) and Anisic acid (AA)

Descriptiona Force constantsb

OAA AAC1ndashC2 621 630C2ndashC3 633 696C3ndashC4 677 626C4ndashC5 675 628C5ndashC6 682 663C6ndashC1 644 648C1ndashC7 465 222C7ndashO8 532 522C7ndashO9 1030 1128C2ndashO11(C4ndashO13) 449 576O11ndashC12(O13ndashC14) 413 499O9ndashH10 644 661C12ndashH13(C14ndashH15) 498 508C12ndashH14(C14ndashH16) 526 470C12ndashH15(C14ndashH17) 498 507C3ndashH16(C2ndashH11) 514 498C4ndashH17(C3ndashH12) 501 496C5ndashH18 505 500C6ndashH19 532 522aThe atoms indicated in the parenthesis belong to AAbStretching force constants are given in mdyn A

minus1

For numbering of atoms refer to Figures 1(a) and 1(b)

and 1435 cmminus1 in OAA and 1468 and 1461 cmminus1 in AA areassigned as asymmetric deformation vibrations The IR bandat 1411 cmminus1 for OAA and 1429 cmminus1 for AA are symmet-ric deformation mode The CH

3deformation absorption

occurs at 1466 cmminus1 and 1429 cmminus1 this vibration is knownas umbrella mode that overlaps with CC ring stretchingvibrations for the title compounds These are also supportedby the literature

The tensional modes appeared in the range of 265ndash185 cmminus1 [30] This modes are strongly coupled with other

vibrations that are observed at 280 cmminus1 inOAAand 165 cmminus1in AAwhich are in agreement with the calculated results also

434 Ring Vibrations The ring CndashC stretching vibrationsoccur in the region of 1600ndash1400 cmminus1 [29]The bands appearat 1600 1579 1312 1184 1153 1062 and 698 cmminus1 in OAAand 1608 1580 1416 1307 1107 1028 and 825 cmminus1 in AAwere assigned to CndashC stretching vibrations The shift in thefrequency of CndashC vibrations towards lower wave numbermay be due to the COOH and OCH

3groups Many ring

modes are affected by the substitutions in the aromatic ringThe bands at 180 cmminus1 and 285 cmminus1 for OAA and AA wereassigned to CndashC bending vibrationsThe out-of-plane and in-plane deformations of the phenyl ring are observed below1000 cmminus1 and these modes are sensitive by the additionof functional groups The out-of-plane bending vibrationswere observed at 170 cmminus1 and 111 cmminus1 for OAA and AASmall changes in the wavenumbers were observed due tothe presence of +I effect in AA and steric effect in OAAThe computed wavenumbers are in good agreement withexperimental data

5 Electronic Properties

Atomic charges on the various atoms of OAA and AAobtained by Mulliken population analysis [31] are given inTable 9 From the listed atomic charge values the oxygen[O8 O9] and O11 in OAA and O13 in AA atoms had a largenegative charge and behaved as electron acceptor It was alsoobserved that there is a large accumulation of charge on O11inOAAO13 in AAmoleculesTherefore C7 andO11 inOAAand C7 and O13 in AA had a greater ionic character

Natural bond orbital analysis provides an efficientmethod for studying steric effect and intermolecular bondingand interaction among bonds and also provides a convenientbasis for investigating charge transfer or conjugative interac-tion in molecular systems Natural charge analysis is givenin Table 10 for the title compounds The results show thatsubstitution of COOH and CH

3group in OAA and AA leads

to a redistribution of electron density The C7 atom in OAAand AA is more positive charge (+08091 +08139) In the

Journal of Spectroscopy 9Ta

ble7Detailedassig

nmento

ffun

damentalvibratio

nsof

O-Anisic

acid

(OAA)b

yno

rmalmod

eanalysis

basedon

SQM

forcefi

eldcalculations

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

1A1015840

3390

mdash3771

3390

72652

155385

120592OH(100)

2A1015840

mdash3098

3273

3098

1612

499564

120592CH

(99)

3A1015840

mdash3083

3233

3083

1700

135114

120592CH

(99)

4A1015840

3069

mdash3207

3069

10674

70382

120592CH

(99)

5A1015840

mdash3020

3186

3024

17253

1372

01120592CH

(99)

6A1015840

3018

mdash3157

3018

38987

58202

120592CH

3(99)

7A10158401015840

3003

mdash3085

3003

5946

78409

120592CH

3(99)

8A1015840

mdash2983

3020

2983

52626

120657

120592CH

3(99)

9A1015840

1670

mdash1822

1670

358567

54628

120592CO

(53)120592CC

(14)bC

CO(14

)bC

OH(12)

10A1015840

1600

mdash1656

1600

15061

16343

120592CC

(60)bCH

(20)R

asym

d(10)

11A1015840

1579

mdash1630

1579

61364

48880

120592CC

(69)bCH

(19)

12A1015840

1494

mdash1539

1494

58214

10686

bCH(48)120592CC

(37)

13A1015840

1466

mdash1513

1466

6534

6058

bCH

3(43)bCH

(25)120592CC

(16)

14A1015840

mdash1439

1506

1439

22318

5639

bCH(39)bCH

3(37)120592CC

(17)

15A10158401015840

1435

mdash1500

1435

3652

510814

bCH

3(88)

16A1015840

1411

mdash1475

1411

11849

19713

bCH

3(74)

17A1015840

1382

1367

4497

1268

bCOH(35)120592CO

(32)bCC

O(13)120592CC

(11)

18A1015840

mdash1312

1350

1312

2182

8877

120592CC

(67)

19A1015840

1288

mdash1320

1288

6319

416

48bC

H(33)R

trigd(20)120592CO

(13)120592CC

(12)

20A1015840

mdash1287

1302

1287

19694

044

9Rtrig

d(26)120592CC

(25)bCH

(20)120592CO

(12)

21A1015840

mdash1184

1210

1184

228252

32980

120592CC

(31)bCH

(19)bC

H3(17)120592CO

(17)

22A1015840

1182

mdash1201

1182

162989

2713

6bC

H(42)120592CC

(34)bCH

3(10)

23A1015840

1170

mdash119

3117

015

764576

bCH

3(57)bCH

(24)

24A1015840

mdash117

3117

31153

7419

1097

120592CC

(31)bCH

(29)bCH

3(25)

25A1015840

1140

mdash1168

1140

0662

4253

bCH

3(96)

26A1015840

1049

mdash1087

1050

1073

0478

09120592CO

(29)120592CC

(27)R

trigd(12)

27A1015840

-1062

1077

1060

104848

21650

120592CC

(41)120592CO

(22)bCH

(12)

28A10158401015840

960

-1060

960

060

90057

120596CH

(91)

29A1015840

mdash974

989

974

2078

710836

120592OC(62)120592CC

(12)120592CO

(11)

30A10158401015840

937

mdash965

935

1244

1294

120596CH

(91)

31A10158401015840

mdash865

869

865

3148

3432

120596CH

(64)ttrigd(19)

32A1015840

mdash795

830

795

12200

4238

120592CO

(29)R

symd(21)120592OC(15)120592CC

(15)

33A10158401015840

761

mdash795

761

1002

0207

tCO(32)ttrigd(28)120596

CH(23)120596

CC(11)

34A10158401015840

mdash755

770

755

41473

1456

120596CH

(51)ttrigd(27)120596

CO(14

)35

A10158401015840

695

mdash747

698

64512

0469

ttrigd(52)120596

CH(23)tCO

(15)

36A1015840

mdash698

712

695

10016

17946

120592CC

(33)120592CO

(23)bCC

O(21)

37A1015840

mdash602

639

602

13503

2683

Rasymd(36)bCC

O(15)

120592CC

(12)R

symd(11)

38A10158401015840

mdash595

594

595

74804

8168

tOH(79)

39A1015840

mdash565

588

565

21902

1740

bCCO

(28)120592CC

(17)bCO

(15)R

symd(14

)bC

CO(13)

10 Journal of Spectroscopy

Table7Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

540

mdash548

540

5598

4848

bCCO

(40)bCC

(16)120592CC

(13)R

asym

d(10)

41A10158401015840

480

mdash540

480

0946

0860

120596CO

(40)120596

CH(16)ttrigd(14

)tsy

m(14

)42

A10158401015840

mdash40

1435

401

3585

0792

tsym

(14)120596CC

(15)

43A1015840

mdash380

388

380

4805

4133

bCO(64)bCC

O(16)

44A1015840

mdash303

383

303

1180

4980

Rsym

d(59)bCO

C(17)120592CC

(15)

45A10158401015840

mdash280

283

280

0092

0016

tCH

3(79)

46A1015840

mdash240

280

240

0927

0935

bCOC(40)bCC

(30)bCC

O(18)

47A10158401015840

mdash180

229

180

0018

2096

120596CC

(30)tCO

(20)tsym

(18)

tasym

(11)120596CH

(10)

48A1015840

mdash170

190

170

3092

0715

bCC(42)bCO

C(29)bCO

(12)

49A10158401015840

mdash115

119115

4502

0508

tCOC(47)tsym

(15)tCH

3(12)

50A10158401015840

mdash110

9696

0922

3779

tsym

(35)tCO

(25)

tCOC(21)tCH

3(13)

51A10158401015840

mdashmdash

1730

1260

0037

tCO(99)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 11Ta

ble8Detailedassig

nmento

ffun

damentalvibratio

nsof

Anisic

acid

(AA)b

yno

rmalmod

eanalysis

basedon

SQM

forcefi

eldcalculations

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

1A1015840

3435

mdash3768

3435

7952

3164209

120592OH(100)

2A1015840

mdash3085

3232

3085

21438

120058

120592CH

(89)

3A1015840

mdash3034

3224

3034

7547

126718

120592CH

(99)

4A1015840

3029

mdash3218

3029

3520

99229

120592CH

(99)

5A1015840

3002

mdash3209

3002

5141

52552

120592CH

(99)

6A1015840

2990

mdash3155

2990

2423

53071

120592CH

ops(99)

7A10158401015840

2956

mdash3087

2956

45319

94074

120592CH

ips(51)120592CH

ss(36)120592CH

ops(12)

8A1015840

2941

mdash3022

2941

42847

91231

120592CH

ss(56)120592CH

ips(44

)9

A1015840

1688

mdash1813

1688

302139

74665

120592CO

(72)bCC

O(17)

10A1015840

1608

mdash1666

1608

216104

153242

120592CC

(62)bCH

(22)R

symd(11)

11A1015840

1580

mdash1624

1580

34785

12359

120592CC

(66)bCH

(14)

12A1015840

1518

mdash1559

1518

41495

8422

bCH(52)120592CC

(30)

13A1015840

1468

mdash1516

1468

37550

10673

bCHsb

(77)

14A10158401015840

1461

mdash1504

1461

14058

1218

3bC

Hop

b(83)

15A1015840

1429

mdash1486

1429

5851

19586

bCHipb(70)120592CC

(10)bCH

(10)

16A1015840

1416

mdash1465

1416

14835

9149

120592CC

(39)bCH

(35)bCH

ipb(18)

17A1015840

1324

mdash1391

1324

31290

5311

bCOH(27)120592CO

(22)bCC

O(21)120592CC

(13)

18A1015840

1307

mdash1371

1307

806

814

44120592CC

ar(65)bCH

(20)

19A1015840

1301

mdash1331

1301

40408

7073

bCH(43)120592CC

(33)

20A1015840

1267

mdash1304

1267

245222

3723

120592CO

(37)R

trigd(20)120592CC

(16)

21A1015840

1181

mdash1221

1181

5734

6023

bCH(61)120592CC

(21)

22A1015840

1172

mdash1209

1172

5690

5161

bCHop

r(61)bC

H(13)

23A1015840

mdash1137

1189

1137

0662

4334

bCHipr(78)bC

Hop

r(14)

24A1015840

1131

mdash117

61131

190946

42508

bCH(35)120592CC

(21)

25A1015840

1107

mdash1139

1107

245972

63024

120592CC

fn(25)R

trigd(23)bCH

(16)120592OC(13)

26A1015840

mdash1100

1114

1100

318070

20809

120592CO

(40)bCO

H(22)bCC

O(11)

27A1015840

1028

mdash1069

1028

0786

11056

120592CC

(58)bCH

(16)

28A1015840

mdash1010

1026

1010

29566

2343

120592OC(51)120592CC

(28)

29A10158401015840

929

mdash991

929

0010

046

4120596CH

(89)

30A10158401015840

854

mdash966

854

1379

1924

120596CH

(82)ttrigd(12)

31A10158401015840

846

mdash863

846

3652

212

44120596CH

(39)120596

CO(32)ttrigd(20)

32A1015840

825

mdash834

825

24090

2237

3120592CC

ar(32)R

symd(27)120592OC(22)

33A10158401015840

774

mdash830

774

0365

4928

120596CH

(84)

34A10158401015840

mdash755

775

755

1082

0243

ttrigd(51)120596

CC(15)120596

CH(14

)tCO(11)

35A1015840

698

mdash725

698

3553

93075

bCCO

(44)120592CO

(25)bCO

H(25)

36A10158401015840

634

mdash710

634

76887

0059

tCO(57)120596

CH(20)ttrigd(12)

37A1015840

617

mdash647

617

0592

644

1Ra

symd(81)

38A1015840

550

mdash603

550

14566

0968

Rsym

d(32)120592CC

fn(13)120592CO

(11)bCC

O(11)bCO

C(10)

39A10158401015840

545

mdash601

545

27876

4847

120596CO

(42)tOH(14

)120596CH

(11)120596

CC(11)

12 Journal of Spectroscopy

Table8Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

525

mdash511

525

12735

1849

bCCO

(82)

41A1015840

505

mdash511

505

50036

5698

tOH(24)ttrigd(23)120596

CO(19)120596

CH(14

)42

A1015840

440

mdash481

440

3190

2294

bCO(35)bCO

C(29)

43A10158401015840

mdash375

427

375

0415

0023

tsym

(60)120596

CH(19

)tasym

(17)

44A1015840

mdash310

335

310

3569

0577

Rsym

d(48)120592CC

fn(25)

45A10158401015840

mdash285

304

285

4416

0596

120596CC

(33)tasym

(24)tCO

(16)

46A1015840

mdash220

267

220

3713

2509

bCOC(29)bCO

(17)

47A10158401015840

mdash165

226

165

0047

0429

tCH

3(85)

48A1015840

mdash111

165

111

0211

0159

bCC(80)

49A10158401015840

mdash98

132

982323

0292

Tasym

(30)tCO

C(30)120596

CC(11)120596

CH(10)tsym

(10)

50A10158401015840

mdash70

7870

1302

1199

tCO(95)

51A10158401015840

mdash60

6560

0898

0216

tCOC(48)tCO

(31)tCH

3(12)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 13

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 3 FT-Raman spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 4 FTIR spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 5 FT-Raman spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

title molecules all the hydrogen atoms have a net positivecharge in particular the hydrogen atoms H(10) that havecharge of 05047 and 05050 respectively The presence oflarge amounts of negative charge on oxygen and net positivecharge on H(10) atoms may suggest the presence of inter-molecular hydrogen bonding in the crystalline phase

Highest occupied molecular orbital and lowest unoc-cupied molecular orbital are very important parametersfor quantum chemistry This is also used by the frontierelectron density for predicting the most reactive position in120587-electron systems and also explains several types of reactionin conjugated system [32] The conjugated molecules are

characterized by a small highest occupied molecular orbitalndashlowest unoccupied molecular orbital (HOMO-LUMO) sep-aration which is the result of a significant degree of inter-molecular charge transfer from the end-capping electron-donating groups to the efficient electron-acceptor groupsthrough 120587 conjugated path [33] Both the highest occupiedmolecular orbital and lowest unoccupied molecular orbitalare the main orbitals that take part in chemical stability[34] Energy difference betweenHOMOand LUMOorbital iscalled energy gap that is an important stability for structureswhich are given in Table 11 We performed an analysis ofall the molecular orbitals involved taking into consideration

14 Journal of Spectroscopy

Table 9 Atomic charges for optimized geometry of O-Anisic acid(OAA) and Anisic acid (AA) obtained by B3LYP6-31Glowastlowast densityfunctional calculations

Atomsa MullikenOAA AA

C1 00018 00373C2 03297 minus01002

C3 minus01368 minus01219

C4 minus00836 03612

C5 minus00943 minus01394

C6 minus01061 minus01118

C7 05570 05445O8 minus04650 minus04848

O9 minus05104 minus05064

H10 03198 03217O11 (H11) minus04841 01203C12 (H12) minus00837 01021H13 (O13) 01064 minus05111

H14 (C14) 01352 minus00831

H15 01211 01099H16 00913 01302H17 00929 01246H18 00886 00913H19 01200 01155aThe atoms indicated in the parenthesis belong to AA

Table 10Natural atomic charges ofO-Anisic acid (OAA) andAnisicacid (AA) calculations performed at the B3LYP6-31Glowastlowast level oftheory

Atomsa OAA AAC1 minus02176 minus02053

C2 03724 minus01746

C3 minus03284 minus02801

C4 minus01952 03443

C5 minus02720 minus03289

C6 minus01806 minus01748

C7 08091 08139O8 minus05861 minus06102

O9 minus07295 minus07217

H10 05047 05050O11 (H11) minus04921 02634C12 (H12) minus03307 02544H13 (O13) 02070 minus05119

H14 (C14) 02390 minus03300

H15 02070 02090H16 02443 02352H17 02426 02090H18 02439 02449H19 02621 02585aThe atoms indicated in the parenthesis belong to AAFor numbering of atoms refer to Figures 1(a) and 1(b)

that orbital 40 is the HOMO and orbital 41 is the LUMO forOAA and AA respectively

Many organic molecules that contain conjugated 120587 elec-trons are characterized as hyperpolarisabilities and are ana-lyzed by means of vibrational spectroscopy The analysis

Table 11 Calculated quantum chemical parameters ofO-Anisic acid(OAA) and Anisic acid (AA) derivatives

Parameters OAA AA119864HOMO minus0227 minus0231

119864LUMO minus0041 minus0036

Δ119864 0186 0195120594 0134 0133Η 0093 0097Σ 10752 10256

Table 12 Calculated 13C NMR chemical shifts (ppm) of O-Anisicacid (OAA) and Anisic acid (AA)

Carbona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAC1 11782 12315 10447 12620C2 15848 13146 14696 13936C3 11204 11384 9681 12272C4 13517 16297 11926 17125C5 12191 11384 10447 11047C6 13347 13146 12019 13751C7 16634 16714 14609 17174C12 (C14) 5674 5544 4322 5549aThe atoms indicated in the parenthesis belong to AA

Table 13 Experimental and calculated 1H NMR chemical shifts(ppm) of O-Anisic acid (OAA) and Anisic acid (AA)

Protona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAH10 1030 13 11 11H13 H14 H15 (H11) 4066 7914 3932 8405H16 (H12) 708 7027 6831 7147H17 (H15 H16 H17) 756 3836 7570 3824H18 710 7027 7069 6673H19 813 7914 3932 8217aThe atoms indicated in the parenthesis belong to AA

of the wave function indicates that the electron absorptioncorresponds to the transition from the ground state to thefirst excited state and is mainly described by the one-electronexcitation from the HOMO to the LUMO The HOMO of 120587nature (ie aromatic ring) is delocalized over the whole CndashC bond By contrast the LUMO is located over the aromaticring Consequently the HOMO-LUMO transition implies anelectron density transfer toCOOHandOCH

3group from the

aromatic ringThe theoretical basis for the new quantities lies in the

density functional formalism [35] Since molecular orbital(MO) theory is by far the most widely used by chemistsit is important to place 120594 and 120578 in a MO framework Ithas already been shown [36] that the MO theory of thechemical bond contains the values of 120594 and 120578 for the bondingfragments Hard molecules have a large HOMO-LUMO gapand soft molecules have a small HOMO-LUMO gap A small

Journal of Spectroscopy 15

HOMO

(a)

LUMO

(b)

Figure 6 Contour surfaces of frontier molecular orbitals of O-Anisic acid

HOMO

(a)

LUMO

(b)

Figure 7 Contour surfaces of frontier molecular orbitals of Anisic acid

HOMO-LUMO gap automatically means small excitationenergies to the manifold of excited states Therefore softmolecules with a small gap will be more polarizable thanhard molecules High polarizability was the most character-istic property attributed to soft acids and bases Energy gapsshould be small for best bonding or bothmolecules should besoft

In the present study the title compound AA is dynam-ically more stable due to the large energy gap OAA is asoft molecule due to small energy gap The Contour surfacesof the frontier molecular orbitals are sketched in Figures 6and 7

51 NMR Spectra DFT methods treat the electronic energyas a function of the electron density of all electrons simul-taneously and thus include electron correlation effect [37]In this study molecular structure of the OAA and AA wasoptimized by using B3LYP method in conjunction with 6-31Glowastlowast 13C and 1H chemical shift calculations of the titlecompounds have been made by using GIAO method andsame basis set The isotropic shielding values were usedto calculate the isotropic chemical shifts 120575 with respect totetramethylsilane (TMS) The isotropic chemical shifts arefrequently used as an aid in identification of reactive ionicspecies The B3LYP method allows calculating the shielding

16 Journal of Spectroscopy

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 150

140

130

120

110

100

90110 120 130 140 150 160 170

(a)

70 75 80 85 90 95 100 1056

7

8

9

10

11

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

(b)

Figure 8 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for O-Anisic acid

constants with the proper accuracy and the GIAOmethod isone of the most common approaches for calculating nuclearmagnetic shielding tensors

Theoretical and experimental chemical shifts of OAA andAA in 1H and 13C NMR spectra are gathered in Tables 12and 13 The range of the 13C NMR chemical shifts for atypical organic molecules usually is gt100 ppm [38 39] andthe accuracy ensures reliable interpretation of spectroscopicparameters In the present study the 13C NMR chemicalshifts in the ring are gt100 ppm as they would be expectedThe 13C chemical shifts carbonyl carbons vary from 150 to220 ppm This depends on the decrease in electron donatingor shielding ability of the attached atoms [40] The C=Ogroups of carboxylic acids and derivatives are in the range of150ndash185 ppm [29]

Hydrogens bonded to an aromatic ring are stronglydeshielded and absorb downfieldWhen the120587-electrons enterthe magnetic field they circulate around the ring to generatea ring current This produces a small induced magnetic fieldthat reinforces the applied field outside the ring resultingin aromatic protons being deshielded [41] A related effectis observed for carboxylic acids For these compoundscirculation of electrons in the double bonds produces inducedmagnetic field These are responsible for the high chemicalshift values of acid protons (H10) Carboxylic acids asstable hydrogen-bonded dimers in nonpolar solvents even athigh dilution The carboxylic proton therefore absorbs in acharacteristically narrow range 132 to 100 and is affectedonly slightly by concentration [29]

In a methyl group a proton is covalently bonded tocarbon oxygen or other atoms by a sigma bond Whenplaced in a strong magnetic field the electrons of the sigmabond circulate to generate a small magnetic field whichopposes the applied field A nearby electronegative atomwithdraws electron density from the neighbourhood of theproton so that a smaller applied field is needed to cause thespin state of the proton to flip The signal for a deshielded

Table 14 Theoretically computed energies (au) zero-point vibra-tional energies (kcalmolminus1) rotational constants (GHz) entropies(calmolminus1 Kminus1) nuclear repulsion energy (Hartrees) and dipolemoment (Debye) for OAA and AA

Parameters B3LYP6-31Glowastlowast

OAA AAZero-point energy 9306056 9314966

Rotational constants139942 344405114384 056752063193 048875

EntropyTotal 99243 97126Translational 40967 40967Rotational 30142 30199Vibrational 28134 25960Dipole moment 24181 35822Nuclear repulsion energy 592968293 573992628

proton (1 surrounded by less electron density) is observed tobe more downfield than the signals for protons that are notdeshielded by electronegative atoms [40] The chemical shiftvalue of C7 (OAA and AA) has bigger value than the othercarbons due to the electronegative property of oxygen atom

The linear correlations between calculated and experi-mental data of 13CNMRand 1HNMRspectra are determinedas 09 and 10 for OAA and 09 and 09 for AA respectivelyThere is an excellent linear relationship between experimentaland computed results which are shown in Figures 8 and 9

6 Thermodynamic Properties

Several calculated thermodynamical parameters are pre-sented in Table 14 for OAA andAA respectively Scale factorshave been recommended [42] for an accurate prediction in

Journal of Spectroscopy 17

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 180

170

160

150

140

130

120

110110

120 130 140 150 160 170

(a)

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

11

10

9

8

7

7 8 9 10 11 12 13

(b)

Figure 9 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for Anisic acid

determining the zero-point vibration energies (ZPVE) andthe entropy 119878vib(119879) The total energies and the change inthe total entropy at room temperature using B3LYP6-31Glowastlowastmethod are presented

7 Conclusion

Attempts have been made in the present work for the molec-ular parameters and frequency assignments for the com-pounds OAA and AA from the FTIR and FT-Raman spectraThe equilibrium geometries and harmonic and anharmonicfrequencies for the title compounds were determined andanalyzed at DFT level of theory utilizing 6-31Glowastlowast basis setThe assignments of most of the fundamentals of the titlecompounds provided in this work are quite comparableThe excellent agreement of the calculated and observedvibrational spectra reveals the advantages of a smaller basisset for quantum chemical calculations HOMO and LUMOenergy gap explains the eventual charge transfer interactionstaking place within the molecule The experimental andtheoretical investigation of the title compounds have beenperformed successfully by using 1H and 13C NMR Thevarious modes of vibrations were unambiguously assignedon the basis of the result of the PED output obtainedfrom normal coordinate analysis These studies confirm thepresence of COOH and OCH

3group Dimeric molecules are

held together by hydrogen bridges between carbonyl groupsThe obtained data and simulations both show the way to thecharacterization of the molecules and help in spectra studiesin the future

References

[1] GMelentyeva and LAntonovaPharmaceutical ChemistryMirPublishers Moscow Russia 1988

[2] ldquoo-Anisic acid(579-75-9) catalog of chemical suppliersrdquo httpwwwchemexpercomchemicalssuppliercas579-75-9html

[3] B A Hess Jr L J Schaad P Carsky and R Zaharaduick ldquoAbinitio calculations of vibrational spectra and their use in theidentification of unusual moleculesrdquo Chemical Reviews vol 86no 4 pp 709ndash730 1986

[4] P Pulay X Zhou and G Forgarasi in Recent Experimental andComputational Advances in Molecular Spectroscopy R Faustoand R Fransto Eds vol 406 ofNATOASI Series p 99 KluwerDordrecht Netherlands 1993

[5] P Pulay G Fogarasi G Pongor J E Boggs and A VarghaldquoCombination of theoretical ab initio and experimental infor-mation to obtain reliable harmonic force constants ScaledQuantum Mechanical (SQM) force fields for glyoxal acroleinbutadiene formaldehyde and ethylenerdquo Journal of the Ameri-can Chemical Society vol 105 no 24 pp 7037ndash7047 1983

[6] C E Blom and C Altona ldquoApplication of self-consistent-fieldab initio calculations to organic moleculesrdquo Molecular Physicsvol 31 no 5 pp 1377ndash1391 1976

[7] G Fogarasi and P Pulay in Vibrational Spectra and Structure JR Durig Ed vol 14 Elsevier Amsterdam Netherlands 1985

[8] G Fogarasi ldquoRecent developments in the method of SQM forcefields with application to 1-methyladeninerdquo Spectrochimica ActaA vol 53 no 8 pp 1211ndash1224 1997

[9] G R deMare N Yu Panchenko andW Ch Bock ldquoAnMP26-31GlowastMP26-31Glowast vibrational analysis of s-trans- and s-cis-acryloyl fluoride CH2=CH-CF=Ordquo The Journal of PhysicalChemistry vol 98 no 5 pp 1416ndash1420 1994

[10] G Pongor P Pulay G Fogarasi and J E Boggs ldquoTheoreticalprediction of vibrational spectra 1 The in-plane force fieldand vibrational spectra of pyridinerdquo Journal of the AmericanChemical Society vol 106 no 10 pp 2765ndash2769 1984

[11] Y Yamakitu and M Tasumi ldquoVibrational analyses of p-benzoquinodimethane and p-benzoquinone based on ab initioHartree-Fock and second-order Moller-Plesset calculationsrdquoThe Journal of Physical Chemistry vol 99 no 21 pp 8524ndash85341995

18 Journal of Spectroscopy

[12] M Karabacak A Coruh and M Kurt ldquoFT-IR FT-RamanNMR spectra and molecular structure investigation of 23-dibromo-N-methylmaleimide a combined experimental andtheoretical studyrdquo Journal of Molecular Structure vol 892 no1ndash3 pp 125ndash131 2008

[13] M S Masoud M K Awad M A Shaker and M M T El-Tahawy ldquoThe role of structural chemistry in the inhibitiveperformance of some aminopyrimidines on the corrosion ofsteelrdquo Corrosion Science vol 52 no 7 pp 2387ndash2396 2010

[14] M J Frisch G W Trucks H B Schlegel et al Gaussian 03Revision B4 Gaussian Inc Pittsburgh Pa USA 2003

[15] P L Polavarapu ldquoAb initio vibrational Raman and Ramanoptical activity spectrardquo Journal of Physical Chemistry vol 94no 21 pp 8106ndash8112 1990

[16] G Keresztury S Holly J Varga G Besenyei A Wang andJ R Durig ldquoVibrational spectra of monothiocarbamates-IIIR and Raman spectra vibrational assignment conforma-tional analysis and ab initio calculations of S-methyl-NN-dimethylthiocarbamaterdquo Spectrochimica Acta A vol 49 no 13-14 pp 2007ndash2017 1993

[17] G Keresztury ldquoRaman spectroscopy theoryrdquo in Handbook ofVibrational Spectroscopy J M Chalmers and P R Griffths Edsvol 1 p 71 John Wiley and Sons 2002

[18] R G Parr R A Donnelly M Levy and W E Palke ldquoElec-tronegativity the density functional viewpointrdquo The Journal ofChemical Physics vol 68 no 8 pp 3801ndash3807 1977

[19] R G Parr and R G Pearson ldquoAbsolute hardness companionparameter to absolute electronegativityrdquo Journal of theAmericanChemical Society vol 105 no 26 pp 7512ndash7516 1983

[20] R G Pearson ldquoAbsolute electronegativity and hardness appli-cation to inorganic chemistryrdquo Inorganic Chemistry vol 27 no4 pp 734ndash740 1988

[21] P Geerlings F De Proft and W Langenaeker ldquoConceptualdensity functional theoryrdquo Chemical Reviews vol 103 no 5 pp1793ndash1873 2003

[22] R Ditchfield ldquoMolecular orbital theory of magnetic shieldingand magnetic susceptibilityrdquo Journal of Physical Chemistry vol56 no 11 article 5688 4 pages 1972

[23] KWolinski J F Hilton and P Pulay ldquoEfficient implementationof the gauge-independent atomic orbital method for NMRchemical shift calculationsrdquo Journal of the American ChemicalSociety vol 112 no 23 pp 8251ndash8260 1990

[24] M Kurt M Yurdakul and S Yurdakul ldquoMolecular structureand vibrational spectra of 3-chloro-4-methyl aniline by densityfunctional theory and ab initio Hartree-Fock calculationsrdquoJournal of Molecular Structure vol 711 no 1ndash3 pp 25ndash32 2004

[25] D Steele and D H Whiffen ldquoThe vibration frequencies ofpentafluorobenzenerdquo Spectrochimica Acta vol 16 no 3 pp368ndash375 1960

[26] D N Sathyanarayanan Vibrational Spectroscopy Theory andApplication New Age International publishers New DelhiIndia 1996

[27] L D S YadavOrganic Spectroscopy Springer NewDelhi India2004

[28] J Mohan Organic Spectroscopy Principles and ApplicationsNarosa Publishing House New Delhi 2nd edition 2009

[29] R M Silverstein G C Bassler and T C Morrill SpectrometricIdentification of Organic Compounds John Wiley amp Sons NewYork NY USA 1981

[30] G Socrates Infrared Characteristic Group Frequencies WileyNew York NY USA 1980

[31] R S Mulliken ldquoElectronic population analysis on LCAO-MOmolecular wave functionsrdquoThe Journal of Chemical Physics vol23 no 10 pp 1833ndash1840 1955

[32] K Fukuli T Yonezawa and H Shingu ldquoA molecular orbitaltheory of reactivity in aromatic hydrocarbonsrdquo Journal ofPhysical Chemistry vol 20 no 4 article 722 4 pages 1952

[33] C H Choi and M Kertesz ldquoConformational information fromvibrational spectra of styrene trans-stilbene and cis-stilbenerdquoJournal of Physical Chemistry A vol 101 no 20 pp 3823ndash38311997

[34] S Gunasekaran R Arun Balaji S Kumaresan G Anandand S Srinivasan ldquoExperimental and theoretical investigationsof spectroscopic properties of N-acetyl-5-methoxytryptaminerdquoCanadian Journal of Analytical Sciences and Spectroscopy vol53 no 4 pp 149ndash162 2008

[35] P Hohenberg and W Kohn ldquoInhomogeneous electron gasrdquoPhysical Review vol 136 no 3 pp B864ndashB871 1964

[36] R G Pearson ldquoAbsolute electronegativity and absolute hard-ness of Lewis acids and basesrdquo Journal of the American ChemicalSociety vol 107 no 24 pp 6801ndash6806 1985

[37] D Avci Y Atalay M Sekerci and M Dincer ldquoMolecular struc-ture and vibrational and chemical shift assignments of 3-(2-Hydroxyphenyl)-4-phenyl-1H-124-triazole-5-(4H)-thione byDFT and ab initio HF calculationsrdquo Spectrochimica Acta A vol73 no 1 pp 212ndash217 2009

[38] H O Kalinowski S Berger and S Braun Carbon13 NMRSpectroscopy John Wiley amp Sons Chichester UK 1988

[39] K Pihlaja and E Kleinpeter Carbon-13 NMR Chemical Shiftsin Structural and Sterochemical Analysis VCH PublishersDeerfield Beach Fla USA 1994

[40] P S Kalsi Spectroscopy of Organic Compounds New AgeInternational 2004

[41] A F Parsons Keynotes in Organic Chemistry Blackwell Pub-lishing Oxford UK 2003

[42] M A Palafox ldquoScaling factors for the prediction of vibrationalspectra I benzenemoleculerdquo International Journal of QuantumChemistry vol 77 no 3 pp 661ndash684 2000

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

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Carbohydrate Chemistry

International Journal of

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Journal of

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Advances in

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Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

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The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

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Theoretical ChemistryJournal of

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Analytical ChemistryInternational Journal of

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Journal of

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Quantum Chemistry

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ElectrochemistryInternational Journal of

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CatalystsJournal of

Page 4: Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. · Molecular Structure, NMR, HOMO, LUMO, ... ects of carbonyl and methyl substitutions

4 Journal of Spectroscopy

Table 2 Definition of internal coordinates of O-Anisic acid (OAA)

No (i) Symbol Type DefinitionStretching

1ndash4 119903119894

CndashH C3ndashH16 C4ndashH17 C5ndashH18 C6ndashH195ndash11 119903

119894CndashC C1ndashC2 C2ndashC3 C3ndashC4 C4ndashC5 C5ndashC6 C6ndashC1 C1ndashC7

12ndash14 119903119894

CndashO C7ndashO8 C7ndashO9 C2ndashO1115 119903

119894OndashC O11ndashC12

16 119903119894

OndashH O9ndashH1017ndash19 119903

119894CndashH(methyl) C12ndashH13 C12ndashH14 C12ndashH15

Bending20-21 120573

119894CndashCndashC C2ndashC1ndashC7 C6ndashC1ndashC7

22ndash29 120573119894

CndashCndashH C2ndashC3ndashH16 C4ndashC3ndashH16 C3ndashC4ndashH17 C5ndashC4ndashH17C4ndashC5ndashH18 C6ndashC5ndashH18 C5ndashC6ndashH19 C1ndashC6ndashH19

30ndash32 120573119894

CndashCndashH(methyl) O11ndashC12ndashH13 O11ndashC12ndashH14 O11ndashC12ndashH1533ndash35 120573

119894HndashCndashH H13ndashC12ndashH14 H13ndashC12ndashH15 H14ndashC12ndashH15

36-37 120573119894

CndashCndashO C1ndashC7ndashO8 C1ndashC7ndashO938 120573

119894CndashOndashH C7ndashO9ndashH10

39-40 120573119894

CndashCndashO C1ndashC2ndashO11 C3ndashC2ndashO1141 120573

119894CndashOndashC C2ndashO11ndashC12

42ndash47 120573119894

CndashCndashC (Ring) C1ndashC2ndashC3 C2ndashC3ndashC4 C3ndashC4ndashC5 C4ndashC5ndashC6C5ndashC6ndashC1 C6ndashC1ndashC2

Out-of-plane bending

48ndash51 120596119894

CndashH H16ndashC3ndashC2ndashC4 H17ndashC4ndashC5ndashC3 H18ndashC5ndashC6ndashC4H19ndashC6ndashC1ndashC5

52 120596119894

CndashC C7ndashC1ndashC6ndashC253 120596

119894CndashO O11ndashC2ndashC1ndashC3

Torsion54-55 120591

119894CndashO C2ndashC1ndashC7ndashO8 C2ndashC1ndashC7ndashO9

56-57 120591119894

CndashOndashC C1ndashC2ndashO11ndashC12 C3ndashC2ndashO11ndashC12

58ndash60 120591119894

CndashH(methyl) C2ndashO11ndashC12ndashH13 C2ndashO11ndashC12ndashH14C2ndashO11ndashC12ndashH15

61 120591119894

OndashH C1ndashC7ndashO9ndashH10

62ndash67 120591119894

tring C1ndashC2ndashC3ndashC4 C2ndashC3ndashC4ndashC5 C3ndashC4ndashC5ndashC6C4ndashC5ndashC6ndashC1 C5ndashC6ndashC1ndashC2 C6ndashC1ndashC2ndashC3

For numbering of atoms refer to Figure 1(a)

observed in the IR region are very sharp broad and lessintense The title compounds belong to 119862

119904point group The

19 atoms present in OAA and AA molecular structure eachhas 51 fundamental modes of vibrations For molecules of119862119904symmetry group theory analysis indicates that the 51

fundamental vibrations are distributed among the symmetryspecies as

Γvib = 35A1015840 (in-plane) + 16A10158401015840 (out-of-plane) (5)

for bothOAA andAA respectively From the structural pointof view of the molecules OAA and AA have 18 stretchingvibrations 33 bending vibrations respectively All the vibra-tions were found to be active both in Raman scattering andinfrared absorption

The observed and calculated wave numbers calculatedIR and Raman intensities and normal mode descriptions(characterized by potential energy distribution (PED)) for

the fundamental vibrations of OAA and AA are depictedin Tables 7 and 8 For visual comparison the observed andsimulated FTIR and FT-Raman spectra of the compoundsare presented in Figures 2 3 4 and 5 which help to under-stand the observed spectral features The root mean square(RMS) error of the observed and calculated wavenumbers(unscaledB3LYP6-31Glowastlowast) of OAA and AA was found to be843 cmminus1 and 891 cmminus1 respectively This is understandablesince the mechanical force fields usually differ appreciablyfrom the observed ones This is partly due to the neglectof anharmonicity and partly due to the approximate natureof the quantum mechanical methods However for reliableinformation on the vibrational properties the use of selectivescaling is necessary The calculated wavenumbers are scaledusing the set of transferable scale factors recommended byFogarasi and Pulay [7]The SQM treatment has resulted in anRMS deviation of 967 cmminus1 and 113 cmminus1 for OAA and AA

Journal of Spectroscopy 5

Table 3 Definition of internal coordinates of Anisic acid (AA)

No (i) Symbol Type DefinitionStretching

1ndash4 119903119894

CndashH C2ndashH11 C3ndashH12 C5ndashH18 C6ndashH195ndash10 119903

119894CndashC C1ndashC2 C2ndashC3 C3ndashC4 C4ndashC5 C5ndashC6C6ndashC1

11 119903119894

CndashCfn C1ndashC712ndash14 119903

119894CndashO C7ndashO8 C7ndashO9 C4ndashO13

15 119903119894

OndashC O13ndashC1416 119903

119894OndashH O9ndashH10

17ndash19 119903119894

CndashH(methyl) C14ndashH15 C14ndashH16 C14ndashH17Bending

20-21 120573119894

CndashC C2ndashC1ndashC7 C6ndashC1ndashC7

22ndash29 120573119894

CndashCndashHC1ndashC2ndashH11 C3ndashC2ndashH11C2ndashC3ndashH12 C4ndashC3ndashH12C4ndashC5ndashH18 C6ndashC5ndashH18C5ndashC6ndashH19 C1ndashC6ndashH19

30ndash35 120573119894

CndashCndashH(methyl) O13ndashC14ndashH15 O13ndashC14ndashH16 O13ndashC14ndashH17H17ndashC14ndashH15 H15ndashC14ndashH16 H17ndashC14ndashH16

36-37 120573119894

CndashCndashO C3ndashC4ndashO13 C5ndashC4ndashO1338 120573

119894CndashOndashH C7ndashO9ndashH10

39-40 120573119894

CndashCndashO C1ndashC7ndashO8 C1ndashC7ndashO941 120573

119894CndashOndashC C4ndashO13ndashC14

42ndash47 120573119894

CndashCndashC (Ring) C1ndashC2ndashC3 C2ndashC3ndashC4 C3ndashC4ndashC5 C4ndashC5ndashC6C5ndashC6ndashC1 C6ndashC1ndashC2

Out-of-plane bending

48ndash51 120596119894

CndashH H11ndashC2ndashC3ndashC1 H12ndashC3ndashC4ndashC2 H18ndashC5ndashC6ndashC4H19ndashC6ndashC1ndashC5

52 120596119894

CndashC C7ndashC1ndashC6ndashC253 120596

119894CndashO O13ndashC4ndashC5ndashC3

Torsion54ndash55 120591

119894CndashO C2ndashC1ndashC7ndashO8 C2ndashC1ndashC7ndashO9

56-57 120591119894

CndashOndashC C3ndashC4ndashO13ndashC14 C5ndashC4ndashO13ndashC14

58ndash60 120591119894

CndashH(methyl) C4ndashO13ndashC14ndashH15 C4ndashO13ndashC14ndashH16C4ndashO13ndashC14ndashH16

61 120591119894

OndashH C1ndashC7ndashO9ndashH10

62ndash67 120591119894

tring C1ndashC2ndashC3ndashC4 C2ndashC3ndashC4ndashC5 C3ndashC4ndashC5ndashC6C4ndashC5ndashC6ndashC1 C5ndashC6ndashC1ndashC2 C6ndashC1ndashC2ndashC3

For numbering of atoms refer to Figure 1(b)

respectively The RMS values of wavenumbers were obtainedin this study using the following expression

RMS = radic1

119899 minus 1

119899

sum

119894

(120592calc119894

minus 120592exp119894

)2

(6)

431 CH Vibrations Aromatic compounds commonly ex-hibit multiple weak bands in the region 3100ndash3000 cmminus1 [26]due to aromatic CndashH stretching vibrations According to thePED analysis the bands observed in experimental spectrumat 3098 3083 3069 3020 cmminus1 in OAA and 3085 3034 3029and 3002 cmminus1 inAAwere assigned to stretching vibrations of

CndashH bond According to these studies all the CndashH stretchingvibrations are not mixed with other types of vibrations

The CndashH in-plane deformation vibrations are assigned inthe region 1100ndash1400 cmminus1 [27] The in-plane deformationsof CndashH groups are noticed on PED analysis at 1494 14391288 and 1182 in OAA and 1518 1301 1181 and 1131 cmminus1 inAAThere is slight increase in the CndashH in-plane deformationfrequency because of steric effect in OAA and inductive effect(+I) in AAThese values of calculated frequencies are typicaland in very good agreement with experimental data The in-plane CndashH deformation vibrations are slightly mixed in bothOAA and AA

The CndashH out-of-plane deformation vibrations areassigned in the region 900ndash600 cmminus1 [26] The bands

6 Journal of Spectroscopy

Table 4 Definition of natural internal coordinates of O-Anisic acid (OAA)

No (i) Symbola Definitionb

1ndash4 CndashH stretch 1199031 1199032 1199033 1199034

5ndash11 CndashC stretch 1199035 1199036 1199037 1199038 1199039 11990310 11990311

12ndash14 CndashO stretch 11990312 11990313 11990314

15 OndashC stretch 11990315

16 OndashH stretch 11990316

17 CH3 ss (11990317+ 11990318+ 11990319) radic3

18 CH3 ips (211990317minus 11990318minus 11990319) radic6

19 CH3 ops (11990318minus 11990319) radic2

20 bCndashCndashC (12057320minus 12057321) radic2

21ndash24 bCndashCndashH (12057322minus 12057323) radic2 (120573

24minus 12057325) radic2 (120573

26minus 12057327) radic2 (120573

28minus 12057329) radic2

25 CH3 sb (minus12057330minus 12057331minus 12057332+ 12057333+ 12057334+ 12057335) radic6

26 CH3 ipb (minus12057333minus 12057334minus 212057335)radic6

27 CH3 opb (12057333minus 12057334) radic2

28 CH3 ipr (212057330minus 12057331minus 12057332)radic6

29 CH3 opr (12057331minus 12057332)radic2

30 bCndashCndashO (12057336minus 12057337) radic2

31 bCndashOndashH 12057338

32-33 bCndashCndashO 12057339 12057340

34 bCndashOndashC 12057341

35 Rtrigd (12057342minus 12057343+ 12057344minus 12057345+ 12057346minus 12057347) radic6

36 Rsymd (minus12057342minus 12057343+ 12057344minus 12057345minus 12057346+ 212057347)radic12

37 Rasymd (12057342minus 12057343+ 12057345minus 12057346) 2

38ndash41 120596CndashH 12059648 12059649 12059650 12059651

42 120596CndashC 12059652

43 120596CndashO 12059653

44-45 tCndashO 12059154 12059155

46 tCndashOndashC 12 (12059156+ 12059157)

47 tCH3 13 (12059158+ 12059159+ 12059160)

48 tOndashH 12059161

49 Ttrigd (12059162minus 12059163+ 12059164minus 12059165+ 12059166minus 12059167) radic6

50 Tsymd (12059162minus 12059163+ 12059165+ 12059166) 2

51 Tasymd (minus12059162+ 212059163minus 12059164minus 12059165+ 12059166minus 12059167) radic12

aThese symbols are used for description of the normal modes by PED in Table 7bThe internal coordinates used here are defined in Table 2

appearing at 960 937 865 and 755 cmminus1 in OAA and929 854 846 and 774 cmminus1 in AA were assigned toout-of-plane deformation type of vibration (120596) of CndashHgroups There is slight increase in the CndashH out-of-planedeformation frequency because of strong intermolecularhydrogen bonding in OAA In these bands the pronouncedparticipation of other types of vibrations is observed Theseare also supported by the literature

432 Carboxylic Acid Vibrations Due to the presence ofstrong intermolecular hydrogen bonding the FT-IR spectraexhibits spectra exhibit a broad band due to the OndashHstretching vibrations and a strong banddue toC=Ostretchingvibrations The carboxylic acid dimers display a very broadand intenseOndashH stretching absorption in the region of 3300ndash2500 cmminus1 [28] The title molecules both exhibit intermolec-ular hydrogen bonding In our case the bands at 3390 cmminus1

in OAA and 3435 cmminus1 in AA are assigned as OndashH stretchingvibrations There is a slight increase in the OndashH frequencybecause of steric effect in OAA and +I effect in AA The OndashH out-of-plane bending vibration occurs near the region of920 cmminus1 [27] The bands appearing at 595 cmminus1 in OAA and505 cmminus1 in AA are assigned to OndashH out-of-plane bendingvibrationThe OndashH out-of-plane bending vibrations in OAAand AA decrease due to intermolecular hydrogen bonding

The carbonyl stretching vibrations are expected in theregion 1720 cmminus1ndash1680 cmminus1 [28] The IR band at 1670 cmminus1in OAA and FT-Raman band at 1688 cmminus1 in AA are assignedasC=O stretching vibrationsTheCndashObond appears stronglyin the 1320ndash1210 cmminus1 region [29] The bands observed at1049 and 795 cmminus1 in OAA and 1267 and 1100 cmminus1 in AAare assigned to CndashO stretching mode The CndashO stretchingvibrational frequency is lower than general range In thecase of carboxylic acid dimers like OAA and AA the OH

Journal of Spectroscopy 7

Table 5 Definition of natural internal coordinates of Anisic acid (AA)

No (i) Symbola Definitionb

1ndash4 CndashH stretch 1199031 1199032 1199033 1199034

5ndash10 CndashC stretch 1199035 1199036 1199037 1199038 1199039 11990310

11 CndashCfn stretch 11990311

12ndash14 CndashO stretch 11990312 11990313 11990314

15 OndashC stretch 11990315

16 OndashH stretch 11990316

17 CH3 ss (11990317+ 11990318+ 11990319) radic3

18 CH3 ips (211990317minus 11990318minus 11990319) radic6

19 CH3 ops (11990318minus 11990319) radic2

20 bCndashCndashC (12057320minus 12057321) radic2

21ndash24 bCndashCndashH (12057322minus 12057323) radic2 (120573

24minus 12057325) radic2 (120573

26minus 12057327) radic2 (120573

28minus 12057329) radic2

25 CH3 sb (minus12057330minus 12057331minus 12057332+ 12057333+ 12057334+ 12057335) radic6

26 CH3 ipb (minus12057333minus 12057334minus 212057335)radic6

27 CH3 opb (12057333minus 12057334) radic2

28 CH3 ipr (212057330minus 12057331minus 12057332) radic6

29 CH3 opr (12057331minus 12057332) radic2

30 bCndashCndashO (12057335minus 12057336) radic2

31 bCndashOndashH 12057338

32-33 bCndashCndashO 12057339 12057340

34 bCndashOndashC 12057341

35 Rtrigd (12057342minus 12057343+ 12057344minus 12057345+ 12057346minus 12057347) radic6

36 Rsymd (minus12057342minus 12057343+ 12057344minus 12057345minus 12057346+ 212057347) radic12

37 Rasymd (12057342minus 12057343+ 12057345minus 12057346) 2

38ndash41 120596CndashH 12059648 12059649 12059650 12059651

42 120596CndashC 12059652

43 120596CndashO 12059653

44-45 tCndashO 12059154 12059155

46 tCndashOndashC 12 (12059156+ 12059157)

47 tCH3 13 (12059158+ 12059159+ 12059160)

48 tOndashH 12059161

49 Ttrigd (12059162minus 12059163+ 12059164minus 12059165+ 12059166minus 12059167) radic6

50 Tsymd (12059162minus 12059163+ 12059165+ 12059166)2

51 Tasymd (minus12059162+ 212059163minus 12059164minus 12059165+ 12059166minus 12059167) radic12

aThese symbols are used for description of the normal modes by PED in Table 8bThe internal coordinates used here are defined in Table 3

in-plane bending and CndashO stretching bands involve someinteraction between them they are referred to as coupledOH in-plane bending and CndashO stretching vibrations [26]The CndashO bending vibration occurs in the region of 580ndash340 cmminus1 [30] The band observed at 380 cmminus1 in OAA and440 cmminus1 in AA are assigned to CndashO bending mode Thepresent assignments agree very well with the values availablein the literature

433 Methyl Group Vibrations The title molecules OAAand AA under consideration possess one CH

3group For

the assignments of CH3group one can expect that 9 fun-

damentals can be associated with each CH3group namely

the symmetrical stretching (CH3symmetric stretch) and

asymmetrical stretching (CH3asymmetric stretch) in-plane

stretching modes (ie in-plane hydrogen stretching modes)

and the symmetrical (CH3symmetric deform) and asym-

metrical (CH3asymmetric deform) deformation modes in-

plane rocking (CH3ipr) out-of-plane rocking (CH

3opr) and

twisting (tCH3) bending modes

For the methyl group compounds the asymmetricstretching mode appeared in the range 2965ndash3005 cmminus1 andthe symmetric stretching mode appeared in the range of2815ndash2860 cmminus1 [30] The FT-Raman band at 2983 cmminus1 forOAA and IR band at 2941 cmminus1 for AA are symmetricstretching The symmetric stretching vibrational frequencyis higher in OAA and AA due to steric effect and +I effectThe asymmetric methyl stretching band appeared at 30033018 cmminus1 in OAA and 2990 2956 cmminus1 in AA respectivelyThe asymmetric deformation mode appeared in the range1445ndash1485 cmminus1 and symmetric deformation mode appearedin the range of 1420ndash1460 cmminus1 [30] The IR band at 1466

8 Journal of Spectroscopy

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 2 FTIR spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Table 6 Diagonal force constants (102 Nmminus1) of O-Anisic acid(OAA) and Anisic acid (AA)

Descriptiona Force constantsb

OAA AAC1ndashC2 621 630C2ndashC3 633 696C3ndashC4 677 626C4ndashC5 675 628C5ndashC6 682 663C6ndashC1 644 648C1ndashC7 465 222C7ndashO8 532 522C7ndashO9 1030 1128C2ndashO11(C4ndashO13) 449 576O11ndashC12(O13ndashC14) 413 499O9ndashH10 644 661C12ndashH13(C14ndashH15) 498 508C12ndashH14(C14ndashH16) 526 470C12ndashH15(C14ndashH17) 498 507C3ndashH16(C2ndashH11) 514 498C4ndashH17(C3ndashH12) 501 496C5ndashH18 505 500C6ndashH19 532 522aThe atoms indicated in the parenthesis belong to AAbStretching force constants are given in mdyn A

minus1

For numbering of atoms refer to Figures 1(a) and 1(b)

and 1435 cmminus1 in OAA and 1468 and 1461 cmminus1 in AA areassigned as asymmetric deformation vibrations The IR bandat 1411 cmminus1 for OAA and 1429 cmminus1 for AA are symmet-ric deformation mode The CH

3deformation absorption

occurs at 1466 cmminus1 and 1429 cmminus1 this vibration is knownas umbrella mode that overlaps with CC ring stretchingvibrations for the title compounds These are also supportedby the literature

The tensional modes appeared in the range of 265ndash185 cmminus1 [30] This modes are strongly coupled with other

vibrations that are observed at 280 cmminus1 inOAAand 165 cmminus1in AAwhich are in agreement with the calculated results also

434 Ring Vibrations The ring CndashC stretching vibrationsoccur in the region of 1600ndash1400 cmminus1 [29]The bands appearat 1600 1579 1312 1184 1153 1062 and 698 cmminus1 in OAAand 1608 1580 1416 1307 1107 1028 and 825 cmminus1 in AAwere assigned to CndashC stretching vibrations The shift in thefrequency of CndashC vibrations towards lower wave numbermay be due to the COOH and OCH

3groups Many ring

modes are affected by the substitutions in the aromatic ringThe bands at 180 cmminus1 and 285 cmminus1 for OAA and AA wereassigned to CndashC bending vibrationsThe out-of-plane and in-plane deformations of the phenyl ring are observed below1000 cmminus1 and these modes are sensitive by the additionof functional groups The out-of-plane bending vibrationswere observed at 170 cmminus1 and 111 cmminus1 for OAA and AASmall changes in the wavenumbers were observed due tothe presence of +I effect in AA and steric effect in OAAThe computed wavenumbers are in good agreement withexperimental data

5 Electronic Properties

Atomic charges on the various atoms of OAA and AAobtained by Mulliken population analysis [31] are given inTable 9 From the listed atomic charge values the oxygen[O8 O9] and O11 in OAA and O13 in AA atoms had a largenegative charge and behaved as electron acceptor It was alsoobserved that there is a large accumulation of charge on O11inOAAO13 in AAmoleculesTherefore C7 andO11 inOAAand C7 and O13 in AA had a greater ionic character

Natural bond orbital analysis provides an efficientmethod for studying steric effect and intermolecular bondingand interaction among bonds and also provides a convenientbasis for investigating charge transfer or conjugative interac-tion in molecular systems Natural charge analysis is givenin Table 10 for the title compounds The results show thatsubstitution of COOH and CH

3group in OAA and AA leads

to a redistribution of electron density The C7 atom in OAAand AA is more positive charge (+08091 +08139) In the

Journal of Spectroscopy 9Ta

ble7Detailedassig

nmento

ffun

damentalvibratio

nsof

O-Anisic

acid

(OAA)b

yno

rmalmod

eanalysis

basedon

SQM

forcefi

eldcalculations

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

1A1015840

3390

mdash3771

3390

72652

155385

120592OH(100)

2A1015840

mdash3098

3273

3098

1612

499564

120592CH

(99)

3A1015840

mdash3083

3233

3083

1700

135114

120592CH

(99)

4A1015840

3069

mdash3207

3069

10674

70382

120592CH

(99)

5A1015840

mdash3020

3186

3024

17253

1372

01120592CH

(99)

6A1015840

3018

mdash3157

3018

38987

58202

120592CH

3(99)

7A10158401015840

3003

mdash3085

3003

5946

78409

120592CH

3(99)

8A1015840

mdash2983

3020

2983

52626

120657

120592CH

3(99)

9A1015840

1670

mdash1822

1670

358567

54628

120592CO

(53)120592CC

(14)bC

CO(14

)bC

OH(12)

10A1015840

1600

mdash1656

1600

15061

16343

120592CC

(60)bCH

(20)R

asym

d(10)

11A1015840

1579

mdash1630

1579

61364

48880

120592CC

(69)bCH

(19)

12A1015840

1494

mdash1539

1494

58214

10686

bCH(48)120592CC

(37)

13A1015840

1466

mdash1513

1466

6534

6058

bCH

3(43)bCH

(25)120592CC

(16)

14A1015840

mdash1439

1506

1439

22318

5639

bCH(39)bCH

3(37)120592CC

(17)

15A10158401015840

1435

mdash1500

1435

3652

510814

bCH

3(88)

16A1015840

1411

mdash1475

1411

11849

19713

bCH

3(74)

17A1015840

1382

1367

4497

1268

bCOH(35)120592CO

(32)bCC

O(13)120592CC

(11)

18A1015840

mdash1312

1350

1312

2182

8877

120592CC

(67)

19A1015840

1288

mdash1320

1288

6319

416

48bC

H(33)R

trigd(20)120592CO

(13)120592CC

(12)

20A1015840

mdash1287

1302

1287

19694

044

9Rtrig

d(26)120592CC

(25)bCH

(20)120592CO

(12)

21A1015840

mdash1184

1210

1184

228252

32980

120592CC

(31)bCH

(19)bC

H3(17)120592CO

(17)

22A1015840

1182

mdash1201

1182

162989

2713

6bC

H(42)120592CC

(34)bCH

3(10)

23A1015840

1170

mdash119

3117

015

764576

bCH

3(57)bCH

(24)

24A1015840

mdash117

3117

31153

7419

1097

120592CC

(31)bCH

(29)bCH

3(25)

25A1015840

1140

mdash1168

1140

0662

4253

bCH

3(96)

26A1015840

1049

mdash1087

1050

1073

0478

09120592CO

(29)120592CC

(27)R

trigd(12)

27A1015840

-1062

1077

1060

104848

21650

120592CC

(41)120592CO

(22)bCH

(12)

28A10158401015840

960

-1060

960

060

90057

120596CH

(91)

29A1015840

mdash974

989

974

2078

710836

120592OC(62)120592CC

(12)120592CO

(11)

30A10158401015840

937

mdash965

935

1244

1294

120596CH

(91)

31A10158401015840

mdash865

869

865

3148

3432

120596CH

(64)ttrigd(19)

32A1015840

mdash795

830

795

12200

4238

120592CO

(29)R

symd(21)120592OC(15)120592CC

(15)

33A10158401015840

761

mdash795

761

1002

0207

tCO(32)ttrigd(28)120596

CH(23)120596

CC(11)

34A10158401015840

mdash755

770

755

41473

1456

120596CH

(51)ttrigd(27)120596

CO(14

)35

A10158401015840

695

mdash747

698

64512

0469

ttrigd(52)120596

CH(23)tCO

(15)

36A1015840

mdash698

712

695

10016

17946

120592CC

(33)120592CO

(23)bCC

O(21)

37A1015840

mdash602

639

602

13503

2683

Rasymd(36)bCC

O(15)

120592CC

(12)R

symd(11)

38A10158401015840

mdash595

594

595

74804

8168

tOH(79)

39A1015840

mdash565

588

565

21902

1740

bCCO

(28)120592CC

(17)bCO

(15)R

symd(14

)bC

CO(13)

10 Journal of Spectroscopy

Table7Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

540

mdash548

540

5598

4848

bCCO

(40)bCC

(16)120592CC

(13)R

asym

d(10)

41A10158401015840

480

mdash540

480

0946

0860

120596CO

(40)120596

CH(16)ttrigd(14

)tsy

m(14

)42

A10158401015840

mdash40

1435

401

3585

0792

tsym

(14)120596CC

(15)

43A1015840

mdash380

388

380

4805

4133

bCO(64)bCC

O(16)

44A1015840

mdash303

383

303

1180

4980

Rsym

d(59)bCO

C(17)120592CC

(15)

45A10158401015840

mdash280

283

280

0092

0016

tCH

3(79)

46A1015840

mdash240

280

240

0927

0935

bCOC(40)bCC

(30)bCC

O(18)

47A10158401015840

mdash180

229

180

0018

2096

120596CC

(30)tCO

(20)tsym

(18)

tasym

(11)120596CH

(10)

48A1015840

mdash170

190

170

3092

0715

bCC(42)bCO

C(29)bCO

(12)

49A10158401015840

mdash115

119115

4502

0508

tCOC(47)tsym

(15)tCH

3(12)

50A10158401015840

mdash110

9696

0922

3779

tsym

(35)tCO

(25)

tCOC(21)tCH

3(13)

51A10158401015840

mdashmdash

1730

1260

0037

tCO(99)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 11Ta

ble8Detailedassig

nmento

ffun

damentalvibratio

nsof

Anisic

acid

(AA)b

yno

rmalmod

eanalysis

basedon

SQM

forcefi

eldcalculations

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

1A1015840

3435

mdash3768

3435

7952

3164209

120592OH(100)

2A1015840

mdash3085

3232

3085

21438

120058

120592CH

(89)

3A1015840

mdash3034

3224

3034

7547

126718

120592CH

(99)

4A1015840

3029

mdash3218

3029

3520

99229

120592CH

(99)

5A1015840

3002

mdash3209

3002

5141

52552

120592CH

(99)

6A1015840

2990

mdash3155

2990

2423

53071

120592CH

ops(99)

7A10158401015840

2956

mdash3087

2956

45319

94074

120592CH

ips(51)120592CH

ss(36)120592CH

ops(12)

8A1015840

2941

mdash3022

2941

42847

91231

120592CH

ss(56)120592CH

ips(44

)9

A1015840

1688

mdash1813

1688

302139

74665

120592CO

(72)bCC

O(17)

10A1015840

1608

mdash1666

1608

216104

153242

120592CC

(62)bCH

(22)R

symd(11)

11A1015840

1580

mdash1624

1580

34785

12359

120592CC

(66)bCH

(14)

12A1015840

1518

mdash1559

1518

41495

8422

bCH(52)120592CC

(30)

13A1015840

1468

mdash1516

1468

37550

10673

bCHsb

(77)

14A10158401015840

1461

mdash1504

1461

14058

1218

3bC

Hop

b(83)

15A1015840

1429

mdash1486

1429

5851

19586

bCHipb(70)120592CC

(10)bCH

(10)

16A1015840

1416

mdash1465

1416

14835

9149

120592CC

(39)bCH

(35)bCH

ipb(18)

17A1015840

1324

mdash1391

1324

31290

5311

bCOH(27)120592CO

(22)bCC

O(21)120592CC

(13)

18A1015840

1307

mdash1371

1307

806

814

44120592CC

ar(65)bCH

(20)

19A1015840

1301

mdash1331

1301

40408

7073

bCH(43)120592CC

(33)

20A1015840

1267

mdash1304

1267

245222

3723

120592CO

(37)R

trigd(20)120592CC

(16)

21A1015840

1181

mdash1221

1181

5734

6023

bCH(61)120592CC

(21)

22A1015840

1172

mdash1209

1172

5690

5161

bCHop

r(61)bC

H(13)

23A1015840

mdash1137

1189

1137

0662

4334

bCHipr(78)bC

Hop

r(14)

24A1015840

1131

mdash117

61131

190946

42508

bCH(35)120592CC

(21)

25A1015840

1107

mdash1139

1107

245972

63024

120592CC

fn(25)R

trigd(23)bCH

(16)120592OC(13)

26A1015840

mdash1100

1114

1100

318070

20809

120592CO

(40)bCO

H(22)bCC

O(11)

27A1015840

1028

mdash1069

1028

0786

11056

120592CC

(58)bCH

(16)

28A1015840

mdash1010

1026

1010

29566

2343

120592OC(51)120592CC

(28)

29A10158401015840

929

mdash991

929

0010

046

4120596CH

(89)

30A10158401015840

854

mdash966

854

1379

1924

120596CH

(82)ttrigd(12)

31A10158401015840

846

mdash863

846

3652

212

44120596CH

(39)120596

CO(32)ttrigd(20)

32A1015840

825

mdash834

825

24090

2237

3120592CC

ar(32)R

symd(27)120592OC(22)

33A10158401015840

774

mdash830

774

0365

4928

120596CH

(84)

34A10158401015840

mdash755

775

755

1082

0243

ttrigd(51)120596

CC(15)120596

CH(14

)tCO(11)

35A1015840

698

mdash725

698

3553

93075

bCCO

(44)120592CO

(25)bCO

H(25)

36A10158401015840

634

mdash710

634

76887

0059

tCO(57)120596

CH(20)ttrigd(12)

37A1015840

617

mdash647

617

0592

644

1Ra

symd(81)

38A1015840

550

mdash603

550

14566

0968

Rsym

d(32)120592CC

fn(13)120592CO

(11)bCC

O(11)bCO

C(10)

39A10158401015840

545

mdash601

545

27876

4847

120596CO

(42)tOH(14

)120596CH

(11)120596

CC(11)

12 Journal of Spectroscopy

Table8Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

525

mdash511

525

12735

1849

bCCO

(82)

41A1015840

505

mdash511

505

50036

5698

tOH(24)ttrigd(23)120596

CO(19)120596

CH(14

)42

A1015840

440

mdash481

440

3190

2294

bCO(35)bCO

C(29)

43A10158401015840

mdash375

427

375

0415

0023

tsym

(60)120596

CH(19

)tasym

(17)

44A1015840

mdash310

335

310

3569

0577

Rsym

d(48)120592CC

fn(25)

45A10158401015840

mdash285

304

285

4416

0596

120596CC

(33)tasym

(24)tCO

(16)

46A1015840

mdash220

267

220

3713

2509

bCOC(29)bCO

(17)

47A10158401015840

mdash165

226

165

0047

0429

tCH

3(85)

48A1015840

mdash111

165

111

0211

0159

bCC(80)

49A10158401015840

mdash98

132

982323

0292

Tasym

(30)tCO

C(30)120596

CC(11)120596

CH(10)tsym

(10)

50A10158401015840

mdash70

7870

1302

1199

tCO(95)

51A10158401015840

mdash60

6560

0898

0216

tCOC(48)tCO

(31)tCH

3(12)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 13

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 3 FT-Raman spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 4 FTIR spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 5 FT-Raman spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

title molecules all the hydrogen atoms have a net positivecharge in particular the hydrogen atoms H(10) that havecharge of 05047 and 05050 respectively The presence oflarge amounts of negative charge on oxygen and net positivecharge on H(10) atoms may suggest the presence of inter-molecular hydrogen bonding in the crystalline phase

Highest occupied molecular orbital and lowest unoc-cupied molecular orbital are very important parametersfor quantum chemistry This is also used by the frontierelectron density for predicting the most reactive position in120587-electron systems and also explains several types of reactionin conjugated system [32] The conjugated molecules are

characterized by a small highest occupied molecular orbitalndashlowest unoccupied molecular orbital (HOMO-LUMO) sep-aration which is the result of a significant degree of inter-molecular charge transfer from the end-capping electron-donating groups to the efficient electron-acceptor groupsthrough 120587 conjugated path [33] Both the highest occupiedmolecular orbital and lowest unoccupied molecular orbitalare the main orbitals that take part in chemical stability[34] Energy difference betweenHOMOand LUMOorbital iscalled energy gap that is an important stability for structureswhich are given in Table 11 We performed an analysis ofall the molecular orbitals involved taking into consideration

14 Journal of Spectroscopy

Table 9 Atomic charges for optimized geometry of O-Anisic acid(OAA) and Anisic acid (AA) obtained by B3LYP6-31Glowastlowast densityfunctional calculations

Atomsa MullikenOAA AA

C1 00018 00373C2 03297 minus01002

C3 minus01368 minus01219

C4 minus00836 03612

C5 minus00943 minus01394

C6 minus01061 minus01118

C7 05570 05445O8 minus04650 minus04848

O9 minus05104 minus05064

H10 03198 03217O11 (H11) minus04841 01203C12 (H12) minus00837 01021H13 (O13) 01064 minus05111

H14 (C14) 01352 minus00831

H15 01211 01099H16 00913 01302H17 00929 01246H18 00886 00913H19 01200 01155aThe atoms indicated in the parenthesis belong to AA

Table 10Natural atomic charges ofO-Anisic acid (OAA) andAnisicacid (AA) calculations performed at the B3LYP6-31Glowastlowast level oftheory

Atomsa OAA AAC1 minus02176 minus02053

C2 03724 minus01746

C3 minus03284 minus02801

C4 minus01952 03443

C5 minus02720 minus03289

C6 minus01806 minus01748

C7 08091 08139O8 minus05861 minus06102

O9 minus07295 minus07217

H10 05047 05050O11 (H11) minus04921 02634C12 (H12) minus03307 02544H13 (O13) 02070 minus05119

H14 (C14) 02390 minus03300

H15 02070 02090H16 02443 02352H17 02426 02090H18 02439 02449H19 02621 02585aThe atoms indicated in the parenthesis belong to AAFor numbering of atoms refer to Figures 1(a) and 1(b)

that orbital 40 is the HOMO and orbital 41 is the LUMO forOAA and AA respectively

Many organic molecules that contain conjugated 120587 elec-trons are characterized as hyperpolarisabilities and are ana-lyzed by means of vibrational spectroscopy The analysis

Table 11 Calculated quantum chemical parameters ofO-Anisic acid(OAA) and Anisic acid (AA) derivatives

Parameters OAA AA119864HOMO minus0227 minus0231

119864LUMO minus0041 minus0036

Δ119864 0186 0195120594 0134 0133Η 0093 0097Σ 10752 10256

Table 12 Calculated 13C NMR chemical shifts (ppm) of O-Anisicacid (OAA) and Anisic acid (AA)

Carbona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAC1 11782 12315 10447 12620C2 15848 13146 14696 13936C3 11204 11384 9681 12272C4 13517 16297 11926 17125C5 12191 11384 10447 11047C6 13347 13146 12019 13751C7 16634 16714 14609 17174C12 (C14) 5674 5544 4322 5549aThe atoms indicated in the parenthesis belong to AA

Table 13 Experimental and calculated 1H NMR chemical shifts(ppm) of O-Anisic acid (OAA) and Anisic acid (AA)

Protona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAH10 1030 13 11 11H13 H14 H15 (H11) 4066 7914 3932 8405H16 (H12) 708 7027 6831 7147H17 (H15 H16 H17) 756 3836 7570 3824H18 710 7027 7069 6673H19 813 7914 3932 8217aThe atoms indicated in the parenthesis belong to AA

of the wave function indicates that the electron absorptioncorresponds to the transition from the ground state to thefirst excited state and is mainly described by the one-electronexcitation from the HOMO to the LUMO The HOMO of 120587nature (ie aromatic ring) is delocalized over the whole CndashC bond By contrast the LUMO is located over the aromaticring Consequently the HOMO-LUMO transition implies anelectron density transfer toCOOHandOCH

3group from the

aromatic ringThe theoretical basis for the new quantities lies in the

density functional formalism [35] Since molecular orbital(MO) theory is by far the most widely used by chemistsit is important to place 120594 and 120578 in a MO framework Ithas already been shown [36] that the MO theory of thechemical bond contains the values of 120594 and 120578 for the bondingfragments Hard molecules have a large HOMO-LUMO gapand soft molecules have a small HOMO-LUMO gap A small

Journal of Spectroscopy 15

HOMO

(a)

LUMO

(b)

Figure 6 Contour surfaces of frontier molecular orbitals of O-Anisic acid

HOMO

(a)

LUMO

(b)

Figure 7 Contour surfaces of frontier molecular orbitals of Anisic acid

HOMO-LUMO gap automatically means small excitationenergies to the manifold of excited states Therefore softmolecules with a small gap will be more polarizable thanhard molecules High polarizability was the most character-istic property attributed to soft acids and bases Energy gapsshould be small for best bonding or bothmolecules should besoft

In the present study the title compound AA is dynam-ically more stable due to the large energy gap OAA is asoft molecule due to small energy gap The Contour surfacesof the frontier molecular orbitals are sketched in Figures 6and 7

51 NMR Spectra DFT methods treat the electronic energyas a function of the electron density of all electrons simul-taneously and thus include electron correlation effect [37]In this study molecular structure of the OAA and AA wasoptimized by using B3LYP method in conjunction with 6-31Glowastlowast 13C and 1H chemical shift calculations of the titlecompounds have been made by using GIAO method andsame basis set The isotropic shielding values were usedto calculate the isotropic chemical shifts 120575 with respect totetramethylsilane (TMS) The isotropic chemical shifts arefrequently used as an aid in identification of reactive ionicspecies The B3LYP method allows calculating the shielding

16 Journal of Spectroscopy

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 150

140

130

120

110

100

90110 120 130 140 150 160 170

(a)

70 75 80 85 90 95 100 1056

7

8

9

10

11

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

(b)

Figure 8 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for O-Anisic acid

constants with the proper accuracy and the GIAOmethod isone of the most common approaches for calculating nuclearmagnetic shielding tensors

Theoretical and experimental chemical shifts of OAA andAA in 1H and 13C NMR spectra are gathered in Tables 12and 13 The range of the 13C NMR chemical shifts for atypical organic molecules usually is gt100 ppm [38 39] andthe accuracy ensures reliable interpretation of spectroscopicparameters In the present study the 13C NMR chemicalshifts in the ring are gt100 ppm as they would be expectedThe 13C chemical shifts carbonyl carbons vary from 150 to220 ppm This depends on the decrease in electron donatingor shielding ability of the attached atoms [40] The C=Ogroups of carboxylic acids and derivatives are in the range of150ndash185 ppm [29]

Hydrogens bonded to an aromatic ring are stronglydeshielded and absorb downfieldWhen the120587-electrons enterthe magnetic field they circulate around the ring to generatea ring current This produces a small induced magnetic fieldthat reinforces the applied field outside the ring resultingin aromatic protons being deshielded [41] A related effectis observed for carboxylic acids For these compoundscirculation of electrons in the double bonds produces inducedmagnetic field These are responsible for the high chemicalshift values of acid protons (H10) Carboxylic acids asstable hydrogen-bonded dimers in nonpolar solvents even athigh dilution The carboxylic proton therefore absorbs in acharacteristically narrow range 132 to 100 and is affectedonly slightly by concentration [29]

In a methyl group a proton is covalently bonded tocarbon oxygen or other atoms by a sigma bond Whenplaced in a strong magnetic field the electrons of the sigmabond circulate to generate a small magnetic field whichopposes the applied field A nearby electronegative atomwithdraws electron density from the neighbourhood of theproton so that a smaller applied field is needed to cause thespin state of the proton to flip The signal for a deshielded

Table 14 Theoretically computed energies (au) zero-point vibra-tional energies (kcalmolminus1) rotational constants (GHz) entropies(calmolminus1 Kminus1) nuclear repulsion energy (Hartrees) and dipolemoment (Debye) for OAA and AA

Parameters B3LYP6-31Glowastlowast

OAA AAZero-point energy 9306056 9314966

Rotational constants139942 344405114384 056752063193 048875

EntropyTotal 99243 97126Translational 40967 40967Rotational 30142 30199Vibrational 28134 25960Dipole moment 24181 35822Nuclear repulsion energy 592968293 573992628

proton (1 surrounded by less electron density) is observed tobe more downfield than the signals for protons that are notdeshielded by electronegative atoms [40] The chemical shiftvalue of C7 (OAA and AA) has bigger value than the othercarbons due to the electronegative property of oxygen atom

The linear correlations between calculated and experi-mental data of 13CNMRand 1HNMRspectra are determinedas 09 and 10 for OAA and 09 and 09 for AA respectivelyThere is an excellent linear relationship between experimentaland computed results which are shown in Figures 8 and 9

6 Thermodynamic Properties

Several calculated thermodynamical parameters are pre-sented in Table 14 for OAA andAA respectively Scale factorshave been recommended [42] for an accurate prediction in

Journal of Spectroscopy 17

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 180

170

160

150

140

130

120

110110

120 130 140 150 160 170

(a)

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

11

10

9

8

7

7 8 9 10 11 12 13

(b)

Figure 9 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for Anisic acid

determining the zero-point vibration energies (ZPVE) andthe entropy 119878vib(119879) The total energies and the change inthe total entropy at room temperature using B3LYP6-31Glowastlowastmethod are presented

7 Conclusion

Attempts have been made in the present work for the molec-ular parameters and frequency assignments for the com-pounds OAA and AA from the FTIR and FT-Raman spectraThe equilibrium geometries and harmonic and anharmonicfrequencies for the title compounds were determined andanalyzed at DFT level of theory utilizing 6-31Glowastlowast basis setThe assignments of most of the fundamentals of the titlecompounds provided in this work are quite comparableThe excellent agreement of the calculated and observedvibrational spectra reveals the advantages of a smaller basisset for quantum chemical calculations HOMO and LUMOenergy gap explains the eventual charge transfer interactionstaking place within the molecule The experimental andtheoretical investigation of the title compounds have beenperformed successfully by using 1H and 13C NMR Thevarious modes of vibrations were unambiguously assignedon the basis of the result of the PED output obtainedfrom normal coordinate analysis These studies confirm thepresence of COOH and OCH

3group Dimeric molecules are

held together by hydrogen bridges between carbonyl groupsThe obtained data and simulations both show the way to thecharacterization of the molecules and help in spectra studiesin the future

References

[1] GMelentyeva and LAntonovaPharmaceutical ChemistryMirPublishers Moscow Russia 1988

[2] ldquoo-Anisic acid(579-75-9) catalog of chemical suppliersrdquo httpwwwchemexpercomchemicalssuppliercas579-75-9html

[3] B A Hess Jr L J Schaad P Carsky and R Zaharaduick ldquoAbinitio calculations of vibrational spectra and their use in theidentification of unusual moleculesrdquo Chemical Reviews vol 86no 4 pp 709ndash730 1986

[4] P Pulay X Zhou and G Forgarasi in Recent Experimental andComputational Advances in Molecular Spectroscopy R Faustoand R Fransto Eds vol 406 ofNATOASI Series p 99 KluwerDordrecht Netherlands 1993

[5] P Pulay G Fogarasi G Pongor J E Boggs and A VarghaldquoCombination of theoretical ab initio and experimental infor-mation to obtain reliable harmonic force constants ScaledQuantum Mechanical (SQM) force fields for glyoxal acroleinbutadiene formaldehyde and ethylenerdquo Journal of the Ameri-can Chemical Society vol 105 no 24 pp 7037ndash7047 1983

[6] C E Blom and C Altona ldquoApplication of self-consistent-fieldab initio calculations to organic moleculesrdquo Molecular Physicsvol 31 no 5 pp 1377ndash1391 1976

[7] G Fogarasi and P Pulay in Vibrational Spectra and Structure JR Durig Ed vol 14 Elsevier Amsterdam Netherlands 1985

[8] G Fogarasi ldquoRecent developments in the method of SQM forcefields with application to 1-methyladeninerdquo Spectrochimica ActaA vol 53 no 8 pp 1211ndash1224 1997

[9] G R deMare N Yu Panchenko andW Ch Bock ldquoAnMP26-31GlowastMP26-31Glowast vibrational analysis of s-trans- and s-cis-acryloyl fluoride CH2=CH-CF=Ordquo The Journal of PhysicalChemistry vol 98 no 5 pp 1416ndash1420 1994

[10] G Pongor P Pulay G Fogarasi and J E Boggs ldquoTheoreticalprediction of vibrational spectra 1 The in-plane force fieldand vibrational spectra of pyridinerdquo Journal of the AmericanChemical Society vol 106 no 10 pp 2765ndash2769 1984

[11] Y Yamakitu and M Tasumi ldquoVibrational analyses of p-benzoquinodimethane and p-benzoquinone based on ab initioHartree-Fock and second-order Moller-Plesset calculationsrdquoThe Journal of Physical Chemistry vol 99 no 21 pp 8524ndash85341995

18 Journal of Spectroscopy

[12] M Karabacak A Coruh and M Kurt ldquoFT-IR FT-RamanNMR spectra and molecular structure investigation of 23-dibromo-N-methylmaleimide a combined experimental andtheoretical studyrdquo Journal of Molecular Structure vol 892 no1ndash3 pp 125ndash131 2008

[13] M S Masoud M K Awad M A Shaker and M M T El-Tahawy ldquoThe role of structural chemistry in the inhibitiveperformance of some aminopyrimidines on the corrosion ofsteelrdquo Corrosion Science vol 52 no 7 pp 2387ndash2396 2010

[14] M J Frisch G W Trucks H B Schlegel et al Gaussian 03Revision B4 Gaussian Inc Pittsburgh Pa USA 2003

[15] P L Polavarapu ldquoAb initio vibrational Raman and Ramanoptical activity spectrardquo Journal of Physical Chemistry vol 94no 21 pp 8106ndash8112 1990

[16] G Keresztury S Holly J Varga G Besenyei A Wang andJ R Durig ldquoVibrational spectra of monothiocarbamates-IIIR and Raman spectra vibrational assignment conforma-tional analysis and ab initio calculations of S-methyl-NN-dimethylthiocarbamaterdquo Spectrochimica Acta A vol 49 no 13-14 pp 2007ndash2017 1993

[17] G Keresztury ldquoRaman spectroscopy theoryrdquo in Handbook ofVibrational Spectroscopy J M Chalmers and P R Griffths Edsvol 1 p 71 John Wiley and Sons 2002

[18] R G Parr R A Donnelly M Levy and W E Palke ldquoElec-tronegativity the density functional viewpointrdquo The Journal ofChemical Physics vol 68 no 8 pp 3801ndash3807 1977

[19] R G Parr and R G Pearson ldquoAbsolute hardness companionparameter to absolute electronegativityrdquo Journal of theAmericanChemical Society vol 105 no 26 pp 7512ndash7516 1983

[20] R G Pearson ldquoAbsolute electronegativity and hardness appli-cation to inorganic chemistryrdquo Inorganic Chemistry vol 27 no4 pp 734ndash740 1988

[21] P Geerlings F De Proft and W Langenaeker ldquoConceptualdensity functional theoryrdquo Chemical Reviews vol 103 no 5 pp1793ndash1873 2003

[22] R Ditchfield ldquoMolecular orbital theory of magnetic shieldingand magnetic susceptibilityrdquo Journal of Physical Chemistry vol56 no 11 article 5688 4 pages 1972

[23] KWolinski J F Hilton and P Pulay ldquoEfficient implementationof the gauge-independent atomic orbital method for NMRchemical shift calculationsrdquo Journal of the American ChemicalSociety vol 112 no 23 pp 8251ndash8260 1990

[24] M Kurt M Yurdakul and S Yurdakul ldquoMolecular structureand vibrational spectra of 3-chloro-4-methyl aniline by densityfunctional theory and ab initio Hartree-Fock calculationsrdquoJournal of Molecular Structure vol 711 no 1ndash3 pp 25ndash32 2004

[25] D Steele and D H Whiffen ldquoThe vibration frequencies ofpentafluorobenzenerdquo Spectrochimica Acta vol 16 no 3 pp368ndash375 1960

[26] D N Sathyanarayanan Vibrational Spectroscopy Theory andApplication New Age International publishers New DelhiIndia 1996

[27] L D S YadavOrganic Spectroscopy Springer NewDelhi India2004

[28] J Mohan Organic Spectroscopy Principles and ApplicationsNarosa Publishing House New Delhi 2nd edition 2009

[29] R M Silverstein G C Bassler and T C Morrill SpectrometricIdentification of Organic Compounds John Wiley amp Sons NewYork NY USA 1981

[30] G Socrates Infrared Characteristic Group Frequencies WileyNew York NY USA 1980

[31] R S Mulliken ldquoElectronic population analysis on LCAO-MOmolecular wave functionsrdquoThe Journal of Chemical Physics vol23 no 10 pp 1833ndash1840 1955

[32] K Fukuli T Yonezawa and H Shingu ldquoA molecular orbitaltheory of reactivity in aromatic hydrocarbonsrdquo Journal ofPhysical Chemistry vol 20 no 4 article 722 4 pages 1952

[33] C H Choi and M Kertesz ldquoConformational information fromvibrational spectra of styrene trans-stilbene and cis-stilbenerdquoJournal of Physical Chemistry A vol 101 no 20 pp 3823ndash38311997

[34] S Gunasekaran R Arun Balaji S Kumaresan G Anandand S Srinivasan ldquoExperimental and theoretical investigationsof spectroscopic properties of N-acetyl-5-methoxytryptaminerdquoCanadian Journal of Analytical Sciences and Spectroscopy vol53 no 4 pp 149ndash162 2008

[35] P Hohenberg and W Kohn ldquoInhomogeneous electron gasrdquoPhysical Review vol 136 no 3 pp B864ndashB871 1964

[36] R G Pearson ldquoAbsolute electronegativity and absolute hard-ness of Lewis acids and basesrdquo Journal of the American ChemicalSociety vol 107 no 24 pp 6801ndash6806 1985

[37] D Avci Y Atalay M Sekerci and M Dincer ldquoMolecular struc-ture and vibrational and chemical shift assignments of 3-(2-Hydroxyphenyl)-4-phenyl-1H-124-triazole-5-(4H)-thione byDFT and ab initio HF calculationsrdquo Spectrochimica Acta A vol73 no 1 pp 212ndash217 2009

[38] H O Kalinowski S Berger and S Braun Carbon13 NMRSpectroscopy John Wiley amp Sons Chichester UK 1988

[39] K Pihlaja and E Kleinpeter Carbon-13 NMR Chemical Shiftsin Structural and Sterochemical Analysis VCH PublishersDeerfield Beach Fla USA 1994

[40] P S Kalsi Spectroscopy of Organic Compounds New AgeInternational 2004

[41] A F Parsons Keynotes in Organic Chemistry Blackwell Pub-lishing Oxford UK 2003

[42] M A Palafox ldquoScaling factors for the prediction of vibrationalspectra I benzenemoleculerdquo International Journal of QuantumChemistry vol 77 no 3 pp 661ndash684 2000

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

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International Journal ofPhotoenergy

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CatalystsJournal of

Page 5: Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. · Molecular Structure, NMR, HOMO, LUMO, ... ects of carbonyl and methyl substitutions

Journal of Spectroscopy 5

Table 3 Definition of internal coordinates of Anisic acid (AA)

No (i) Symbol Type DefinitionStretching

1ndash4 119903119894

CndashH C2ndashH11 C3ndashH12 C5ndashH18 C6ndashH195ndash10 119903

119894CndashC C1ndashC2 C2ndashC3 C3ndashC4 C4ndashC5 C5ndashC6C6ndashC1

11 119903119894

CndashCfn C1ndashC712ndash14 119903

119894CndashO C7ndashO8 C7ndashO9 C4ndashO13

15 119903119894

OndashC O13ndashC1416 119903

119894OndashH O9ndashH10

17ndash19 119903119894

CndashH(methyl) C14ndashH15 C14ndashH16 C14ndashH17Bending

20-21 120573119894

CndashC C2ndashC1ndashC7 C6ndashC1ndashC7

22ndash29 120573119894

CndashCndashHC1ndashC2ndashH11 C3ndashC2ndashH11C2ndashC3ndashH12 C4ndashC3ndashH12C4ndashC5ndashH18 C6ndashC5ndashH18C5ndashC6ndashH19 C1ndashC6ndashH19

30ndash35 120573119894

CndashCndashH(methyl) O13ndashC14ndashH15 O13ndashC14ndashH16 O13ndashC14ndashH17H17ndashC14ndashH15 H15ndashC14ndashH16 H17ndashC14ndashH16

36-37 120573119894

CndashCndashO C3ndashC4ndashO13 C5ndashC4ndashO1338 120573

119894CndashOndashH C7ndashO9ndashH10

39-40 120573119894

CndashCndashO C1ndashC7ndashO8 C1ndashC7ndashO941 120573

119894CndashOndashC C4ndashO13ndashC14

42ndash47 120573119894

CndashCndashC (Ring) C1ndashC2ndashC3 C2ndashC3ndashC4 C3ndashC4ndashC5 C4ndashC5ndashC6C5ndashC6ndashC1 C6ndashC1ndashC2

Out-of-plane bending

48ndash51 120596119894

CndashH H11ndashC2ndashC3ndashC1 H12ndashC3ndashC4ndashC2 H18ndashC5ndashC6ndashC4H19ndashC6ndashC1ndashC5

52 120596119894

CndashC C7ndashC1ndashC6ndashC253 120596

119894CndashO O13ndashC4ndashC5ndashC3

Torsion54ndash55 120591

119894CndashO C2ndashC1ndashC7ndashO8 C2ndashC1ndashC7ndashO9

56-57 120591119894

CndashOndashC C3ndashC4ndashO13ndashC14 C5ndashC4ndashO13ndashC14

58ndash60 120591119894

CndashH(methyl) C4ndashO13ndashC14ndashH15 C4ndashO13ndashC14ndashH16C4ndashO13ndashC14ndashH16

61 120591119894

OndashH C1ndashC7ndashO9ndashH10

62ndash67 120591119894

tring C1ndashC2ndashC3ndashC4 C2ndashC3ndashC4ndashC5 C3ndashC4ndashC5ndashC6C4ndashC5ndashC6ndashC1 C5ndashC6ndashC1ndashC2 C6ndashC1ndashC2ndashC3

For numbering of atoms refer to Figure 1(b)

respectively The RMS values of wavenumbers were obtainedin this study using the following expression

RMS = radic1

119899 minus 1

119899

sum

119894

(120592calc119894

minus 120592exp119894

)2

(6)

431 CH Vibrations Aromatic compounds commonly ex-hibit multiple weak bands in the region 3100ndash3000 cmminus1 [26]due to aromatic CndashH stretching vibrations According to thePED analysis the bands observed in experimental spectrumat 3098 3083 3069 3020 cmminus1 in OAA and 3085 3034 3029and 3002 cmminus1 inAAwere assigned to stretching vibrations of

CndashH bond According to these studies all the CndashH stretchingvibrations are not mixed with other types of vibrations

The CndashH in-plane deformation vibrations are assigned inthe region 1100ndash1400 cmminus1 [27] The in-plane deformationsof CndashH groups are noticed on PED analysis at 1494 14391288 and 1182 in OAA and 1518 1301 1181 and 1131 cmminus1 inAAThere is slight increase in the CndashH in-plane deformationfrequency because of steric effect in OAA and inductive effect(+I) in AAThese values of calculated frequencies are typicaland in very good agreement with experimental data The in-plane CndashH deformation vibrations are slightly mixed in bothOAA and AA

The CndashH out-of-plane deformation vibrations areassigned in the region 900ndash600 cmminus1 [26] The bands

6 Journal of Spectroscopy

Table 4 Definition of natural internal coordinates of O-Anisic acid (OAA)

No (i) Symbola Definitionb

1ndash4 CndashH stretch 1199031 1199032 1199033 1199034

5ndash11 CndashC stretch 1199035 1199036 1199037 1199038 1199039 11990310 11990311

12ndash14 CndashO stretch 11990312 11990313 11990314

15 OndashC stretch 11990315

16 OndashH stretch 11990316

17 CH3 ss (11990317+ 11990318+ 11990319) radic3

18 CH3 ips (211990317minus 11990318minus 11990319) radic6

19 CH3 ops (11990318minus 11990319) radic2

20 bCndashCndashC (12057320minus 12057321) radic2

21ndash24 bCndashCndashH (12057322minus 12057323) radic2 (120573

24minus 12057325) radic2 (120573

26minus 12057327) radic2 (120573

28minus 12057329) radic2

25 CH3 sb (minus12057330minus 12057331minus 12057332+ 12057333+ 12057334+ 12057335) radic6

26 CH3 ipb (minus12057333minus 12057334minus 212057335)radic6

27 CH3 opb (12057333minus 12057334) radic2

28 CH3 ipr (212057330minus 12057331minus 12057332)radic6

29 CH3 opr (12057331minus 12057332)radic2

30 bCndashCndashO (12057336minus 12057337) radic2

31 bCndashOndashH 12057338

32-33 bCndashCndashO 12057339 12057340

34 bCndashOndashC 12057341

35 Rtrigd (12057342minus 12057343+ 12057344minus 12057345+ 12057346minus 12057347) radic6

36 Rsymd (minus12057342minus 12057343+ 12057344minus 12057345minus 12057346+ 212057347)radic12

37 Rasymd (12057342minus 12057343+ 12057345minus 12057346) 2

38ndash41 120596CndashH 12059648 12059649 12059650 12059651

42 120596CndashC 12059652

43 120596CndashO 12059653

44-45 tCndashO 12059154 12059155

46 tCndashOndashC 12 (12059156+ 12059157)

47 tCH3 13 (12059158+ 12059159+ 12059160)

48 tOndashH 12059161

49 Ttrigd (12059162minus 12059163+ 12059164minus 12059165+ 12059166minus 12059167) radic6

50 Tsymd (12059162minus 12059163+ 12059165+ 12059166) 2

51 Tasymd (minus12059162+ 212059163minus 12059164minus 12059165+ 12059166minus 12059167) radic12

aThese symbols are used for description of the normal modes by PED in Table 7bThe internal coordinates used here are defined in Table 2

appearing at 960 937 865 and 755 cmminus1 in OAA and929 854 846 and 774 cmminus1 in AA were assigned toout-of-plane deformation type of vibration (120596) of CndashHgroups There is slight increase in the CndashH out-of-planedeformation frequency because of strong intermolecularhydrogen bonding in OAA In these bands the pronouncedparticipation of other types of vibrations is observed Theseare also supported by the literature

432 Carboxylic Acid Vibrations Due to the presence ofstrong intermolecular hydrogen bonding the FT-IR spectraexhibits spectra exhibit a broad band due to the OndashHstretching vibrations and a strong banddue toC=Ostretchingvibrations The carboxylic acid dimers display a very broadand intenseOndashH stretching absorption in the region of 3300ndash2500 cmminus1 [28] The title molecules both exhibit intermolec-ular hydrogen bonding In our case the bands at 3390 cmminus1

in OAA and 3435 cmminus1 in AA are assigned as OndashH stretchingvibrations There is a slight increase in the OndashH frequencybecause of steric effect in OAA and +I effect in AA The OndashH out-of-plane bending vibration occurs near the region of920 cmminus1 [27] The bands appearing at 595 cmminus1 in OAA and505 cmminus1 in AA are assigned to OndashH out-of-plane bendingvibrationThe OndashH out-of-plane bending vibrations in OAAand AA decrease due to intermolecular hydrogen bonding

The carbonyl stretching vibrations are expected in theregion 1720 cmminus1ndash1680 cmminus1 [28] The IR band at 1670 cmminus1in OAA and FT-Raman band at 1688 cmminus1 in AA are assignedasC=O stretching vibrationsTheCndashObond appears stronglyin the 1320ndash1210 cmminus1 region [29] The bands observed at1049 and 795 cmminus1 in OAA and 1267 and 1100 cmminus1 in AAare assigned to CndashO stretching mode The CndashO stretchingvibrational frequency is lower than general range In thecase of carboxylic acid dimers like OAA and AA the OH

Journal of Spectroscopy 7

Table 5 Definition of natural internal coordinates of Anisic acid (AA)

No (i) Symbola Definitionb

1ndash4 CndashH stretch 1199031 1199032 1199033 1199034

5ndash10 CndashC stretch 1199035 1199036 1199037 1199038 1199039 11990310

11 CndashCfn stretch 11990311

12ndash14 CndashO stretch 11990312 11990313 11990314

15 OndashC stretch 11990315

16 OndashH stretch 11990316

17 CH3 ss (11990317+ 11990318+ 11990319) radic3

18 CH3 ips (211990317minus 11990318minus 11990319) radic6

19 CH3 ops (11990318minus 11990319) radic2

20 bCndashCndashC (12057320minus 12057321) radic2

21ndash24 bCndashCndashH (12057322minus 12057323) radic2 (120573

24minus 12057325) radic2 (120573

26minus 12057327) radic2 (120573

28minus 12057329) radic2

25 CH3 sb (minus12057330minus 12057331minus 12057332+ 12057333+ 12057334+ 12057335) radic6

26 CH3 ipb (minus12057333minus 12057334minus 212057335)radic6

27 CH3 opb (12057333minus 12057334) radic2

28 CH3 ipr (212057330minus 12057331minus 12057332) radic6

29 CH3 opr (12057331minus 12057332) radic2

30 bCndashCndashO (12057335minus 12057336) radic2

31 bCndashOndashH 12057338

32-33 bCndashCndashO 12057339 12057340

34 bCndashOndashC 12057341

35 Rtrigd (12057342minus 12057343+ 12057344minus 12057345+ 12057346minus 12057347) radic6

36 Rsymd (minus12057342minus 12057343+ 12057344minus 12057345minus 12057346+ 212057347) radic12

37 Rasymd (12057342minus 12057343+ 12057345minus 12057346) 2

38ndash41 120596CndashH 12059648 12059649 12059650 12059651

42 120596CndashC 12059652

43 120596CndashO 12059653

44-45 tCndashO 12059154 12059155

46 tCndashOndashC 12 (12059156+ 12059157)

47 tCH3 13 (12059158+ 12059159+ 12059160)

48 tOndashH 12059161

49 Ttrigd (12059162minus 12059163+ 12059164minus 12059165+ 12059166minus 12059167) radic6

50 Tsymd (12059162minus 12059163+ 12059165+ 12059166)2

51 Tasymd (minus12059162+ 212059163minus 12059164minus 12059165+ 12059166minus 12059167) radic12

aThese symbols are used for description of the normal modes by PED in Table 8bThe internal coordinates used here are defined in Table 3

in-plane bending and CndashO stretching bands involve someinteraction between them they are referred to as coupledOH in-plane bending and CndashO stretching vibrations [26]The CndashO bending vibration occurs in the region of 580ndash340 cmminus1 [30] The band observed at 380 cmminus1 in OAA and440 cmminus1 in AA are assigned to CndashO bending mode Thepresent assignments agree very well with the values availablein the literature

433 Methyl Group Vibrations The title molecules OAAand AA under consideration possess one CH

3group For

the assignments of CH3group one can expect that 9 fun-

damentals can be associated with each CH3group namely

the symmetrical stretching (CH3symmetric stretch) and

asymmetrical stretching (CH3asymmetric stretch) in-plane

stretching modes (ie in-plane hydrogen stretching modes)

and the symmetrical (CH3symmetric deform) and asym-

metrical (CH3asymmetric deform) deformation modes in-

plane rocking (CH3ipr) out-of-plane rocking (CH

3opr) and

twisting (tCH3) bending modes

For the methyl group compounds the asymmetricstretching mode appeared in the range 2965ndash3005 cmminus1 andthe symmetric stretching mode appeared in the range of2815ndash2860 cmminus1 [30] The FT-Raman band at 2983 cmminus1 forOAA and IR band at 2941 cmminus1 for AA are symmetricstretching The symmetric stretching vibrational frequencyis higher in OAA and AA due to steric effect and +I effectThe asymmetric methyl stretching band appeared at 30033018 cmminus1 in OAA and 2990 2956 cmminus1 in AA respectivelyThe asymmetric deformation mode appeared in the range1445ndash1485 cmminus1 and symmetric deformation mode appearedin the range of 1420ndash1460 cmminus1 [30] The IR band at 1466

8 Journal of Spectroscopy

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 2 FTIR spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Table 6 Diagonal force constants (102 Nmminus1) of O-Anisic acid(OAA) and Anisic acid (AA)

Descriptiona Force constantsb

OAA AAC1ndashC2 621 630C2ndashC3 633 696C3ndashC4 677 626C4ndashC5 675 628C5ndashC6 682 663C6ndashC1 644 648C1ndashC7 465 222C7ndashO8 532 522C7ndashO9 1030 1128C2ndashO11(C4ndashO13) 449 576O11ndashC12(O13ndashC14) 413 499O9ndashH10 644 661C12ndashH13(C14ndashH15) 498 508C12ndashH14(C14ndashH16) 526 470C12ndashH15(C14ndashH17) 498 507C3ndashH16(C2ndashH11) 514 498C4ndashH17(C3ndashH12) 501 496C5ndashH18 505 500C6ndashH19 532 522aThe atoms indicated in the parenthesis belong to AAbStretching force constants are given in mdyn A

minus1

For numbering of atoms refer to Figures 1(a) and 1(b)

and 1435 cmminus1 in OAA and 1468 and 1461 cmminus1 in AA areassigned as asymmetric deformation vibrations The IR bandat 1411 cmminus1 for OAA and 1429 cmminus1 for AA are symmet-ric deformation mode The CH

3deformation absorption

occurs at 1466 cmminus1 and 1429 cmminus1 this vibration is knownas umbrella mode that overlaps with CC ring stretchingvibrations for the title compounds These are also supportedby the literature

The tensional modes appeared in the range of 265ndash185 cmminus1 [30] This modes are strongly coupled with other

vibrations that are observed at 280 cmminus1 inOAAand 165 cmminus1in AAwhich are in agreement with the calculated results also

434 Ring Vibrations The ring CndashC stretching vibrationsoccur in the region of 1600ndash1400 cmminus1 [29]The bands appearat 1600 1579 1312 1184 1153 1062 and 698 cmminus1 in OAAand 1608 1580 1416 1307 1107 1028 and 825 cmminus1 in AAwere assigned to CndashC stretching vibrations The shift in thefrequency of CndashC vibrations towards lower wave numbermay be due to the COOH and OCH

3groups Many ring

modes are affected by the substitutions in the aromatic ringThe bands at 180 cmminus1 and 285 cmminus1 for OAA and AA wereassigned to CndashC bending vibrationsThe out-of-plane and in-plane deformations of the phenyl ring are observed below1000 cmminus1 and these modes are sensitive by the additionof functional groups The out-of-plane bending vibrationswere observed at 170 cmminus1 and 111 cmminus1 for OAA and AASmall changes in the wavenumbers were observed due tothe presence of +I effect in AA and steric effect in OAAThe computed wavenumbers are in good agreement withexperimental data

5 Electronic Properties

Atomic charges on the various atoms of OAA and AAobtained by Mulliken population analysis [31] are given inTable 9 From the listed atomic charge values the oxygen[O8 O9] and O11 in OAA and O13 in AA atoms had a largenegative charge and behaved as electron acceptor It was alsoobserved that there is a large accumulation of charge on O11inOAAO13 in AAmoleculesTherefore C7 andO11 inOAAand C7 and O13 in AA had a greater ionic character

Natural bond orbital analysis provides an efficientmethod for studying steric effect and intermolecular bondingand interaction among bonds and also provides a convenientbasis for investigating charge transfer or conjugative interac-tion in molecular systems Natural charge analysis is givenin Table 10 for the title compounds The results show thatsubstitution of COOH and CH

3group in OAA and AA leads

to a redistribution of electron density The C7 atom in OAAand AA is more positive charge (+08091 +08139) In the

Journal of Spectroscopy 9Ta

ble7Detailedassig

nmento

ffun

damentalvibratio

nsof

O-Anisic

acid

(OAA)b

yno

rmalmod

eanalysis

basedon

SQM

forcefi

eldcalculations

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

1A1015840

3390

mdash3771

3390

72652

155385

120592OH(100)

2A1015840

mdash3098

3273

3098

1612

499564

120592CH

(99)

3A1015840

mdash3083

3233

3083

1700

135114

120592CH

(99)

4A1015840

3069

mdash3207

3069

10674

70382

120592CH

(99)

5A1015840

mdash3020

3186

3024

17253

1372

01120592CH

(99)

6A1015840

3018

mdash3157

3018

38987

58202

120592CH

3(99)

7A10158401015840

3003

mdash3085

3003

5946

78409

120592CH

3(99)

8A1015840

mdash2983

3020

2983

52626

120657

120592CH

3(99)

9A1015840

1670

mdash1822

1670

358567

54628

120592CO

(53)120592CC

(14)bC

CO(14

)bC

OH(12)

10A1015840

1600

mdash1656

1600

15061

16343

120592CC

(60)bCH

(20)R

asym

d(10)

11A1015840

1579

mdash1630

1579

61364

48880

120592CC

(69)bCH

(19)

12A1015840

1494

mdash1539

1494

58214

10686

bCH(48)120592CC

(37)

13A1015840

1466

mdash1513

1466

6534

6058

bCH

3(43)bCH

(25)120592CC

(16)

14A1015840

mdash1439

1506

1439

22318

5639

bCH(39)bCH

3(37)120592CC

(17)

15A10158401015840

1435

mdash1500

1435

3652

510814

bCH

3(88)

16A1015840

1411

mdash1475

1411

11849

19713

bCH

3(74)

17A1015840

1382

1367

4497

1268

bCOH(35)120592CO

(32)bCC

O(13)120592CC

(11)

18A1015840

mdash1312

1350

1312

2182

8877

120592CC

(67)

19A1015840

1288

mdash1320

1288

6319

416

48bC

H(33)R

trigd(20)120592CO

(13)120592CC

(12)

20A1015840

mdash1287

1302

1287

19694

044

9Rtrig

d(26)120592CC

(25)bCH

(20)120592CO

(12)

21A1015840

mdash1184

1210

1184

228252

32980

120592CC

(31)bCH

(19)bC

H3(17)120592CO

(17)

22A1015840

1182

mdash1201

1182

162989

2713

6bC

H(42)120592CC

(34)bCH

3(10)

23A1015840

1170

mdash119

3117

015

764576

bCH

3(57)bCH

(24)

24A1015840

mdash117

3117

31153

7419

1097

120592CC

(31)bCH

(29)bCH

3(25)

25A1015840

1140

mdash1168

1140

0662

4253

bCH

3(96)

26A1015840

1049

mdash1087

1050

1073

0478

09120592CO

(29)120592CC

(27)R

trigd(12)

27A1015840

-1062

1077

1060

104848

21650

120592CC

(41)120592CO

(22)bCH

(12)

28A10158401015840

960

-1060

960

060

90057

120596CH

(91)

29A1015840

mdash974

989

974

2078

710836

120592OC(62)120592CC

(12)120592CO

(11)

30A10158401015840

937

mdash965

935

1244

1294

120596CH

(91)

31A10158401015840

mdash865

869

865

3148

3432

120596CH

(64)ttrigd(19)

32A1015840

mdash795

830

795

12200

4238

120592CO

(29)R

symd(21)120592OC(15)120592CC

(15)

33A10158401015840

761

mdash795

761

1002

0207

tCO(32)ttrigd(28)120596

CH(23)120596

CC(11)

34A10158401015840

mdash755

770

755

41473

1456

120596CH

(51)ttrigd(27)120596

CO(14

)35

A10158401015840

695

mdash747

698

64512

0469

ttrigd(52)120596

CH(23)tCO

(15)

36A1015840

mdash698

712

695

10016

17946

120592CC

(33)120592CO

(23)bCC

O(21)

37A1015840

mdash602

639

602

13503

2683

Rasymd(36)bCC

O(15)

120592CC

(12)R

symd(11)

38A10158401015840

mdash595

594

595

74804

8168

tOH(79)

39A1015840

mdash565

588

565

21902

1740

bCCO

(28)120592CC

(17)bCO

(15)R

symd(14

)bC

CO(13)

10 Journal of Spectroscopy

Table7Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

540

mdash548

540

5598

4848

bCCO

(40)bCC

(16)120592CC

(13)R

asym

d(10)

41A10158401015840

480

mdash540

480

0946

0860

120596CO

(40)120596

CH(16)ttrigd(14

)tsy

m(14

)42

A10158401015840

mdash40

1435

401

3585

0792

tsym

(14)120596CC

(15)

43A1015840

mdash380

388

380

4805

4133

bCO(64)bCC

O(16)

44A1015840

mdash303

383

303

1180

4980

Rsym

d(59)bCO

C(17)120592CC

(15)

45A10158401015840

mdash280

283

280

0092

0016

tCH

3(79)

46A1015840

mdash240

280

240

0927

0935

bCOC(40)bCC

(30)bCC

O(18)

47A10158401015840

mdash180

229

180

0018

2096

120596CC

(30)tCO

(20)tsym

(18)

tasym

(11)120596CH

(10)

48A1015840

mdash170

190

170

3092

0715

bCC(42)bCO

C(29)bCO

(12)

49A10158401015840

mdash115

119115

4502

0508

tCOC(47)tsym

(15)tCH

3(12)

50A10158401015840

mdash110

9696

0922

3779

tsym

(35)tCO

(25)

tCOC(21)tCH

3(13)

51A10158401015840

mdashmdash

1730

1260

0037

tCO(99)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 11Ta

ble8Detailedassig

nmento

ffun

damentalvibratio

nsof

Anisic

acid

(AA)b

yno

rmalmod

eanalysis

basedon

SQM

forcefi

eldcalculations

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

1A1015840

3435

mdash3768

3435

7952

3164209

120592OH(100)

2A1015840

mdash3085

3232

3085

21438

120058

120592CH

(89)

3A1015840

mdash3034

3224

3034

7547

126718

120592CH

(99)

4A1015840

3029

mdash3218

3029

3520

99229

120592CH

(99)

5A1015840

3002

mdash3209

3002

5141

52552

120592CH

(99)

6A1015840

2990

mdash3155

2990

2423

53071

120592CH

ops(99)

7A10158401015840

2956

mdash3087

2956

45319

94074

120592CH

ips(51)120592CH

ss(36)120592CH

ops(12)

8A1015840

2941

mdash3022

2941

42847

91231

120592CH

ss(56)120592CH

ips(44

)9

A1015840

1688

mdash1813

1688

302139

74665

120592CO

(72)bCC

O(17)

10A1015840

1608

mdash1666

1608

216104

153242

120592CC

(62)bCH

(22)R

symd(11)

11A1015840

1580

mdash1624

1580

34785

12359

120592CC

(66)bCH

(14)

12A1015840

1518

mdash1559

1518

41495

8422

bCH(52)120592CC

(30)

13A1015840

1468

mdash1516

1468

37550

10673

bCHsb

(77)

14A10158401015840

1461

mdash1504

1461

14058

1218

3bC

Hop

b(83)

15A1015840

1429

mdash1486

1429

5851

19586

bCHipb(70)120592CC

(10)bCH

(10)

16A1015840

1416

mdash1465

1416

14835

9149

120592CC

(39)bCH

(35)bCH

ipb(18)

17A1015840

1324

mdash1391

1324

31290

5311

bCOH(27)120592CO

(22)bCC

O(21)120592CC

(13)

18A1015840

1307

mdash1371

1307

806

814

44120592CC

ar(65)bCH

(20)

19A1015840

1301

mdash1331

1301

40408

7073

bCH(43)120592CC

(33)

20A1015840

1267

mdash1304

1267

245222

3723

120592CO

(37)R

trigd(20)120592CC

(16)

21A1015840

1181

mdash1221

1181

5734

6023

bCH(61)120592CC

(21)

22A1015840

1172

mdash1209

1172

5690

5161

bCHop

r(61)bC

H(13)

23A1015840

mdash1137

1189

1137

0662

4334

bCHipr(78)bC

Hop

r(14)

24A1015840

1131

mdash117

61131

190946

42508

bCH(35)120592CC

(21)

25A1015840

1107

mdash1139

1107

245972

63024

120592CC

fn(25)R

trigd(23)bCH

(16)120592OC(13)

26A1015840

mdash1100

1114

1100

318070

20809

120592CO

(40)bCO

H(22)bCC

O(11)

27A1015840

1028

mdash1069

1028

0786

11056

120592CC

(58)bCH

(16)

28A1015840

mdash1010

1026

1010

29566

2343

120592OC(51)120592CC

(28)

29A10158401015840

929

mdash991

929

0010

046

4120596CH

(89)

30A10158401015840

854

mdash966

854

1379

1924

120596CH

(82)ttrigd(12)

31A10158401015840

846

mdash863

846

3652

212

44120596CH

(39)120596

CO(32)ttrigd(20)

32A1015840

825

mdash834

825

24090

2237

3120592CC

ar(32)R

symd(27)120592OC(22)

33A10158401015840

774

mdash830

774

0365

4928

120596CH

(84)

34A10158401015840

mdash755

775

755

1082

0243

ttrigd(51)120596

CC(15)120596

CH(14

)tCO(11)

35A1015840

698

mdash725

698

3553

93075

bCCO

(44)120592CO

(25)bCO

H(25)

36A10158401015840

634

mdash710

634

76887

0059

tCO(57)120596

CH(20)ttrigd(12)

37A1015840

617

mdash647

617

0592

644

1Ra

symd(81)

38A1015840

550

mdash603

550

14566

0968

Rsym

d(32)120592CC

fn(13)120592CO

(11)bCC

O(11)bCO

C(10)

39A10158401015840

545

mdash601

545

27876

4847

120596CO

(42)tOH(14

)120596CH

(11)120596

CC(11)

12 Journal of Spectroscopy

Table8Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

525

mdash511

525

12735

1849

bCCO

(82)

41A1015840

505

mdash511

505

50036

5698

tOH(24)ttrigd(23)120596

CO(19)120596

CH(14

)42

A1015840

440

mdash481

440

3190

2294

bCO(35)bCO

C(29)

43A10158401015840

mdash375

427

375

0415

0023

tsym

(60)120596

CH(19

)tasym

(17)

44A1015840

mdash310

335

310

3569

0577

Rsym

d(48)120592CC

fn(25)

45A10158401015840

mdash285

304

285

4416

0596

120596CC

(33)tasym

(24)tCO

(16)

46A1015840

mdash220

267

220

3713

2509

bCOC(29)bCO

(17)

47A10158401015840

mdash165

226

165

0047

0429

tCH

3(85)

48A1015840

mdash111

165

111

0211

0159

bCC(80)

49A10158401015840

mdash98

132

982323

0292

Tasym

(30)tCO

C(30)120596

CC(11)120596

CH(10)tsym

(10)

50A10158401015840

mdash70

7870

1302

1199

tCO(95)

51A10158401015840

mdash60

6560

0898

0216

tCOC(48)tCO

(31)tCH

3(12)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 13

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 3 FT-Raman spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 4 FTIR spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 5 FT-Raman spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

title molecules all the hydrogen atoms have a net positivecharge in particular the hydrogen atoms H(10) that havecharge of 05047 and 05050 respectively The presence oflarge amounts of negative charge on oxygen and net positivecharge on H(10) atoms may suggest the presence of inter-molecular hydrogen bonding in the crystalline phase

Highest occupied molecular orbital and lowest unoc-cupied molecular orbital are very important parametersfor quantum chemistry This is also used by the frontierelectron density for predicting the most reactive position in120587-electron systems and also explains several types of reactionin conjugated system [32] The conjugated molecules are

characterized by a small highest occupied molecular orbitalndashlowest unoccupied molecular orbital (HOMO-LUMO) sep-aration which is the result of a significant degree of inter-molecular charge transfer from the end-capping electron-donating groups to the efficient electron-acceptor groupsthrough 120587 conjugated path [33] Both the highest occupiedmolecular orbital and lowest unoccupied molecular orbitalare the main orbitals that take part in chemical stability[34] Energy difference betweenHOMOand LUMOorbital iscalled energy gap that is an important stability for structureswhich are given in Table 11 We performed an analysis ofall the molecular orbitals involved taking into consideration

14 Journal of Spectroscopy

Table 9 Atomic charges for optimized geometry of O-Anisic acid(OAA) and Anisic acid (AA) obtained by B3LYP6-31Glowastlowast densityfunctional calculations

Atomsa MullikenOAA AA

C1 00018 00373C2 03297 minus01002

C3 minus01368 minus01219

C4 minus00836 03612

C5 minus00943 minus01394

C6 minus01061 minus01118

C7 05570 05445O8 minus04650 minus04848

O9 minus05104 minus05064

H10 03198 03217O11 (H11) minus04841 01203C12 (H12) minus00837 01021H13 (O13) 01064 minus05111

H14 (C14) 01352 minus00831

H15 01211 01099H16 00913 01302H17 00929 01246H18 00886 00913H19 01200 01155aThe atoms indicated in the parenthesis belong to AA

Table 10Natural atomic charges ofO-Anisic acid (OAA) andAnisicacid (AA) calculations performed at the B3LYP6-31Glowastlowast level oftheory

Atomsa OAA AAC1 minus02176 minus02053

C2 03724 minus01746

C3 minus03284 minus02801

C4 minus01952 03443

C5 minus02720 minus03289

C6 minus01806 minus01748

C7 08091 08139O8 minus05861 minus06102

O9 minus07295 minus07217

H10 05047 05050O11 (H11) minus04921 02634C12 (H12) minus03307 02544H13 (O13) 02070 minus05119

H14 (C14) 02390 minus03300

H15 02070 02090H16 02443 02352H17 02426 02090H18 02439 02449H19 02621 02585aThe atoms indicated in the parenthesis belong to AAFor numbering of atoms refer to Figures 1(a) and 1(b)

that orbital 40 is the HOMO and orbital 41 is the LUMO forOAA and AA respectively

Many organic molecules that contain conjugated 120587 elec-trons are characterized as hyperpolarisabilities and are ana-lyzed by means of vibrational spectroscopy The analysis

Table 11 Calculated quantum chemical parameters ofO-Anisic acid(OAA) and Anisic acid (AA) derivatives

Parameters OAA AA119864HOMO minus0227 minus0231

119864LUMO minus0041 minus0036

Δ119864 0186 0195120594 0134 0133Η 0093 0097Σ 10752 10256

Table 12 Calculated 13C NMR chemical shifts (ppm) of O-Anisicacid (OAA) and Anisic acid (AA)

Carbona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAC1 11782 12315 10447 12620C2 15848 13146 14696 13936C3 11204 11384 9681 12272C4 13517 16297 11926 17125C5 12191 11384 10447 11047C6 13347 13146 12019 13751C7 16634 16714 14609 17174C12 (C14) 5674 5544 4322 5549aThe atoms indicated in the parenthesis belong to AA

Table 13 Experimental and calculated 1H NMR chemical shifts(ppm) of O-Anisic acid (OAA) and Anisic acid (AA)

Protona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAH10 1030 13 11 11H13 H14 H15 (H11) 4066 7914 3932 8405H16 (H12) 708 7027 6831 7147H17 (H15 H16 H17) 756 3836 7570 3824H18 710 7027 7069 6673H19 813 7914 3932 8217aThe atoms indicated in the parenthesis belong to AA

of the wave function indicates that the electron absorptioncorresponds to the transition from the ground state to thefirst excited state and is mainly described by the one-electronexcitation from the HOMO to the LUMO The HOMO of 120587nature (ie aromatic ring) is delocalized over the whole CndashC bond By contrast the LUMO is located over the aromaticring Consequently the HOMO-LUMO transition implies anelectron density transfer toCOOHandOCH

3group from the

aromatic ringThe theoretical basis for the new quantities lies in the

density functional formalism [35] Since molecular orbital(MO) theory is by far the most widely used by chemistsit is important to place 120594 and 120578 in a MO framework Ithas already been shown [36] that the MO theory of thechemical bond contains the values of 120594 and 120578 for the bondingfragments Hard molecules have a large HOMO-LUMO gapand soft molecules have a small HOMO-LUMO gap A small

Journal of Spectroscopy 15

HOMO

(a)

LUMO

(b)

Figure 6 Contour surfaces of frontier molecular orbitals of O-Anisic acid

HOMO

(a)

LUMO

(b)

Figure 7 Contour surfaces of frontier molecular orbitals of Anisic acid

HOMO-LUMO gap automatically means small excitationenergies to the manifold of excited states Therefore softmolecules with a small gap will be more polarizable thanhard molecules High polarizability was the most character-istic property attributed to soft acids and bases Energy gapsshould be small for best bonding or bothmolecules should besoft

In the present study the title compound AA is dynam-ically more stable due to the large energy gap OAA is asoft molecule due to small energy gap The Contour surfacesof the frontier molecular orbitals are sketched in Figures 6and 7

51 NMR Spectra DFT methods treat the electronic energyas a function of the electron density of all electrons simul-taneously and thus include electron correlation effect [37]In this study molecular structure of the OAA and AA wasoptimized by using B3LYP method in conjunction with 6-31Glowastlowast 13C and 1H chemical shift calculations of the titlecompounds have been made by using GIAO method andsame basis set The isotropic shielding values were usedto calculate the isotropic chemical shifts 120575 with respect totetramethylsilane (TMS) The isotropic chemical shifts arefrequently used as an aid in identification of reactive ionicspecies The B3LYP method allows calculating the shielding

16 Journal of Spectroscopy

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 150

140

130

120

110

100

90110 120 130 140 150 160 170

(a)

70 75 80 85 90 95 100 1056

7

8

9

10

11

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

(b)

Figure 8 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for O-Anisic acid

constants with the proper accuracy and the GIAOmethod isone of the most common approaches for calculating nuclearmagnetic shielding tensors

Theoretical and experimental chemical shifts of OAA andAA in 1H and 13C NMR spectra are gathered in Tables 12and 13 The range of the 13C NMR chemical shifts for atypical organic molecules usually is gt100 ppm [38 39] andthe accuracy ensures reliable interpretation of spectroscopicparameters In the present study the 13C NMR chemicalshifts in the ring are gt100 ppm as they would be expectedThe 13C chemical shifts carbonyl carbons vary from 150 to220 ppm This depends on the decrease in electron donatingor shielding ability of the attached atoms [40] The C=Ogroups of carboxylic acids and derivatives are in the range of150ndash185 ppm [29]

Hydrogens bonded to an aromatic ring are stronglydeshielded and absorb downfieldWhen the120587-electrons enterthe magnetic field they circulate around the ring to generatea ring current This produces a small induced magnetic fieldthat reinforces the applied field outside the ring resultingin aromatic protons being deshielded [41] A related effectis observed for carboxylic acids For these compoundscirculation of electrons in the double bonds produces inducedmagnetic field These are responsible for the high chemicalshift values of acid protons (H10) Carboxylic acids asstable hydrogen-bonded dimers in nonpolar solvents even athigh dilution The carboxylic proton therefore absorbs in acharacteristically narrow range 132 to 100 and is affectedonly slightly by concentration [29]

In a methyl group a proton is covalently bonded tocarbon oxygen or other atoms by a sigma bond Whenplaced in a strong magnetic field the electrons of the sigmabond circulate to generate a small magnetic field whichopposes the applied field A nearby electronegative atomwithdraws electron density from the neighbourhood of theproton so that a smaller applied field is needed to cause thespin state of the proton to flip The signal for a deshielded

Table 14 Theoretically computed energies (au) zero-point vibra-tional energies (kcalmolminus1) rotational constants (GHz) entropies(calmolminus1 Kminus1) nuclear repulsion energy (Hartrees) and dipolemoment (Debye) for OAA and AA

Parameters B3LYP6-31Glowastlowast

OAA AAZero-point energy 9306056 9314966

Rotational constants139942 344405114384 056752063193 048875

EntropyTotal 99243 97126Translational 40967 40967Rotational 30142 30199Vibrational 28134 25960Dipole moment 24181 35822Nuclear repulsion energy 592968293 573992628

proton (1 surrounded by less electron density) is observed tobe more downfield than the signals for protons that are notdeshielded by electronegative atoms [40] The chemical shiftvalue of C7 (OAA and AA) has bigger value than the othercarbons due to the electronegative property of oxygen atom

The linear correlations between calculated and experi-mental data of 13CNMRand 1HNMRspectra are determinedas 09 and 10 for OAA and 09 and 09 for AA respectivelyThere is an excellent linear relationship between experimentaland computed results which are shown in Figures 8 and 9

6 Thermodynamic Properties

Several calculated thermodynamical parameters are pre-sented in Table 14 for OAA andAA respectively Scale factorshave been recommended [42] for an accurate prediction in

Journal of Spectroscopy 17

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 180

170

160

150

140

130

120

110110

120 130 140 150 160 170

(a)

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

11

10

9

8

7

7 8 9 10 11 12 13

(b)

Figure 9 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for Anisic acid

determining the zero-point vibration energies (ZPVE) andthe entropy 119878vib(119879) The total energies and the change inthe total entropy at room temperature using B3LYP6-31Glowastlowastmethod are presented

7 Conclusion

Attempts have been made in the present work for the molec-ular parameters and frequency assignments for the com-pounds OAA and AA from the FTIR and FT-Raman spectraThe equilibrium geometries and harmonic and anharmonicfrequencies for the title compounds were determined andanalyzed at DFT level of theory utilizing 6-31Glowastlowast basis setThe assignments of most of the fundamentals of the titlecompounds provided in this work are quite comparableThe excellent agreement of the calculated and observedvibrational spectra reveals the advantages of a smaller basisset for quantum chemical calculations HOMO and LUMOenergy gap explains the eventual charge transfer interactionstaking place within the molecule The experimental andtheoretical investigation of the title compounds have beenperformed successfully by using 1H and 13C NMR Thevarious modes of vibrations were unambiguously assignedon the basis of the result of the PED output obtainedfrom normal coordinate analysis These studies confirm thepresence of COOH and OCH

3group Dimeric molecules are

held together by hydrogen bridges between carbonyl groupsThe obtained data and simulations both show the way to thecharacterization of the molecules and help in spectra studiesin the future

References

[1] GMelentyeva and LAntonovaPharmaceutical ChemistryMirPublishers Moscow Russia 1988

[2] ldquoo-Anisic acid(579-75-9) catalog of chemical suppliersrdquo httpwwwchemexpercomchemicalssuppliercas579-75-9html

[3] B A Hess Jr L J Schaad P Carsky and R Zaharaduick ldquoAbinitio calculations of vibrational spectra and their use in theidentification of unusual moleculesrdquo Chemical Reviews vol 86no 4 pp 709ndash730 1986

[4] P Pulay X Zhou and G Forgarasi in Recent Experimental andComputational Advances in Molecular Spectroscopy R Faustoand R Fransto Eds vol 406 ofNATOASI Series p 99 KluwerDordrecht Netherlands 1993

[5] P Pulay G Fogarasi G Pongor J E Boggs and A VarghaldquoCombination of theoretical ab initio and experimental infor-mation to obtain reliable harmonic force constants ScaledQuantum Mechanical (SQM) force fields for glyoxal acroleinbutadiene formaldehyde and ethylenerdquo Journal of the Ameri-can Chemical Society vol 105 no 24 pp 7037ndash7047 1983

[6] C E Blom and C Altona ldquoApplication of self-consistent-fieldab initio calculations to organic moleculesrdquo Molecular Physicsvol 31 no 5 pp 1377ndash1391 1976

[7] G Fogarasi and P Pulay in Vibrational Spectra and Structure JR Durig Ed vol 14 Elsevier Amsterdam Netherlands 1985

[8] G Fogarasi ldquoRecent developments in the method of SQM forcefields with application to 1-methyladeninerdquo Spectrochimica ActaA vol 53 no 8 pp 1211ndash1224 1997

[9] G R deMare N Yu Panchenko andW Ch Bock ldquoAnMP26-31GlowastMP26-31Glowast vibrational analysis of s-trans- and s-cis-acryloyl fluoride CH2=CH-CF=Ordquo The Journal of PhysicalChemistry vol 98 no 5 pp 1416ndash1420 1994

[10] G Pongor P Pulay G Fogarasi and J E Boggs ldquoTheoreticalprediction of vibrational spectra 1 The in-plane force fieldand vibrational spectra of pyridinerdquo Journal of the AmericanChemical Society vol 106 no 10 pp 2765ndash2769 1984

[11] Y Yamakitu and M Tasumi ldquoVibrational analyses of p-benzoquinodimethane and p-benzoquinone based on ab initioHartree-Fock and second-order Moller-Plesset calculationsrdquoThe Journal of Physical Chemistry vol 99 no 21 pp 8524ndash85341995

18 Journal of Spectroscopy

[12] M Karabacak A Coruh and M Kurt ldquoFT-IR FT-RamanNMR spectra and molecular structure investigation of 23-dibromo-N-methylmaleimide a combined experimental andtheoretical studyrdquo Journal of Molecular Structure vol 892 no1ndash3 pp 125ndash131 2008

[13] M S Masoud M K Awad M A Shaker and M M T El-Tahawy ldquoThe role of structural chemistry in the inhibitiveperformance of some aminopyrimidines on the corrosion ofsteelrdquo Corrosion Science vol 52 no 7 pp 2387ndash2396 2010

[14] M J Frisch G W Trucks H B Schlegel et al Gaussian 03Revision B4 Gaussian Inc Pittsburgh Pa USA 2003

[15] P L Polavarapu ldquoAb initio vibrational Raman and Ramanoptical activity spectrardquo Journal of Physical Chemistry vol 94no 21 pp 8106ndash8112 1990

[16] G Keresztury S Holly J Varga G Besenyei A Wang andJ R Durig ldquoVibrational spectra of monothiocarbamates-IIIR and Raman spectra vibrational assignment conforma-tional analysis and ab initio calculations of S-methyl-NN-dimethylthiocarbamaterdquo Spectrochimica Acta A vol 49 no 13-14 pp 2007ndash2017 1993

[17] G Keresztury ldquoRaman spectroscopy theoryrdquo in Handbook ofVibrational Spectroscopy J M Chalmers and P R Griffths Edsvol 1 p 71 John Wiley and Sons 2002

[18] R G Parr R A Donnelly M Levy and W E Palke ldquoElec-tronegativity the density functional viewpointrdquo The Journal ofChemical Physics vol 68 no 8 pp 3801ndash3807 1977

[19] R G Parr and R G Pearson ldquoAbsolute hardness companionparameter to absolute electronegativityrdquo Journal of theAmericanChemical Society vol 105 no 26 pp 7512ndash7516 1983

[20] R G Pearson ldquoAbsolute electronegativity and hardness appli-cation to inorganic chemistryrdquo Inorganic Chemistry vol 27 no4 pp 734ndash740 1988

[21] P Geerlings F De Proft and W Langenaeker ldquoConceptualdensity functional theoryrdquo Chemical Reviews vol 103 no 5 pp1793ndash1873 2003

[22] R Ditchfield ldquoMolecular orbital theory of magnetic shieldingand magnetic susceptibilityrdquo Journal of Physical Chemistry vol56 no 11 article 5688 4 pages 1972

[23] KWolinski J F Hilton and P Pulay ldquoEfficient implementationof the gauge-independent atomic orbital method for NMRchemical shift calculationsrdquo Journal of the American ChemicalSociety vol 112 no 23 pp 8251ndash8260 1990

[24] M Kurt M Yurdakul and S Yurdakul ldquoMolecular structureand vibrational spectra of 3-chloro-4-methyl aniline by densityfunctional theory and ab initio Hartree-Fock calculationsrdquoJournal of Molecular Structure vol 711 no 1ndash3 pp 25ndash32 2004

[25] D Steele and D H Whiffen ldquoThe vibration frequencies ofpentafluorobenzenerdquo Spectrochimica Acta vol 16 no 3 pp368ndash375 1960

[26] D N Sathyanarayanan Vibrational Spectroscopy Theory andApplication New Age International publishers New DelhiIndia 1996

[27] L D S YadavOrganic Spectroscopy Springer NewDelhi India2004

[28] J Mohan Organic Spectroscopy Principles and ApplicationsNarosa Publishing House New Delhi 2nd edition 2009

[29] R M Silverstein G C Bassler and T C Morrill SpectrometricIdentification of Organic Compounds John Wiley amp Sons NewYork NY USA 1981

[30] G Socrates Infrared Characteristic Group Frequencies WileyNew York NY USA 1980

[31] R S Mulliken ldquoElectronic population analysis on LCAO-MOmolecular wave functionsrdquoThe Journal of Chemical Physics vol23 no 10 pp 1833ndash1840 1955

[32] K Fukuli T Yonezawa and H Shingu ldquoA molecular orbitaltheory of reactivity in aromatic hydrocarbonsrdquo Journal ofPhysical Chemistry vol 20 no 4 article 722 4 pages 1952

[33] C H Choi and M Kertesz ldquoConformational information fromvibrational spectra of styrene trans-stilbene and cis-stilbenerdquoJournal of Physical Chemistry A vol 101 no 20 pp 3823ndash38311997

[34] S Gunasekaran R Arun Balaji S Kumaresan G Anandand S Srinivasan ldquoExperimental and theoretical investigationsof spectroscopic properties of N-acetyl-5-methoxytryptaminerdquoCanadian Journal of Analytical Sciences and Spectroscopy vol53 no 4 pp 149ndash162 2008

[35] P Hohenberg and W Kohn ldquoInhomogeneous electron gasrdquoPhysical Review vol 136 no 3 pp B864ndashB871 1964

[36] R G Pearson ldquoAbsolute electronegativity and absolute hard-ness of Lewis acids and basesrdquo Journal of the American ChemicalSociety vol 107 no 24 pp 6801ndash6806 1985

[37] D Avci Y Atalay M Sekerci and M Dincer ldquoMolecular struc-ture and vibrational and chemical shift assignments of 3-(2-Hydroxyphenyl)-4-phenyl-1H-124-triazole-5-(4H)-thione byDFT and ab initio HF calculationsrdquo Spectrochimica Acta A vol73 no 1 pp 212ndash217 2009

[38] H O Kalinowski S Berger and S Braun Carbon13 NMRSpectroscopy John Wiley amp Sons Chichester UK 1988

[39] K Pihlaja and E Kleinpeter Carbon-13 NMR Chemical Shiftsin Structural and Sterochemical Analysis VCH PublishersDeerfield Beach Fla USA 1994

[40] P S Kalsi Spectroscopy of Organic Compounds New AgeInternational 2004

[41] A F Parsons Keynotes in Organic Chemistry Blackwell Pub-lishing Oxford UK 2003

[42] M A Palafox ldquoScaling factors for the prediction of vibrationalspectra I benzenemoleculerdquo International Journal of QuantumChemistry vol 77 no 3 pp 661ndash684 2000

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

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Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

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Journal of

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Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

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Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

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CatalystsJournal of

Page 6: Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. · Molecular Structure, NMR, HOMO, LUMO, ... ects of carbonyl and methyl substitutions

6 Journal of Spectroscopy

Table 4 Definition of natural internal coordinates of O-Anisic acid (OAA)

No (i) Symbola Definitionb

1ndash4 CndashH stretch 1199031 1199032 1199033 1199034

5ndash11 CndashC stretch 1199035 1199036 1199037 1199038 1199039 11990310 11990311

12ndash14 CndashO stretch 11990312 11990313 11990314

15 OndashC stretch 11990315

16 OndashH stretch 11990316

17 CH3 ss (11990317+ 11990318+ 11990319) radic3

18 CH3 ips (211990317minus 11990318minus 11990319) radic6

19 CH3 ops (11990318minus 11990319) radic2

20 bCndashCndashC (12057320minus 12057321) radic2

21ndash24 bCndashCndashH (12057322minus 12057323) radic2 (120573

24minus 12057325) radic2 (120573

26minus 12057327) radic2 (120573

28minus 12057329) radic2

25 CH3 sb (minus12057330minus 12057331minus 12057332+ 12057333+ 12057334+ 12057335) radic6

26 CH3 ipb (minus12057333minus 12057334minus 212057335)radic6

27 CH3 opb (12057333minus 12057334) radic2

28 CH3 ipr (212057330minus 12057331minus 12057332)radic6

29 CH3 opr (12057331minus 12057332)radic2

30 bCndashCndashO (12057336minus 12057337) radic2

31 bCndashOndashH 12057338

32-33 bCndashCndashO 12057339 12057340

34 bCndashOndashC 12057341

35 Rtrigd (12057342minus 12057343+ 12057344minus 12057345+ 12057346minus 12057347) radic6

36 Rsymd (minus12057342minus 12057343+ 12057344minus 12057345minus 12057346+ 212057347)radic12

37 Rasymd (12057342minus 12057343+ 12057345minus 12057346) 2

38ndash41 120596CndashH 12059648 12059649 12059650 12059651

42 120596CndashC 12059652

43 120596CndashO 12059653

44-45 tCndashO 12059154 12059155

46 tCndashOndashC 12 (12059156+ 12059157)

47 tCH3 13 (12059158+ 12059159+ 12059160)

48 tOndashH 12059161

49 Ttrigd (12059162minus 12059163+ 12059164minus 12059165+ 12059166minus 12059167) radic6

50 Tsymd (12059162minus 12059163+ 12059165+ 12059166) 2

51 Tasymd (minus12059162+ 212059163minus 12059164minus 12059165+ 12059166minus 12059167) radic12

aThese symbols are used for description of the normal modes by PED in Table 7bThe internal coordinates used here are defined in Table 2

appearing at 960 937 865 and 755 cmminus1 in OAA and929 854 846 and 774 cmminus1 in AA were assigned toout-of-plane deformation type of vibration (120596) of CndashHgroups There is slight increase in the CndashH out-of-planedeformation frequency because of strong intermolecularhydrogen bonding in OAA In these bands the pronouncedparticipation of other types of vibrations is observed Theseare also supported by the literature

432 Carboxylic Acid Vibrations Due to the presence ofstrong intermolecular hydrogen bonding the FT-IR spectraexhibits spectra exhibit a broad band due to the OndashHstretching vibrations and a strong banddue toC=Ostretchingvibrations The carboxylic acid dimers display a very broadand intenseOndashH stretching absorption in the region of 3300ndash2500 cmminus1 [28] The title molecules both exhibit intermolec-ular hydrogen bonding In our case the bands at 3390 cmminus1

in OAA and 3435 cmminus1 in AA are assigned as OndashH stretchingvibrations There is a slight increase in the OndashH frequencybecause of steric effect in OAA and +I effect in AA The OndashH out-of-plane bending vibration occurs near the region of920 cmminus1 [27] The bands appearing at 595 cmminus1 in OAA and505 cmminus1 in AA are assigned to OndashH out-of-plane bendingvibrationThe OndashH out-of-plane bending vibrations in OAAand AA decrease due to intermolecular hydrogen bonding

The carbonyl stretching vibrations are expected in theregion 1720 cmminus1ndash1680 cmminus1 [28] The IR band at 1670 cmminus1in OAA and FT-Raman band at 1688 cmminus1 in AA are assignedasC=O stretching vibrationsTheCndashObond appears stronglyin the 1320ndash1210 cmminus1 region [29] The bands observed at1049 and 795 cmminus1 in OAA and 1267 and 1100 cmminus1 in AAare assigned to CndashO stretching mode The CndashO stretchingvibrational frequency is lower than general range In thecase of carboxylic acid dimers like OAA and AA the OH

Journal of Spectroscopy 7

Table 5 Definition of natural internal coordinates of Anisic acid (AA)

No (i) Symbola Definitionb

1ndash4 CndashH stretch 1199031 1199032 1199033 1199034

5ndash10 CndashC stretch 1199035 1199036 1199037 1199038 1199039 11990310

11 CndashCfn stretch 11990311

12ndash14 CndashO stretch 11990312 11990313 11990314

15 OndashC stretch 11990315

16 OndashH stretch 11990316

17 CH3 ss (11990317+ 11990318+ 11990319) radic3

18 CH3 ips (211990317minus 11990318minus 11990319) radic6

19 CH3 ops (11990318minus 11990319) radic2

20 bCndashCndashC (12057320minus 12057321) radic2

21ndash24 bCndashCndashH (12057322minus 12057323) radic2 (120573

24minus 12057325) radic2 (120573

26minus 12057327) radic2 (120573

28minus 12057329) radic2

25 CH3 sb (minus12057330minus 12057331minus 12057332+ 12057333+ 12057334+ 12057335) radic6

26 CH3 ipb (minus12057333minus 12057334minus 212057335)radic6

27 CH3 opb (12057333minus 12057334) radic2

28 CH3 ipr (212057330minus 12057331minus 12057332) radic6

29 CH3 opr (12057331minus 12057332) radic2

30 bCndashCndashO (12057335minus 12057336) radic2

31 bCndashOndashH 12057338

32-33 bCndashCndashO 12057339 12057340

34 bCndashOndashC 12057341

35 Rtrigd (12057342minus 12057343+ 12057344minus 12057345+ 12057346minus 12057347) radic6

36 Rsymd (minus12057342minus 12057343+ 12057344minus 12057345minus 12057346+ 212057347) radic12

37 Rasymd (12057342minus 12057343+ 12057345minus 12057346) 2

38ndash41 120596CndashH 12059648 12059649 12059650 12059651

42 120596CndashC 12059652

43 120596CndashO 12059653

44-45 tCndashO 12059154 12059155

46 tCndashOndashC 12 (12059156+ 12059157)

47 tCH3 13 (12059158+ 12059159+ 12059160)

48 tOndashH 12059161

49 Ttrigd (12059162minus 12059163+ 12059164minus 12059165+ 12059166minus 12059167) radic6

50 Tsymd (12059162minus 12059163+ 12059165+ 12059166)2

51 Tasymd (minus12059162+ 212059163minus 12059164minus 12059165+ 12059166minus 12059167) radic12

aThese symbols are used for description of the normal modes by PED in Table 8bThe internal coordinates used here are defined in Table 3

in-plane bending and CndashO stretching bands involve someinteraction between them they are referred to as coupledOH in-plane bending and CndashO stretching vibrations [26]The CndashO bending vibration occurs in the region of 580ndash340 cmminus1 [30] The band observed at 380 cmminus1 in OAA and440 cmminus1 in AA are assigned to CndashO bending mode Thepresent assignments agree very well with the values availablein the literature

433 Methyl Group Vibrations The title molecules OAAand AA under consideration possess one CH

3group For

the assignments of CH3group one can expect that 9 fun-

damentals can be associated with each CH3group namely

the symmetrical stretching (CH3symmetric stretch) and

asymmetrical stretching (CH3asymmetric stretch) in-plane

stretching modes (ie in-plane hydrogen stretching modes)

and the symmetrical (CH3symmetric deform) and asym-

metrical (CH3asymmetric deform) deformation modes in-

plane rocking (CH3ipr) out-of-plane rocking (CH

3opr) and

twisting (tCH3) bending modes

For the methyl group compounds the asymmetricstretching mode appeared in the range 2965ndash3005 cmminus1 andthe symmetric stretching mode appeared in the range of2815ndash2860 cmminus1 [30] The FT-Raman band at 2983 cmminus1 forOAA and IR band at 2941 cmminus1 for AA are symmetricstretching The symmetric stretching vibrational frequencyis higher in OAA and AA due to steric effect and +I effectThe asymmetric methyl stretching band appeared at 30033018 cmminus1 in OAA and 2990 2956 cmminus1 in AA respectivelyThe asymmetric deformation mode appeared in the range1445ndash1485 cmminus1 and symmetric deformation mode appearedin the range of 1420ndash1460 cmminus1 [30] The IR band at 1466

8 Journal of Spectroscopy

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 2 FTIR spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Table 6 Diagonal force constants (102 Nmminus1) of O-Anisic acid(OAA) and Anisic acid (AA)

Descriptiona Force constantsb

OAA AAC1ndashC2 621 630C2ndashC3 633 696C3ndashC4 677 626C4ndashC5 675 628C5ndashC6 682 663C6ndashC1 644 648C1ndashC7 465 222C7ndashO8 532 522C7ndashO9 1030 1128C2ndashO11(C4ndashO13) 449 576O11ndashC12(O13ndashC14) 413 499O9ndashH10 644 661C12ndashH13(C14ndashH15) 498 508C12ndashH14(C14ndashH16) 526 470C12ndashH15(C14ndashH17) 498 507C3ndashH16(C2ndashH11) 514 498C4ndashH17(C3ndashH12) 501 496C5ndashH18 505 500C6ndashH19 532 522aThe atoms indicated in the parenthesis belong to AAbStretching force constants are given in mdyn A

minus1

For numbering of atoms refer to Figures 1(a) and 1(b)

and 1435 cmminus1 in OAA and 1468 and 1461 cmminus1 in AA areassigned as asymmetric deformation vibrations The IR bandat 1411 cmminus1 for OAA and 1429 cmminus1 for AA are symmet-ric deformation mode The CH

3deformation absorption

occurs at 1466 cmminus1 and 1429 cmminus1 this vibration is knownas umbrella mode that overlaps with CC ring stretchingvibrations for the title compounds These are also supportedby the literature

The tensional modes appeared in the range of 265ndash185 cmminus1 [30] This modes are strongly coupled with other

vibrations that are observed at 280 cmminus1 inOAAand 165 cmminus1in AAwhich are in agreement with the calculated results also

434 Ring Vibrations The ring CndashC stretching vibrationsoccur in the region of 1600ndash1400 cmminus1 [29]The bands appearat 1600 1579 1312 1184 1153 1062 and 698 cmminus1 in OAAand 1608 1580 1416 1307 1107 1028 and 825 cmminus1 in AAwere assigned to CndashC stretching vibrations The shift in thefrequency of CndashC vibrations towards lower wave numbermay be due to the COOH and OCH

3groups Many ring

modes are affected by the substitutions in the aromatic ringThe bands at 180 cmminus1 and 285 cmminus1 for OAA and AA wereassigned to CndashC bending vibrationsThe out-of-plane and in-plane deformations of the phenyl ring are observed below1000 cmminus1 and these modes are sensitive by the additionof functional groups The out-of-plane bending vibrationswere observed at 170 cmminus1 and 111 cmminus1 for OAA and AASmall changes in the wavenumbers were observed due tothe presence of +I effect in AA and steric effect in OAAThe computed wavenumbers are in good agreement withexperimental data

5 Electronic Properties

Atomic charges on the various atoms of OAA and AAobtained by Mulliken population analysis [31] are given inTable 9 From the listed atomic charge values the oxygen[O8 O9] and O11 in OAA and O13 in AA atoms had a largenegative charge and behaved as electron acceptor It was alsoobserved that there is a large accumulation of charge on O11inOAAO13 in AAmoleculesTherefore C7 andO11 inOAAand C7 and O13 in AA had a greater ionic character

Natural bond orbital analysis provides an efficientmethod for studying steric effect and intermolecular bondingand interaction among bonds and also provides a convenientbasis for investigating charge transfer or conjugative interac-tion in molecular systems Natural charge analysis is givenin Table 10 for the title compounds The results show thatsubstitution of COOH and CH

3group in OAA and AA leads

to a redistribution of electron density The C7 atom in OAAand AA is more positive charge (+08091 +08139) In the

Journal of Spectroscopy 9Ta

ble7Detailedassig

nmento

ffun

damentalvibratio

nsof

O-Anisic

acid

(OAA)b

yno

rmalmod

eanalysis

basedon

SQM

forcefi

eldcalculations

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

1A1015840

3390

mdash3771

3390

72652

155385

120592OH(100)

2A1015840

mdash3098

3273

3098

1612

499564

120592CH

(99)

3A1015840

mdash3083

3233

3083

1700

135114

120592CH

(99)

4A1015840

3069

mdash3207

3069

10674

70382

120592CH

(99)

5A1015840

mdash3020

3186

3024

17253

1372

01120592CH

(99)

6A1015840

3018

mdash3157

3018

38987

58202

120592CH

3(99)

7A10158401015840

3003

mdash3085

3003

5946

78409

120592CH

3(99)

8A1015840

mdash2983

3020

2983

52626

120657

120592CH

3(99)

9A1015840

1670

mdash1822

1670

358567

54628

120592CO

(53)120592CC

(14)bC

CO(14

)bC

OH(12)

10A1015840

1600

mdash1656

1600

15061

16343

120592CC

(60)bCH

(20)R

asym

d(10)

11A1015840

1579

mdash1630

1579

61364

48880

120592CC

(69)bCH

(19)

12A1015840

1494

mdash1539

1494

58214

10686

bCH(48)120592CC

(37)

13A1015840

1466

mdash1513

1466

6534

6058

bCH

3(43)bCH

(25)120592CC

(16)

14A1015840

mdash1439

1506

1439

22318

5639

bCH(39)bCH

3(37)120592CC

(17)

15A10158401015840

1435

mdash1500

1435

3652

510814

bCH

3(88)

16A1015840

1411

mdash1475

1411

11849

19713

bCH

3(74)

17A1015840

1382

1367

4497

1268

bCOH(35)120592CO

(32)bCC

O(13)120592CC

(11)

18A1015840

mdash1312

1350

1312

2182

8877

120592CC

(67)

19A1015840

1288

mdash1320

1288

6319

416

48bC

H(33)R

trigd(20)120592CO

(13)120592CC

(12)

20A1015840

mdash1287

1302

1287

19694

044

9Rtrig

d(26)120592CC

(25)bCH

(20)120592CO

(12)

21A1015840

mdash1184

1210

1184

228252

32980

120592CC

(31)bCH

(19)bC

H3(17)120592CO

(17)

22A1015840

1182

mdash1201

1182

162989

2713

6bC

H(42)120592CC

(34)bCH

3(10)

23A1015840

1170

mdash119

3117

015

764576

bCH

3(57)bCH

(24)

24A1015840

mdash117

3117

31153

7419

1097

120592CC

(31)bCH

(29)bCH

3(25)

25A1015840

1140

mdash1168

1140

0662

4253

bCH

3(96)

26A1015840

1049

mdash1087

1050

1073

0478

09120592CO

(29)120592CC

(27)R

trigd(12)

27A1015840

-1062

1077

1060

104848

21650

120592CC

(41)120592CO

(22)bCH

(12)

28A10158401015840

960

-1060

960

060

90057

120596CH

(91)

29A1015840

mdash974

989

974

2078

710836

120592OC(62)120592CC

(12)120592CO

(11)

30A10158401015840

937

mdash965

935

1244

1294

120596CH

(91)

31A10158401015840

mdash865

869

865

3148

3432

120596CH

(64)ttrigd(19)

32A1015840

mdash795

830

795

12200

4238

120592CO

(29)R

symd(21)120592OC(15)120592CC

(15)

33A10158401015840

761

mdash795

761

1002

0207

tCO(32)ttrigd(28)120596

CH(23)120596

CC(11)

34A10158401015840

mdash755

770

755

41473

1456

120596CH

(51)ttrigd(27)120596

CO(14

)35

A10158401015840

695

mdash747

698

64512

0469

ttrigd(52)120596

CH(23)tCO

(15)

36A1015840

mdash698

712

695

10016

17946

120592CC

(33)120592CO

(23)bCC

O(21)

37A1015840

mdash602

639

602

13503

2683

Rasymd(36)bCC

O(15)

120592CC

(12)R

symd(11)

38A10158401015840

mdash595

594

595

74804

8168

tOH(79)

39A1015840

mdash565

588

565

21902

1740

bCCO

(28)120592CC

(17)bCO

(15)R

symd(14

)bC

CO(13)

10 Journal of Spectroscopy

Table7Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

540

mdash548

540

5598

4848

bCCO

(40)bCC

(16)120592CC

(13)R

asym

d(10)

41A10158401015840

480

mdash540

480

0946

0860

120596CO

(40)120596

CH(16)ttrigd(14

)tsy

m(14

)42

A10158401015840

mdash40

1435

401

3585

0792

tsym

(14)120596CC

(15)

43A1015840

mdash380

388

380

4805

4133

bCO(64)bCC

O(16)

44A1015840

mdash303

383

303

1180

4980

Rsym

d(59)bCO

C(17)120592CC

(15)

45A10158401015840

mdash280

283

280

0092

0016

tCH

3(79)

46A1015840

mdash240

280

240

0927

0935

bCOC(40)bCC

(30)bCC

O(18)

47A10158401015840

mdash180

229

180

0018

2096

120596CC

(30)tCO

(20)tsym

(18)

tasym

(11)120596CH

(10)

48A1015840

mdash170

190

170

3092

0715

bCC(42)bCO

C(29)bCO

(12)

49A10158401015840

mdash115

119115

4502

0508

tCOC(47)tsym

(15)tCH

3(12)

50A10158401015840

mdash110

9696

0922

3779

tsym

(35)tCO

(25)

tCOC(21)tCH

3(13)

51A10158401015840

mdashmdash

1730

1260

0037

tCO(99)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 11Ta

ble8Detailedassig

nmento

ffun

damentalvibratio

nsof

Anisic

acid

(AA)b

yno

rmalmod

eanalysis

basedon

SQM

forcefi

eldcalculations

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

1A1015840

3435

mdash3768

3435

7952

3164209

120592OH(100)

2A1015840

mdash3085

3232

3085

21438

120058

120592CH

(89)

3A1015840

mdash3034

3224

3034

7547

126718

120592CH

(99)

4A1015840

3029

mdash3218

3029

3520

99229

120592CH

(99)

5A1015840

3002

mdash3209

3002

5141

52552

120592CH

(99)

6A1015840

2990

mdash3155

2990

2423

53071

120592CH

ops(99)

7A10158401015840

2956

mdash3087

2956

45319

94074

120592CH

ips(51)120592CH

ss(36)120592CH

ops(12)

8A1015840

2941

mdash3022

2941

42847

91231

120592CH

ss(56)120592CH

ips(44

)9

A1015840

1688

mdash1813

1688

302139

74665

120592CO

(72)bCC

O(17)

10A1015840

1608

mdash1666

1608

216104

153242

120592CC

(62)bCH

(22)R

symd(11)

11A1015840

1580

mdash1624

1580

34785

12359

120592CC

(66)bCH

(14)

12A1015840

1518

mdash1559

1518

41495

8422

bCH(52)120592CC

(30)

13A1015840

1468

mdash1516

1468

37550

10673

bCHsb

(77)

14A10158401015840

1461

mdash1504

1461

14058

1218

3bC

Hop

b(83)

15A1015840

1429

mdash1486

1429

5851

19586

bCHipb(70)120592CC

(10)bCH

(10)

16A1015840

1416

mdash1465

1416

14835

9149

120592CC

(39)bCH

(35)bCH

ipb(18)

17A1015840

1324

mdash1391

1324

31290

5311

bCOH(27)120592CO

(22)bCC

O(21)120592CC

(13)

18A1015840

1307

mdash1371

1307

806

814

44120592CC

ar(65)bCH

(20)

19A1015840

1301

mdash1331

1301

40408

7073

bCH(43)120592CC

(33)

20A1015840

1267

mdash1304

1267

245222

3723

120592CO

(37)R

trigd(20)120592CC

(16)

21A1015840

1181

mdash1221

1181

5734

6023

bCH(61)120592CC

(21)

22A1015840

1172

mdash1209

1172

5690

5161

bCHop

r(61)bC

H(13)

23A1015840

mdash1137

1189

1137

0662

4334

bCHipr(78)bC

Hop

r(14)

24A1015840

1131

mdash117

61131

190946

42508

bCH(35)120592CC

(21)

25A1015840

1107

mdash1139

1107

245972

63024

120592CC

fn(25)R

trigd(23)bCH

(16)120592OC(13)

26A1015840

mdash1100

1114

1100

318070

20809

120592CO

(40)bCO

H(22)bCC

O(11)

27A1015840

1028

mdash1069

1028

0786

11056

120592CC

(58)bCH

(16)

28A1015840

mdash1010

1026

1010

29566

2343

120592OC(51)120592CC

(28)

29A10158401015840

929

mdash991

929

0010

046

4120596CH

(89)

30A10158401015840

854

mdash966

854

1379

1924

120596CH

(82)ttrigd(12)

31A10158401015840

846

mdash863

846

3652

212

44120596CH

(39)120596

CO(32)ttrigd(20)

32A1015840

825

mdash834

825

24090

2237

3120592CC

ar(32)R

symd(27)120592OC(22)

33A10158401015840

774

mdash830

774

0365

4928

120596CH

(84)

34A10158401015840

mdash755

775

755

1082

0243

ttrigd(51)120596

CC(15)120596

CH(14

)tCO(11)

35A1015840

698

mdash725

698

3553

93075

bCCO

(44)120592CO

(25)bCO

H(25)

36A10158401015840

634

mdash710

634

76887

0059

tCO(57)120596

CH(20)ttrigd(12)

37A1015840

617

mdash647

617

0592

644

1Ra

symd(81)

38A1015840

550

mdash603

550

14566

0968

Rsym

d(32)120592CC

fn(13)120592CO

(11)bCC

O(11)bCO

C(10)

39A10158401015840

545

mdash601

545

27876

4847

120596CO

(42)tOH(14

)120596CH

(11)120596

CC(11)

12 Journal of Spectroscopy

Table8Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

525

mdash511

525

12735

1849

bCCO

(82)

41A1015840

505

mdash511

505

50036

5698

tOH(24)ttrigd(23)120596

CO(19)120596

CH(14

)42

A1015840

440

mdash481

440

3190

2294

bCO(35)bCO

C(29)

43A10158401015840

mdash375

427

375

0415

0023

tsym

(60)120596

CH(19

)tasym

(17)

44A1015840

mdash310

335

310

3569

0577

Rsym

d(48)120592CC

fn(25)

45A10158401015840

mdash285

304

285

4416

0596

120596CC

(33)tasym

(24)tCO

(16)

46A1015840

mdash220

267

220

3713

2509

bCOC(29)bCO

(17)

47A10158401015840

mdash165

226

165

0047

0429

tCH

3(85)

48A1015840

mdash111

165

111

0211

0159

bCC(80)

49A10158401015840

mdash98

132

982323

0292

Tasym

(30)tCO

C(30)120596

CC(11)120596

CH(10)tsym

(10)

50A10158401015840

mdash70

7870

1302

1199

tCO(95)

51A10158401015840

mdash60

6560

0898

0216

tCOC(48)tCO

(31)tCH

3(12)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 13

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 3 FT-Raman spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 4 FTIR spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 5 FT-Raman spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

title molecules all the hydrogen atoms have a net positivecharge in particular the hydrogen atoms H(10) that havecharge of 05047 and 05050 respectively The presence oflarge amounts of negative charge on oxygen and net positivecharge on H(10) atoms may suggest the presence of inter-molecular hydrogen bonding in the crystalline phase

Highest occupied molecular orbital and lowest unoc-cupied molecular orbital are very important parametersfor quantum chemistry This is also used by the frontierelectron density for predicting the most reactive position in120587-electron systems and also explains several types of reactionin conjugated system [32] The conjugated molecules are

characterized by a small highest occupied molecular orbitalndashlowest unoccupied molecular orbital (HOMO-LUMO) sep-aration which is the result of a significant degree of inter-molecular charge transfer from the end-capping electron-donating groups to the efficient electron-acceptor groupsthrough 120587 conjugated path [33] Both the highest occupiedmolecular orbital and lowest unoccupied molecular orbitalare the main orbitals that take part in chemical stability[34] Energy difference betweenHOMOand LUMOorbital iscalled energy gap that is an important stability for structureswhich are given in Table 11 We performed an analysis ofall the molecular orbitals involved taking into consideration

14 Journal of Spectroscopy

Table 9 Atomic charges for optimized geometry of O-Anisic acid(OAA) and Anisic acid (AA) obtained by B3LYP6-31Glowastlowast densityfunctional calculations

Atomsa MullikenOAA AA

C1 00018 00373C2 03297 minus01002

C3 minus01368 minus01219

C4 minus00836 03612

C5 minus00943 minus01394

C6 minus01061 minus01118

C7 05570 05445O8 minus04650 minus04848

O9 minus05104 minus05064

H10 03198 03217O11 (H11) minus04841 01203C12 (H12) minus00837 01021H13 (O13) 01064 minus05111

H14 (C14) 01352 minus00831

H15 01211 01099H16 00913 01302H17 00929 01246H18 00886 00913H19 01200 01155aThe atoms indicated in the parenthesis belong to AA

Table 10Natural atomic charges ofO-Anisic acid (OAA) andAnisicacid (AA) calculations performed at the B3LYP6-31Glowastlowast level oftheory

Atomsa OAA AAC1 minus02176 minus02053

C2 03724 minus01746

C3 minus03284 minus02801

C4 minus01952 03443

C5 minus02720 minus03289

C6 minus01806 minus01748

C7 08091 08139O8 minus05861 minus06102

O9 minus07295 minus07217

H10 05047 05050O11 (H11) minus04921 02634C12 (H12) minus03307 02544H13 (O13) 02070 minus05119

H14 (C14) 02390 minus03300

H15 02070 02090H16 02443 02352H17 02426 02090H18 02439 02449H19 02621 02585aThe atoms indicated in the parenthesis belong to AAFor numbering of atoms refer to Figures 1(a) and 1(b)

that orbital 40 is the HOMO and orbital 41 is the LUMO forOAA and AA respectively

Many organic molecules that contain conjugated 120587 elec-trons are characterized as hyperpolarisabilities and are ana-lyzed by means of vibrational spectroscopy The analysis

Table 11 Calculated quantum chemical parameters ofO-Anisic acid(OAA) and Anisic acid (AA) derivatives

Parameters OAA AA119864HOMO minus0227 minus0231

119864LUMO minus0041 minus0036

Δ119864 0186 0195120594 0134 0133Η 0093 0097Σ 10752 10256

Table 12 Calculated 13C NMR chemical shifts (ppm) of O-Anisicacid (OAA) and Anisic acid (AA)

Carbona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAC1 11782 12315 10447 12620C2 15848 13146 14696 13936C3 11204 11384 9681 12272C4 13517 16297 11926 17125C5 12191 11384 10447 11047C6 13347 13146 12019 13751C7 16634 16714 14609 17174C12 (C14) 5674 5544 4322 5549aThe atoms indicated in the parenthesis belong to AA

Table 13 Experimental and calculated 1H NMR chemical shifts(ppm) of O-Anisic acid (OAA) and Anisic acid (AA)

Protona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAH10 1030 13 11 11H13 H14 H15 (H11) 4066 7914 3932 8405H16 (H12) 708 7027 6831 7147H17 (H15 H16 H17) 756 3836 7570 3824H18 710 7027 7069 6673H19 813 7914 3932 8217aThe atoms indicated in the parenthesis belong to AA

of the wave function indicates that the electron absorptioncorresponds to the transition from the ground state to thefirst excited state and is mainly described by the one-electronexcitation from the HOMO to the LUMO The HOMO of 120587nature (ie aromatic ring) is delocalized over the whole CndashC bond By contrast the LUMO is located over the aromaticring Consequently the HOMO-LUMO transition implies anelectron density transfer toCOOHandOCH

3group from the

aromatic ringThe theoretical basis for the new quantities lies in the

density functional formalism [35] Since molecular orbital(MO) theory is by far the most widely used by chemistsit is important to place 120594 and 120578 in a MO framework Ithas already been shown [36] that the MO theory of thechemical bond contains the values of 120594 and 120578 for the bondingfragments Hard molecules have a large HOMO-LUMO gapand soft molecules have a small HOMO-LUMO gap A small

Journal of Spectroscopy 15

HOMO

(a)

LUMO

(b)

Figure 6 Contour surfaces of frontier molecular orbitals of O-Anisic acid

HOMO

(a)

LUMO

(b)

Figure 7 Contour surfaces of frontier molecular orbitals of Anisic acid

HOMO-LUMO gap automatically means small excitationenergies to the manifold of excited states Therefore softmolecules with a small gap will be more polarizable thanhard molecules High polarizability was the most character-istic property attributed to soft acids and bases Energy gapsshould be small for best bonding or bothmolecules should besoft

In the present study the title compound AA is dynam-ically more stable due to the large energy gap OAA is asoft molecule due to small energy gap The Contour surfacesof the frontier molecular orbitals are sketched in Figures 6and 7

51 NMR Spectra DFT methods treat the electronic energyas a function of the electron density of all electrons simul-taneously and thus include electron correlation effect [37]In this study molecular structure of the OAA and AA wasoptimized by using B3LYP method in conjunction with 6-31Glowastlowast 13C and 1H chemical shift calculations of the titlecompounds have been made by using GIAO method andsame basis set The isotropic shielding values were usedto calculate the isotropic chemical shifts 120575 with respect totetramethylsilane (TMS) The isotropic chemical shifts arefrequently used as an aid in identification of reactive ionicspecies The B3LYP method allows calculating the shielding

16 Journal of Spectroscopy

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 150

140

130

120

110

100

90110 120 130 140 150 160 170

(a)

70 75 80 85 90 95 100 1056

7

8

9

10

11

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

(b)

Figure 8 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for O-Anisic acid

constants with the proper accuracy and the GIAOmethod isone of the most common approaches for calculating nuclearmagnetic shielding tensors

Theoretical and experimental chemical shifts of OAA andAA in 1H and 13C NMR spectra are gathered in Tables 12and 13 The range of the 13C NMR chemical shifts for atypical organic molecules usually is gt100 ppm [38 39] andthe accuracy ensures reliable interpretation of spectroscopicparameters In the present study the 13C NMR chemicalshifts in the ring are gt100 ppm as they would be expectedThe 13C chemical shifts carbonyl carbons vary from 150 to220 ppm This depends on the decrease in electron donatingor shielding ability of the attached atoms [40] The C=Ogroups of carboxylic acids and derivatives are in the range of150ndash185 ppm [29]

Hydrogens bonded to an aromatic ring are stronglydeshielded and absorb downfieldWhen the120587-electrons enterthe magnetic field they circulate around the ring to generatea ring current This produces a small induced magnetic fieldthat reinforces the applied field outside the ring resultingin aromatic protons being deshielded [41] A related effectis observed for carboxylic acids For these compoundscirculation of electrons in the double bonds produces inducedmagnetic field These are responsible for the high chemicalshift values of acid protons (H10) Carboxylic acids asstable hydrogen-bonded dimers in nonpolar solvents even athigh dilution The carboxylic proton therefore absorbs in acharacteristically narrow range 132 to 100 and is affectedonly slightly by concentration [29]

In a methyl group a proton is covalently bonded tocarbon oxygen or other atoms by a sigma bond Whenplaced in a strong magnetic field the electrons of the sigmabond circulate to generate a small magnetic field whichopposes the applied field A nearby electronegative atomwithdraws electron density from the neighbourhood of theproton so that a smaller applied field is needed to cause thespin state of the proton to flip The signal for a deshielded

Table 14 Theoretically computed energies (au) zero-point vibra-tional energies (kcalmolminus1) rotational constants (GHz) entropies(calmolminus1 Kminus1) nuclear repulsion energy (Hartrees) and dipolemoment (Debye) for OAA and AA

Parameters B3LYP6-31Glowastlowast

OAA AAZero-point energy 9306056 9314966

Rotational constants139942 344405114384 056752063193 048875

EntropyTotal 99243 97126Translational 40967 40967Rotational 30142 30199Vibrational 28134 25960Dipole moment 24181 35822Nuclear repulsion energy 592968293 573992628

proton (1 surrounded by less electron density) is observed tobe more downfield than the signals for protons that are notdeshielded by electronegative atoms [40] The chemical shiftvalue of C7 (OAA and AA) has bigger value than the othercarbons due to the electronegative property of oxygen atom

The linear correlations between calculated and experi-mental data of 13CNMRand 1HNMRspectra are determinedas 09 and 10 for OAA and 09 and 09 for AA respectivelyThere is an excellent linear relationship between experimentaland computed results which are shown in Figures 8 and 9

6 Thermodynamic Properties

Several calculated thermodynamical parameters are pre-sented in Table 14 for OAA andAA respectively Scale factorshave been recommended [42] for an accurate prediction in

Journal of Spectroscopy 17

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 180

170

160

150

140

130

120

110110

120 130 140 150 160 170

(a)

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

11

10

9

8

7

7 8 9 10 11 12 13

(b)

Figure 9 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for Anisic acid

determining the zero-point vibration energies (ZPVE) andthe entropy 119878vib(119879) The total energies and the change inthe total entropy at room temperature using B3LYP6-31Glowastlowastmethod are presented

7 Conclusion

Attempts have been made in the present work for the molec-ular parameters and frequency assignments for the com-pounds OAA and AA from the FTIR and FT-Raman spectraThe equilibrium geometries and harmonic and anharmonicfrequencies for the title compounds were determined andanalyzed at DFT level of theory utilizing 6-31Glowastlowast basis setThe assignments of most of the fundamentals of the titlecompounds provided in this work are quite comparableThe excellent agreement of the calculated and observedvibrational spectra reveals the advantages of a smaller basisset for quantum chemical calculations HOMO and LUMOenergy gap explains the eventual charge transfer interactionstaking place within the molecule The experimental andtheoretical investigation of the title compounds have beenperformed successfully by using 1H and 13C NMR Thevarious modes of vibrations were unambiguously assignedon the basis of the result of the PED output obtainedfrom normal coordinate analysis These studies confirm thepresence of COOH and OCH

3group Dimeric molecules are

held together by hydrogen bridges between carbonyl groupsThe obtained data and simulations both show the way to thecharacterization of the molecules and help in spectra studiesin the future

References

[1] GMelentyeva and LAntonovaPharmaceutical ChemistryMirPublishers Moscow Russia 1988

[2] ldquoo-Anisic acid(579-75-9) catalog of chemical suppliersrdquo httpwwwchemexpercomchemicalssuppliercas579-75-9html

[3] B A Hess Jr L J Schaad P Carsky and R Zaharaduick ldquoAbinitio calculations of vibrational spectra and their use in theidentification of unusual moleculesrdquo Chemical Reviews vol 86no 4 pp 709ndash730 1986

[4] P Pulay X Zhou and G Forgarasi in Recent Experimental andComputational Advances in Molecular Spectroscopy R Faustoand R Fransto Eds vol 406 ofNATOASI Series p 99 KluwerDordrecht Netherlands 1993

[5] P Pulay G Fogarasi G Pongor J E Boggs and A VarghaldquoCombination of theoretical ab initio and experimental infor-mation to obtain reliable harmonic force constants ScaledQuantum Mechanical (SQM) force fields for glyoxal acroleinbutadiene formaldehyde and ethylenerdquo Journal of the Ameri-can Chemical Society vol 105 no 24 pp 7037ndash7047 1983

[6] C E Blom and C Altona ldquoApplication of self-consistent-fieldab initio calculations to organic moleculesrdquo Molecular Physicsvol 31 no 5 pp 1377ndash1391 1976

[7] G Fogarasi and P Pulay in Vibrational Spectra and Structure JR Durig Ed vol 14 Elsevier Amsterdam Netherlands 1985

[8] G Fogarasi ldquoRecent developments in the method of SQM forcefields with application to 1-methyladeninerdquo Spectrochimica ActaA vol 53 no 8 pp 1211ndash1224 1997

[9] G R deMare N Yu Panchenko andW Ch Bock ldquoAnMP26-31GlowastMP26-31Glowast vibrational analysis of s-trans- and s-cis-acryloyl fluoride CH2=CH-CF=Ordquo The Journal of PhysicalChemistry vol 98 no 5 pp 1416ndash1420 1994

[10] G Pongor P Pulay G Fogarasi and J E Boggs ldquoTheoreticalprediction of vibrational spectra 1 The in-plane force fieldand vibrational spectra of pyridinerdquo Journal of the AmericanChemical Society vol 106 no 10 pp 2765ndash2769 1984

[11] Y Yamakitu and M Tasumi ldquoVibrational analyses of p-benzoquinodimethane and p-benzoquinone based on ab initioHartree-Fock and second-order Moller-Plesset calculationsrdquoThe Journal of Physical Chemistry vol 99 no 21 pp 8524ndash85341995

18 Journal of Spectroscopy

[12] M Karabacak A Coruh and M Kurt ldquoFT-IR FT-RamanNMR spectra and molecular structure investigation of 23-dibromo-N-methylmaleimide a combined experimental andtheoretical studyrdquo Journal of Molecular Structure vol 892 no1ndash3 pp 125ndash131 2008

[13] M S Masoud M K Awad M A Shaker and M M T El-Tahawy ldquoThe role of structural chemistry in the inhibitiveperformance of some aminopyrimidines on the corrosion ofsteelrdquo Corrosion Science vol 52 no 7 pp 2387ndash2396 2010

[14] M J Frisch G W Trucks H B Schlegel et al Gaussian 03Revision B4 Gaussian Inc Pittsburgh Pa USA 2003

[15] P L Polavarapu ldquoAb initio vibrational Raman and Ramanoptical activity spectrardquo Journal of Physical Chemistry vol 94no 21 pp 8106ndash8112 1990

[16] G Keresztury S Holly J Varga G Besenyei A Wang andJ R Durig ldquoVibrational spectra of monothiocarbamates-IIIR and Raman spectra vibrational assignment conforma-tional analysis and ab initio calculations of S-methyl-NN-dimethylthiocarbamaterdquo Spectrochimica Acta A vol 49 no 13-14 pp 2007ndash2017 1993

[17] G Keresztury ldquoRaman spectroscopy theoryrdquo in Handbook ofVibrational Spectroscopy J M Chalmers and P R Griffths Edsvol 1 p 71 John Wiley and Sons 2002

[18] R G Parr R A Donnelly M Levy and W E Palke ldquoElec-tronegativity the density functional viewpointrdquo The Journal ofChemical Physics vol 68 no 8 pp 3801ndash3807 1977

[19] R G Parr and R G Pearson ldquoAbsolute hardness companionparameter to absolute electronegativityrdquo Journal of theAmericanChemical Society vol 105 no 26 pp 7512ndash7516 1983

[20] R G Pearson ldquoAbsolute electronegativity and hardness appli-cation to inorganic chemistryrdquo Inorganic Chemistry vol 27 no4 pp 734ndash740 1988

[21] P Geerlings F De Proft and W Langenaeker ldquoConceptualdensity functional theoryrdquo Chemical Reviews vol 103 no 5 pp1793ndash1873 2003

[22] R Ditchfield ldquoMolecular orbital theory of magnetic shieldingand magnetic susceptibilityrdquo Journal of Physical Chemistry vol56 no 11 article 5688 4 pages 1972

[23] KWolinski J F Hilton and P Pulay ldquoEfficient implementationof the gauge-independent atomic orbital method for NMRchemical shift calculationsrdquo Journal of the American ChemicalSociety vol 112 no 23 pp 8251ndash8260 1990

[24] M Kurt M Yurdakul and S Yurdakul ldquoMolecular structureand vibrational spectra of 3-chloro-4-methyl aniline by densityfunctional theory and ab initio Hartree-Fock calculationsrdquoJournal of Molecular Structure vol 711 no 1ndash3 pp 25ndash32 2004

[25] D Steele and D H Whiffen ldquoThe vibration frequencies ofpentafluorobenzenerdquo Spectrochimica Acta vol 16 no 3 pp368ndash375 1960

[26] D N Sathyanarayanan Vibrational Spectroscopy Theory andApplication New Age International publishers New DelhiIndia 1996

[27] L D S YadavOrganic Spectroscopy Springer NewDelhi India2004

[28] J Mohan Organic Spectroscopy Principles and ApplicationsNarosa Publishing House New Delhi 2nd edition 2009

[29] R M Silverstein G C Bassler and T C Morrill SpectrometricIdentification of Organic Compounds John Wiley amp Sons NewYork NY USA 1981

[30] G Socrates Infrared Characteristic Group Frequencies WileyNew York NY USA 1980

[31] R S Mulliken ldquoElectronic population analysis on LCAO-MOmolecular wave functionsrdquoThe Journal of Chemical Physics vol23 no 10 pp 1833ndash1840 1955

[32] K Fukuli T Yonezawa and H Shingu ldquoA molecular orbitaltheory of reactivity in aromatic hydrocarbonsrdquo Journal ofPhysical Chemistry vol 20 no 4 article 722 4 pages 1952

[33] C H Choi and M Kertesz ldquoConformational information fromvibrational spectra of styrene trans-stilbene and cis-stilbenerdquoJournal of Physical Chemistry A vol 101 no 20 pp 3823ndash38311997

[34] S Gunasekaran R Arun Balaji S Kumaresan G Anandand S Srinivasan ldquoExperimental and theoretical investigationsof spectroscopic properties of N-acetyl-5-methoxytryptaminerdquoCanadian Journal of Analytical Sciences and Spectroscopy vol53 no 4 pp 149ndash162 2008

[35] P Hohenberg and W Kohn ldquoInhomogeneous electron gasrdquoPhysical Review vol 136 no 3 pp B864ndashB871 1964

[36] R G Pearson ldquoAbsolute electronegativity and absolute hard-ness of Lewis acids and basesrdquo Journal of the American ChemicalSociety vol 107 no 24 pp 6801ndash6806 1985

[37] D Avci Y Atalay M Sekerci and M Dincer ldquoMolecular struc-ture and vibrational and chemical shift assignments of 3-(2-Hydroxyphenyl)-4-phenyl-1H-124-triazole-5-(4H)-thione byDFT and ab initio HF calculationsrdquo Spectrochimica Acta A vol73 no 1 pp 212ndash217 2009

[38] H O Kalinowski S Berger and S Braun Carbon13 NMRSpectroscopy John Wiley amp Sons Chichester UK 1988

[39] K Pihlaja and E Kleinpeter Carbon-13 NMR Chemical Shiftsin Structural and Sterochemical Analysis VCH PublishersDeerfield Beach Fla USA 1994

[40] P S Kalsi Spectroscopy of Organic Compounds New AgeInternational 2004

[41] A F Parsons Keynotes in Organic Chemistry Blackwell Pub-lishing Oxford UK 2003

[42] M A Palafox ldquoScaling factors for the prediction of vibrationalspectra I benzenemoleculerdquo International Journal of QuantumChemistry vol 77 no 3 pp 661ndash684 2000

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

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Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Analytical ChemistryInternational Journal of

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Journal of

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CatalystsJournal of

Page 7: Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. · Molecular Structure, NMR, HOMO, LUMO, ... ects of carbonyl and methyl substitutions

Journal of Spectroscopy 7

Table 5 Definition of natural internal coordinates of Anisic acid (AA)

No (i) Symbola Definitionb

1ndash4 CndashH stretch 1199031 1199032 1199033 1199034

5ndash10 CndashC stretch 1199035 1199036 1199037 1199038 1199039 11990310

11 CndashCfn stretch 11990311

12ndash14 CndashO stretch 11990312 11990313 11990314

15 OndashC stretch 11990315

16 OndashH stretch 11990316

17 CH3 ss (11990317+ 11990318+ 11990319) radic3

18 CH3 ips (211990317minus 11990318minus 11990319) radic6

19 CH3 ops (11990318minus 11990319) radic2

20 bCndashCndashC (12057320minus 12057321) radic2

21ndash24 bCndashCndashH (12057322minus 12057323) radic2 (120573

24minus 12057325) radic2 (120573

26minus 12057327) radic2 (120573

28minus 12057329) radic2

25 CH3 sb (minus12057330minus 12057331minus 12057332+ 12057333+ 12057334+ 12057335) radic6

26 CH3 ipb (minus12057333minus 12057334minus 212057335)radic6

27 CH3 opb (12057333minus 12057334) radic2

28 CH3 ipr (212057330minus 12057331minus 12057332) radic6

29 CH3 opr (12057331minus 12057332) radic2

30 bCndashCndashO (12057335minus 12057336) radic2

31 bCndashOndashH 12057338

32-33 bCndashCndashO 12057339 12057340

34 bCndashOndashC 12057341

35 Rtrigd (12057342minus 12057343+ 12057344minus 12057345+ 12057346minus 12057347) radic6

36 Rsymd (minus12057342minus 12057343+ 12057344minus 12057345minus 12057346+ 212057347) radic12

37 Rasymd (12057342minus 12057343+ 12057345minus 12057346) 2

38ndash41 120596CndashH 12059648 12059649 12059650 12059651

42 120596CndashC 12059652

43 120596CndashO 12059653

44-45 tCndashO 12059154 12059155

46 tCndashOndashC 12 (12059156+ 12059157)

47 tCH3 13 (12059158+ 12059159+ 12059160)

48 tOndashH 12059161

49 Ttrigd (12059162minus 12059163+ 12059164minus 12059165+ 12059166minus 12059167) radic6

50 Tsymd (12059162minus 12059163+ 12059165+ 12059166)2

51 Tasymd (minus12059162+ 212059163minus 12059164minus 12059165+ 12059166minus 12059167) radic12

aThese symbols are used for description of the normal modes by PED in Table 8bThe internal coordinates used here are defined in Table 3

in-plane bending and CndashO stretching bands involve someinteraction between them they are referred to as coupledOH in-plane bending and CndashO stretching vibrations [26]The CndashO bending vibration occurs in the region of 580ndash340 cmminus1 [30] The band observed at 380 cmminus1 in OAA and440 cmminus1 in AA are assigned to CndashO bending mode Thepresent assignments agree very well with the values availablein the literature

433 Methyl Group Vibrations The title molecules OAAand AA under consideration possess one CH

3group For

the assignments of CH3group one can expect that 9 fun-

damentals can be associated with each CH3group namely

the symmetrical stretching (CH3symmetric stretch) and

asymmetrical stretching (CH3asymmetric stretch) in-plane

stretching modes (ie in-plane hydrogen stretching modes)

and the symmetrical (CH3symmetric deform) and asym-

metrical (CH3asymmetric deform) deformation modes in-

plane rocking (CH3ipr) out-of-plane rocking (CH

3opr) and

twisting (tCH3) bending modes

For the methyl group compounds the asymmetricstretching mode appeared in the range 2965ndash3005 cmminus1 andthe symmetric stretching mode appeared in the range of2815ndash2860 cmminus1 [30] The FT-Raman band at 2983 cmminus1 forOAA and IR band at 2941 cmminus1 for AA are symmetricstretching The symmetric stretching vibrational frequencyis higher in OAA and AA due to steric effect and +I effectThe asymmetric methyl stretching band appeared at 30033018 cmminus1 in OAA and 2990 2956 cmminus1 in AA respectivelyThe asymmetric deformation mode appeared in the range1445ndash1485 cmminus1 and symmetric deformation mode appearedin the range of 1420ndash1460 cmminus1 [30] The IR band at 1466

8 Journal of Spectroscopy

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 2 FTIR spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Table 6 Diagonal force constants (102 Nmminus1) of O-Anisic acid(OAA) and Anisic acid (AA)

Descriptiona Force constantsb

OAA AAC1ndashC2 621 630C2ndashC3 633 696C3ndashC4 677 626C4ndashC5 675 628C5ndashC6 682 663C6ndashC1 644 648C1ndashC7 465 222C7ndashO8 532 522C7ndashO9 1030 1128C2ndashO11(C4ndashO13) 449 576O11ndashC12(O13ndashC14) 413 499O9ndashH10 644 661C12ndashH13(C14ndashH15) 498 508C12ndashH14(C14ndashH16) 526 470C12ndashH15(C14ndashH17) 498 507C3ndashH16(C2ndashH11) 514 498C4ndashH17(C3ndashH12) 501 496C5ndashH18 505 500C6ndashH19 532 522aThe atoms indicated in the parenthesis belong to AAbStretching force constants are given in mdyn A

minus1

For numbering of atoms refer to Figures 1(a) and 1(b)

and 1435 cmminus1 in OAA and 1468 and 1461 cmminus1 in AA areassigned as asymmetric deformation vibrations The IR bandat 1411 cmminus1 for OAA and 1429 cmminus1 for AA are symmet-ric deformation mode The CH

3deformation absorption

occurs at 1466 cmminus1 and 1429 cmminus1 this vibration is knownas umbrella mode that overlaps with CC ring stretchingvibrations for the title compounds These are also supportedby the literature

The tensional modes appeared in the range of 265ndash185 cmminus1 [30] This modes are strongly coupled with other

vibrations that are observed at 280 cmminus1 inOAAand 165 cmminus1in AAwhich are in agreement with the calculated results also

434 Ring Vibrations The ring CndashC stretching vibrationsoccur in the region of 1600ndash1400 cmminus1 [29]The bands appearat 1600 1579 1312 1184 1153 1062 and 698 cmminus1 in OAAand 1608 1580 1416 1307 1107 1028 and 825 cmminus1 in AAwere assigned to CndashC stretching vibrations The shift in thefrequency of CndashC vibrations towards lower wave numbermay be due to the COOH and OCH

3groups Many ring

modes are affected by the substitutions in the aromatic ringThe bands at 180 cmminus1 and 285 cmminus1 for OAA and AA wereassigned to CndashC bending vibrationsThe out-of-plane and in-plane deformations of the phenyl ring are observed below1000 cmminus1 and these modes are sensitive by the additionof functional groups The out-of-plane bending vibrationswere observed at 170 cmminus1 and 111 cmminus1 for OAA and AASmall changes in the wavenumbers were observed due tothe presence of +I effect in AA and steric effect in OAAThe computed wavenumbers are in good agreement withexperimental data

5 Electronic Properties

Atomic charges on the various atoms of OAA and AAobtained by Mulliken population analysis [31] are given inTable 9 From the listed atomic charge values the oxygen[O8 O9] and O11 in OAA and O13 in AA atoms had a largenegative charge and behaved as electron acceptor It was alsoobserved that there is a large accumulation of charge on O11inOAAO13 in AAmoleculesTherefore C7 andO11 inOAAand C7 and O13 in AA had a greater ionic character

Natural bond orbital analysis provides an efficientmethod for studying steric effect and intermolecular bondingand interaction among bonds and also provides a convenientbasis for investigating charge transfer or conjugative interac-tion in molecular systems Natural charge analysis is givenin Table 10 for the title compounds The results show thatsubstitution of COOH and CH

3group in OAA and AA leads

to a redistribution of electron density The C7 atom in OAAand AA is more positive charge (+08091 +08139) In the

Journal of Spectroscopy 9Ta

ble7Detailedassig

nmento

ffun

damentalvibratio

nsof

O-Anisic

acid

(OAA)b

yno

rmalmod

eanalysis

basedon

SQM

forcefi

eldcalculations

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

1A1015840

3390

mdash3771

3390

72652

155385

120592OH(100)

2A1015840

mdash3098

3273

3098

1612

499564

120592CH

(99)

3A1015840

mdash3083

3233

3083

1700

135114

120592CH

(99)

4A1015840

3069

mdash3207

3069

10674

70382

120592CH

(99)

5A1015840

mdash3020

3186

3024

17253

1372

01120592CH

(99)

6A1015840

3018

mdash3157

3018

38987

58202

120592CH

3(99)

7A10158401015840

3003

mdash3085

3003

5946

78409

120592CH

3(99)

8A1015840

mdash2983

3020

2983

52626

120657

120592CH

3(99)

9A1015840

1670

mdash1822

1670

358567

54628

120592CO

(53)120592CC

(14)bC

CO(14

)bC

OH(12)

10A1015840

1600

mdash1656

1600

15061

16343

120592CC

(60)bCH

(20)R

asym

d(10)

11A1015840

1579

mdash1630

1579

61364

48880

120592CC

(69)bCH

(19)

12A1015840

1494

mdash1539

1494

58214

10686

bCH(48)120592CC

(37)

13A1015840

1466

mdash1513

1466

6534

6058

bCH

3(43)bCH

(25)120592CC

(16)

14A1015840

mdash1439

1506

1439

22318

5639

bCH(39)bCH

3(37)120592CC

(17)

15A10158401015840

1435

mdash1500

1435

3652

510814

bCH

3(88)

16A1015840

1411

mdash1475

1411

11849

19713

bCH

3(74)

17A1015840

1382

1367

4497

1268

bCOH(35)120592CO

(32)bCC

O(13)120592CC

(11)

18A1015840

mdash1312

1350

1312

2182

8877

120592CC

(67)

19A1015840

1288

mdash1320

1288

6319

416

48bC

H(33)R

trigd(20)120592CO

(13)120592CC

(12)

20A1015840

mdash1287

1302

1287

19694

044

9Rtrig

d(26)120592CC

(25)bCH

(20)120592CO

(12)

21A1015840

mdash1184

1210

1184

228252

32980

120592CC

(31)bCH

(19)bC

H3(17)120592CO

(17)

22A1015840

1182

mdash1201

1182

162989

2713

6bC

H(42)120592CC

(34)bCH

3(10)

23A1015840

1170

mdash119

3117

015

764576

bCH

3(57)bCH

(24)

24A1015840

mdash117

3117

31153

7419

1097

120592CC

(31)bCH

(29)bCH

3(25)

25A1015840

1140

mdash1168

1140

0662

4253

bCH

3(96)

26A1015840

1049

mdash1087

1050

1073

0478

09120592CO

(29)120592CC

(27)R

trigd(12)

27A1015840

-1062

1077

1060

104848

21650

120592CC

(41)120592CO

(22)bCH

(12)

28A10158401015840

960

-1060

960

060

90057

120596CH

(91)

29A1015840

mdash974

989

974

2078

710836

120592OC(62)120592CC

(12)120592CO

(11)

30A10158401015840

937

mdash965

935

1244

1294

120596CH

(91)

31A10158401015840

mdash865

869

865

3148

3432

120596CH

(64)ttrigd(19)

32A1015840

mdash795

830

795

12200

4238

120592CO

(29)R

symd(21)120592OC(15)120592CC

(15)

33A10158401015840

761

mdash795

761

1002

0207

tCO(32)ttrigd(28)120596

CH(23)120596

CC(11)

34A10158401015840

mdash755

770

755

41473

1456

120596CH

(51)ttrigd(27)120596

CO(14

)35

A10158401015840

695

mdash747

698

64512

0469

ttrigd(52)120596

CH(23)tCO

(15)

36A1015840

mdash698

712

695

10016

17946

120592CC

(33)120592CO

(23)bCC

O(21)

37A1015840

mdash602

639

602

13503

2683

Rasymd(36)bCC

O(15)

120592CC

(12)R

symd(11)

38A10158401015840

mdash595

594

595

74804

8168

tOH(79)

39A1015840

mdash565

588

565

21902

1740

bCCO

(28)120592CC

(17)bCO

(15)R

symd(14

)bC

CO(13)

10 Journal of Spectroscopy

Table7Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

540

mdash548

540

5598

4848

bCCO

(40)bCC

(16)120592CC

(13)R

asym

d(10)

41A10158401015840

480

mdash540

480

0946

0860

120596CO

(40)120596

CH(16)ttrigd(14

)tsy

m(14

)42

A10158401015840

mdash40

1435

401

3585

0792

tsym

(14)120596CC

(15)

43A1015840

mdash380

388

380

4805

4133

bCO(64)bCC

O(16)

44A1015840

mdash303

383

303

1180

4980

Rsym

d(59)bCO

C(17)120592CC

(15)

45A10158401015840

mdash280

283

280

0092

0016

tCH

3(79)

46A1015840

mdash240

280

240

0927

0935

bCOC(40)bCC

(30)bCC

O(18)

47A10158401015840

mdash180

229

180

0018

2096

120596CC

(30)tCO

(20)tsym

(18)

tasym

(11)120596CH

(10)

48A1015840

mdash170

190

170

3092

0715

bCC(42)bCO

C(29)bCO

(12)

49A10158401015840

mdash115

119115

4502

0508

tCOC(47)tsym

(15)tCH

3(12)

50A10158401015840

mdash110

9696

0922

3779

tsym

(35)tCO

(25)

tCOC(21)tCH

3(13)

51A10158401015840

mdashmdash

1730

1260

0037

tCO(99)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 11Ta

ble8Detailedassig

nmento

ffun

damentalvibratio

nsof

Anisic

acid

(AA)b

yno

rmalmod

eanalysis

basedon

SQM

forcefi

eldcalculations

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

1A1015840

3435

mdash3768

3435

7952

3164209

120592OH(100)

2A1015840

mdash3085

3232

3085

21438

120058

120592CH

(89)

3A1015840

mdash3034

3224

3034

7547

126718

120592CH

(99)

4A1015840

3029

mdash3218

3029

3520

99229

120592CH

(99)

5A1015840

3002

mdash3209

3002

5141

52552

120592CH

(99)

6A1015840

2990

mdash3155

2990

2423

53071

120592CH

ops(99)

7A10158401015840

2956

mdash3087

2956

45319

94074

120592CH

ips(51)120592CH

ss(36)120592CH

ops(12)

8A1015840

2941

mdash3022

2941

42847

91231

120592CH

ss(56)120592CH

ips(44

)9

A1015840

1688

mdash1813

1688

302139

74665

120592CO

(72)bCC

O(17)

10A1015840

1608

mdash1666

1608

216104

153242

120592CC

(62)bCH

(22)R

symd(11)

11A1015840

1580

mdash1624

1580

34785

12359

120592CC

(66)bCH

(14)

12A1015840

1518

mdash1559

1518

41495

8422

bCH(52)120592CC

(30)

13A1015840

1468

mdash1516

1468

37550

10673

bCHsb

(77)

14A10158401015840

1461

mdash1504

1461

14058

1218

3bC

Hop

b(83)

15A1015840

1429

mdash1486

1429

5851

19586

bCHipb(70)120592CC

(10)bCH

(10)

16A1015840

1416

mdash1465

1416

14835

9149

120592CC

(39)bCH

(35)bCH

ipb(18)

17A1015840

1324

mdash1391

1324

31290

5311

bCOH(27)120592CO

(22)bCC

O(21)120592CC

(13)

18A1015840

1307

mdash1371

1307

806

814

44120592CC

ar(65)bCH

(20)

19A1015840

1301

mdash1331

1301

40408

7073

bCH(43)120592CC

(33)

20A1015840

1267

mdash1304

1267

245222

3723

120592CO

(37)R

trigd(20)120592CC

(16)

21A1015840

1181

mdash1221

1181

5734

6023

bCH(61)120592CC

(21)

22A1015840

1172

mdash1209

1172

5690

5161

bCHop

r(61)bC

H(13)

23A1015840

mdash1137

1189

1137

0662

4334

bCHipr(78)bC

Hop

r(14)

24A1015840

1131

mdash117

61131

190946

42508

bCH(35)120592CC

(21)

25A1015840

1107

mdash1139

1107

245972

63024

120592CC

fn(25)R

trigd(23)bCH

(16)120592OC(13)

26A1015840

mdash1100

1114

1100

318070

20809

120592CO

(40)bCO

H(22)bCC

O(11)

27A1015840

1028

mdash1069

1028

0786

11056

120592CC

(58)bCH

(16)

28A1015840

mdash1010

1026

1010

29566

2343

120592OC(51)120592CC

(28)

29A10158401015840

929

mdash991

929

0010

046

4120596CH

(89)

30A10158401015840

854

mdash966

854

1379

1924

120596CH

(82)ttrigd(12)

31A10158401015840

846

mdash863

846

3652

212

44120596CH

(39)120596

CO(32)ttrigd(20)

32A1015840

825

mdash834

825

24090

2237

3120592CC

ar(32)R

symd(27)120592OC(22)

33A10158401015840

774

mdash830

774

0365

4928

120596CH

(84)

34A10158401015840

mdash755

775

755

1082

0243

ttrigd(51)120596

CC(15)120596

CH(14

)tCO(11)

35A1015840

698

mdash725

698

3553

93075

bCCO

(44)120592CO

(25)bCO

H(25)

36A10158401015840

634

mdash710

634

76887

0059

tCO(57)120596

CH(20)ttrigd(12)

37A1015840

617

mdash647

617

0592

644

1Ra

symd(81)

38A1015840

550

mdash603

550

14566

0968

Rsym

d(32)120592CC

fn(13)120592CO

(11)bCC

O(11)bCO

C(10)

39A10158401015840

545

mdash601

545

27876

4847

120596CO

(42)tOH(14

)120596CH

(11)120596

CC(11)

12 Journal of Spectroscopy

Table8Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

525

mdash511

525

12735

1849

bCCO

(82)

41A1015840

505

mdash511

505

50036

5698

tOH(24)ttrigd(23)120596

CO(19)120596

CH(14

)42

A1015840

440

mdash481

440

3190

2294

bCO(35)bCO

C(29)

43A10158401015840

mdash375

427

375

0415

0023

tsym

(60)120596

CH(19

)tasym

(17)

44A1015840

mdash310

335

310

3569

0577

Rsym

d(48)120592CC

fn(25)

45A10158401015840

mdash285

304

285

4416

0596

120596CC

(33)tasym

(24)tCO

(16)

46A1015840

mdash220

267

220

3713

2509

bCOC(29)bCO

(17)

47A10158401015840

mdash165

226

165

0047

0429

tCH

3(85)

48A1015840

mdash111

165

111

0211

0159

bCC(80)

49A10158401015840

mdash98

132

982323

0292

Tasym

(30)tCO

C(30)120596

CC(11)120596

CH(10)tsym

(10)

50A10158401015840

mdash70

7870

1302

1199

tCO(95)

51A10158401015840

mdash60

6560

0898

0216

tCOC(48)tCO

(31)tCH

3(12)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 13

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 3 FT-Raman spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 4 FTIR spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 5 FT-Raman spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

title molecules all the hydrogen atoms have a net positivecharge in particular the hydrogen atoms H(10) that havecharge of 05047 and 05050 respectively The presence oflarge amounts of negative charge on oxygen and net positivecharge on H(10) atoms may suggest the presence of inter-molecular hydrogen bonding in the crystalline phase

Highest occupied molecular orbital and lowest unoc-cupied molecular orbital are very important parametersfor quantum chemistry This is also used by the frontierelectron density for predicting the most reactive position in120587-electron systems and also explains several types of reactionin conjugated system [32] The conjugated molecules are

characterized by a small highest occupied molecular orbitalndashlowest unoccupied molecular orbital (HOMO-LUMO) sep-aration which is the result of a significant degree of inter-molecular charge transfer from the end-capping electron-donating groups to the efficient electron-acceptor groupsthrough 120587 conjugated path [33] Both the highest occupiedmolecular orbital and lowest unoccupied molecular orbitalare the main orbitals that take part in chemical stability[34] Energy difference betweenHOMOand LUMOorbital iscalled energy gap that is an important stability for structureswhich are given in Table 11 We performed an analysis ofall the molecular orbitals involved taking into consideration

14 Journal of Spectroscopy

Table 9 Atomic charges for optimized geometry of O-Anisic acid(OAA) and Anisic acid (AA) obtained by B3LYP6-31Glowastlowast densityfunctional calculations

Atomsa MullikenOAA AA

C1 00018 00373C2 03297 minus01002

C3 minus01368 minus01219

C4 minus00836 03612

C5 minus00943 minus01394

C6 minus01061 minus01118

C7 05570 05445O8 minus04650 minus04848

O9 minus05104 minus05064

H10 03198 03217O11 (H11) minus04841 01203C12 (H12) minus00837 01021H13 (O13) 01064 minus05111

H14 (C14) 01352 minus00831

H15 01211 01099H16 00913 01302H17 00929 01246H18 00886 00913H19 01200 01155aThe atoms indicated in the parenthesis belong to AA

Table 10Natural atomic charges ofO-Anisic acid (OAA) andAnisicacid (AA) calculations performed at the B3LYP6-31Glowastlowast level oftheory

Atomsa OAA AAC1 minus02176 minus02053

C2 03724 minus01746

C3 minus03284 minus02801

C4 minus01952 03443

C5 minus02720 minus03289

C6 minus01806 minus01748

C7 08091 08139O8 minus05861 minus06102

O9 minus07295 minus07217

H10 05047 05050O11 (H11) minus04921 02634C12 (H12) minus03307 02544H13 (O13) 02070 minus05119

H14 (C14) 02390 minus03300

H15 02070 02090H16 02443 02352H17 02426 02090H18 02439 02449H19 02621 02585aThe atoms indicated in the parenthesis belong to AAFor numbering of atoms refer to Figures 1(a) and 1(b)

that orbital 40 is the HOMO and orbital 41 is the LUMO forOAA and AA respectively

Many organic molecules that contain conjugated 120587 elec-trons are characterized as hyperpolarisabilities and are ana-lyzed by means of vibrational spectroscopy The analysis

Table 11 Calculated quantum chemical parameters ofO-Anisic acid(OAA) and Anisic acid (AA) derivatives

Parameters OAA AA119864HOMO minus0227 minus0231

119864LUMO minus0041 minus0036

Δ119864 0186 0195120594 0134 0133Η 0093 0097Σ 10752 10256

Table 12 Calculated 13C NMR chemical shifts (ppm) of O-Anisicacid (OAA) and Anisic acid (AA)

Carbona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAC1 11782 12315 10447 12620C2 15848 13146 14696 13936C3 11204 11384 9681 12272C4 13517 16297 11926 17125C5 12191 11384 10447 11047C6 13347 13146 12019 13751C7 16634 16714 14609 17174C12 (C14) 5674 5544 4322 5549aThe atoms indicated in the parenthesis belong to AA

Table 13 Experimental and calculated 1H NMR chemical shifts(ppm) of O-Anisic acid (OAA) and Anisic acid (AA)

Protona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAH10 1030 13 11 11H13 H14 H15 (H11) 4066 7914 3932 8405H16 (H12) 708 7027 6831 7147H17 (H15 H16 H17) 756 3836 7570 3824H18 710 7027 7069 6673H19 813 7914 3932 8217aThe atoms indicated in the parenthesis belong to AA

of the wave function indicates that the electron absorptioncorresponds to the transition from the ground state to thefirst excited state and is mainly described by the one-electronexcitation from the HOMO to the LUMO The HOMO of 120587nature (ie aromatic ring) is delocalized over the whole CndashC bond By contrast the LUMO is located over the aromaticring Consequently the HOMO-LUMO transition implies anelectron density transfer toCOOHandOCH

3group from the

aromatic ringThe theoretical basis for the new quantities lies in the

density functional formalism [35] Since molecular orbital(MO) theory is by far the most widely used by chemistsit is important to place 120594 and 120578 in a MO framework Ithas already been shown [36] that the MO theory of thechemical bond contains the values of 120594 and 120578 for the bondingfragments Hard molecules have a large HOMO-LUMO gapand soft molecules have a small HOMO-LUMO gap A small

Journal of Spectroscopy 15

HOMO

(a)

LUMO

(b)

Figure 6 Contour surfaces of frontier molecular orbitals of O-Anisic acid

HOMO

(a)

LUMO

(b)

Figure 7 Contour surfaces of frontier molecular orbitals of Anisic acid

HOMO-LUMO gap automatically means small excitationenergies to the manifold of excited states Therefore softmolecules with a small gap will be more polarizable thanhard molecules High polarizability was the most character-istic property attributed to soft acids and bases Energy gapsshould be small for best bonding or bothmolecules should besoft

In the present study the title compound AA is dynam-ically more stable due to the large energy gap OAA is asoft molecule due to small energy gap The Contour surfacesof the frontier molecular orbitals are sketched in Figures 6and 7

51 NMR Spectra DFT methods treat the electronic energyas a function of the electron density of all electrons simul-taneously and thus include electron correlation effect [37]In this study molecular structure of the OAA and AA wasoptimized by using B3LYP method in conjunction with 6-31Glowastlowast 13C and 1H chemical shift calculations of the titlecompounds have been made by using GIAO method andsame basis set The isotropic shielding values were usedto calculate the isotropic chemical shifts 120575 with respect totetramethylsilane (TMS) The isotropic chemical shifts arefrequently used as an aid in identification of reactive ionicspecies The B3LYP method allows calculating the shielding

16 Journal of Spectroscopy

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 150

140

130

120

110

100

90110 120 130 140 150 160 170

(a)

70 75 80 85 90 95 100 1056

7

8

9

10

11

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

(b)

Figure 8 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for O-Anisic acid

constants with the proper accuracy and the GIAOmethod isone of the most common approaches for calculating nuclearmagnetic shielding tensors

Theoretical and experimental chemical shifts of OAA andAA in 1H and 13C NMR spectra are gathered in Tables 12and 13 The range of the 13C NMR chemical shifts for atypical organic molecules usually is gt100 ppm [38 39] andthe accuracy ensures reliable interpretation of spectroscopicparameters In the present study the 13C NMR chemicalshifts in the ring are gt100 ppm as they would be expectedThe 13C chemical shifts carbonyl carbons vary from 150 to220 ppm This depends on the decrease in electron donatingor shielding ability of the attached atoms [40] The C=Ogroups of carboxylic acids and derivatives are in the range of150ndash185 ppm [29]

Hydrogens bonded to an aromatic ring are stronglydeshielded and absorb downfieldWhen the120587-electrons enterthe magnetic field they circulate around the ring to generatea ring current This produces a small induced magnetic fieldthat reinforces the applied field outside the ring resultingin aromatic protons being deshielded [41] A related effectis observed for carboxylic acids For these compoundscirculation of electrons in the double bonds produces inducedmagnetic field These are responsible for the high chemicalshift values of acid protons (H10) Carboxylic acids asstable hydrogen-bonded dimers in nonpolar solvents even athigh dilution The carboxylic proton therefore absorbs in acharacteristically narrow range 132 to 100 and is affectedonly slightly by concentration [29]

In a methyl group a proton is covalently bonded tocarbon oxygen or other atoms by a sigma bond Whenplaced in a strong magnetic field the electrons of the sigmabond circulate to generate a small magnetic field whichopposes the applied field A nearby electronegative atomwithdraws electron density from the neighbourhood of theproton so that a smaller applied field is needed to cause thespin state of the proton to flip The signal for a deshielded

Table 14 Theoretically computed energies (au) zero-point vibra-tional energies (kcalmolminus1) rotational constants (GHz) entropies(calmolminus1 Kminus1) nuclear repulsion energy (Hartrees) and dipolemoment (Debye) for OAA and AA

Parameters B3LYP6-31Glowastlowast

OAA AAZero-point energy 9306056 9314966

Rotational constants139942 344405114384 056752063193 048875

EntropyTotal 99243 97126Translational 40967 40967Rotational 30142 30199Vibrational 28134 25960Dipole moment 24181 35822Nuclear repulsion energy 592968293 573992628

proton (1 surrounded by less electron density) is observed tobe more downfield than the signals for protons that are notdeshielded by electronegative atoms [40] The chemical shiftvalue of C7 (OAA and AA) has bigger value than the othercarbons due to the electronegative property of oxygen atom

The linear correlations between calculated and experi-mental data of 13CNMRand 1HNMRspectra are determinedas 09 and 10 for OAA and 09 and 09 for AA respectivelyThere is an excellent linear relationship between experimentaland computed results which are shown in Figures 8 and 9

6 Thermodynamic Properties

Several calculated thermodynamical parameters are pre-sented in Table 14 for OAA andAA respectively Scale factorshave been recommended [42] for an accurate prediction in

Journal of Spectroscopy 17

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 180

170

160

150

140

130

120

110110

120 130 140 150 160 170

(a)

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

11

10

9

8

7

7 8 9 10 11 12 13

(b)

Figure 9 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for Anisic acid

determining the zero-point vibration energies (ZPVE) andthe entropy 119878vib(119879) The total energies and the change inthe total entropy at room temperature using B3LYP6-31Glowastlowastmethod are presented

7 Conclusion

Attempts have been made in the present work for the molec-ular parameters and frequency assignments for the com-pounds OAA and AA from the FTIR and FT-Raman spectraThe equilibrium geometries and harmonic and anharmonicfrequencies for the title compounds were determined andanalyzed at DFT level of theory utilizing 6-31Glowastlowast basis setThe assignments of most of the fundamentals of the titlecompounds provided in this work are quite comparableThe excellent agreement of the calculated and observedvibrational spectra reveals the advantages of a smaller basisset for quantum chemical calculations HOMO and LUMOenergy gap explains the eventual charge transfer interactionstaking place within the molecule The experimental andtheoretical investigation of the title compounds have beenperformed successfully by using 1H and 13C NMR Thevarious modes of vibrations were unambiguously assignedon the basis of the result of the PED output obtainedfrom normal coordinate analysis These studies confirm thepresence of COOH and OCH

3group Dimeric molecules are

held together by hydrogen bridges between carbonyl groupsThe obtained data and simulations both show the way to thecharacterization of the molecules and help in spectra studiesin the future

References

[1] GMelentyeva and LAntonovaPharmaceutical ChemistryMirPublishers Moscow Russia 1988

[2] ldquoo-Anisic acid(579-75-9) catalog of chemical suppliersrdquo httpwwwchemexpercomchemicalssuppliercas579-75-9html

[3] B A Hess Jr L J Schaad P Carsky and R Zaharaduick ldquoAbinitio calculations of vibrational spectra and their use in theidentification of unusual moleculesrdquo Chemical Reviews vol 86no 4 pp 709ndash730 1986

[4] P Pulay X Zhou and G Forgarasi in Recent Experimental andComputational Advances in Molecular Spectroscopy R Faustoand R Fransto Eds vol 406 ofNATOASI Series p 99 KluwerDordrecht Netherlands 1993

[5] P Pulay G Fogarasi G Pongor J E Boggs and A VarghaldquoCombination of theoretical ab initio and experimental infor-mation to obtain reliable harmonic force constants ScaledQuantum Mechanical (SQM) force fields for glyoxal acroleinbutadiene formaldehyde and ethylenerdquo Journal of the Ameri-can Chemical Society vol 105 no 24 pp 7037ndash7047 1983

[6] C E Blom and C Altona ldquoApplication of self-consistent-fieldab initio calculations to organic moleculesrdquo Molecular Physicsvol 31 no 5 pp 1377ndash1391 1976

[7] G Fogarasi and P Pulay in Vibrational Spectra and Structure JR Durig Ed vol 14 Elsevier Amsterdam Netherlands 1985

[8] G Fogarasi ldquoRecent developments in the method of SQM forcefields with application to 1-methyladeninerdquo Spectrochimica ActaA vol 53 no 8 pp 1211ndash1224 1997

[9] G R deMare N Yu Panchenko andW Ch Bock ldquoAnMP26-31GlowastMP26-31Glowast vibrational analysis of s-trans- and s-cis-acryloyl fluoride CH2=CH-CF=Ordquo The Journal of PhysicalChemistry vol 98 no 5 pp 1416ndash1420 1994

[10] G Pongor P Pulay G Fogarasi and J E Boggs ldquoTheoreticalprediction of vibrational spectra 1 The in-plane force fieldand vibrational spectra of pyridinerdquo Journal of the AmericanChemical Society vol 106 no 10 pp 2765ndash2769 1984

[11] Y Yamakitu and M Tasumi ldquoVibrational analyses of p-benzoquinodimethane and p-benzoquinone based on ab initioHartree-Fock and second-order Moller-Plesset calculationsrdquoThe Journal of Physical Chemistry vol 99 no 21 pp 8524ndash85341995

18 Journal of Spectroscopy

[12] M Karabacak A Coruh and M Kurt ldquoFT-IR FT-RamanNMR spectra and molecular structure investigation of 23-dibromo-N-methylmaleimide a combined experimental andtheoretical studyrdquo Journal of Molecular Structure vol 892 no1ndash3 pp 125ndash131 2008

[13] M S Masoud M K Awad M A Shaker and M M T El-Tahawy ldquoThe role of structural chemistry in the inhibitiveperformance of some aminopyrimidines on the corrosion ofsteelrdquo Corrosion Science vol 52 no 7 pp 2387ndash2396 2010

[14] M J Frisch G W Trucks H B Schlegel et al Gaussian 03Revision B4 Gaussian Inc Pittsburgh Pa USA 2003

[15] P L Polavarapu ldquoAb initio vibrational Raman and Ramanoptical activity spectrardquo Journal of Physical Chemistry vol 94no 21 pp 8106ndash8112 1990

[16] G Keresztury S Holly J Varga G Besenyei A Wang andJ R Durig ldquoVibrational spectra of monothiocarbamates-IIIR and Raman spectra vibrational assignment conforma-tional analysis and ab initio calculations of S-methyl-NN-dimethylthiocarbamaterdquo Spectrochimica Acta A vol 49 no 13-14 pp 2007ndash2017 1993

[17] G Keresztury ldquoRaman spectroscopy theoryrdquo in Handbook ofVibrational Spectroscopy J M Chalmers and P R Griffths Edsvol 1 p 71 John Wiley and Sons 2002

[18] R G Parr R A Donnelly M Levy and W E Palke ldquoElec-tronegativity the density functional viewpointrdquo The Journal ofChemical Physics vol 68 no 8 pp 3801ndash3807 1977

[19] R G Parr and R G Pearson ldquoAbsolute hardness companionparameter to absolute electronegativityrdquo Journal of theAmericanChemical Society vol 105 no 26 pp 7512ndash7516 1983

[20] R G Pearson ldquoAbsolute electronegativity and hardness appli-cation to inorganic chemistryrdquo Inorganic Chemistry vol 27 no4 pp 734ndash740 1988

[21] P Geerlings F De Proft and W Langenaeker ldquoConceptualdensity functional theoryrdquo Chemical Reviews vol 103 no 5 pp1793ndash1873 2003

[22] R Ditchfield ldquoMolecular orbital theory of magnetic shieldingand magnetic susceptibilityrdquo Journal of Physical Chemistry vol56 no 11 article 5688 4 pages 1972

[23] KWolinski J F Hilton and P Pulay ldquoEfficient implementationof the gauge-independent atomic orbital method for NMRchemical shift calculationsrdquo Journal of the American ChemicalSociety vol 112 no 23 pp 8251ndash8260 1990

[24] M Kurt M Yurdakul and S Yurdakul ldquoMolecular structureand vibrational spectra of 3-chloro-4-methyl aniline by densityfunctional theory and ab initio Hartree-Fock calculationsrdquoJournal of Molecular Structure vol 711 no 1ndash3 pp 25ndash32 2004

[25] D Steele and D H Whiffen ldquoThe vibration frequencies ofpentafluorobenzenerdquo Spectrochimica Acta vol 16 no 3 pp368ndash375 1960

[26] D N Sathyanarayanan Vibrational Spectroscopy Theory andApplication New Age International publishers New DelhiIndia 1996

[27] L D S YadavOrganic Spectroscopy Springer NewDelhi India2004

[28] J Mohan Organic Spectroscopy Principles and ApplicationsNarosa Publishing House New Delhi 2nd edition 2009

[29] R M Silverstein G C Bassler and T C Morrill SpectrometricIdentification of Organic Compounds John Wiley amp Sons NewYork NY USA 1981

[30] G Socrates Infrared Characteristic Group Frequencies WileyNew York NY USA 1980

[31] R S Mulliken ldquoElectronic population analysis on LCAO-MOmolecular wave functionsrdquoThe Journal of Chemical Physics vol23 no 10 pp 1833ndash1840 1955

[32] K Fukuli T Yonezawa and H Shingu ldquoA molecular orbitaltheory of reactivity in aromatic hydrocarbonsrdquo Journal ofPhysical Chemistry vol 20 no 4 article 722 4 pages 1952

[33] C H Choi and M Kertesz ldquoConformational information fromvibrational spectra of styrene trans-stilbene and cis-stilbenerdquoJournal of Physical Chemistry A vol 101 no 20 pp 3823ndash38311997

[34] S Gunasekaran R Arun Balaji S Kumaresan G Anandand S Srinivasan ldquoExperimental and theoretical investigationsof spectroscopic properties of N-acetyl-5-methoxytryptaminerdquoCanadian Journal of Analytical Sciences and Spectroscopy vol53 no 4 pp 149ndash162 2008

[35] P Hohenberg and W Kohn ldquoInhomogeneous electron gasrdquoPhysical Review vol 136 no 3 pp B864ndashB871 1964

[36] R G Pearson ldquoAbsolute electronegativity and absolute hard-ness of Lewis acids and basesrdquo Journal of the American ChemicalSociety vol 107 no 24 pp 6801ndash6806 1985

[37] D Avci Y Atalay M Sekerci and M Dincer ldquoMolecular struc-ture and vibrational and chemical shift assignments of 3-(2-Hydroxyphenyl)-4-phenyl-1H-124-triazole-5-(4H)-thione byDFT and ab initio HF calculationsrdquo Spectrochimica Acta A vol73 no 1 pp 212ndash217 2009

[38] H O Kalinowski S Berger and S Braun Carbon13 NMRSpectroscopy John Wiley amp Sons Chichester UK 1988

[39] K Pihlaja and E Kleinpeter Carbon-13 NMR Chemical Shiftsin Structural and Sterochemical Analysis VCH PublishersDeerfield Beach Fla USA 1994

[40] P S Kalsi Spectroscopy of Organic Compounds New AgeInternational 2004

[41] A F Parsons Keynotes in Organic Chemistry Blackwell Pub-lishing Oxford UK 2003

[42] M A Palafox ldquoScaling factors for the prediction of vibrationalspectra I benzenemoleculerdquo International Journal of QuantumChemistry vol 77 no 3 pp 661ndash684 2000

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

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CatalystsJournal of

Page 8: Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. · Molecular Structure, NMR, HOMO, LUMO, ... ects of carbonyl and methyl substitutions

8 Journal of Spectroscopy

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 2 FTIR spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Table 6 Diagonal force constants (102 Nmminus1) of O-Anisic acid(OAA) and Anisic acid (AA)

Descriptiona Force constantsb

OAA AAC1ndashC2 621 630C2ndashC3 633 696C3ndashC4 677 626C4ndashC5 675 628C5ndashC6 682 663C6ndashC1 644 648C1ndashC7 465 222C7ndashO8 532 522C7ndashO9 1030 1128C2ndashO11(C4ndashO13) 449 576O11ndashC12(O13ndashC14) 413 499O9ndashH10 644 661C12ndashH13(C14ndashH15) 498 508C12ndashH14(C14ndashH16) 526 470C12ndashH15(C14ndashH17) 498 507C3ndashH16(C2ndashH11) 514 498C4ndashH17(C3ndashH12) 501 496C5ndashH18 505 500C6ndashH19 532 522aThe atoms indicated in the parenthesis belong to AAbStretching force constants are given in mdyn A

minus1

For numbering of atoms refer to Figures 1(a) and 1(b)

and 1435 cmminus1 in OAA and 1468 and 1461 cmminus1 in AA areassigned as asymmetric deformation vibrations The IR bandat 1411 cmminus1 for OAA and 1429 cmminus1 for AA are symmet-ric deformation mode The CH

3deformation absorption

occurs at 1466 cmminus1 and 1429 cmminus1 this vibration is knownas umbrella mode that overlaps with CC ring stretchingvibrations for the title compounds These are also supportedby the literature

The tensional modes appeared in the range of 265ndash185 cmminus1 [30] This modes are strongly coupled with other

vibrations that are observed at 280 cmminus1 inOAAand 165 cmminus1in AAwhich are in agreement with the calculated results also

434 Ring Vibrations The ring CndashC stretching vibrationsoccur in the region of 1600ndash1400 cmminus1 [29]The bands appearat 1600 1579 1312 1184 1153 1062 and 698 cmminus1 in OAAand 1608 1580 1416 1307 1107 1028 and 825 cmminus1 in AAwere assigned to CndashC stretching vibrations The shift in thefrequency of CndashC vibrations towards lower wave numbermay be due to the COOH and OCH

3groups Many ring

modes are affected by the substitutions in the aromatic ringThe bands at 180 cmminus1 and 285 cmminus1 for OAA and AA wereassigned to CndashC bending vibrationsThe out-of-plane and in-plane deformations of the phenyl ring are observed below1000 cmminus1 and these modes are sensitive by the additionof functional groups The out-of-plane bending vibrationswere observed at 170 cmminus1 and 111 cmminus1 for OAA and AASmall changes in the wavenumbers were observed due tothe presence of +I effect in AA and steric effect in OAAThe computed wavenumbers are in good agreement withexperimental data

5 Electronic Properties

Atomic charges on the various atoms of OAA and AAobtained by Mulliken population analysis [31] are given inTable 9 From the listed atomic charge values the oxygen[O8 O9] and O11 in OAA and O13 in AA atoms had a largenegative charge and behaved as electron acceptor It was alsoobserved that there is a large accumulation of charge on O11inOAAO13 in AAmoleculesTherefore C7 andO11 inOAAand C7 and O13 in AA had a greater ionic character

Natural bond orbital analysis provides an efficientmethod for studying steric effect and intermolecular bondingand interaction among bonds and also provides a convenientbasis for investigating charge transfer or conjugative interac-tion in molecular systems Natural charge analysis is givenin Table 10 for the title compounds The results show thatsubstitution of COOH and CH

3group in OAA and AA leads

to a redistribution of electron density The C7 atom in OAAand AA is more positive charge (+08091 +08139) In the

Journal of Spectroscopy 9Ta

ble7Detailedassig

nmento

ffun

damentalvibratio

nsof

O-Anisic

acid

(OAA)b

yno

rmalmod

eanalysis

basedon

SQM

forcefi

eldcalculations

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

1A1015840

3390

mdash3771

3390

72652

155385

120592OH(100)

2A1015840

mdash3098

3273

3098

1612

499564

120592CH

(99)

3A1015840

mdash3083

3233

3083

1700

135114

120592CH

(99)

4A1015840

3069

mdash3207

3069

10674

70382

120592CH

(99)

5A1015840

mdash3020

3186

3024

17253

1372

01120592CH

(99)

6A1015840

3018

mdash3157

3018

38987

58202

120592CH

3(99)

7A10158401015840

3003

mdash3085

3003

5946

78409

120592CH

3(99)

8A1015840

mdash2983

3020

2983

52626

120657

120592CH

3(99)

9A1015840

1670

mdash1822

1670

358567

54628

120592CO

(53)120592CC

(14)bC

CO(14

)bC

OH(12)

10A1015840

1600

mdash1656

1600

15061

16343

120592CC

(60)bCH

(20)R

asym

d(10)

11A1015840

1579

mdash1630

1579

61364

48880

120592CC

(69)bCH

(19)

12A1015840

1494

mdash1539

1494

58214

10686

bCH(48)120592CC

(37)

13A1015840

1466

mdash1513

1466

6534

6058

bCH

3(43)bCH

(25)120592CC

(16)

14A1015840

mdash1439

1506

1439

22318

5639

bCH(39)bCH

3(37)120592CC

(17)

15A10158401015840

1435

mdash1500

1435

3652

510814

bCH

3(88)

16A1015840

1411

mdash1475

1411

11849

19713

bCH

3(74)

17A1015840

1382

1367

4497

1268

bCOH(35)120592CO

(32)bCC

O(13)120592CC

(11)

18A1015840

mdash1312

1350

1312

2182

8877

120592CC

(67)

19A1015840

1288

mdash1320

1288

6319

416

48bC

H(33)R

trigd(20)120592CO

(13)120592CC

(12)

20A1015840

mdash1287

1302

1287

19694

044

9Rtrig

d(26)120592CC

(25)bCH

(20)120592CO

(12)

21A1015840

mdash1184

1210

1184

228252

32980

120592CC

(31)bCH

(19)bC

H3(17)120592CO

(17)

22A1015840

1182

mdash1201

1182

162989

2713

6bC

H(42)120592CC

(34)bCH

3(10)

23A1015840

1170

mdash119

3117

015

764576

bCH

3(57)bCH

(24)

24A1015840

mdash117

3117

31153

7419

1097

120592CC

(31)bCH

(29)bCH

3(25)

25A1015840

1140

mdash1168

1140

0662

4253

bCH

3(96)

26A1015840

1049

mdash1087

1050

1073

0478

09120592CO

(29)120592CC

(27)R

trigd(12)

27A1015840

-1062

1077

1060

104848

21650

120592CC

(41)120592CO

(22)bCH

(12)

28A10158401015840

960

-1060

960

060

90057

120596CH

(91)

29A1015840

mdash974

989

974

2078

710836

120592OC(62)120592CC

(12)120592CO

(11)

30A10158401015840

937

mdash965

935

1244

1294

120596CH

(91)

31A10158401015840

mdash865

869

865

3148

3432

120596CH

(64)ttrigd(19)

32A1015840

mdash795

830

795

12200

4238

120592CO

(29)R

symd(21)120592OC(15)120592CC

(15)

33A10158401015840

761

mdash795

761

1002

0207

tCO(32)ttrigd(28)120596

CH(23)120596

CC(11)

34A10158401015840

mdash755

770

755

41473

1456

120596CH

(51)ttrigd(27)120596

CO(14

)35

A10158401015840

695

mdash747

698

64512

0469

ttrigd(52)120596

CH(23)tCO

(15)

36A1015840

mdash698

712

695

10016

17946

120592CC

(33)120592CO

(23)bCC

O(21)

37A1015840

mdash602

639

602

13503

2683

Rasymd(36)bCC

O(15)

120592CC

(12)R

symd(11)

38A10158401015840

mdash595

594

595

74804

8168

tOH(79)

39A1015840

mdash565

588

565

21902

1740

bCCO

(28)120592CC

(17)bCO

(15)R

symd(14

)bC

CO(13)

10 Journal of Spectroscopy

Table7Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

540

mdash548

540

5598

4848

bCCO

(40)bCC

(16)120592CC

(13)R

asym

d(10)

41A10158401015840

480

mdash540

480

0946

0860

120596CO

(40)120596

CH(16)ttrigd(14

)tsy

m(14

)42

A10158401015840

mdash40

1435

401

3585

0792

tsym

(14)120596CC

(15)

43A1015840

mdash380

388

380

4805

4133

bCO(64)bCC

O(16)

44A1015840

mdash303

383

303

1180

4980

Rsym

d(59)bCO

C(17)120592CC

(15)

45A10158401015840

mdash280

283

280

0092

0016

tCH

3(79)

46A1015840

mdash240

280

240

0927

0935

bCOC(40)bCC

(30)bCC

O(18)

47A10158401015840

mdash180

229

180

0018

2096

120596CC

(30)tCO

(20)tsym

(18)

tasym

(11)120596CH

(10)

48A1015840

mdash170

190

170

3092

0715

bCC(42)bCO

C(29)bCO

(12)

49A10158401015840

mdash115

119115

4502

0508

tCOC(47)tsym

(15)tCH

3(12)

50A10158401015840

mdash110

9696

0922

3779

tsym

(35)tCO

(25)

tCOC(21)tCH

3(13)

51A10158401015840

mdashmdash

1730

1260

0037

tCO(99)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 11Ta

ble8Detailedassig

nmento

ffun

damentalvibratio

nsof

Anisic

acid

(AA)b

yno

rmalmod

eanalysis

basedon

SQM

forcefi

eldcalculations

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

1A1015840

3435

mdash3768

3435

7952

3164209

120592OH(100)

2A1015840

mdash3085

3232

3085

21438

120058

120592CH

(89)

3A1015840

mdash3034

3224

3034

7547

126718

120592CH

(99)

4A1015840

3029

mdash3218

3029

3520

99229

120592CH

(99)

5A1015840

3002

mdash3209

3002

5141

52552

120592CH

(99)

6A1015840

2990

mdash3155

2990

2423

53071

120592CH

ops(99)

7A10158401015840

2956

mdash3087

2956

45319

94074

120592CH

ips(51)120592CH

ss(36)120592CH

ops(12)

8A1015840

2941

mdash3022

2941

42847

91231

120592CH

ss(56)120592CH

ips(44

)9

A1015840

1688

mdash1813

1688

302139

74665

120592CO

(72)bCC

O(17)

10A1015840

1608

mdash1666

1608

216104

153242

120592CC

(62)bCH

(22)R

symd(11)

11A1015840

1580

mdash1624

1580

34785

12359

120592CC

(66)bCH

(14)

12A1015840

1518

mdash1559

1518

41495

8422

bCH(52)120592CC

(30)

13A1015840

1468

mdash1516

1468

37550

10673

bCHsb

(77)

14A10158401015840

1461

mdash1504

1461

14058

1218

3bC

Hop

b(83)

15A1015840

1429

mdash1486

1429

5851

19586

bCHipb(70)120592CC

(10)bCH

(10)

16A1015840

1416

mdash1465

1416

14835

9149

120592CC

(39)bCH

(35)bCH

ipb(18)

17A1015840

1324

mdash1391

1324

31290

5311

bCOH(27)120592CO

(22)bCC

O(21)120592CC

(13)

18A1015840

1307

mdash1371

1307

806

814

44120592CC

ar(65)bCH

(20)

19A1015840

1301

mdash1331

1301

40408

7073

bCH(43)120592CC

(33)

20A1015840

1267

mdash1304

1267

245222

3723

120592CO

(37)R

trigd(20)120592CC

(16)

21A1015840

1181

mdash1221

1181

5734

6023

bCH(61)120592CC

(21)

22A1015840

1172

mdash1209

1172

5690

5161

bCHop

r(61)bC

H(13)

23A1015840

mdash1137

1189

1137

0662

4334

bCHipr(78)bC

Hop

r(14)

24A1015840

1131

mdash117

61131

190946

42508

bCH(35)120592CC

(21)

25A1015840

1107

mdash1139

1107

245972

63024

120592CC

fn(25)R

trigd(23)bCH

(16)120592OC(13)

26A1015840

mdash1100

1114

1100

318070

20809

120592CO

(40)bCO

H(22)bCC

O(11)

27A1015840

1028

mdash1069

1028

0786

11056

120592CC

(58)bCH

(16)

28A1015840

mdash1010

1026

1010

29566

2343

120592OC(51)120592CC

(28)

29A10158401015840

929

mdash991

929

0010

046

4120596CH

(89)

30A10158401015840

854

mdash966

854

1379

1924

120596CH

(82)ttrigd(12)

31A10158401015840

846

mdash863

846

3652

212

44120596CH

(39)120596

CO(32)ttrigd(20)

32A1015840

825

mdash834

825

24090

2237

3120592CC

ar(32)R

symd(27)120592OC(22)

33A10158401015840

774

mdash830

774

0365

4928

120596CH

(84)

34A10158401015840

mdash755

775

755

1082

0243

ttrigd(51)120596

CC(15)120596

CH(14

)tCO(11)

35A1015840

698

mdash725

698

3553

93075

bCCO

(44)120592CO

(25)bCO

H(25)

36A10158401015840

634

mdash710

634

76887

0059

tCO(57)120596

CH(20)ttrigd(12)

37A1015840

617

mdash647

617

0592

644

1Ra

symd(81)

38A1015840

550

mdash603

550

14566

0968

Rsym

d(32)120592CC

fn(13)120592CO

(11)bCC

O(11)bCO

C(10)

39A10158401015840

545

mdash601

545

27876

4847

120596CO

(42)tOH(14

)120596CH

(11)120596

CC(11)

12 Journal of Spectroscopy

Table8Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

525

mdash511

525

12735

1849

bCCO

(82)

41A1015840

505

mdash511

505

50036

5698

tOH(24)ttrigd(23)120596

CO(19)120596

CH(14

)42

A1015840

440

mdash481

440

3190

2294

bCO(35)bCO

C(29)

43A10158401015840

mdash375

427

375

0415

0023

tsym

(60)120596

CH(19

)tasym

(17)

44A1015840

mdash310

335

310

3569

0577

Rsym

d(48)120592CC

fn(25)

45A10158401015840

mdash285

304

285

4416

0596

120596CC

(33)tasym

(24)tCO

(16)

46A1015840

mdash220

267

220

3713

2509

bCOC(29)bCO

(17)

47A10158401015840

mdash165

226

165

0047

0429

tCH

3(85)

48A1015840

mdash111

165

111

0211

0159

bCC(80)

49A10158401015840

mdash98

132

982323

0292

Tasym

(30)tCO

C(30)120596

CC(11)120596

CH(10)tsym

(10)

50A10158401015840

mdash70

7870

1302

1199

tCO(95)

51A10158401015840

mdash60

6560

0898

0216

tCOC(48)tCO

(31)tCH

3(12)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 13

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 3 FT-Raman spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 4 FTIR spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 5 FT-Raman spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

title molecules all the hydrogen atoms have a net positivecharge in particular the hydrogen atoms H(10) that havecharge of 05047 and 05050 respectively The presence oflarge amounts of negative charge on oxygen and net positivecharge on H(10) atoms may suggest the presence of inter-molecular hydrogen bonding in the crystalline phase

Highest occupied molecular orbital and lowest unoc-cupied molecular orbital are very important parametersfor quantum chemistry This is also used by the frontierelectron density for predicting the most reactive position in120587-electron systems and also explains several types of reactionin conjugated system [32] The conjugated molecules are

characterized by a small highest occupied molecular orbitalndashlowest unoccupied molecular orbital (HOMO-LUMO) sep-aration which is the result of a significant degree of inter-molecular charge transfer from the end-capping electron-donating groups to the efficient electron-acceptor groupsthrough 120587 conjugated path [33] Both the highest occupiedmolecular orbital and lowest unoccupied molecular orbitalare the main orbitals that take part in chemical stability[34] Energy difference betweenHOMOand LUMOorbital iscalled energy gap that is an important stability for structureswhich are given in Table 11 We performed an analysis ofall the molecular orbitals involved taking into consideration

14 Journal of Spectroscopy

Table 9 Atomic charges for optimized geometry of O-Anisic acid(OAA) and Anisic acid (AA) obtained by B3LYP6-31Glowastlowast densityfunctional calculations

Atomsa MullikenOAA AA

C1 00018 00373C2 03297 minus01002

C3 minus01368 minus01219

C4 minus00836 03612

C5 minus00943 minus01394

C6 minus01061 minus01118

C7 05570 05445O8 minus04650 minus04848

O9 minus05104 minus05064

H10 03198 03217O11 (H11) minus04841 01203C12 (H12) minus00837 01021H13 (O13) 01064 minus05111

H14 (C14) 01352 minus00831

H15 01211 01099H16 00913 01302H17 00929 01246H18 00886 00913H19 01200 01155aThe atoms indicated in the parenthesis belong to AA

Table 10Natural atomic charges ofO-Anisic acid (OAA) andAnisicacid (AA) calculations performed at the B3LYP6-31Glowastlowast level oftheory

Atomsa OAA AAC1 minus02176 minus02053

C2 03724 minus01746

C3 minus03284 minus02801

C4 minus01952 03443

C5 minus02720 minus03289

C6 minus01806 minus01748

C7 08091 08139O8 minus05861 minus06102

O9 minus07295 minus07217

H10 05047 05050O11 (H11) minus04921 02634C12 (H12) minus03307 02544H13 (O13) 02070 minus05119

H14 (C14) 02390 minus03300

H15 02070 02090H16 02443 02352H17 02426 02090H18 02439 02449H19 02621 02585aThe atoms indicated in the parenthesis belong to AAFor numbering of atoms refer to Figures 1(a) and 1(b)

that orbital 40 is the HOMO and orbital 41 is the LUMO forOAA and AA respectively

Many organic molecules that contain conjugated 120587 elec-trons are characterized as hyperpolarisabilities and are ana-lyzed by means of vibrational spectroscopy The analysis

Table 11 Calculated quantum chemical parameters ofO-Anisic acid(OAA) and Anisic acid (AA) derivatives

Parameters OAA AA119864HOMO minus0227 minus0231

119864LUMO minus0041 minus0036

Δ119864 0186 0195120594 0134 0133Η 0093 0097Σ 10752 10256

Table 12 Calculated 13C NMR chemical shifts (ppm) of O-Anisicacid (OAA) and Anisic acid (AA)

Carbona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAC1 11782 12315 10447 12620C2 15848 13146 14696 13936C3 11204 11384 9681 12272C4 13517 16297 11926 17125C5 12191 11384 10447 11047C6 13347 13146 12019 13751C7 16634 16714 14609 17174C12 (C14) 5674 5544 4322 5549aThe atoms indicated in the parenthesis belong to AA

Table 13 Experimental and calculated 1H NMR chemical shifts(ppm) of O-Anisic acid (OAA) and Anisic acid (AA)

Protona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAH10 1030 13 11 11H13 H14 H15 (H11) 4066 7914 3932 8405H16 (H12) 708 7027 6831 7147H17 (H15 H16 H17) 756 3836 7570 3824H18 710 7027 7069 6673H19 813 7914 3932 8217aThe atoms indicated in the parenthesis belong to AA

of the wave function indicates that the electron absorptioncorresponds to the transition from the ground state to thefirst excited state and is mainly described by the one-electronexcitation from the HOMO to the LUMO The HOMO of 120587nature (ie aromatic ring) is delocalized over the whole CndashC bond By contrast the LUMO is located over the aromaticring Consequently the HOMO-LUMO transition implies anelectron density transfer toCOOHandOCH

3group from the

aromatic ringThe theoretical basis for the new quantities lies in the

density functional formalism [35] Since molecular orbital(MO) theory is by far the most widely used by chemistsit is important to place 120594 and 120578 in a MO framework Ithas already been shown [36] that the MO theory of thechemical bond contains the values of 120594 and 120578 for the bondingfragments Hard molecules have a large HOMO-LUMO gapand soft molecules have a small HOMO-LUMO gap A small

Journal of Spectroscopy 15

HOMO

(a)

LUMO

(b)

Figure 6 Contour surfaces of frontier molecular orbitals of O-Anisic acid

HOMO

(a)

LUMO

(b)

Figure 7 Contour surfaces of frontier molecular orbitals of Anisic acid

HOMO-LUMO gap automatically means small excitationenergies to the manifold of excited states Therefore softmolecules with a small gap will be more polarizable thanhard molecules High polarizability was the most character-istic property attributed to soft acids and bases Energy gapsshould be small for best bonding or bothmolecules should besoft

In the present study the title compound AA is dynam-ically more stable due to the large energy gap OAA is asoft molecule due to small energy gap The Contour surfacesof the frontier molecular orbitals are sketched in Figures 6and 7

51 NMR Spectra DFT methods treat the electronic energyas a function of the electron density of all electrons simul-taneously and thus include electron correlation effect [37]In this study molecular structure of the OAA and AA wasoptimized by using B3LYP method in conjunction with 6-31Glowastlowast 13C and 1H chemical shift calculations of the titlecompounds have been made by using GIAO method andsame basis set The isotropic shielding values were usedto calculate the isotropic chemical shifts 120575 with respect totetramethylsilane (TMS) The isotropic chemical shifts arefrequently used as an aid in identification of reactive ionicspecies The B3LYP method allows calculating the shielding

16 Journal of Spectroscopy

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 150

140

130

120

110

100

90110 120 130 140 150 160 170

(a)

70 75 80 85 90 95 100 1056

7

8

9

10

11

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

(b)

Figure 8 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for O-Anisic acid

constants with the proper accuracy and the GIAOmethod isone of the most common approaches for calculating nuclearmagnetic shielding tensors

Theoretical and experimental chemical shifts of OAA andAA in 1H and 13C NMR spectra are gathered in Tables 12and 13 The range of the 13C NMR chemical shifts for atypical organic molecules usually is gt100 ppm [38 39] andthe accuracy ensures reliable interpretation of spectroscopicparameters In the present study the 13C NMR chemicalshifts in the ring are gt100 ppm as they would be expectedThe 13C chemical shifts carbonyl carbons vary from 150 to220 ppm This depends on the decrease in electron donatingor shielding ability of the attached atoms [40] The C=Ogroups of carboxylic acids and derivatives are in the range of150ndash185 ppm [29]

Hydrogens bonded to an aromatic ring are stronglydeshielded and absorb downfieldWhen the120587-electrons enterthe magnetic field they circulate around the ring to generatea ring current This produces a small induced magnetic fieldthat reinforces the applied field outside the ring resultingin aromatic protons being deshielded [41] A related effectis observed for carboxylic acids For these compoundscirculation of electrons in the double bonds produces inducedmagnetic field These are responsible for the high chemicalshift values of acid protons (H10) Carboxylic acids asstable hydrogen-bonded dimers in nonpolar solvents even athigh dilution The carboxylic proton therefore absorbs in acharacteristically narrow range 132 to 100 and is affectedonly slightly by concentration [29]

In a methyl group a proton is covalently bonded tocarbon oxygen or other atoms by a sigma bond Whenplaced in a strong magnetic field the electrons of the sigmabond circulate to generate a small magnetic field whichopposes the applied field A nearby electronegative atomwithdraws electron density from the neighbourhood of theproton so that a smaller applied field is needed to cause thespin state of the proton to flip The signal for a deshielded

Table 14 Theoretically computed energies (au) zero-point vibra-tional energies (kcalmolminus1) rotational constants (GHz) entropies(calmolminus1 Kminus1) nuclear repulsion energy (Hartrees) and dipolemoment (Debye) for OAA and AA

Parameters B3LYP6-31Glowastlowast

OAA AAZero-point energy 9306056 9314966

Rotational constants139942 344405114384 056752063193 048875

EntropyTotal 99243 97126Translational 40967 40967Rotational 30142 30199Vibrational 28134 25960Dipole moment 24181 35822Nuclear repulsion energy 592968293 573992628

proton (1 surrounded by less electron density) is observed tobe more downfield than the signals for protons that are notdeshielded by electronegative atoms [40] The chemical shiftvalue of C7 (OAA and AA) has bigger value than the othercarbons due to the electronegative property of oxygen atom

The linear correlations between calculated and experi-mental data of 13CNMRand 1HNMRspectra are determinedas 09 and 10 for OAA and 09 and 09 for AA respectivelyThere is an excellent linear relationship between experimentaland computed results which are shown in Figures 8 and 9

6 Thermodynamic Properties

Several calculated thermodynamical parameters are pre-sented in Table 14 for OAA andAA respectively Scale factorshave been recommended [42] for an accurate prediction in

Journal of Spectroscopy 17

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 180

170

160

150

140

130

120

110110

120 130 140 150 160 170

(a)

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

11

10

9

8

7

7 8 9 10 11 12 13

(b)

Figure 9 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for Anisic acid

determining the zero-point vibration energies (ZPVE) andthe entropy 119878vib(119879) The total energies and the change inthe total entropy at room temperature using B3LYP6-31Glowastlowastmethod are presented

7 Conclusion

Attempts have been made in the present work for the molec-ular parameters and frequency assignments for the com-pounds OAA and AA from the FTIR and FT-Raman spectraThe equilibrium geometries and harmonic and anharmonicfrequencies for the title compounds were determined andanalyzed at DFT level of theory utilizing 6-31Glowastlowast basis setThe assignments of most of the fundamentals of the titlecompounds provided in this work are quite comparableThe excellent agreement of the calculated and observedvibrational spectra reveals the advantages of a smaller basisset for quantum chemical calculations HOMO and LUMOenergy gap explains the eventual charge transfer interactionstaking place within the molecule The experimental andtheoretical investigation of the title compounds have beenperformed successfully by using 1H and 13C NMR Thevarious modes of vibrations were unambiguously assignedon the basis of the result of the PED output obtainedfrom normal coordinate analysis These studies confirm thepresence of COOH and OCH

3group Dimeric molecules are

held together by hydrogen bridges between carbonyl groupsThe obtained data and simulations both show the way to thecharacterization of the molecules and help in spectra studiesin the future

References

[1] GMelentyeva and LAntonovaPharmaceutical ChemistryMirPublishers Moscow Russia 1988

[2] ldquoo-Anisic acid(579-75-9) catalog of chemical suppliersrdquo httpwwwchemexpercomchemicalssuppliercas579-75-9html

[3] B A Hess Jr L J Schaad P Carsky and R Zaharaduick ldquoAbinitio calculations of vibrational spectra and their use in theidentification of unusual moleculesrdquo Chemical Reviews vol 86no 4 pp 709ndash730 1986

[4] P Pulay X Zhou and G Forgarasi in Recent Experimental andComputational Advances in Molecular Spectroscopy R Faustoand R Fransto Eds vol 406 ofNATOASI Series p 99 KluwerDordrecht Netherlands 1993

[5] P Pulay G Fogarasi G Pongor J E Boggs and A VarghaldquoCombination of theoretical ab initio and experimental infor-mation to obtain reliable harmonic force constants ScaledQuantum Mechanical (SQM) force fields for glyoxal acroleinbutadiene formaldehyde and ethylenerdquo Journal of the Ameri-can Chemical Society vol 105 no 24 pp 7037ndash7047 1983

[6] C E Blom and C Altona ldquoApplication of self-consistent-fieldab initio calculations to organic moleculesrdquo Molecular Physicsvol 31 no 5 pp 1377ndash1391 1976

[7] G Fogarasi and P Pulay in Vibrational Spectra and Structure JR Durig Ed vol 14 Elsevier Amsterdam Netherlands 1985

[8] G Fogarasi ldquoRecent developments in the method of SQM forcefields with application to 1-methyladeninerdquo Spectrochimica ActaA vol 53 no 8 pp 1211ndash1224 1997

[9] G R deMare N Yu Panchenko andW Ch Bock ldquoAnMP26-31GlowastMP26-31Glowast vibrational analysis of s-trans- and s-cis-acryloyl fluoride CH2=CH-CF=Ordquo The Journal of PhysicalChemistry vol 98 no 5 pp 1416ndash1420 1994

[10] G Pongor P Pulay G Fogarasi and J E Boggs ldquoTheoreticalprediction of vibrational spectra 1 The in-plane force fieldand vibrational spectra of pyridinerdquo Journal of the AmericanChemical Society vol 106 no 10 pp 2765ndash2769 1984

[11] Y Yamakitu and M Tasumi ldquoVibrational analyses of p-benzoquinodimethane and p-benzoquinone based on ab initioHartree-Fock and second-order Moller-Plesset calculationsrdquoThe Journal of Physical Chemistry vol 99 no 21 pp 8524ndash85341995

18 Journal of Spectroscopy

[12] M Karabacak A Coruh and M Kurt ldquoFT-IR FT-RamanNMR spectra and molecular structure investigation of 23-dibromo-N-methylmaleimide a combined experimental andtheoretical studyrdquo Journal of Molecular Structure vol 892 no1ndash3 pp 125ndash131 2008

[13] M S Masoud M K Awad M A Shaker and M M T El-Tahawy ldquoThe role of structural chemistry in the inhibitiveperformance of some aminopyrimidines on the corrosion ofsteelrdquo Corrosion Science vol 52 no 7 pp 2387ndash2396 2010

[14] M J Frisch G W Trucks H B Schlegel et al Gaussian 03Revision B4 Gaussian Inc Pittsburgh Pa USA 2003

[15] P L Polavarapu ldquoAb initio vibrational Raman and Ramanoptical activity spectrardquo Journal of Physical Chemistry vol 94no 21 pp 8106ndash8112 1990

[16] G Keresztury S Holly J Varga G Besenyei A Wang andJ R Durig ldquoVibrational spectra of monothiocarbamates-IIIR and Raman spectra vibrational assignment conforma-tional analysis and ab initio calculations of S-methyl-NN-dimethylthiocarbamaterdquo Spectrochimica Acta A vol 49 no 13-14 pp 2007ndash2017 1993

[17] G Keresztury ldquoRaman spectroscopy theoryrdquo in Handbook ofVibrational Spectroscopy J M Chalmers and P R Griffths Edsvol 1 p 71 John Wiley and Sons 2002

[18] R G Parr R A Donnelly M Levy and W E Palke ldquoElec-tronegativity the density functional viewpointrdquo The Journal ofChemical Physics vol 68 no 8 pp 3801ndash3807 1977

[19] R G Parr and R G Pearson ldquoAbsolute hardness companionparameter to absolute electronegativityrdquo Journal of theAmericanChemical Society vol 105 no 26 pp 7512ndash7516 1983

[20] R G Pearson ldquoAbsolute electronegativity and hardness appli-cation to inorganic chemistryrdquo Inorganic Chemistry vol 27 no4 pp 734ndash740 1988

[21] P Geerlings F De Proft and W Langenaeker ldquoConceptualdensity functional theoryrdquo Chemical Reviews vol 103 no 5 pp1793ndash1873 2003

[22] R Ditchfield ldquoMolecular orbital theory of magnetic shieldingand magnetic susceptibilityrdquo Journal of Physical Chemistry vol56 no 11 article 5688 4 pages 1972

[23] KWolinski J F Hilton and P Pulay ldquoEfficient implementationof the gauge-independent atomic orbital method for NMRchemical shift calculationsrdquo Journal of the American ChemicalSociety vol 112 no 23 pp 8251ndash8260 1990

[24] M Kurt M Yurdakul and S Yurdakul ldquoMolecular structureand vibrational spectra of 3-chloro-4-methyl aniline by densityfunctional theory and ab initio Hartree-Fock calculationsrdquoJournal of Molecular Structure vol 711 no 1ndash3 pp 25ndash32 2004

[25] D Steele and D H Whiffen ldquoThe vibration frequencies ofpentafluorobenzenerdquo Spectrochimica Acta vol 16 no 3 pp368ndash375 1960

[26] D N Sathyanarayanan Vibrational Spectroscopy Theory andApplication New Age International publishers New DelhiIndia 1996

[27] L D S YadavOrganic Spectroscopy Springer NewDelhi India2004

[28] J Mohan Organic Spectroscopy Principles and ApplicationsNarosa Publishing House New Delhi 2nd edition 2009

[29] R M Silverstein G C Bassler and T C Morrill SpectrometricIdentification of Organic Compounds John Wiley amp Sons NewYork NY USA 1981

[30] G Socrates Infrared Characteristic Group Frequencies WileyNew York NY USA 1980

[31] R S Mulliken ldquoElectronic population analysis on LCAO-MOmolecular wave functionsrdquoThe Journal of Chemical Physics vol23 no 10 pp 1833ndash1840 1955

[32] K Fukuli T Yonezawa and H Shingu ldquoA molecular orbitaltheory of reactivity in aromatic hydrocarbonsrdquo Journal ofPhysical Chemistry vol 20 no 4 article 722 4 pages 1952

[33] C H Choi and M Kertesz ldquoConformational information fromvibrational spectra of styrene trans-stilbene and cis-stilbenerdquoJournal of Physical Chemistry A vol 101 no 20 pp 3823ndash38311997

[34] S Gunasekaran R Arun Balaji S Kumaresan G Anandand S Srinivasan ldquoExperimental and theoretical investigationsof spectroscopic properties of N-acetyl-5-methoxytryptaminerdquoCanadian Journal of Analytical Sciences and Spectroscopy vol53 no 4 pp 149ndash162 2008

[35] P Hohenberg and W Kohn ldquoInhomogeneous electron gasrdquoPhysical Review vol 136 no 3 pp B864ndashB871 1964

[36] R G Pearson ldquoAbsolute electronegativity and absolute hard-ness of Lewis acids and basesrdquo Journal of the American ChemicalSociety vol 107 no 24 pp 6801ndash6806 1985

[37] D Avci Y Atalay M Sekerci and M Dincer ldquoMolecular struc-ture and vibrational and chemical shift assignments of 3-(2-Hydroxyphenyl)-4-phenyl-1H-124-triazole-5-(4H)-thione byDFT and ab initio HF calculationsrdquo Spectrochimica Acta A vol73 no 1 pp 212ndash217 2009

[38] H O Kalinowski S Berger and S Braun Carbon13 NMRSpectroscopy John Wiley amp Sons Chichester UK 1988

[39] K Pihlaja and E Kleinpeter Carbon-13 NMR Chemical Shiftsin Structural and Sterochemical Analysis VCH PublishersDeerfield Beach Fla USA 1994

[40] P S Kalsi Spectroscopy of Organic Compounds New AgeInternational 2004

[41] A F Parsons Keynotes in Organic Chemistry Blackwell Pub-lishing Oxford UK 2003

[42] M A Palafox ldquoScaling factors for the prediction of vibrationalspectra I benzenemoleculerdquo International Journal of QuantumChemistry vol 77 no 3 pp 661ndash684 2000

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

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Journal of

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Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

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Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

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CatalystsJournal of

Page 9: Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. · Molecular Structure, NMR, HOMO, LUMO, ... ects of carbonyl and methyl substitutions

Journal of Spectroscopy 9Ta

ble7Detailedassig

nmento

ffun

damentalvibratio

nsof

O-Anisic

acid

(OAA)b

yno

rmalmod

eanalysis

basedon

SQM

forcefi

eldcalculations

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

1A1015840

3390

mdash3771

3390

72652

155385

120592OH(100)

2A1015840

mdash3098

3273

3098

1612

499564

120592CH

(99)

3A1015840

mdash3083

3233

3083

1700

135114

120592CH

(99)

4A1015840

3069

mdash3207

3069

10674

70382

120592CH

(99)

5A1015840

mdash3020

3186

3024

17253

1372

01120592CH

(99)

6A1015840

3018

mdash3157

3018

38987

58202

120592CH

3(99)

7A10158401015840

3003

mdash3085

3003

5946

78409

120592CH

3(99)

8A1015840

mdash2983

3020

2983

52626

120657

120592CH

3(99)

9A1015840

1670

mdash1822

1670

358567

54628

120592CO

(53)120592CC

(14)bC

CO(14

)bC

OH(12)

10A1015840

1600

mdash1656

1600

15061

16343

120592CC

(60)bCH

(20)R

asym

d(10)

11A1015840

1579

mdash1630

1579

61364

48880

120592CC

(69)bCH

(19)

12A1015840

1494

mdash1539

1494

58214

10686

bCH(48)120592CC

(37)

13A1015840

1466

mdash1513

1466

6534

6058

bCH

3(43)bCH

(25)120592CC

(16)

14A1015840

mdash1439

1506

1439

22318

5639

bCH(39)bCH

3(37)120592CC

(17)

15A10158401015840

1435

mdash1500

1435

3652

510814

bCH

3(88)

16A1015840

1411

mdash1475

1411

11849

19713

bCH

3(74)

17A1015840

1382

1367

4497

1268

bCOH(35)120592CO

(32)bCC

O(13)120592CC

(11)

18A1015840

mdash1312

1350

1312

2182

8877

120592CC

(67)

19A1015840

1288

mdash1320

1288

6319

416

48bC

H(33)R

trigd(20)120592CO

(13)120592CC

(12)

20A1015840

mdash1287

1302

1287

19694

044

9Rtrig

d(26)120592CC

(25)bCH

(20)120592CO

(12)

21A1015840

mdash1184

1210

1184

228252

32980

120592CC

(31)bCH

(19)bC

H3(17)120592CO

(17)

22A1015840

1182

mdash1201

1182

162989

2713

6bC

H(42)120592CC

(34)bCH

3(10)

23A1015840

1170

mdash119

3117

015

764576

bCH

3(57)bCH

(24)

24A1015840

mdash117

3117

31153

7419

1097

120592CC

(31)bCH

(29)bCH

3(25)

25A1015840

1140

mdash1168

1140

0662

4253

bCH

3(96)

26A1015840

1049

mdash1087

1050

1073

0478

09120592CO

(29)120592CC

(27)R

trigd(12)

27A1015840

-1062

1077

1060

104848

21650

120592CC

(41)120592CO

(22)bCH

(12)

28A10158401015840

960

-1060

960

060

90057

120596CH

(91)

29A1015840

mdash974

989

974

2078

710836

120592OC(62)120592CC

(12)120592CO

(11)

30A10158401015840

937

mdash965

935

1244

1294

120596CH

(91)

31A10158401015840

mdash865

869

865

3148

3432

120596CH

(64)ttrigd(19)

32A1015840

mdash795

830

795

12200

4238

120592CO

(29)R

symd(21)120592OC(15)120592CC

(15)

33A10158401015840

761

mdash795

761

1002

0207

tCO(32)ttrigd(28)120596

CH(23)120596

CC(11)

34A10158401015840

mdash755

770

755

41473

1456

120596CH

(51)ttrigd(27)120596

CO(14

)35

A10158401015840

695

mdash747

698

64512

0469

ttrigd(52)120596

CH(23)tCO

(15)

36A1015840

mdash698

712

695

10016

17946

120592CC

(33)120592CO

(23)bCC

O(21)

37A1015840

mdash602

639

602

13503

2683

Rasymd(36)bCC

O(15)

120592CC

(12)R

symd(11)

38A10158401015840

mdash595

594

595

74804

8168

tOH(79)

39A1015840

mdash565

588

565

21902

1740

bCCO

(28)120592CC

(17)bCO

(15)R

symd(14

)bC

CO(13)

10 Journal of Spectroscopy

Table7Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

540

mdash548

540

5598

4848

bCCO

(40)bCC

(16)120592CC

(13)R

asym

d(10)

41A10158401015840

480

mdash540

480

0946

0860

120596CO

(40)120596

CH(16)ttrigd(14

)tsy

m(14

)42

A10158401015840

mdash40

1435

401

3585

0792

tsym

(14)120596CC

(15)

43A1015840

mdash380

388

380

4805

4133

bCO(64)bCC

O(16)

44A1015840

mdash303

383

303

1180

4980

Rsym

d(59)bCO

C(17)120592CC

(15)

45A10158401015840

mdash280

283

280

0092

0016

tCH

3(79)

46A1015840

mdash240

280

240

0927

0935

bCOC(40)bCC

(30)bCC

O(18)

47A10158401015840

mdash180

229

180

0018

2096

120596CC

(30)tCO

(20)tsym

(18)

tasym

(11)120596CH

(10)

48A1015840

mdash170

190

170

3092

0715

bCC(42)bCO

C(29)bCO

(12)

49A10158401015840

mdash115

119115

4502

0508

tCOC(47)tsym

(15)tCH

3(12)

50A10158401015840

mdash110

9696

0922

3779

tsym

(35)tCO

(25)

tCOC(21)tCH

3(13)

51A10158401015840

mdashmdash

1730

1260

0037

tCO(99)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 11Ta

ble8Detailedassig

nmento

ffun

damentalvibratio

nsof

Anisic

acid

(AA)b

yno

rmalmod

eanalysis

basedon

SQM

forcefi

eldcalculations

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

1A1015840

3435

mdash3768

3435

7952

3164209

120592OH(100)

2A1015840

mdash3085

3232

3085

21438

120058

120592CH

(89)

3A1015840

mdash3034

3224

3034

7547

126718

120592CH

(99)

4A1015840

3029

mdash3218

3029

3520

99229

120592CH

(99)

5A1015840

3002

mdash3209

3002

5141

52552

120592CH

(99)

6A1015840

2990

mdash3155

2990

2423

53071

120592CH

ops(99)

7A10158401015840

2956

mdash3087

2956

45319

94074

120592CH

ips(51)120592CH

ss(36)120592CH

ops(12)

8A1015840

2941

mdash3022

2941

42847

91231

120592CH

ss(56)120592CH

ips(44

)9

A1015840

1688

mdash1813

1688

302139

74665

120592CO

(72)bCC

O(17)

10A1015840

1608

mdash1666

1608

216104

153242

120592CC

(62)bCH

(22)R

symd(11)

11A1015840

1580

mdash1624

1580

34785

12359

120592CC

(66)bCH

(14)

12A1015840

1518

mdash1559

1518

41495

8422

bCH(52)120592CC

(30)

13A1015840

1468

mdash1516

1468

37550

10673

bCHsb

(77)

14A10158401015840

1461

mdash1504

1461

14058

1218

3bC

Hop

b(83)

15A1015840

1429

mdash1486

1429

5851

19586

bCHipb(70)120592CC

(10)bCH

(10)

16A1015840

1416

mdash1465

1416

14835

9149

120592CC

(39)bCH

(35)bCH

ipb(18)

17A1015840

1324

mdash1391

1324

31290

5311

bCOH(27)120592CO

(22)bCC

O(21)120592CC

(13)

18A1015840

1307

mdash1371

1307

806

814

44120592CC

ar(65)bCH

(20)

19A1015840

1301

mdash1331

1301

40408

7073

bCH(43)120592CC

(33)

20A1015840

1267

mdash1304

1267

245222

3723

120592CO

(37)R

trigd(20)120592CC

(16)

21A1015840

1181

mdash1221

1181

5734

6023

bCH(61)120592CC

(21)

22A1015840

1172

mdash1209

1172

5690

5161

bCHop

r(61)bC

H(13)

23A1015840

mdash1137

1189

1137

0662

4334

bCHipr(78)bC

Hop

r(14)

24A1015840

1131

mdash117

61131

190946

42508

bCH(35)120592CC

(21)

25A1015840

1107

mdash1139

1107

245972

63024

120592CC

fn(25)R

trigd(23)bCH

(16)120592OC(13)

26A1015840

mdash1100

1114

1100

318070

20809

120592CO

(40)bCO

H(22)bCC

O(11)

27A1015840

1028

mdash1069

1028

0786

11056

120592CC

(58)bCH

(16)

28A1015840

mdash1010

1026

1010

29566

2343

120592OC(51)120592CC

(28)

29A10158401015840

929

mdash991

929

0010

046

4120596CH

(89)

30A10158401015840

854

mdash966

854

1379

1924

120596CH

(82)ttrigd(12)

31A10158401015840

846

mdash863

846

3652

212

44120596CH

(39)120596

CO(32)ttrigd(20)

32A1015840

825

mdash834

825

24090

2237

3120592CC

ar(32)R

symd(27)120592OC(22)

33A10158401015840

774

mdash830

774

0365

4928

120596CH

(84)

34A10158401015840

mdash755

775

755

1082

0243

ttrigd(51)120596

CC(15)120596

CH(14

)tCO(11)

35A1015840

698

mdash725

698

3553

93075

bCCO

(44)120592CO

(25)bCO

H(25)

36A10158401015840

634

mdash710

634

76887

0059

tCO(57)120596

CH(20)ttrigd(12)

37A1015840

617

mdash647

617

0592

644

1Ra

symd(81)

38A1015840

550

mdash603

550

14566

0968

Rsym

d(32)120592CC

fn(13)120592CO

(11)bCC

O(11)bCO

C(10)

39A10158401015840

545

mdash601

545

27876

4847

120596CO

(42)tOH(14

)120596CH

(11)120596

CC(11)

12 Journal of Spectroscopy

Table8Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

525

mdash511

525

12735

1849

bCCO

(82)

41A1015840

505

mdash511

505

50036

5698

tOH(24)ttrigd(23)120596

CO(19)120596

CH(14

)42

A1015840

440

mdash481

440

3190

2294

bCO(35)bCO

C(29)

43A10158401015840

mdash375

427

375

0415

0023

tsym

(60)120596

CH(19

)tasym

(17)

44A1015840

mdash310

335

310

3569

0577

Rsym

d(48)120592CC

fn(25)

45A10158401015840

mdash285

304

285

4416

0596

120596CC

(33)tasym

(24)tCO

(16)

46A1015840

mdash220

267

220

3713

2509

bCOC(29)bCO

(17)

47A10158401015840

mdash165

226

165

0047

0429

tCH

3(85)

48A1015840

mdash111

165

111

0211

0159

bCC(80)

49A10158401015840

mdash98

132

982323

0292

Tasym

(30)tCO

C(30)120596

CC(11)120596

CH(10)tsym

(10)

50A10158401015840

mdash70

7870

1302

1199

tCO(95)

51A10158401015840

mdash60

6560

0898

0216

tCOC(48)tCO

(31)tCH

3(12)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 13

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 3 FT-Raman spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 4 FTIR spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 5 FT-Raman spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

title molecules all the hydrogen atoms have a net positivecharge in particular the hydrogen atoms H(10) that havecharge of 05047 and 05050 respectively The presence oflarge amounts of negative charge on oxygen and net positivecharge on H(10) atoms may suggest the presence of inter-molecular hydrogen bonding in the crystalline phase

Highest occupied molecular orbital and lowest unoc-cupied molecular orbital are very important parametersfor quantum chemistry This is also used by the frontierelectron density for predicting the most reactive position in120587-electron systems and also explains several types of reactionin conjugated system [32] The conjugated molecules are

characterized by a small highest occupied molecular orbitalndashlowest unoccupied molecular orbital (HOMO-LUMO) sep-aration which is the result of a significant degree of inter-molecular charge transfer from the end-capping electron-donating groups to the efficient electron-acceptor groupsthrough 120587 conjugated path [33] Both the highest occupiedmolecular orbital and lowest unoccupied molecular orbitalare the main orbitals that take part in chemical stability[34] Energy difference betweenHOMOand LUMOorbital iscalled energy gap that is an important stability for structureswhich are given in Table 11 We performed an analysis ofall the molecular orbitals involved taking into consideration

14 Journal of Spectroscopy

Table 9 Atomic charges for optimized geometry of O-Anisic acid(OAA) and Anisic acid (AA) obtained by B3LYP6-31Glowastlowast densityfunctional calculations

Atomsa MullikenOAA AA

C1 00018 00373C2 03297 minus01002

C3 minus01368 minus01219

C4 minus00836 03612

C5 minus00943 minus01394

C6 minus01061 minus01118

C7 05570 05445O8 minus04650 minus04848

O9 minus05104 minus05064

H10 03198 03217O11 (H11) minus04841 01203C12 (H12) minus00837 01021H13 (O13) 01064 minus05111

H14 (C14) 01352 minus00831

H15 01211 01099H16 00913 01302H17 00929 01246H18 00886 00913H19 01200 01155aThe atoms indicated in the parenthesis belong to AA

Table 10Natural atomic charges ofO-Anisic acid (OAA) andAnisicacid (AA) calculations performed at the B3LYP6-31Glowastlowast level oftheory

Atomsa OAA AAC1 minus02176 minus02053

C2 03724 minus01746

C3 minus03284 minus02801

C4 minus01952 03443

C5 minus02720 minus03289

C6 minus01806 minus01748

C7 08091 08139O8 minus05861 minus06102

O9 minus07295 minus07217

H10 05047 05050O11 (H11) minus04921 02634C12 (H12) minus03307 02544H13 (O13) 02070 minus05119

H14 (C14) 02390 minus03300

H15 02070 02090H16 02443 02352H17 02426 02090H18 02439 02449H19 02621 02585aThe atoms indicated in the parenthesis belong to AAFor numbering of atoms refer to Figures 1(a) and 1(b)

that orbital 40 is the HOMO and orbital 41 is the LUMO forOAA and AA respectively

Many organic molecules that contain conjugated 120587 elec-trons are characterized as hyperpolarisabilities and are ana-lyzed by means of vibrational spectroscopy The analysis

Table 11 Calculated quantum chemical parameters ofO-Anisic acid(OAA) and Anisic acid (AA) derivatives

Parameters OAA AA119864HOMO minus0227 minus0231

119864LUMO minus0041 minus0036

Δ119864 0186 0195120594 0134 0133Η 0093 0097Σ 10752 10256

Table 12 Calculated 13C NMR chemical shifts (ppm) of O-Anisicacid (OAA) and Anisic acid (AA)

Carbona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAC1 11782 12315 10447 12620C2 15848 13146 14696 13936C3 11204 11384 9681 12272C4 13517 16297 11926 17125C5 12191 11384 10447 11047C6 13347 13146 12019 13751C7 16634 16714 14609 17174C12 (C14) 5674 5544 4322 5549aThe atoms indicated in the parenthesis belong to AA

Table 13 Experimental and calculated 1H NMR chemical shifts(ppm) of O-Anisic acid (OAA) and Anisic acid (AA)

Protona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAH10 1030 13 11 11H13 H14 H15 (H11) 4066 7914 3932 8405H16 (H12) 708 7027 6831 7147H17 (H15 H16 H17) 756 3836 7570 3824H18 710 7027 7069 6673H19 813 7914 3932 8217aThe atoms indicated in the parenthesis belong to AA

of the wave function indicates that the electron absorptioncorresponds to the transition from the ground state to thefirst excited state and is mainly described by the one-electronexcitation from the HOMO to the LUMO The HOMO of 120587nature (ie aromatic ring) is delocalized over the whole CndashC bond By contrast the LUMO is located over the aromaticring Consequently the HOMO-LUMO transition implies anelectron density transfer toCOOHandOCH

3group from the

aromatic ringThe theoretical basis for the new quantities lies in the

density functional formalism [35] Since molecular orbital(MO) theory is by far the most widely used by chemistsit is important to place 120594 and 120578 in a MO framework Ithas already been shown [36] that the MO theory of thechemical bond contains the values of 120594 and 120578 for the bondingfragments Hard molecules have a large HOMO-LUMO gapand soft molecules have a small HOMO-LUMO gap A small

Journal of Spectroscopy 15

HOMO

(a)

LUMO

(b)

Figure 6 Contour surfaces of frontier molecular orbitals of O-Anisic acid

HOMO

(a)

LUMO

(b)

Figure 7 Contour surfaces of frontier molecular orbitals of Anisic acid

HOMO-LUMO gap automatically means small excitationenergies to the manifold of excited states Therefore softmolecules with a small gap will be more polarizable thanhard molecules High polarizability was the most character-istic property attributed to soft acids and bases Energy gapsshould be small for best bonding or bothmolecules should besoft

In the present study the title compound AA is dynam-ically more stable due to the large energy gap OAA is asoft molecule due to small energy gap The Contour surfacesof the frontier molecular orbitals are sketched in Figures 6and 7

51 NMR Spectra DFT methods treat the electronic energyas a function of the electron density of all electrons simul-taneously and thus include electron correlation effect [37]In this study molecular structure of the OAA and AA wasoptimized by using B3LYP method in conjunction with 6-31Glowastlowast 13C and 1H chemical shift calculations of the titlecompounds have been made by using GIAO method andsame basis set The isotropic shielding values were usedto calculate the isotropic chemical shifts 120575 with respect totetramethylsilane (TMS) The isotropic chemical shifts arefrequently used as an aid in identification of reactive ionicspecies The B3LYP method allows calculating the shielding

16 Journal of Spectroscopy

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 150

140

130

120

110

100

90110 120 130 140 150 160 170

(a)

70 75 80 85 90 95 100 1056

7

8

9

10

11

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

(b)

Figure 8 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for O-Anisic acid

constants with the proper accuracy and the GIAOmethod isone of the most common approaches for calculating nuclearmagnetic shielding tensors

Theoretical and experimental chemical shifts of OAA andAA in 1H and 13C NMR spectra are gathered in Tables 12and 13 The range of the 13C NMR chemical shifts for atypical organic molecules usually is gt100 ppm [38 39] andthe accuracy ensures reliable interpretation of spectroscopicparameters In the present study the 13C NMR chemicalshifts in the ring are gt100 ppm as they would be expectedThe 13C chemical shifts carbonyl carbons vary from 150 to220 ppm This depends on the decrease in electron donatingor shielding ability of the attached atoms [40] The C=Ogroups of carboxylic acids and derivatives are in the range of150ndash185 ppm [29]

Hydrogens bonded to an aromatic ring are stronglydeshielded and absorb downfieldWhen the120587-electrons enterthe magnetic field they circulate around the ring to generatea ring current This produces a small induced magnetic fieldthat reinforces the applied field outside the ring resultingin aromatic protons being deshielded [41] A related effectis observed for carboxylic acids For these compoundscirculation of electrons in the double bonds produces inducedmagnetic field These are responsible for the high chemicalshift values of acid protons (H10) Carboxylic acids asstable hydrogen-bonded dimers in nonpolar solvents even athigh dilution The carboxylic proton therefore absorbs in acharacteristically narrow range 132 to 100 and is affectedonly slightly by concentration [29]

In a methyl group a proton is covalently bonded tocarbon oxygen or other atoms by a sigma bond Whenplaced in a strong magnetic field the electrons of the sigmabond circulate to generate a small magnetic field whichopposes the applied field A nearby electronegative atomwithdraws electron density from the neighbourhood of theproton so that a smaller applied field is needed to cause thespin state of the proton to flip The signal for a deshielded

Table 14 Theoretically computed energies (au) zero-point vibra-tional energies (kcalmolminus1) rotational constants (GHz) entropies(calmolminus1 Kminus1) nuclear repulsion energy (Hartrees) and dipolemoment (Debye) for OAA and AA

Parameters B3LYP6-31Glowastlowast

OAA AAZero-point energy 9306056 9314966

Rotational constants139942 344405114384 056752063193 048875

EntropyTotal 99243 97126Translational 40967 40967Rotational 30142 30199Vibrational 28134 25960Dipole moment 24181 35822Nuclear repulsion energy 592968293 573992628

proton (1 surrounded by less electron density) is observed tobe more downfield than the signals for protons that are notdeshielded by electronegative atoms [40] The chemical shiftvalue of C7 (OAA and AA) has bigger value than the othercarbons due to the electronegative property of oxygen atom

The linear correlations between calculated and experi-mental data of 13CNMRand 1HNMRspectra are determinedas 09 and 10 for OAA and 09 and 09 for AA respectivelyThere is an excellent linear relationship between experimentaland computed results which are shown in Figures 8 and 9

6 Thermodynamic Properties

Several calculated thermodynamical parameters are pre-sented in Table 14 for OAA andAA respectively Scale factorshave been recommended [42] for an accurate prediction in

Journal of Spectroscopy 17

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 180

170

160

150

140

130

120

110110

120 130 140 150 160 170

(a)

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

11

10

9

8

7

7 8 9 10 11 12 13

(b)

Figure 9 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for Anisic acid

determining the zero-point vibration energies (ZPVE) andthe entropy 119878vib(119879) The total energies and the change inthe total entropy at room temperature using B3LYP6-31Glowastlowastmethod are presented

7 Conclusion

Attempts have been made in the present work for the molec-ular parameters and frequency assignments for the com-pounds OAA and AA from the FTIR and FT-Raman spectraThe equilibrium geometries and harmonic and anharmonicfrequencies for the title compounds were determined andanalyzed at DFT level of theory utilizing 6-31Glowastlowast basis setThe assignments of most of the fundamentals of the titlecompounds provided in this work are quite comparableThe excellent agreement of the calculated and observedvibrational spectra reveals the advantages of a smaller basisset for quantum chemical calculations HOMO and LUMOenergy gap explains the eventual charge transfer interactionstaking place within the molecule The experimental andtheoretical investigation of the title compounds have beenperformed successfully by using 1H and 13C NMR Thevarious modes of vibrations were unambiguously assignedon the basis of the result of the PED output obtainedfrom normal coordinate analysis These studies confirm thepresence of COOH and OCH

3group Dimeric molecules are

held together by hydrogen bridges between carbonyl groupsThe obtained data and simulations both show the way to thecharacterization of the molecules and help in spectra studiesin the future

References

[1] GMelentyeva and LAntonovaPharmaceutical ChemistryMirPublishers Moscow Russia 1988

[2] ldquoo-Anisic acid(579-75-9) catalog of chemical suppliersrdquo httpwwwchemexpercomchemicalssuppliercas579-75-9html

[3] B A Hess Jr L J Schaad P Carsky and R Zaharaduick ldquoAbinitio calculations of vibrational spectra and their use in theidentification of unusual moleculesrdquo Chemical Reviews vol 86no 4 pp 709ndash730 1986

[4] P Pulay X Zhou and G Forgarasi in Recent Experimental andComputational Advances in Molecular Spectroscopy R Faustoand R Fransto Eds vol 406 ofNATOASI Series p 99 KluwerDordrecht Netherlands 1993

[5] P Pulay G Fogarasi G Pongor J E Boggs and A VarghaldquoCombination of theoretical ab initio and experimental infor-mation to obtain reliable harmonic force constants ScaledQuantum Mechanical (SQM) force fields for glyoxal acroleinbutadiene formaldehyde and ethylenerdquo Journal of the Ameri-can Chemical Society vol 105 no 24 pp 7037ndash7047 1983

[6] C E Blom and C Altona ldquoApplication of self-consistent-fieldab initio calculations to organic moleculesrdquo Molecular Physicsvol 31 no 5 pp 1377ndash1391 1976

[7] G Fogarasi and P Pulay in Vibrational Spectra and Structure JR Durig Ed vol 14 Elsevier Amsterdam Netherlands 1985

[8] G Fogarasi ldquoRecent developments in the method of SQM forcefields with application to 1-methyladeninerdquo Spectrochimica ActaA vol 53 no 8 pp 1211ndash1224 1997

[9] G R deMare N Yu Panchenko andW Ch Bock ldquoAnMP26-31GlowastMP26-31Glowast vibrational analysis of s-trans- and s-cis-acryloyl fluoride CH2=CH-CF=Ordquo The Journal of PhysicalChemistry vol 98 no 5 pp 1416ndash1420 1994

[10] G Pongor P Pulay G Fogarasi and J E Boggs ldquoTheoreticalprediction of vibrational spectra 1 The in-plane force fieldand vibrational spectra of pyridinerdquo Journal of the AmericanChemical Society vol 106 no 10 pp 2765ndash2769 1984

[11] Y Yamakitu and M Tasumi ldquoVibrational analyses of p-benzoquinodimethane and p-benzoquinone based on ab initioHartree-Fock and second-order Moller-Plesset calculationsrdquoThe Journal of Physical Chemistry vol 99 no 21 pp 8524ndash85341995

18 Journal of Spectroscopy

[12] M Karabacak A Coruh and M Kurt ldquoFT-IR FT-RamanNMR spectra and molecular structure investigation of 23-dibromo-N-methylmaleimide a combined experimental andtheoretical studyrdquo Journal of Molecular Structure vol 892 no1ndash3 pp 125ndash131 2008

[13] M S Masoud M K Awad M A Shaker and M M T El-Tahawy ldquoThe role of structural chemistry in the inhibitiveperformance of some aminopyrimidines on the corrosion ofsteelrdquo Corrosion Science vol 52 no 7 pp 2387ndash2396 2010

[14] M J Frisch G W Trucks H B Schlegel et al Gaussian 03Revision B4 Gaussian Inc Pittsburgh Pa USA 2003

[15] P L Polavarapu ldquoAb initio vibrational Raman and Ramanoptical activity spectrardquo Journal of Physical Chemistry vol 94no 21 pp 8106ndash8112 1990

[16] G Keresztury S Holly J Varga G Besenyei A Wang andJ R Durig ldquoVibrational spectra of monothiocarbamates-IIIR and Raman spectra vibrational assignment conforma-tional analysis and ab initio calculations of S-methyl-NN-dimethylthiocarbamaterdquo Spectrochimica Acta A vol 49 no 13-14 pp 2007ndash2017 1993

[17] G Keresztury ldquoRaman spectroscopy theoryrdquo in Handbook ofVibrational Spectroscopy J M Chalmers and P R Griffths Edsvol 1 p 71 John Wiley and Sons 2002

[18] R G Parr R A Donnelly M Levy and W E Palke ldquoElec-tronegativity the density functional viewpointrdquo The Journal ofChemical Physics vol 68 no 8 pp 3801ndash3807 1977

[19] R G Parr and R G Pearson ldquoAbsolute hardness companionparameter to absolute electronegativityrdquo Journal of theAmericanChemical Society vol 105 no 26 pp 7512ndash7516 1983

[20] R G Pearson ldquoAbsolute electronegativity and hardness appli-cation to inorganic chemistryrdquo Inorganic Chemistry vol 27 no4 pp 734ndash740 1988

[21] P Geerlings F De Proft and W Langenaeker ldquoConceptualdensity functional theoryrdquo Chemical Reviews vol 103 no 5 pp1793ndash1873 2003

[22] R Ditchfield ldquoMolecular orbital theory of magnetic shieldingand magnetic susceptibilityrdquo Journal of Physical Chemistry vol56 no 11 article 5688 4 pages 1972

[23] KWolinski J F Hilton and P Pulay ldquoEfficient implementationof the gauge-independent atomic orbital method for NMRchemical shift calculationsrdquo Journal of the American ChemicalSociety vol 112 no 23 pp 8251ndash8260 1990

[24] M Kurt M Yurdakul and S Yurdakul ldquoMolecular structureand vibrational spectra of 3-chloro-4-methyl aniline by densityfunctional theory and ab initio Hartree-Fock calculationsrdquoJournal of Molecular Structure vol 711 no 1ndash3 pp 25ndash32 2004

[25] D Steele and D H Whiffen ldquoThe vibration frequencies ofpentafluorobenzenerdquo Spectrochimica Acta vol 16 no 3 pp368ndash375 1960

[26] D N Sathyanarayanan Vibrational Spectroscopy Theory andApplication New Age International publishers New DelhiIndia 1996

[27] L D S YadavOrganic Spectroscopy Springer NewDelhi India2004

[28] J Mohan Organic Spectroscopy Principles and ApplicationsNarosa Publishing House New Delhi 2nd edition 2009

[29] R M Silverstein G C Bassler and T C Morrill SpectrometricIdentification of Organic Compounds John Wiley amp Sons NewYork NY USA 1981

[30] G Socrates Infrared Characteristic Group Frequencies WileyNew York NY USA 1980

[31] R S Mulliken ldquoElectronic population analysis on LCAO-MOmolecular wave functionsrdquoThe Journal of Chemical Physics vol23 no 10 pp 1833ndash1840 1955

[32] K Fukuli T Yonezawa and H Shingu ldquoA molecular orbitaltheory of reactivity in aromatic hydrocarbonsrdquo Journal ofPhysical Chemistry vol 20 no 4 article 722 4 pages 1952

[33] C H Choi and M Kertesz ldquoConformational information fromvibrational spectra of styrene trans-stilbene and cis-stilbenerdquoJournal of Physical Chemistry A vol 101 no 20 pp 3823ndash38311997

[34] S Gunasekaran R Arun Balaji S Kumaresan G Anandand S Srinivasan ldquoExperimental and theoretical investigationsof spectroscopic properties of N-acetyl-5-methoxytryptaminerdquoCanadian Journal of Analytical Sciences and Spectroscopy vol53 no 4 pp 149ndash162 2008

[35] P Hohenberg and W Kohn ldquoInhomogeneous electron gasrdquoPhysical Review vol 136 no 3 pp B864ndashB871 1964

[36] R G Pearson ldquoAbsolute electronegativity and absolute hard-ness of Lewis acids and basesrdquo Journal of the American ChemicalSociety vol 107 no 24 pp 6801ndash6806 1985

[37] D Avci Y Atalay M Sekerci and M Dincer ldquoMolecular struc-ture and vibrational and chemical shift assignments of 3-(2-Hydroxyphenyl)-4-phenyl-1H-124-triazole-5-(4H)-thione byDFT and ab initio HF calculationsrdquo Spectrochimica Acta A vol73 no 1 pp 212ndash217 2009

[38] H O Kalinowski S Berger and S Braun Carbon13 NMRSpectroscopy John Wiley amp Sons Chichester UK 1988

[39] K Pihlaja and E Kleinpeter Carbon-13 NMR Chemical Shiftsin Structural and Sterochemical Analysis VCH PublishersDeerfield Beach Fla USA 1994

[40] P S Kalsi Spectroscopy of Organic Compounds New AgeInternational 2004

[41] A F Parsons Keynotes in Organic Chemistry Blackwell Pub-lishing Oxford UK 2003

[42] M A Palafox ldquoScaling factors for the prediction of vibrationalspectra I benzenemoleculerdquo International Journal of QuantumChemistry vol 77 no 3 pp 661ndash684 2000

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Page 10: Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. · Molecular Structure, NMR, HOMO, LUMO, ... ects of carbonyl and methyl substitutions

10 Journal of Spectroscopy

Table7Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

540

mdash548

540

5598

4848

bCCO

(40)bCC

(16)120592CC

(13)R

asym

d(10)

41A10158401015840

480

mdash540

480

0946

0860

120596CO

(40)120596

CH(16)ttrigd(14

)tsy

m(14

)42

A10158401015840

mdash40

1435

401

3585

0792

tsym

(14)120596CC

(15)

43A1015840

mdash380

388

380

4805

4133

bCO(64)bCC

O(16)

44A1015840

mdash303

383

303

1180

4980

Rsym

d(59)bCO

C(17)120592CC

(15)

45A10158401015840

mdash280

283

280

0092

0016

tCH

3(79)

46A1015840

mdash240

280

240

0927

0935

bCOC(40)bCC

(30)bCC

O(18)

47A10158401015840

mdash180

229

180

0018

2096

120596CC

(30)tCO

(20)tsym

(18)

tasym

(11)120596CH

(10)

48A1015840

mdash170

190

170

3092

0715

bCC(42)bCO

C(29)bCO

(12)

49A10158401015840

mdash115

119115

4502

0508

tCOC(47)tsym

(15)tCH

3(12)

50A10158401015840

mdash110

9696

0922

3779

tsym

(35)tCO

(25)

tCOC(21)tCH

3(13)

51A10158401015840

mdashmdash

1730

1260

0037

tCO(99)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 11Ta

ble8Detailedassig

nmento

ffun

damentalvibratio

nsof

Anisic

acid

(AA)b

yno

rmalmod

eanalysis

basedon

SQM

forcefi

eldcalculations

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

1A1015840

3435

mdash3768

3435

7952

3164209

120592OH(100)

2A1015840

mdash3085

3232

3085

21438

120058

120592CH

(89)

3A1015840

mdash3034

3224

3034

7547

126718

120592CH

(99)

4A1015840

3029

mdash3218

3029

3520

99229

120592CH

(99)

5A1015840

3002

mdash3209

3002

5141

52552

120592CH

(99)

6A1015840

2990

mdash3155

2990

2423

53071

120592CH

ops(99)

7A10158401015840

2956

mdash3087

2956

45319

94074

120592CH

ips(51)120592CH

ss(36)120592CH

ops(12)

8A1015840

2941

mdash3022

2941

42847

91231

120592CH

ss(56)120592CH

ips(44

)9

A1015840

1688

mdash1813

1688

302139

74665

120592CO

(72)bCC

O(17)

10A1015840

1608

mdash1666

1608

216104

153242

120592CC

(62)bCH

(22)R

symd(11)

11A1015840

1580

mdash1624

1580

34785

12359

120592CC

(66)bCH

(14)

12A1015840

1518

mdash1559

1518

41495

8422

bCH(52)120592CC

(30)

13A1015840

1468

mdash1516

1468

37550

10673

bCHsb

(77)

14A10158401015840

1461

mdash1504

1461

14058

1218

3bC

Hop

b(83)

15A1015840

1429

mdash1486

1429

5851

19586

bCHipb(70)120592CC

(10)bCH

(10)

16A1015840

1416

mdash1465

1416

14835

9149

120592CC

(39)bCH

(35)bCH

ipb(18)

17A1015840

1324

mdash1391

1324

31290

5311

bCOH(27)120592CO

(22)bCC

O(21)120592CC

(13)

18A1015840

1307

mdash1371

1307

806

814

44120592CC

ar(65)bCH

(20)

19A1015840

1301

mdash1331

1301

40408

7073

bCH(43)120592CC

(33)

20A1015840

1267

mdash1304

1267

245222

3723

120592CO

(37)R

trigd(20)120592CC

(16)

21A1015840

1181

mdash1221

1181

5734

6023

bCH(61)120592CC

(21)

22A1015840

1172

mdash1209

1172

5690

5161

bCHop

r(61)bC

H(13)

23A1015840

mdash1137

1189

1137

0662

4334

bCHipr(78)bC

Hop

r(14)

24A1015840

1131

mdash117

61131

190946

42508

bCH(35)120592CC

(21)

25A1015840

1107

mdash1139

1107

245972

63024

120592CC

fn(25)R

trigd(23)bCH

(16)120592OC(13)

26A1015840

mdash1100

1114

1100

318070

20809

120592CO

(40)bCO

H(22)bCC

O(11)

27A1015840

1028

mdash1069

1028

0786

11056

120592CC

(58)bCH

(16)

28A1015840

mdash1010

1026

1010

29566

2343

120592OC(51)120592CC

(28)

29A10158401015840

929

mdash991

929

0010

046

4120596CH

(89)

30A10158401015840

854

mdash966

854

1379

1924

120596CH

(82)ttrigd(12)

31A10158401015840

846

mdash863

846

3652

212

44120596CH

(39)120596

CO(32)ttrigd(20)

32A1015840

825

mdash834

825

24090

2237

3120592CC

ar(32)R

symd(27)120592OC(22)

33A10158401015840

774

mdash830

774

0365

4928

120596CH

(84)

34A10158401015840

mdash755

775

755

1082

0243

ttrigd(51)120596

CC(15)120596

CH(14

)tCO(11)

35A1015840

698

mdash725

698

3553

93075

bCCO

(44)120592CO

(25)bCO

H(25)

36A10158401015840

634

mdash710

634

76887

0059

tCO(57)120596

CH(20)ttrigd(12)

37A1015840

617

mdash647

617

0592

644

1Ra

symd(81)

38A1015840

550

mdash603

550

14566

0968

Rsym

d(32)120592CC

fn(13)120592CO

(11)bCC

O(11)bCO

C(10)

39A10158401015840

545

mdash601

545

27876

4847

120596CO

(42)tOH(14

)120596CH

(11)120596

CC(11)

12 Journal of Spectroscopy

Table8Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

525

mdash511

525

12735

1849

bCCO

(82)

41A1015840

505

mdash511

505

50036

5698

tOH(24)ttrigd(23)120596

CO(19)120596

CH(14

)42

A1015840

440

mdash481

440

3190

2294

bCO(35)bCO

C(29)

43A10158401015840

mdash375

427

375

0415

0023

tsym

(60)120596

CH(19

)tasym

(17)

44A1015840

mdash310

335

310

3569

0577

Rsym

d(48)120592CC

fn(25)

45A10158401015840

mdash285

304

285

4416

0596

120596CC

(33)tasym

(24)tCO

(16)

46A1015840

mdash220

267

220

3713

2509

bCOC(29)bCO

(17)

47A10158401015840

mdash165

226

165

0047

0429

tCH

3(85)

48A1015840

mdash111

165

111

0211

0159

bCC(80)

49A10158401015840

mdash98

132

982323

0292

Tasym

(30)tCO

C(30)120596

CC(11)120596

CH(10)tsym

(10)

50A10158401015840

mdash70

7870

1302

1199

tCO(95)

51A10158401015840

mdash60

6560

0898

0216

tCOC(48)tCO

(31)tCH

3(12)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 13

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 3 FT-Raman spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 4 FTIR spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 5 FT-Raman spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

title molecules all the hydrogen atoms have a net positivecharge in particular the hydrogen atoms H(10) that havecharge of 05047 and 05050 respectively The presence oflarge amounts of negative charge on oxygen and net positivecharge on H(10) atoms may suggest the presence of inter-molecular hydrogen bonding in the crystalline phase

Highest occupied molecular orbital and lowest unoc-cupied molecular orbital are very important parametersfor quantum chemistry This is also used by the frontierelectron density for predicting the most reactive position in120587-electron systems and also explains several types of reactionin conjugated system [32] The conjugated molecules are

characterized by a small highest occupied molecular orbitalndashlowest unoccupied molecular orbital (HOMO-LUMO) sep-aration which is the result of a significant degree of inter-molecular charge transfer from the end-capping electron-donating groups to the efficient electron-acceptor groupsthrough 120587 conjugated path [33] Both the highest occupiedmolecular orbital and lowest unoccupied molecular orbitalare the main orbitals that take part in chemical stability[34] Energy difference betweenHOMOand LUMOorbital iscalled energy gap that is an important stability for structureswhich are given in Table 11 We performed an analysis ofall the molecular orbitals involved taking into consideration

14 Journal of Spectroscopy

Table 9 Atomic charges for optimized geometry of O-Anisic acid(OAA) and Anisic acid (AA) obtained by B3LYP6-31Glowastlowast densityfunctional calculations

Atomsa MullikenOAA AA

C1 00018 00373C2 03297 minus01002

C3 minus01368 minus01219

C4 minus00836 03612

C5 minus00943 minus01394

C6 minus01061 minus01118

C7 05570 05445O8 minus04650 minus04848

O9 minus05104 minus05064

H10 03198 03217O11 (H11) minus04841 01203C12 (H12) minus00837 01021H13 (O13) 01064 minus05111

H14 (C14) 01352 minus00831

H15 01211 01099H16 00913 01302H17 00929 01246H18 00886 00913H19 01200 01155aThe atoms indicated in the parenthesis belong to AA

Table 10Natural atomic charges ofO-Anisic acid (OAA) andAnisicacid (AA) calculations performed at the B3LYP6-31Glowastlowast level oftheory

Atomsa OAA AAC1 minus02176 minus02053

C2 03724 minus01746

C3 minus03284 minus02801

C4 minus01952 03443

C5 minus02720 minus03289

C6 minus01806 minus01748

C7 08091 08139O8 minus05861 minus06102

O9 minus07295 minus07217

H10 05047 05050O11 (H11) minus04921 02634C12 (H12) minus03307 02544H13 (O13) 02070 minus05119

H14 (C14) 02390 minus03300

H15 02070 02090H16 02443 02352H17 02426 02090H18 02439 02449H19 02621 02585aThe atoms indicated in the parenthesis belong to AAFor numbering of atoms refer to Figures 1(a) and 1(b)

that orbital 40 is the HOMO and orbital 41 is the LUMO forOAA and AA respectively

Many organic molecules that contain conjugated 120587 elec-trons are characterized as hyperpolarisabilities and are ana-lyzed by means of vibrational spectroscopy The analysis

Table 11 Calculated quantum chemical parameters ofO-Anisic acid(OAA) and Anisic acid (AA) derivatives

Parameters OAA AA119864HOMO minus0227 minus0231

119864LUMO minus0041 minus0036

Δ119864 0186 0195120594 0134 0133Η 0093 0097Σ 10752 10256

Table 12 Calculated 13C NMR chemical shifts (ppm) of O-Anisicacid (OAA) and Anisic acid (AA)

Carbona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAC1 11782 12315 10447 12620C2 15848 13146 14696 13936C3 11204 11384 9681 12272C4 13517 16297 11926 17125C5 12191 11384 10447 11047C6 13347 13146 12019 13751C7 16634 16714 14609 17174C12 (C14) 5674 5544 4322 5549aThe atoms indicated in the parenthesis belong to AA

Table 13 Experimental and calculated 1H NMR chemical shifts(ppm) of O-Anisic acid (OAA) and Anisic acid (AA)

Protona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAH10 1030 13 11 11H13 H14 H15 (H11) 4066 7914 3932 8405H16 (H12) 708 7027 6831 7147H17 (H15 H16 H17) 756 3836 7570 3824H18 710 7027 7069 6673H19 813 7914 3932 8217aThe atoms indicated in the parenthesis belong to AA

of the wave function indicates that the electron absorptioncorresponds to the transition from the ground state to thefirst excited state and is mainly described by the one-electronexcitation from the HOMO to the LUMO The HOMO of 120587nature (ie aromatic ring) is delocalized over the whole CndashC bond By contrast the LUMO is located over the aromaticring Consequently the HOMO-LUMO transition implies anelectron density transfer toCOOHandOCH

3group from the

aromatic ringThe theoretical basis for the new quantities lies in the

density functional formalism [35] Since molecular orbital(MO) theory is by far the most widely used by chemistsit is important to place 120594 and 120578 in a MO framework Ithas already been shown [36] that the MO theory of thechemical bond contains the values of 120594 and 120578 for the bondingfragments Hard molecules have a large HOMO-LUMO gapand soft molecules have a small HOMO-LUMO gap A small

Journal of Spectroscopy 15

HOMO

(a)

LUMO

(b)

Figure 6 Contour surfaces of frontier molecular orbitals of O-Anisic acid

HOMO

(a)

LUMO

(b)

Figure 7 Contour surfaces of frontier molecular orbitals of Anisic acid

HOMO-LUMO gap automatically means small excitationenergies to the manifold of excited states Therefore softmolecules with a small gap will be more polarizable thanhard molecules High polarizability was the most character-istic property attributed to soft acids and bases Energy gapsshould be small for best bonding or bothmolecules should besoft

In the present study the title compound AA is dynam-ically more stable due to the large energy gap OAA is asoft molecule due to small energy gap The Contour surfacesof the frontier molecular orbitals are sketched in Figures 6and 7

51 NMR Spectra DFT methods treat the electronic energyas a function of the electron density of all electrons simul-taneously and thus include electron correlation effect [37]In this study molecular structure of the OAA and AA wasoptimized by using B3LYP method in conjunction with 6-31Glowastlowast 13C and 1H chemical shift calculations of the titlecompounds have been made by using GIAO method andsame basis set The isotropic shielding values were usedto calculate the isotropic chemical shifts 120575 with respect totetramethylsilane (TMS) The isotropic chemical shifts arefrequently used as an aid in identification of reactive ionicspecies The B3LYP method allows calculating the shielding

16 Journal of Spectroscopy

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 150

140

130

120

110

100

90110 120 130 140 150 160 170

(a)

70 75 80 85 90 95 100 1056

7

8

9

10

11

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

(b)

Figure 8 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for O-Anisic acid

constants with the proper accuracy and the GIAOmethod isone of the most common approaches for calculating nuclearmagnetic shielding tensors

Theoretical and experimental chemical shifts of OAA andAA in 1H and 13C NMR spectra are gathered in Tables 12and 13 The range of the 13C NMR chemical shifts for atypical organic molecules usually is gt100 ppm [38 39] andthe accuracy ensures reliable interpretation of spectroscopicparameters In the present study the 13C NMR chemicalshifts in the ring are gt100 ppm as they would be expectedThe 13C chemical shifts carbonyl carbons vary from 150 to220 ppm This depends on the decrease in electron donatingor shielding ability of the attached atoms [40] The C=Ogroups of carboxylic acids and derivatives are in the range of150ndash185 ppm [29]

Hydrogens bonded to an aromatic ring are stronglydeshielded and absorb downfieldWhen the120587-electrons enterthe magnetic field they circulate around the ring to generatea ring current This produces a small induced magnetic fieldthat reinforces the applied field outside the ring resultingin aromatic protons being deshielded [41] A related effectis observed for carboxylic acids For these compoundscirculation of electrons in the double bonds produces inducedmagnetic field These are responsible for the high chemicalshift values of acid protons (H10) Carboxylic acids asstable hydrogen-bonded dimers in nonpolar solvents even athigh dilution The carboxylic proton therefore absorbs in acharacteristically narrow range 132 to 100 and is affectedonly slightly by concentration [29]

In a methyl group a proton is covalently bonded tocarbon oxygen or other atoms by a sigma bond Whenplaced in a strong magnetic field the electrons of the sigmabond circulate to generate a small magnetic field whichopposes the applied field A nearby electronegative atomwithdraws electron density from the neighbourhood of theproton so that a smaller applied field is needed to cause thespin state of the proton to flip The signal for a deshielded

Table 14 Theoretically computed energies (au) zero-point vibra-tional energies (kcalmolminus1) rotational constants (GHz) entropies(calmolminus1 Kminus1) nuclear repulsion energy (Hartrees) and dipolemoment (Debye) for OAA and AA

Parameters B3LYP6-31Glowastlowast

OAA AAZero-point energy 9306056 9314966

Rotational constants139942 344405114384 056752063193 048875

EntropyTotal 99243 97126Translational 40967 40967Rotational 30142 30199Vibrational 28134 25960Dipole moment 24181 35822Nuclear repulsion energy 592968293 573992628

proton (1 surrounded by less electron density) is observed tobe more downfield than the signals for protons that are notdeshielded by electronegative atoms [40] The chemical shiftvalue of C7 (OAA and AA) has bigger value than the othercarbons due to the electronegative property of oxygen atom

The linear correlations between calculated and experi-mental data of 13CNMRand 1HNMRspectra are determinedas 09 and 10 for OAA and 09 and 09 for AA respectivelyThere is an excellent linear relationship between experimentaland computed results which are shown in Figures 8 and 9

6 Thermodynamic Properties

Several calculated thermodynamical parameters are pre-sented in Table 14 for OAA andAA respectively Scale factorshave been recommended [42] for an accurate prediction in

Journal of Spectroscopy 17

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 180

170

160

150

140

130

120

110110

120 130 140 150 160 170

(a)

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

11

10

9

8

7

7 8 9 10 11 12 13

(b)

Figure 9 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for Anisic acid

determining the zero-point vibration energies (ZPVE) andthe entropy 119878vib(119879) The total energies and the change inthe total entropy at room temperature using B3LYP6-31Glowastlowastmethod are presented

7 Conclusion

Attempts have been made in the present work for the molec-ular parameters and frequency assignments for the com-pounds OAA and AA from the FTIR and FT-Raman spectraThe equilibrium geometries and harmonic and anharmonicfrequencies for the title compounds were determined andanalyzed at DFT level of theory utilizing 6-31Glowastlowast basis setThe assignments of most of the fundamentals of the titlecompounds provided in this work are quite comparableThe excellent agreement of the calculated and observedvibrational spectra reveals the advantages of a smaller basisset for quantum chemical calculations HOMO and LUMOenergy gap explains the eventual charge transfer interactionstaking place within the molecule The experimental andtheoretical investigation of the title compounds have beenperformed successfully by using 1H and 13C NMR Thevarious modes of vibrations were unambiguously assignedon the basis of the result of the PED output obtainedfrom normal coordinate analysis These studies confirm thepresence of COOH and OCH

3group Dimeric molecules are

held together by hydrogen bridges between carbonyl groupsThe obtained data and simulations both show the way to thecharacterization of the molecules and help in spectra studiesin the future

References

[1] GMelentyeva and LAntonovaPharmaceutical ChemistryMirPublishers Moscow Russia 1988

[2] ldquoo-Anisic acid(579-75-9) catalog of chemical suppliersrdquo httpwwwchemexpercomchemicalssuppliercas579-75-9html

[3] B A Hess Jr L J Schaad P Carsky and R Zaharaduick ldquoAbinitio calculations of vibrational spectra and their use in theidentification of unusual moleculesrdquo Chemical Reviews vol 86no 4 pp 709ndash730 1986

[4] P Pulay X Zhou and G Forgarasi in Recent Experimental andComputational Advances in Molecular Spectroscopy R Faustoand R Fransto Eds vol 406 ofNATOASI Series p 99 KluwerDordrecht Netherlands 1993

[5] P Pulay G Fogarasi G Pongor J E Boggs and A VarghaldquoCombination of theoretical ab initio and experimental infor-mation to obtain reliable harmonic force constants ScaledQuantum Mechanical (SQM) force fields for glyoxal acroleinbutadiene formaldehyde and ethylenerdquo Journal of the Ameri-can Chemical Society vol 105 no 24 pp 7037ndash7047 1983

[6] C E Blom and C Altona ldquoApplication of self-consistent-fieldab initio calculations to organic moleculesrdquo Molecular Physicsvol 31 no 5 pp 1377ndash1391 1976

[7] G Fogarasi and P Pulay in Vibrational Spectra and Structure JR Durig Ed vol 14 Elsevier Amsterdam Netherlands 1985

[8] G Fogarasi ldquoRecent developments in the method of SQM forcefields with application to 1-methyladeninerdquo Spectrochimica ActaA vol 53 no 8 pp 1211ndash1224 1997

[9] G R deMare N Yu Panchenko andW Ch Bock ldquoAnMP26-31GlowastMP26-31Glowast vibrational analysis of s-trans- and s-cis-acryloyl fluoride CH2=CH-CF=Ordquo The Journal of PhysicalChemistry vol 98 no 5 pp 1416ndash1420 1994

[10] G Pongor P Pulay G Fogarasi and J E Boggs ldquoTheoreticalprediction of vibrational spectra 1 The in-plane force fieldand vibrational spectra of pyridinerdquo Journal of the AmericanChemical Society vol 106 no 10 pp 2765ndash2769 1984

[11] Y Yamakitu and M Tasumi ldquoVibrational analyses of p-benzoquinodimethane and p-benzoquinone based on ab initioHartree-Fock and second-order Moller-Plesset calculationsrdquoThe Journal of Physical Chemistry vol 99 no 21 pp 8524ndash85341995

18 Journal of Spectroscopy

[12] M Karabacak A Coruh and M Kurt ldquoFT-IR FT-RamanNMR spectra and molecular structure investigation of 23-dibromo-N-methylmaleimide a combined experimental andtheoretical studyrdquo Journal of Molecular Structure vol 892 no1ndash3 pp 125ndash131 2008

[13] M S Masoud M K Awad M A Shaker and M M T El-Tahawy ldquoThe role of structural chemistry in the inhibitiveperformance of some aminopyrimidines on the corrosion ofsteelrdquo Corrosion Science vol 52 no 7 pp 2387ndash2396 2010

[14] M J Frisch G W Trucks H B Schlegel et al Gaussian 03Revision B4 Gaussian Inc Pittsburgh Pa USA 2003

[15] P L Polavarapu ldquoAb initio vibrational Raman and Ramanoptical activity spectrardquo Journal of Physical Chemistry vol 94no 21 pp 8106ndash8112 1990

[16] G Keresztury S Holly J Varga G Besenyei A Wang andJ R Durig ldquoVibrational spectra of monothiocarbamates-IIIR and Raman spectra vibrational assignment conforma-tional analysis and ab initio calculations of S-methyl-NN-dimethylthiocarbamaterdquo Spectrochimica Acta A vol 49 no 13-14 pp 2007ndash2017 1993

[17] G Keresztury ldquoRaman spectroscopy theoryrdquo in Handbook ofVibrational Spectroscopy J M Chalmers and P R Griffths Edsvol 1 p 71 John Wiley and Sons 2002

[18] R G Parr R A Donnelly M Levy and W E Palke ldquoElec-tronegativity the density functional viewpointrdquo The Journal ofChemical Physics vol 68 no 8 pp 3801ndash3807 1977

[19] R G Parr and R G Pearson ldquoAbsolute hardness companionparameter to absolute electronegativityrdquo Journal of theAmericanChemical Society vol 105 no 26 pp 7512ndash7516 1983

[20] R G Pearson ldquoAbsolute electronegativity and hardness appli-cation to inorganic chemistryrdquo Inorganic Chemistry vol 27 no4 pp 734ndash740 1988

[21] P Geerlings F De Proft and W Langenaeker ldquoConceptualdensity functional theoryrdquo Chemical Reviews vol 103 no 5 pp1793ndash1873 2003

[22] R Ditchfield ldquoMolecular orbital theory of magnetic shieldingand magnetic susceptibilityrdquo Journal of Physical Chemistry vol56 no 11 article 5688 4 pages 1972

[23] KWolinski J F Hilton and P Pulay ldquoEfficient implementationof the gauge-independent atomic orbital method for NMRchemical shift calculationsrdquo Journal of the American ChemicalSociety vol 112 no 23 pp 8251ndash8260 1990

[24] M Kurt M Yurdakul and S Yurdakul ldquoMolecular structureand vibrational spectra of 3-chloro-4-methyl aniline by densityfunctional theory and ab initio Hartree-Fock calculationsrdquoJournal of Molecular Structure vol 711 no 1ndash3 pp 25ndash32 2004

[25] D Steele and D H Whiffen ldquoThe vibration frequencies ofpentafluorobenzenerdquo Spectrochimica Acta vol 16 no 3 pp368ndash375 1960

[26] D N Sathyanarayanan Vibrational Spectroscopy Theory andApplication New Age International publishers New DelhiIndia 1996

[27] L D S YadavOrganic Spectroscopy Springer NewDelhi India2004

[28] J Mohan Organic Spectroscopy Principles and ApplicationsNarosa Publishing House New Delhi 2nd edition 2009

[29] R M Silverstein G C Bassler and T C Morrill SpectrometricIdentification of Organic Compounds John Wiley amp Sons NewYork NY USA 1981

[30] G Socrates Infrared Characteristic Group Frequencies WileyNew York NY USA 1980

[31] R S Mulliken ldquoElectronic population analysis on LCAO-MOmolecular wave functionsrdquoThe Journal of Chemical Physics vol23 no 10 pp 1833ndash1840 1955

[32] K Fukuli T Yonezawa and H Shingu ldquoA molecular orbitaltheory of reactivity in aromatic hydrocarbonsrdquo Journal ofPhysical Chemistry vol 20 no 4 article 722 4 pages 1952

[33] C H Choi and M Kertesz ldquoConformational information fromvibrational spectra of styrene trans-stilbene and cis-stilbenerdquoJournal of Physical Chemistry A vol 101 no 20 pp 3823ndash38311997

[34] S Gunasekaran R Arun Balaji S Kumaresan G Anandand S Srinivasan ldquoExperimental and theoretical investigationsof spectroscopic properties of N-acetyl-5-methoxytryptaminerdquoCanadian Journal of Analytical Sciences and Spectroscopy vol53 no 4 pp 149ndash162 2008

[35] P Hohenberg and W Kohn ldquoInhomogeneous electron gasrdquoPhysical Review vol 136 no 3 pp B864ndashB871 1964

[36] R G Pearson ldquoAbsolute electronegativity and absolute hard-ness of Lewis acids and basesrdquo Journal of the American ChemicalSociety vol 107 no 24 pp 6801ndash6806 1985

[37] D Avci Y Atalay M Sekerci and M Dincer ldquoMolecular struc-ture and vibrational and chemical shift assignments of 3-(2-Hydroxyphenyl)-4-phenyl-1H-124-triazole-5-(4H)-thione byDFT and ab initio HF calculationsrdquo Spectrochimica Acta A vol73 no 1 pp 212ndash217 2009

[38] H O Kalinowski S Berger and S Braun Carbon13 NMRSpectroscopy John Wiley amp Sons Chichester UK 1988

[39] K Pihlaja and E Kleinpeter Carbon-13 NMR Chemical Shiftsin Structural and Sterochemical Analysis VCH PublishersDeerfield Beach Fla USA 1994

[40] P S Kalsi Spectroscopy of Organic Compounds New AgeInternational 2004

[41] A F Parsons Keynotes in Organic Chemistry Blackwell Pub-lishing Oxford UK 2003

[42] M A Palafox ldquoScaling factors for the prediction of vibrationalspectra I benzenemoleculerdquo International Journal of QuantumChemistry vol 77 no 3 pp 661ndash684 2000

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

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Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

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CatalystsJournal of

Page 11: Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. · Molecular Structure, NMR, HOMO, LUMO, ... ects of carbonyl and methyl substitutions

Journal of Spectroscopy 11Ta

ble8Detailedassig

nmento

ffun

damentalvibratio

nsof

Anisic

acid

(AA)b

yno

rmalmod

eanalysis

basedon

SQM

forcefi

eldcalculations

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

1A1015840

3435

mdash3768

3435

7952

3164209

120592OH(100)

2A1015840

mdash3085

3232

3085

21438

120058

120592CH

(89)

3A1015840

mdash3034

3224

3034

7547

126718

120592CH

(99)

4A1015840

3029

mdash3218

3029

3520

99229

120592CH

(99)

5A1015840

3002

mdash3209

3002

5141

52552

120592CH

(99)

6A1015840

2990

mdash3155

2990

2423

53071

120592CH

ops(99)

7A10158401015840

2956

mdash3087

2956

45319

94074

120592CH

ips(51)120592CH

ss(36)120592CH

ops(12)

8A1015840

2941

mdash3022

2941

42847

91231

120592CH

ss(56)120592CH

ips(44

)9

A1015840

1688

mdash1813

1688

302139

74665

120592CO

(72)bCC

O(17)

10A1015840

1608

mdash1666

1608

216104

153242

120592CC

(62)bCH

(22)R

symd(11)

11A1015840

1580

mdash1624

1580

34785

12359

120592CC

(66)bCH

(14)

12A1015840

1518

mdash1559

1518

41495

8422

bCH(52)120592CC

(30)

13A1015840

1468

mdash1516

1468

37550

10673

bCHsb

(77)

14A10158401015840

1461

mdash1504

1461

14058

1218

3bC

Hop

b(83)

15A1015840

1429

mdash1486

1429

5851

19586

bCHipb(70)120592CC

(10)bCH

(10)

16A1015840

1416

mdash1465

1416

14835

9149

120592CC

(39)bCH

(35)bCH

ipb(18)

17A1015840

1324

mdash1391

1324

31290

5311

bCOH(27)120592CO

(22)bCC

O(21)120592CC

(13)

18A1015840

1307

mdash1371

1307

806

814

44120592CC

ar(65)bCH

(20)

19A1015840

1301

mdash1331

1301

40408

7073

bCH(43)120592CC

(33)

20A1015840

1267

mdash1304

1267

245222

3723

120592CO

(37)R

trigd(20)120592CC

(16)

21A1015840

1181

mdash1221

1181

5734

6023

bCH(61)120592CC

(21)

22A1015840

1172

mdash1209

1172

5690

5161

bCHop

r(61)bC

H(13)

23A1015840

mdash1137

1189

1137

0662

4334

bCHipr(78)bC

Hop

r(14)

24A1015840

1131

mdash117

61131

190946

42508

bCH(35)120592CC

(21)

25A1015840

1107

mdash1139

1107

245972

63024

120592CC

fn(25)R

trigd(23)bCH

(16)120592OC(13)

26A1015840

mdash1100

1114

1100

318070

20809

120592CO

(40)bCO

H(22)bCC

O(11)

27A1015840

1028

mdash1069

1028

0786

11056

120592CC

(58)bCH

(16)

28A1015840

mdash1010

1026

1010

29566

2343

120592OC(51)120592CC

(28)

29A10158401015840

929

mdash991

929

0010

046

4120596CH

(89)

30A10158401015840

854

mdash966

854

1379

1924

120596CH

(82)ttrigd(12)

31A10158401015840

846

mdash863

846

3652

212

44120596CH

(39)120596

CO(32)ttrigd(20)

32A1015840

825

mdash834

825

24090

2237

3120592CC

ar(32)R

symd(27)120592OC(22)

33A10158401015840

774

mdash830

774

0365

4928

120596CH

(84)

34A10158401015840

mdash755

775

755

1082

0243

ttrigd(51)120596

CC(15)120596

CH(14

)tCO(11)

35A1015840

698

mdash725

698

3553

93075

bCCO

(44)120592CO

(25)bCO

H(25)

36A10158401015840

634

mdash710

634

76887

0059

tCO(57)120596

CH(20)ttrigd(12)

37A1015840

617

mdash647

617

0592

644

1Ra

symd(81)

38A1015840

550

mdash603

550

14566

0968

Rsym

d(32)120592CC

fn(13)120592CO

(11)bCC

O(11)bCO

C(10)

39A10158401015840

545

mdash601

545

27876

4847

120596CO

(42)tOH(14

)120596CH

(11)120596

CC(11)

12 Journal of Spectroscopy

Table8Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

525

mdash511

525

12735

1849

bCCO

(82)

41A1015840

505

mdash511

505

50036

5698

tOH(24)ttrigd(23)120596

CO(19)120596

CH(14

)42

A1015840

440

mdash481

440

3190

2294

bCO(35)bCO

C(29)

43A10158401015840

mdash375

427

375

0415

0023

tsym

(60)120596

CH(19

)tasym

(17)

44A1015840

mdash310

335

310

3569

0577

Rsym

d(48)120592CC

fn(25)

45A10158401015840

mdash285

304

285

4416

0596

120596CC

(33)tasym

(24)tCO

(16)

46A1015840

mdash220

267

220

3713

2509

bCOC(29)bCO

(17)

47A10158401015840

mdash165

226

165

0047

0429

tCH

3(85)

48A1015840

mdash111

165

111

0211

0159

bCC(80)

49A10158401015840

mdash98

132

982323

0292

Tasym

(30)tCO

C(30)120596

CC(11)120596

CH(10)tsym

(10)

50A10158401015840

mdash70

7870

1302

1199

tCO(95)

51A10158401015840

mdash60

6560

0898

0216

tCOC(48)tCO

(31)tCH

3(12)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 13

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 3 FT-Raman spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 4 FTIR spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 5 FT-Raman spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

title molecules all the hydrogen atoms have a net positivecharge in particular the hydrogen atoms H(10) that havecharge of 05047 and 05050 respectively The presence oflarge amounts of negative charge on oxygen and net positivecharge on H(10) atoms may suggest the presence of inter-molecular hydrogen bonding in the crystalline phase

Highest occupied molecular orbital and lowest unoc-cupied molecular orbital are very important parametersfor quantum chemistry This is also used by the frontierelectron density for predicting the most reactive position in120587-electron systems and also explains several types of reactionin conjugated system [32] The conjugated molecules are

characterized by a small highest occupied molecular orbitalndashlowest unoccupied molecular orbital (HOMO-LUMO) sep-aration which is the result of a significant degree of inter-molecular charge transfer from the end-capping electron-donating groups to the efficient electron-acceptor groupsthrough 120587 conjugated path [33] Both the highest occupiedmolecular orbital and lowest unoccupied molecular orbitalare the main orbitals that take part in chemical stability[34] Energy difference betweenHOMOand LUMOorbital iscalled energy gap that is an important stability for structureswhich are given in Table 11 We performed an analysis ofall the molecular orbitals involved taking into consideration

14 Journal of Spectroscopy

Table 9 Atomic charges for optimized geometry of O-Anisic acid(OAA) and Anisic acid (AA) obtained by B3LYP6-31Glowastlowast densityfunctional calculations

Atomsa MullikenOAA AA

C1 00018 00373C2 03297 minus01002

C3 minus01368 minus01219

C4 minus00836 03612

C5 minus00943 minus01394

C6 minus01061 minus01118

C7 05570 05445O8 minus04650 minus04848

O9 minus05104 minus05064

H10 03198 03217O11 (H11) minus04841 01203C12 (H12) minus00837 01021H13 (O13) 01064 minus05111

H14 (C14) 01352 minus00831

H15 01211 01099H16 00913 01302H17 00929 01246H18 00886 00913H19 01200 01155aThe atoms indicated in the parenthesis belong to AA

Table 10Natural atomic charges ofO-Anisic acid (OAA) andAnisicacid (AA) calculations performed at the B3LYP6-31Glowastlowast level oftheory

Atomsa OAA AAC1 minus02176 minus02053

C2 03724 minus01746

C3 minus03284 minus02801

C4 minus01952 03443

C5 minus02720 minus03289

C6 minus01806 minus01748

C7 08091 08139O8 minus05861 minus06102

O9 minus07295 minus07217

H10 05047 05050O11 (H11) minus04921 02634C12 (H12) minus03307 02544H13 (O13) 02070 minus05119

H14 (C14) 02390 minus03300

H15 02070 02090H16 02443 02352H17 02426 02090H18 02439 02449H19 02621 02585aThe atoms indicated in the parenthesis belong to AAFor numbering of atoms refer to Figures 1(a) and 1(b)

that orbital 40 is the HOMO and orbital 41 is the LUMO forOAA and AA respectively

Many organic molecules that contain conjugated 120587 elec-trons are characterized as hyperpolarisabilities and are ana-lyzed by means of vibrational spectroscopy The analysis

Table 11 Calculated quantum chemical parameters ofO-Anisic acid(OAA) and Anisic acid (AA) derivatives

Parameters OAA AA119864HOMO minus0227 minus0231

119864LUMO minus0041 minus0036

Δ119864 0186 0195120594 0134 0133Η 0093 0097Σ 10752 10256

Table 12 Calculated 13C NMR chemical shifts (ppm) of O-Anisicacid (OAA) and Anisic acid (AA)

Carbona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAC1 11782 12315 10447 12620C2 15848 13146 14696 13936C3 11204 11384 9681 12272C4 13517 16297 11926 17125C5 12191 11384 10447 11047C6 13347 13146 12019 13751C7 16634 16714 14609 17174C12 (C14) 5674 5544 4322 5549aThe atoms indicated in the parenthesis belong to AA

Table 13 Experimental and calculated 1H NMR chemical shifts(ppm) of O-Anisic acid (OAA) and Anisic acid (AA)

Protona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAH10 1030 13 11 11H13 H14 H15 (H11) 4066 7914 3932 8405H16 (H12) 708 7027 6831 7147H17 (H15 H16 H17) 756 3836 7570 3824H18 710 7027 7069 6673H19 813 7914 3932 8217aThe atoms indicated in the parenthesis belong to AA

of the wave function indicates that the electron absorptioncorresponds to the transition from the ground state to thefirst excited state and is mainly described by the one-electronexcitation from the HOMO to the LUMO The HOMO of 120587nature (ie aromatic ring) is delocalized over the whole CndashC bond By contrast the LUMO is located over the aromaticring Consequently the HOMO-LUMO transition implies anelectron density transfer toCOOHandOCH

3group from the

aromatic ringThe theoretical basis for the new quantities lies in the

density functional formalism [35] Since molecular orbital(MO) theory is by far the most widely used by chemistsit is important to place 120594 and 120578 in a MO framework Ithas already been shown [36] that the MO theory of thechemical bond contains the values of 120594 and 120578 for the bondingfragments Hard molecules have a large HOMO-LUMO gapand soft molecules have a small HOMO-LUMO gap A small

Journal of Spectroscopy 15

HOMO

(a)

LUMO

(b)

Figure 6 Contour surfaces of frontier molecular orbitals of O-Anisic acid

HOMO

(a)

LUMO

(b)

Figure 7 Contour surfaces of frontier molecular orbitals of Anisic acid

HOMO-LUMO gap automatically means small excitationenergies to the manifold of excited states Therefore softmolecules with a small gap will be more polarizable thanhard molecules High polarizability was the most character-istic property attributed to soft acids and bases Energy gapsshould be small for best bonding or bothmolecules should besoft

In the present study the title compound AA is dynam-ically more stable due to the large energy gap OAA is asoft molecule due to small energy gap The Contour surfacesof the frontier molecular orbitals are sketched in Figures 6and 7

51 NMR Spectra DFT methods treat the electronic energyas a function of the electron density of all electrons simul-taneously and thus include electron correlation effect [37]In this study molecular structure of the OAA and AA wasoptimized by using B3LYP method in conjunction with 6-31Glowastlowast 13C and 1H chemical shift calculations of the titlecompounds have been made by using GIAO method andsame basis set The isotropic shielding values were usedto calculate the isotropic chemical shifts 120575 with respect totetramethylsilane (TMS) The isotropic chemical shifts arefrequently used as an aid in identification of reactive ionicspecies The B3LYP method allows calculating the shielding

16 Journal of Spectroscopy

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 150

140

130

120

110

100

90110 120 130 140 150 160 170

(a)

70 75 80 85 90 95 100 1056

7

8

9

10

11

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

(b)

Figure 8 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for O-Anisic acid

constants with the proper accuracy and the GIAOmethod isone of the most common approaches for calculating nuclearmagnetic shielding tensors

Theoretical and experimental chemical shifts of OAA andAA in 1H and 13C NMR spectra are gathered in Tables 12and 13 The range of the 13C NMR chemical shifts for atypical organic molecules usually is gt100 ppm [38 39] andthe accuracy ensures reliable interpretation of spectroscopicparameters In the present study the 13C NMR chemicalshifts in the ring are gt100 ppm as they would be expectedThe 13C chemical shifts carbonyl carbons vary from 150 to220 ppm This depends on the decrease in electron donatingor shielding ability of the attached atoms [40] The C=Ogroups of carboxylic acids and derivatives are in the range of150ndash185 ppm [29]

Hydrogens bonded to an aromatic ring are stronglydeshielded and absorb downfieldWhen the120587-electrons enterthe magnetic field they circulate around the ring to generatea ring current This produces a small induced magnetic fieldthat reinforces the applied field outside the ring resultingin aromatic protons being deshielded [41] A related effectis observed for carboxylic acids For these compoundscirculation of electrons in the double bonds produces inducedmagnetic field These are responsible for the high chemicalshift values of acid protons (H10) Carboxylic acids asstable hydrogen-bonded dimers in nonpolar solvents even athigh dilution The carboxylic proton therefore absorbs in acharacteristically narrow range 132 to 100 and is affectedonly slightly by concentration [29]

In a methyl group a proton is covalently bonded tocarbon oxygen or other atoms by a sigma bond Whenplaced in a strong magnetic field the electrons of the sigmabond circulate to generate a small magnetic field whichopposes the applied field A nearby electronegative atomwithdraws electron density from the neighbourhood of theproton so that a smaller applied field is needed to cause thespin state of the proton to flip The signal for a deshielded

Table 14 Theoretically computed energies (au) zero-point vibra-tional energies (kcalmolminus1) rotational constants (GHz) entropies(calmolminus1 Kminus1) nuclear repulsion energy (Hartrees) and dipolemoment (Debye) for OAA and AA

Parameters B3LYP6-31Glowastlowast

OAA AAZero-point energy 9306056 9314966

Rotational constants139942 344405114384 056752063193 048875

EntropyTotal 99243 97126Translational 40967 40967Rotational 30142 30199Vibrational 28134 25960Dipole moment 24181 35822Nuclear repulsion energy 592968293 573992628

proton (1 surrounded by less electron density) is observed tobe more downfield than the signals for protons that are notdeshielded by electronegative atoms [40] The chemical shiftvalue of C7 (OAA and AA) has bigger value than the othercarbons due to the electronegative property of oxygen atom

The linear correlations between calculated and experi-mental data of 13CNMRand 1HNMRspectra are determinedas 09 and 10 for OAA and 09 and 09 for AA respectivelyThere is an excellent linear relationship between experimentaland computed results which are shown in Figures 8 and 9

6 Thermodynamic Properties

Several calculated thermodynamical parameters are pre-sented in Table 14 for OAA andAA respectively Scale factorshave been recommended [42] for an accurate prediction in

Journal of Spectroscopy 17

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 180

170

160

150

140

130

120

110110

120 130 140 150 160 170

(a)

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

11

10

9

8

7

7 8 9 10 11 12 13

(b)

Figure 9 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for Anisic acid

determining the zero-point vibration energies (ZPVE) andthe entropy 119878vib(119879) The total energies and the change inthe total entropy at room temperature using B3LYP6-31Glowastlowastmethod are presented

7 Conclusion

Attempts have been made in the present work for the molec-ular parameters and frequency assignments for the com-pounds OAA and AA from the FTIR and FT-Raman spectraThe equilibrium geometries and harmonic and anharmonicfrequencies for the title compounds were determined andanalyzed at DFT level of theory utilizing 6-31Glowastlowast basis setThe assignments of most of the fundamentals of the titlecompounds provided in this work are quite comparableThe excellent agreement of the calculated and observedvibrational spectra reveals the advantages of a smaller basisset for quantum chemical calculations HOMO and LUMOenergy gap explains the eventual charge transfer interactionstaking place within the molecule The experimental andtheoretical investigation of the title compounds have beenperformed successfully by using 1H and 13C NMR Thevarious modes of vibrations were unambiguously assignedon the basis of the result of the PED output obtainedfrom normal coordinate analysis These studies confirm thepresence of COOH and OCH

3group Dimeric molecules are

held together by hydrogen bridges between carbonyl groupsThe obtained data and simulations both show the way to thecharacterization of the molecules and help in spectra studiesin the future

References

[1] GMelentyeva and LAntonovaPharmaceutical ChemistryMirPublishers Moscow Russia 1988

[2] ldquoo-Anisic acid(579-75-9) catalog of chemical suppliersrdquo httpwwwchemexpercomchemicalssuppliercas579-75-9html

[3] B A Hess Jr L J Schaad P Carsky and R Zaharaduick ldquoAbinitio calculations of vibrational spectra and their use in theidentification of unusual moleculesrdquo Chemical Reviews vol 86no 4 pp 709ndash730 1986

[4] P Pulay X Zhou and G Forgarasi in Recent Experimental andComputational Advances in Molecular Spectroscopy R Faustoand R Fransto Eds vol 406 ofNATOASI Series p 99 KluwerDordrecht Netherlands 1993

[5] P Pulay G Fogarasi G Pongor J E Boggs and A VarghaldquoCombination of theoretical ab initio and experimental infor-mation to obtain reliable harmonic force constants ScaledQuantum Mechanical (SQM) force fields for glyoxal acroleinbutadiene formaldehyde and ethylenerdquo Journal of the Ameri-can Chemical Society vol 105 no 24 pp 7037ndash7047 1983

[6] C E Blom and C Altona ldquoApplication of self-consistent-fieldab initio calculations to organic moleculesrdquo Molecular Physicsvol 31 no 5 pp 1377ndash1391 1976

[7] G Fogarasi and P Pulay in Vibrational Spectra and Structure JR Durig Ed vol 14 Elsevier Amsterdam Netherlands 1985

[8] G Fogarasi ldquoRecent developments in the method of SQM forcefields with application to 1-methyladeninerdquo Spectrochimica ActaA vol 53 no 8 pp 1211ndash1224 1997

[9] G R deMare N Yu Panchenko andW Ch Bock ldquoAnMP26-31GlowastMP26-31Glowast vibrational analysis of s-trans- and s-cis-acryloyl fluoride CH2=CH-CF=Ordquo The Journal of PhysicalChemistry vol 98 no 5 pp 1416ndash1420 1994

[10] G Pongor P Pulay G Fogarasi and J E Boggs ldquoTheoreticalprediction of vibrational spectra 1 The in-plane force fieldand vibrational spectra of pyridinerdquo Journal of the AmericanChemical Society vol 106 no 10 pp 2765ndash2769 1984

[11] Y Yamakitu and M Tasumi ldquoVibrational analyses of p-benzoquinodimethane and p-benzoquinone based on ab initioHartree-Fock and second-order Moller-Plesset calculationsrdquoThe Journal of Physical Chemistry vol 99 no 21 pp 8524ndash85341995

18 Journal of Spectroscopy

[12] M Karabacak A Coruh and M Kurt ldquoFT-IR FT-RamanNMR spectra and molecular structure investigation of 23-dibromo-N-methylmaleimide a combined experimental andtheoretical studyrdquo Journal of Molecular Structure vol 892 no1ndash3 pp 125ndash131 2008

[13] M S Masoud M K Awad M A Shaker and M M T El-Tahawy ldquoThe role of structural chemistry in the inhibitiveperformance of some aminopyrimidines on the corrosion ofsteelrdquo Corrosion Science vol 52 no 7 pp 2387ndash2396 2010

[14] M J Frisch G W Trucks H B Schlegel et al Gaussian 03Revision B4 Gaussian Inc Pittsburgh Pa USA 2003

[15] P L Polavarapu ldquoAb initio vibrational Raman and Ramanoptical activity spectrardquo Journal of Physical Chemistry vol 94no 21 pp 8106ndash8112 1990

[16] G Keresztury S Holly J Varga G Besenyei A Wang andJ R Durig ldquoVibrational spectra of monothiocarbamates-IIIR and Raman spectra vibrational assignment conforma-tional analysis and ab initio calculations of S-methyl-NN-dimethylthiocarbamaterdquo Spectrochimica Acta A vol 49 no 13-14 pp 2007ndash2017 1993

[17] G Keresztury ldquoRaman spectroscopy theoryrdquo in Handbook ofVibrational Spectroscopy J M Chalmers and P R Griffths Edsvol 1 p 71 John Wiley and Sons 2002

[18] R G Parr R A Donnelly M Levy and W E Palke ldquoElec-tronegativity the density functional viewpointrdquo The Journal ofChemical Physics vol 68 no 8 pp 3801ndash3807 1977

[19] R G Parr and R G Pearson ldquoAbsolute hardness companionparameter to absolute electronegativityrdquo Journal of theAmericanChemical Society vol 105 no 26 pp 7512ndash7516 1983

[20] R G Pearson ldquoAbsolute electronegativity and hardness appli-cation to inorganic chemistryrdquo Inorganic Chemistry vol 27 no4 pp 734ndash740 1988

[21] P Geerlings F De Proft and W Langenaeker ldquoConceptualdensity functional theoryrdquo Chemical Reviews vol 103 no 5 pp1793ndash1873 2003

[22] R Ditchfield ldquoMolecular orbital theory of magnetic shieldingand magnetic susceptibilityrdquo Journal of Physical Chemistry vol56 no 11 article 5688 4 pages 1972

[23] KWolinski J F Hilton and P Pulay ldquoEfficient implementationof the gauge-independent atomic orbital method for NMRchemical shift calculationsrdquo Journal of the American ChemicalSociety vol 112 no 23 pp 8251ndash8260 1990

[24] M Kurt M Yurdakul and S Yurdakul ldquoMolecular structureand vibrational spectra of 3-chloro-4-methyl aniline by densityfunctional theory and ab initio Hartree-Fock calculationsrdquoJournal of Molecular Structure vol 711 no 1ndash3 pp 25ndash32 2004

[25] D Steele and D H Whiffen ldquoThe vibration frequencies ofpentafluorobenzenerdquo Spectrochimica Acta vol 16 no 3 pp368ndash375 1960

[26] D N Sathyanarayanan Vibrational Spectroscopy Theory andApplication New Age International publishers New DelhiIndia 1996

[27] L D S YadavOrganic Spectroscopy Springer NewDelhi India2004

[28] J Mohan Organic Spectroscopy Principles and ApplicationsNarosa Publishing House New Delhi 2nd edition 2009

[29] R M Silverstein G C Bassler and T C Morrill SpectrometricIdentification of Organic Compounds John Wiley amp Sons NewYork NY USA 1981

[30] G Socrates Infrared Characteristic Group Frequencies WileyNew York NY USA 1980

[31] R S Mulliken ldquoElectronic population analysis on LCAO-MOmolecular wave functionsrdquoThe Journal of Chemical Physics vol23 no 10 pp 1833ndash1840 1955

[32] K Fukuli T Yonezawa and H Shingu ldquoA molecular orbitaltheory of reactivity in aromatic hydrocarbonsrdquo Journal ofPhysical Chemistry vol 20 no 4 article 722 4 pages 1952

[33] C H Choi and M Kertesz ldquoConformational information fromvibrational spectra of styrene trans-stilbene and cis-stilbenerdquoJournal of Physical Chemistry A vol 101 no 20 pp 3823ndash38311997

[34] S Gunasekaran R Arun Balaji S Kumaresan G Anandand S Srinivasan ldquoExperimental and theoretical investigationsof spectroscopic properties of N-acetyl-5-methoxytryptaminerdquoCanadian Journal of Analytical Sciences and Spectroscopy vol53 no 4 pp 149ndash162 2008

[35] P Hohenberg and W Kohn ldquoInhomogeneous electron gasrdquoPhysical Review vol 136 no 3 pp B864ndashB871 1964

[36] R G Pearson ldquoAbsolute electronegativity and absolute hard-ness of Lewis acids and basesrdquo Journal of the American ChemicalSociety vol 107 no 24 pp 6801ndash6806 1985

[37] D Avci Y Atalay M Sekerci and M Dincer ldquoMolecular struc-ture and vibrational and chemical shift assignments of 3-(2-Hydroxyphenyl)-4-phenyl-1H-124-triazole-5-(4H)-thione byDFT and ab initio HF calculationsrdquo Spectrochimica Acta A vol73 no 1 pp 212ndash217 2009

[38] H O Kalinowski S Berger and S Braun Carbon13 NMRSpectroscopy John Wiley amp Sons Chichester UK 1988

[39] K Pihlaja and E Kleinpeter Carbon-13 NMR Chemical Shiftsin Structural and Sterochemical Analysis VCH PublishersDeerfield Beach Fla USA 1994

[40] P S Kalsi Spectroscopy of Organic Compounds New AgeInternational 2004

[41] A F Parsons Keynotes in Organic Chemistry Blackwell Pub-lishing Oxford UK 2003

[42] M A Palafox ldquoScaling factors for the prediction of vibrationalspectra I benzenemoleculerdquo International Journal of QuantumChemistry vol 77 no 3 pp 661ndash684 2000

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Page 12: Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. · Molecular Structure, NMR, HOMO, LUMO, ... ects of carbonyl and methyl substitutions

12 Journal of Spectroscopy

Table8Con

tinued

Slno

Symmetry

species119862119904

Observed

wavenum

bers

cmminus1

Calculated

wavenum

bers

B3LY

P6-31Glowastlowast

forcefi

eldcmminus1

IRintensity

Raman

activ

ityCh

aracteriz

ationof

norm

almod

eswith

PED(

)

FTIR

Raman

Unscaled

Scaled

40A1015840

525

mdash511

525

12735

1849

bCCO

(82)

41A1015840

505

mdash511

505

50036

5698

tOH(24)ttrigd(23)120596

CO(19)120596

CH(14

)42

A1015840

440

mdash481

440

3190

2294

bCO(35)bCO

C(29)

43A10158401015840

mdash375

427

375

0415

0023

tsym

(60)120596

CH(19

)tasym

(17)

44A1015840

mdash310

335

310

3569

0577

Rsym

d(48)120592CC

fn(25)

45A10158401015840

mdash285

304

285

4416

0596

120596CC

(33)tasym

(24)tCO

(16)

46A1015840

mdash220

267

220

3713

2509

bCOC(29)bCO

(17)

47A10158401015840

mdash165

226

165

0047

0429

tCH

3(85)

48A1015840

mdash111

165

111

0211

0159

bCC(80)

49A10158401015840

mdash98

132

982323

0292

Tasym

(30)tCO

C(30)120596

CC(11)120596

CH(10)tsym

(10)

50A10158401015840

mdash70

7870

1302

1199

tCO(95)

51A10158401015840

mdash60

6560

0898

0216

tCOC(48)tCO

(31)tCH

3(12)

Rrin

gbbend

ingdeform

deformation

symsym

metric

asyasymmetric

120596w

agging

ttorsio

ntrigtrig

onal120592stre

tching

ipsin-planes

tretching

ipb

in-planeb

ending

opsout-of-p

lane

stretchingop

bou

t-of-plane

bend

ingsbsym

metric

bend

ingiprin-plane

rockingop

rou

t-of-p

lane

rocking

Onlycontrib

utions

larger

than

10areg

iven

Journal of Spectroscopy 13

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 3 FT-Raman spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 4 FTIR spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 5 FT-Raman spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

title molecules all the hydrogen atoms have a net positivecharge in particular the hydrogen atoms H(10) that havecharge of 05047 and 05050 respectively The presence oflarge amounts of negative charge on oxygen and net positivecharge on H(10) atoms may suggest the presence of inter-molecular hydrogen bonding in the crystalline phase

Highest occupied molecular orbital and lowest unoc-cupied molecular orbital are very important parametersfor quantum chemistry This is also used by the frontierelectron density for predicting the most reactive position in120587-electron systems and also explains several types of reactionin conjugated system [32] The conjugated molecules are

characterized by a small highest occupied molecular orbitalndashlowest unoccupied molecular orbital (HOMO-LUMO) sep-aration which is the result of a significant degree of inter-molecular charge transfer from the end-capping electron-donating groups to the efficient electron-acceptor groupsthrough 120587 conjugated path [33] Both the highest occupiedmolecular orbital and lowest unoccupied molecular orbitalare the main orbitals that take part in chemical stability[34] Energy difference betweenHOMOand LUMOorbital iscalled energy gap that is an important stability for structureswhich are given in Table 11 We performed an analysis ofall the molecular orbitals involved taking into consideration

14 Journal of Spectroscopy

Table 9 Atomic charges for optimized geometry of O-Anisic acid(OAA) and Anisic acid (AA) obtained by B3LYP6-31Glowastlowast densityfunctional calculations

Atomsa MullikenOAA AA

C1 00018 00373C2 03297 minus01002

C3 minus01368 minus01219

C4 minus00836 03612

C5 minus00943 minus01394

C6 minus01061 minus01118

C7 05570 05445O8 minus04650 minus04848

O9 minus05104 minus05064

H10 03198 03217O11 (H11) minus04841 01203C12 (H12) minus00837 01021H13 (O13) 01064 minus05111

H14 (C14) 01352 minus00831

H15 01211 01099H16 00913 01302H17 00929 01246H18 00886 00913H19 01200 01155aThe atoms indicated in the parenthesis belong to AA

Table 10Natural atomic charges ofO-Anisic acid (OAA) andAnisicacid (AA) calculations performed at the B3LYP6-31Glowastlowast level oftheory

Atomsa OAA AAC1 minus02176 minus02053

C2 03724 minus01746

C3 minus03284 minus02801

C4 minus01952 03443

C5 minus02720 minus03289

C6 minus01806 minus01748

C7 08091 08139O8 minus05861 minus06102

O9 minus07295 minus07217

H10 05047 05050O11 (H11) minus04921 02634C12 (H12) minus03307 02544H13 (O13) 02070 minus05119

H14 (C14) 02390 minus03300

H15 02070 02090H16 02443 02352H17 02426 02090H18 02439 02449H19 02621 02585aThe atoms indicated in the parenthesis belong to AAFor numbering of atoms refer to Figures 1(a) and 1(b)

that orbital 40 is the HOMO and orbital 41 is the LUMO forOAA and AA respectively

Many organic molecules that contain conjugated 120587 elec-trons are characterized as hyperpolarisabilities and are ana-lyzed by means of vibrational spectroscopy The analysis

Table 11 Calculated quantum chemical parameters ofO-Anisic acid(OAA) and Anisic acid (AA) derivatives

Parameters OAA AA119864HOMO minus0227 minus0231

119864LUMO minus0041 minus0036

Δ119864 0186 0195120594 0134 0133Η 0093 0097Σ 10752 10256

Table 12 Calculated 13C NMR chemical shifts (ppm) of O-Anisicacid (OAA) and Anisic acid (AA)

Carbona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAC1 11782 12315 10447 12620C2 15848 13146 14696 13936C3 11204 11384 9681 12272C4 13517 16297 11926 17125C5 12191 11384 10447 11047C6 13347 13146 12019 13751C7 16634 16714 14609 17174C12 (C14) 5674 5544 4322 5549aThe atoms indicated in the parenthesis belong to AA

Table 13 Experimental and calculated 1H NMR chemical shifts(ppm) of O-Anisic acid (OAA) and Anisic acid (AA)

Protona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAH10 1030 13 11 11H13 H14 H15 (H11) 4066 7914 3932 8405H16 (H12) 708 7027 6831 7147H17 (H15 H16 H17) 756 3836 7570 3824H18 710 7027 7069 6673H19 813 7914 3932 8217aThe atoms indicated in the parenthesis belong to AA

of the wave function indicates that the electron absorptioncorresponds to the transition from the ground state to thefirst excited state and is mainly described by the one-electronexcitation from the HOMO to the LUMO The HOMO of 120587nature (ie aromatic ring) is delocalized over the whole CndashC bond By contrast the LUMO is located over the aromaticring Consequently the HOMO-LUMO transition implies anelectron density transfer toCOOHandOCH

3group from the

aromatic ringThe theoretical basis for the new quantities lies in the

density functional formalism [35] Since molecular orbital(MO) theory is by far the most widely used by chemistsit is important to place 120594 and 120578 in a MO framework Ithas already been shown [36] that the MO theory of thechemical bond contains the values of 120594 and 120578 for the bondingfragments Hard molecules have a large HOMO-LUMO gapand soft molecules have a small HOMO-LUMO gap A small

Journal of Spectroscopy 15

HOMO

(a)

LUMO

(b)

Figure 6 Contour surfaces of frontier molecular orbitals of O-Anisic acid

HOMO

(a)

LUMO

(b)

Figure 7 Contour surfaces of frontier molecular orbitals of Anisic acid

HOMO-LUMO gap automatically means small excitationenergies to the manifold of excited states Therefore softmolecules with a small gap will be more polarizable thanhard molecules High polarizability was the most character-istic property attributed to soft acids and bases Energy gapsshould be small for best bonding or bothmolecules should besoft

In the present study the title compound AA is dynam-ically more stable due to the large energy gap OAA is asoft molecule due to small energy gap The Contour surfacesof the frontier molecular orbitals are sketched in Figures 6and 7

51 NMR Spectra DFT methods treat the electronic energyas a function of the electron density of all electrons simul-taneously and thus include electron correlation effect [37]In this study molecular structure of the OAA and AA wasoptimized by using B3LYP method in conjunction with 6-31Glowastlowast 13C and 1H chemical shift calculations of the titlecompounds have been made by using GIAO method andsame basis set The isotropic shielding values were usedto calculate the isotropic chemical shifts 120575 with respect totetramethylsilane (TMS) The isotropic chemical shifts arefrequently used as an aid in identification of reactive ionicspecies The B3LYP method allows calculating the shielding

16 Journal of Spectroscopy

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 150

140

130

120

110

100

90110 120 130 140 150 160 170

(a)

70 75 80 85 90 95 100 1056

7

8

9

10

11

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

(b)

Figure 8 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for O-Anisic acid

constants with the proper accuracy and the GIAOmethod isone of the most common approaches for calculating nuclearmagnetic shielding tensors

Theoretical and experimental chemical shifts of OAA andAA in 1H and 13C NMR spectra are gathered in Tables 12and 13 The range of the 13C NMR chemical shifts for atypical organic molecules usually is gt100 ppm [38 39] andthe accuracy ensures reliable interpretation of spectroscopicparameters In the present study the 13C NMR chemicalshifts in the ring are gt100 ppm as they would be expectedThe 13C chemical shifts carbonyl carbons vary from 150 to220 ppm This depends on the decrease in electron donatingor shielding ability of the attached atoms [40] The C=Ogroups of carboxylic acids and derivatives are in the range of150ndash185 ppm [29]

Hydrogens bonded to an aromatic ring are stronglydeshielded and absorb downfieldWhen the120587-electrons enterthe magnetic field they circulate around the ring to generatea ring current This produces a small induced magnetic fieldthat reinforces the applied field outside the ring resultingin aromatic protons being deshielded [41] A related effectis observed for carboxylic acids For these compoundscirculation of electrons in the double bonds produces inducedmagnetic field These are responsible for the high chemicalshift values of acid protons (H10) Carboxylic acids asstable hydrogen-bonded dimers in nonpolar solvents even athigh dilution The carboxylic proton therefore absorbs in acharacteristically narrow range 132 to 100 and is affectedonly slightly by concentration [29]

In a methyl group a proton is covalently bonded tocarbon oxygen or other atoms by a sigma bond Whenplaced in a strong magnetic field the electrons of the sigmabond circulate to generate a small magnetic field whichopposes the applied field A nearby electronegative atomwithdraws electron density from the neighbourhood of theproton so that a smaller applied field is needed to cause thespin state of the proton to flip The signal for a deshielded

Table 14 Theoretically computed energies (au) zero-point vibra-tional energies (kcalmolminus1) rotational constants (GHz) entropies(calmolminus1 Kminus1) nuclear repulsion energy (Hartrees) and dipolemoment (Debye) for OAA and AA

Parameters B3LYP6-31Glowastlowast

OAA AAZero-point energy 9306056 9314966

Rotational constants139942 344405114384 056752063193 048875

EntropyTotal 99243 97126Translational 40967 40967Rotational 30142 30199Vibrational 28134 25960Dipole moment 24181 35822Nuclear repulsion energy 592968293 573992628

proton (1 surrounded by less electron density) is observed tobe more downfield than the signals for protons that are notdeshielded by electronegative atoms [40] The chemical shiftvalue of C7 (OAA and AA) has bigger value than the othercarbons due to the electronegative property of oxygen atom

The linear correlations between calculated and experi-mental data of 13CNMRand 1HNMRspectra are determinedas 09 and 10 for OAA and 09 and 09 for AA respectivelyThere is an excellent linear relationship between experimentaland computed results which are shown in Figures 8 and 9

6 Thermodynamic Properties

Several calculated thermodynamical parameters are pre-sented in Table 14 for OAA andAA respectively Scale factorshave been recommended [42] for an accurate prediction in

Journal of Spectroscopy 17

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 180

170

160

150

140

130

120

110110

120 130 140 150 160 170

(a)

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

11

10

9

8

7

7 8 9 10 11 12 13

(b)

Figure 9 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for Anisic acid

determining the zero-point vibration energies (ZPVE) andthe entropy 119878vib(119879) The total energies and the change inthe total entropy at room temperature using B3LYP6-31Glowastlowastmethod are presented

7 Conclusion

Attempts have been made in the present work for the molec-ular parameters and frequency assignments for the com-pounds OAA and AA from the FTIR and FT-Raman spectraThe equilibrium geometries and harmonic and anharmonicfrequencies for the title compounds were determined andanalyzed at DFT level of theory utilizing 6-31Glowastlowast basis setThe assignments of most of the fundamentals of the titlecompounds provided in this work are quite comparableThe excellent agreement of the calculated and observedvibrational spectra reveals the advantages of a smaller basisset for quantum chemical calculations HOMO and LUMOenergy gap explains the eventual charge transfer interactionstaking place within the molecule The experimental andtheoretical investigation of the title compounds have beenperformed successfully by using 1H and 13C NMR Thevarious modes of vibrations were unambiguously assignedon the basis of the result of the PED output obtainedfrom normal coordinate analysis These studies confirm thepresence of COOH and OCH

3group Dimeric molecules are

held together by hydrogen bridges between carbonyl groupsThe obtained data and simulations both show the way to thecharacterization of the molecules and help in spectra studiesin the future

References

[1] GMelentyeva and LAntonovaPharmaceutical ChemistryMirPublishers Moscow Russia 1988

[2] ldquoo-Anisic acid(579-75-9) catalog of chemical suppliersrdquo httpwwwchemexpercomchemicalssuppliercas579-75-9html

[3] B A Hess Jr L J Schaad P Carsky and R Zaharaduick ldquoAbinitio calculations of vibrational spectra and their use in theidentification of unusual moleculesrdquo Chemical Reviews vol 86no 4 pp 709ndash730 1986

[4] P Pulay X Zhou and G Forgarasi in Recent Experimental andComputational Advances in Molecular Spectroscopy R Faustoand R Fransto Eds vol 406 ofNATOASI Series p 99 KluwerDordrecht Netherlands 1993

[5] P Pulay G Fogarasi G Pongor J E Boggs and A VarghaldquoCombination of theoretical ab initio and experimental infor-mation to obtain reliable harmonic force constants ScaledQuantum Mechanical (SQM) force fields for glyoxal acroleinbutadiene formaldehyde and ethylenerdquo Journal of the Ameri-can Chemical Society vol 105 no 24 pp 7037ndash7047 1983

[6] C E Blom and C Altona ldquoApplication of self-consistent-fieldab initio calculations to organic moleculesrdquo Molecular Physicsvol 31 no 5 pp 1377ndash1391 1976

[7] G Fogarasi and P Pulay in Vibrational Spectra and Structure JR Durig Ed vol 14 Elsevier Amsterdam Netherlands 1985

[8] G Fogarasi ldquoRecent developments in the method of SQM forcefields with application to 1-methyladeninerdquo Spectrochimica ActaA vol 53 no 8 pp 1211ndash1224 1997

[9] G R deMare N Yu Panchenko andW Ch Bock ldquoAnMP26-31GlowastMP26-31Glowast vibrational analysis of s-trans- and s-cis-acryloyl fluoride CH2=CH-CF=Ordquo The Journal of PhysicalChemistry vol 98 no 5 pp 1416ndash1420 1994

[10] G Pongor P Pulay G Fogarasi and J E Boggs ldquoTheoreticalprediction of vibrational spectra 1 The in-plane force fieldand vibrational spectra of pyridinerdquo Journal of the AmericanChemical Society vol 106 no 10 pp 2765ndash2769 1984

[11] Y Yamakitu and M Tasumi ldquoVibrational analyses of p-benzoquinodimethane and p-benzoquinone based on ab initioHartree-Fock and second-order Moller-Plesset calculationsrdquoThe Journal of Physical Chemistry vol 99 no 21 pp 8524ndash85341995

18 Journal of Spectroscopy

[12] M Karabacak A Coruh and M Kurt ldquoFT-IR FT-RamanNMR spectra and molecular structure investigation of 23-dibromo-N-methylmaleimide a combined experimental andtheoretical studyrdquo Journal of Molecular Structure vol 892 no1ndash3 pp 125ndash131 2008

[13] M S Masoud M K Awad M A Shaker and M M T El-Tahawy ldquoThe role of structural chemistry in the inhibitiveperformance of some aminopyrimidines on the corrosion ofsteelrdquo Corrosion Science vol 52 no 7 pp 2387ndash2396 2010

[14] M J Frisch G W Trucks H B Schlegel et al Gaussian 03Revision B4 Gaussian Inc Pittsburgh Pa USA 2003

[15] P L Polavarapu ldquoAb initio vibrational Raman and Ramanoptical activity spectrardquo Journal of Physical Chemistry vol 94no 21 pp 8106ndash8112 1990

[16] G Keresztury S Holly J Varga G Besenyei A Wang andJ R Durig ldquoVibrational spectra of monothiocarbamates-IIIR and Raman spectra vibrational assignment conforma-tional analysis and ab initio calculations of S-methyl-NN-dimethylthiocarbamaterdquo Spectrochimica Acta A vol 49 no 13-14 pp 2007ndash2017 1993

[17] G Keresztury ldquoRaman spectroscopy theoryrdquo in Handbook ofVibrational Spectroscopy J M Chalmers and P R Griffths Edsvol 1 p 71 John Wiley and Sons 2002

[18] R G Parr R A Donnelly M Levy and W E Palke ldquoElec-tronegativity the density functional viewpointrdquo The Journal ofChemical Physics vol 68 no 8 pp 3801ndash3807 1977

[19] R G Parr and R G Pearson ldquoAbsolute hardness companionparameter to absolute electronegativityrdquo Journal of theAmericanChemical Society vol 105 no 26 pp 7512ndash7516 1983

[20] R G Pearson ldquoAbsolute electronegativity and hardness appli-cation to inorganic chemistryrdquo Inorganic Chemistry vol 27 no4 pp 734ndash740 1988

[21] P Geerlings F De Proft and W Langenaeker ldquoConceptualdensity functional theoryrdquo Chemical Reviews vol 103 no 5 pp1793ndash1873 2003

[22] R Ditchfield ldquoMolecular orbital theory of magnetic shieldingand magnetic susceptibilityrdquo Journal of Physical Chemistry vol56 no 11 article 5688 4 pages 1972

[23] KWolinski J F Hilton and P Pulay ldquoEfficient implementationof the gauge-independent atomic orbital method for NMRchemical shift calculationsrdquo Journal of the American ChemicalSociety vol 112 no 23 pp 8251ndash8260 1990

[24] M Kurt M Yurdakul and S Yurdakul ldquoMolecular structureand vibrational spectra of 3-chloro-4-methyl aniline by densityfunctional theory and ab initio Hartree-Fock calculationsrdquoJournal of Molecular Structure vol 711 no 1ndash3 pp 25ndash32 2004

[25] D Steele and D H Whiffen ldquoThe vibration frequencies ofpentafluorobenzenerdquo Spectrochimica Acta vol 16 no 3 pp368ndash375 1960

[26] D N Sathyanarayanan Vibrational Spectroscopy Theory andApplication New Age International publishers New DelhiIndia 1996

[27] L D S YadavOrganic Spectroscopy Springer NewDelhi India2004

[28] J Mohan Organic Spectroscopy Principles and ApplicationsNarosa Publishing House New Delhi 2nd edition 2009

[29] R M Silverstein G C Bassler and T C Morrill SpectrometricIdentification of Organic Compounds John Wiley amp Sons NewYork NY USA 1981

[30] G Socrates Infrared Characteristic Group Frequencies WileyNew York NY USA 1980

[31] R S Mulliken ldquoElectronic population analysis on LCAO-MOmolecular wave functionsrdquoThe Journal of Chemical Physics vol23 no 10 pp 1833ndash1840 1955

[32] K Fukuli T Yonezawa and H Shingu ldquoA molecular orbitaltheory of reactivity in aromatic hydrocarbonsrdquo Journal ofPhysical Chemistry vol 20 no 4 article 722 4 pages 1952

[33] C H Choi and M Kertesz ldquoConformational information fromvibrational spectra of styrene trans-stilbene and cis-stilbenerdquoJournal of Physical Chemistry A vol 101 no 20 pp 3823ndash38311997

[34] S Gunasekaran R Arun Balaji S Kumaresan G Anandand S Srinivasan ldquoExperimental and theoretical investigationsof spectroscopic properties of N-acetyl-5-methoxytryptaminerdquoCanadian Journal of Analytical Sciences and Spectroscopy vol53 no 4 pp 149ndash162 2008

[35] P Hohenberg and W Kohn ldquoInhomogeneous electron gasrdquoPhysical Review vol 136 no 3 pp B864ndashB871 1964

[36] R G Pearson ldquoAbsolute electronegativity and absolute hard-ness of Lewis acids and basesrdquo Journal of the American ChemicalSociety vol 107 no 24 pp 6801ndash6806 1985

[37] D Avci Y Atalay M Sekerci and M Dincer ldquoMolecular struc-ture and vibrational and chemical shift assignments of 3-(2-Hydroxyphenyl)-4-phenyl-1H-124-triazole-5-(4H)-thione byDFT and ab initio HF calculationsrdquo Spectrochimica Acta A vol73 no 1 pp 212ndash217 2009

[38] H O Kalinowski S Berger and S Braun Carbon13 NMRSpectroscopy John Wiley amp Sons Chichester UK 1988

[39] K Pihlaja and E Kleinpeter Carbon-13 NMR Chemical Shiftsin Structural and Sterochemical Analysis VCH PublishersDeerfield Beach Fla USA 1994

[40] P S Kalsi Spectroscopy of Organic Compounds New AgeInternational 2004

[41] A F Parsons Keynotes in Organic Chemistry Blackwell Pub-lishing Oxford UK 2003

[42] M A Palafox ldquoScaling factors for the prediction of vibrationalspectra I benzenemoleculerdquo International Journal of QuantumChemistry vol 77 no 3 pp 661ndash684 2000

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

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Journal of

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Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Page 13: Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. · Molecular Structure, NMR, HOMO, LUMO, ... ects of carbonyl and methyl substitutions

Journal of Spectroscopy 13

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 3 FT-Raman spectra of O-Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(a)

4000 3000 2000 1500 1000 500Wavenumber (cmminus1)

Abso

rban

ce (a

u)

(b)

Figure 4 FTIR spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(a)

Ram

an in

tens

ity (a

u)

Wavenumber (cmminus1)4000 3000 2000 1500 1000 500 50

(b)

Figure 5 FT-Raman spectra of Anisic acid (a) observed and (b) calculated with B3LYP6-31Glowastlowast

title molecules all the hydrogen atoms have a net positivecharge in particular the hydrogen atoms H(10) that havecharge of 05047 and 05050 respectively The presence oflarge amounts of negative charge on oxygen and net positivecharge on H(10) atoms may suggest the presence of inter-molecular hydrogen bonding in the crystalline phase

Highest occupied molecular orbital and lowest unoc-cupied molecular orbital are very important parametersfor quantum chemistry This is also used by the frontierelectron density for predicting the most reactive position in120587-electron systems and also explains several types of reactionin conjugated system [32] The conjugated molecules are

characterized by a small highest occupied molecular orbitalndashlowest unoccupied molecular orbital (HOMO-LUMO) sep-aration which is the result of a significant degree of inter-molecular charge transfer from the end-capping electron-donating groups to the efficient electron-acceptor groupsthrough 120587 conjugated path [33] Both the highest occupiedmolecular orbital and lowest unoccupied molecular orbitalare the main orbitals that take part in chemical stability[34] Energy difference betweenHOMOand LUMOorbital iscalled energy gap that is an important stability for structureswhich are given in Table 11 We performed an analysis ofall the molecular orbitals involved taking into consideration

14 Journal of Spectroscopy

Table 9 Atomic charges for optimized geometry of O-Anisic acid(OAA) and Anisic acid (AA) obtained by B3LYP6-31Glowastlowast densityfunctional calculations

Atomsa MullikenOAA AA

C1 00018 00373C2 03297 minus01002

C3 minus01368 minus01219

C4 minus00836 03612

C5 minus00943 minus01394

C6 minus01061 minus01118

C7 05570 05445O8 minus04650 minus04848

O9 minus05104 minus05064

H10 03198 03217O11 (H11) minus04841 01203C12 (H12) minus00837 01021H13 (O13) 01064 minus05111

H14 (C14) 01352 minus00831

H15 01211 01099H16 00913 01302H17 00929 01246H18 00886 00913H19 01200 01155aThe atoms indicated in the parenthesis belong to AA

Table 10Natural atomic charges ofO-Anisic acid (OAA) andAnisicacid (AA) calculations performed at the B3LYP6-31Glowastlowast level oftheory

Atomsa OAA AAC1 minus02176 minus02053

C2 03724 minus01746

C3 minus03284 minus02801

C4 minus01952 03443

C5 minus02720 minus03289

C6 minus01806 minus01748

C7 08091 08139O8 minus05861 minus06102

O9 minus07295 minus07217

H10 05047 05050O11 (H11) minus04921 02634C12 (H12) minus03307 02544H13 (O13) 02070 minus05119

H14 (C14) 02390 minus03300

H15 02070 02090H16 02443 02352H17 02426 02090H18 02439 02449H19 02621 02585aThe atoms indicated in the parenthesis belong to AAFor numbering of atoms refer to Figures 1(a) and 1(b)

that orbital 40 is the HOMO and orbital 41 is the LUMO forOAA and AA respectively

Many organic molecules that contain conjugated 120587 elec-trons are characterized as hyperpolarisabilities and are ana-lyzed by means of vibrational spectroscopy The analysis

Table 11 Calculated quantum chemical parameters ofO-Anisic acid(OAA) and Anisic acid (AA) derivatives

Parameters OAA AA119864HOMO minus0227 minus0231

119864LUMO minus0041 minus0036

Δ119864 0186 0195120594 0134 0133Η 0093 0097Σ 10752 10256

Table 12 Calculated 13C NMR chemical shifts (ppm) of O-Anisicacid (OAA) and Anisic acid (AA)

Carbona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAC1 11782 12315 10447 12620C2 15848 13146 14696 13936C3 11204 11384 9681 12272C4 13517 16297 11926 17125C5 12191 11384 10447 11047C6 13347 13146 12019 13751C7 16634 16714 14609 17174C12 (C14) 5674 5544 4322 5549aThe atoms indicated in the parenthesis belong to AA

Table 13 Experimental and calculated 1H NMR chemical shifts(ppm) of O-Anisic acid (OAA) and Anisic acid (AA)

Protona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAH10 1030 13 11 11H13 H14 H15 (H11) 4066 7914 3932 8405H16 (H12) 708 7027 6831 7147H17 (H15 H16 H17) 756 3836 7570 3824H18 710 7027 7069 6673H19 813 7914 3932 8217aThe atoms indicated in the parenthesis belong to AA

of the wave function indicates that the electron absorptioncorresponds to the transition from the ground state to thefirst excited state and is mainly described by the one-electronexcitation from the HOMO to the LUMO The HOMO of 120587nature (ie aromatic ring) is delocalized over the whole CndashC bond By contrast the LUMO is located over the aromaticring Consequently the HOMO-LUMO transition implies anelectron density transfer toCOOHandOCH

3group from the

aromatic ringThe theoretical basis for the new quantities lies in the

density functional formalism [35] Since molecular orbital(MO) theory is by far the most widely used by chemistsit is important to place 120594 and 120578 in a MO framework Ithas already been shown [36] that the MO theory of thechemical bond contains the values of 120594 and 120578 for the bondingfragments Hard molecules have a large HOMO-LUMO gapand soft molecules have a small HOMO-LUMO gap A small

Journal of Spectroscopy 15

HOMO

(a)

LUMO

(b)

Figure 6 Contour surfaces of frontier molecular orbitals of O-Anisic acid

HOMO

(a)

LUMO

(b)

Figure 7 Contour surfaces of frontier molecular orbitals of Anisic acid

HOMO-LUMO gap automatically means small excitationenergies to the manifold of excited states Therefore softmolecules with a small gap will be more polarizable thanhard molecules High polarizability was the most character-istic property attributed to soft acids and bases Energy gapsshould be small for best bonding or bothmolecules should besoft

In the present study the title compound AA is dynam-ically more stable due to the large energy gap OAA is asoft molecule due to small energy gap The Contour surfacesof the frontier molecular orbitals are sketched in Figures 6and 7

51 NMR Spectra DFT methods treat the electronic energyas a function of the electron density of all electrons simul-taneously and thus include electron correlation effect [37]In this study molecular structure of the OAA and AA wasoptimized by using B3LYP method in conjunction with 6-31Glowastlowast 13C and 1H chemical shift calculations of the titlecompounds have been made by using GIAO method andsame basis set The isotropic shielding values were usedto calculate the isotropic chemical shifts 120575 with respect totetramethylsilane (TMS) The isotropic chemical shifts arefrequently used as an aid in identification of reactive ionicspecies The B3LYP method allows calculating the shielding

16 Journal of Spectroscopy

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 150

140

130

120

110

100

90110 120 130 140 150 160 170

(a)

70 75 80 85 90 95 100 1056

7

8

9

10

11

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

(b)

Figure 8 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for O-Anisic acid

constants with the proper accuracy and the GIAOmethod isone of the most common approaches for calculating nuclearmagnetic shielding tensors

Theoretical and experimental chemical shifts of OAA andAA in 1H and 13C NMR spectra are gathered in Tables 12and 13 The range of the 13C NMR chemical shifts for atypical organic molecules usually is gt100 ppm [38 39] andthe accuracy ensures reliable interpretation of spectroscopicparameters In the present study the 13C NMR chemicalshifts in the ring are gt100 ppm as they would be expectedThe 13C chemical shifts carbonyl carbons vary from 150 to220 ppm This depends on the decrease in electron donatingor shielding ability of the attached atoms [40] The C=Ogroups of carboxylic acids and derivatives are in the range of150ndash185 ppm [29]

Hydrogens bonded to an aromatic ring are stronglydeshielded and absorb downfieldWhen the120587-electrons enterthe magnetic field they circulate around the ring to generatea ring current This produces a small induced magnetic fieldthat reinforces the applied field outside the ring resultingin aromatic protons being deshielded [41] A related effectis observed for carboxylic acids For these compoundscirculation of electrons in the double bonds produces inducedmagnetic field These are responsible for the high chemicalshift values of acid protons (H10) Carboxylic acids asstable hydrogen-bonded dimers in nonpolar solvents even athigh dilution The carboxylic proton therefore absorbs in acharacteristically narrow range 132 to 100 and is affectedonly slightly by concentration [29]

In a methyl group a proton is covalently bonded tocarbon oxygen or other atoms by a sigma bond Whenplaced in a strong magnetic field the electrons of the sigmabond circulate to generate a small magnetic field whichopposes the applied field A nearby electronegative atomwithdraws electron density from the neighbourhood of theproton so that a smaller applied field is needed to cause thespin state of the proton to flip The signal for a deshielded

Table 14 Theoretically computed energies (au) zero-point vibra-tional energies (kcalmolminus1) rotational constants (GHz) entropies(calmolminus1 Kminus1) nuclear repulsion energy (Hartrees) and dipolemoment (Debye) for OAA and AA

Parameters B3LYP6-31Glowastlowast

OAA AAZero-point energy 9306056 9314966

Rotational constants139942 344405114384 056752063193 048875

EntropyTotal 99243 97126Translational 40967 40967Rotational 30142 30199Vibrational 28134 25960Dipole moment 24181 35822Nuclear repulsion energy 592968293 573992628

proton (1 surrounded by less electron density) is observed tobe more downfield than the signals for protons that are notdeshielded by electronegative atoms [40] The chemical shiftvalue of C7 (OAA and AA) has bigger value than the othercarbons due to the electronegative property of oxygen atom

The linear correlations between calculated and experi-mental data of 13CNMRand 1HNMRspectra are determinedas 09 and 10 for OAA and 09 and 09 for AA respectivelyThere is an excellent linear relationship between experimentaland computed results which are shown in Figures 8 and 9

6 Thermodynamic Properties

Several calculated thermodynamical parameters are pre-sented in Table 14 for OAA andAA respectively Scale factorshave been recommended [42] for an accurate prediction in

Journal of Spectroscopy 17

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 180

170

160

150

140

130

120

110110

120 130 140 150 160 170

(a)

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

11

10

9

8

7

7 8 9 10 11 12 13

(b)

Figure 9 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for Anisic acid

determining the zero-point vibration energies (ZPVE) andthe entropy 119878vib(119879) The total energies and the change inthe total entropy at room temperature using B3LYP6-31Glowastlowastmethod are presented

7 Conclusion

Attempts have been made in the present work for the molec-ular parameters and frequency assignments for the com-pounds OAA and AA from the FTIR and FT-Raman spectraThe equilibrium geometries and harmonic and anharmonicfrequencies for the title compounds were determined andanalyzed at DFT level of theory utilizing 6-31Glowastlowast basis setThe assignments of most of the fundamentals of the titlecompounds provided in this work are quite comparableThe excellent agreement of the calculated and observedvibrational spectra reveals the advantages of a smaller basisset for quantum chemical calculations HOMO and LUMOenergy gap explains the eventual charge transfer interactionstaking place within the molecule The experimental andtheoretical investigation of the title compounds have beenperformed successfully by using 1H and 13C NMR Thevarious modes of vibrations were unambiguously assignedon the basis of the result of the PED output obtainedfrom normal coordinate analysis These studies confirm thepresence of COOH and OCH

3group Dimeric molecules are

held together by hydrogen bridges between carbonyl groupsThe obtained data and simulations both show the way to thecharacterization of the molecules and help in spectra studiesin the future

References

[1] GMelentyeva and LAntonovaPharmaceutical ChemistryMirPublishers Moscow Russia 1988

[2] ldquoo-Anisic acid(579-75-9) catalog of chemical suppliersrdquo httpwwwchemexpercomchemicalssuppliercas579-75-9html

[3] B A Hess Jr L J Schaad P Carsky and R Zaharaduick ldquoAbinitio calculations of vibrational spectra and their use in theidentification of unusual moleculesrdquo Chemical Reviews vol 86no 4 pp 709ndash730 1986

[4] P Pulay X Zhou and G Forgarasi in Recent Experimental andComputational Advances in Molecular Spectroscopy R Faustoand R Fransto Eds vol 406 ofNATOASI Series p 99 KluwerDordrecht Netherlands 1993

[5] P Pulay G Fogarasi G Pongor J E Boggs and A VarghaldquoCombination of theoretical ab initio and experimental infor-mation to obtain reliable harmonic force constants ScaledQuantum Mechanical (SQM) force fields for glyoxal acroleinbutadiene formaldehyde and ethylenerdquo Journal of the Ameri-can Chemical Society vol 105 no 24 pp 7037ndash7047 1983

[6] C E Blom and C Altona ldquoApplication of self-consistent-fieldab initio calculations to organic moleculesrdquo Molecular Physicsvol 31 no 5 pp 1377ndash1391 1976

[7] G Fogarasi and P Pulay in Vibrational Spectra and Structure JR Durig Ed vol 14 Elsevier Amsterdam Netherlands 1985

[8] G Fogarasi ldquoRecent developments in the method of SQM forcefields with application to 1-methyladeninerdquo Spectrochimica ActaA vol 53 no 8 pp 1211ndash1224 1997

[9] G R deMare N Yu Panchenko andW Ch Bock ldquoAnMP26-31GlowastMP26-31Glowast vibrational analysis of s-trans- and s-cis-acryloyl fluoride CH2=CH-CF=Ordquo The Journal of PhysicalChemistry vol 98 no 5 pp 1416ndash1420 1994

[10] G Pongor P Pulay G Fogarasi and J E Boggs ldquoTheoreticalprediction of vibrational spectra 1 The in-plane force fieldand vibrational spectra of pyridinerdquo Journal of the AmericanChemical Society vol 106 no 10 pp 2765ndash2769 1984

[11] Y Yamakitu and M Tasumi ldquoVibrational analyses of p-benzoquinodimethane and p-benzoquinone based on ab initioHartree-Fock and second-order Moller-Plesset calculationsrdquoThe Journal of Physical Chemistry vol 99 no 21 pp 8524ndash85341995

18 Journal of Spectroscopy

[12] M Karabacak A Coruh and M Kurt ldquoFT-IR FT-RamanNMR spectra and molecular structure investigation of 23-dibromo-N-methylmaleimide a combined experimental andtheoretical studyrdquo Journal of Molecular Structure vol 892 no1ndash3 pp 125ndash131 2008

[13] M S Masoud M K Awad M A Shaker and M M T El-Tahawy ldquoThe role of structural chemistry in the inhibitiveperformance of some aminopyrimidines on the corrosion ofsteelrdquo Corrosion Science vol 52 no 7 pp 2387ndash2396 2010

[14] M J Frisch G W Trucks H B Schlegel et al Gaussian 03Revision B4 Gaussian Inc Pittsburgh Pa USA 2003

[15] P L Polavarapu ldquoAb initio vibrational Raman and Ramanoptical activity spectrardquo Journal of Physical Chemistry vol 94no 21 pp 8106ndash8112 1990

[16] G Keresztury S Holly J Varga G Besenyei A Wang andJ R Durig ldquoVibrational spectra of monothiocarbamates-IIIR and Raman spectra vibrational assignment conforma-tional analysis and ab initio calculations of S-methyl-NN-dimethylthiocarbamaterdquo Spectrochimica Acta A vol 49 no 13-14 pp 2007ndash2017 1993

[17] G Keresztury ldquoRaman spectroscopy theoryrdquo in Handbook ofVibrational Spectroscopy J M Chalmers and P R Griffths Edsvol 1 p 71 John Wiley and Sons 2002

[18] R G Parr R A Donnelly M Levy and W E Palke ldquoElec-tronegativity the density functional viewpointrdquo The Journal ofChemical Physics vol 68 no 8 pp 3801ndash3807 1977

[19] R G Parr and R G Pearson ldquoAbsolute hardness companionparameter to absolute electronegativityrdquo Journal of theAmericanChemical Society vol 105 no 26 pp 7512ndash7516 1983

[20] R G Pearson ldquoAbsolute electronegativity and hardness appli-cation to inorganic chemistryrdquo Inorganic Chemistry vol 27 no4 pp 734ndash740 1988

[21] P Geerlings F De Proft and W Langenaeker ldquoConceptualdensity functional theoryrdquo Chemical Reviews vol 103 no 5 pp1793ndash1873 2003

[22] R Ditchfield ldquoMolecular orbital theory of magnetic shieldingand magnetic susceptibilityrdquo Journal of Physical Chemistry vol56 no 11 article 5688 4 pages 1972

[23] KWolinski J F Hilton and P Pulay ldquoEfficient implementationof the gauge-independent atomic orbital method for NMRchemical shift calculationsrdquo Journal of the American ChemicalSociety vol 112 no 23 pp 8251ndash8260 1990

[24] M Kurt M Yurdakul and S Yurdakul ldquoMolecular structureand vibrational spectra of 3-chloro-4-methyl aniline by densityfunctional theory and ab initio Hartree-Fock calculationsrdquoJournal of Molecular Structure vol 711 no 1ndash3 pp 25ndash32 2004

[25] D Steele and D H Whiffen ldquoThe vibration frequencies ofpentafluorobenzenerdquo Spectrochimica Acta vol 16 no 3 pp368ndash375 1960

[26] D N Sathyanarayanan Vibrational Spectroscopy Theory andApplication New Age International publishers New DelhiIndia 1996

[27] L D S YadavOrganic Spectroscopy Springer NewDelhi India2004

[28] J Mohan Organic Spectroscopy Principles and ApplicationsNarosa Publishing House New Delhi 2nd edition 2009

[29] R M Silverstein G C Bassler and T C Morrill SpectrometricIdentification of Organic Compounds John Wiley amp Sons NewYork NY USA 1981

[30] G Socrates Infrared Characteristic Group Frequencies WileyNew York NY USA 1980

[31] R S Mulliken ldquoElectronic population analysis on LCAO-MOmolecular wave functionsrdquoThe Journal of Chemical Physics vol23 no 10 pp 1833ndash1840 1955

[32] K Fukuli T Yonezawa and H Shingu ldquoA molecular orbitaltheory of reactivity in aromatic hydrocarbonsrdquo Journal ofPhysical Chemistry vol 20 no 4 article 722 4 pages 1952

[33] C H Choi and M Kertesz ldquoConformational information fromvibrational spectra of styrene trans-stilbene and cis-stilbenerdquoJournal of Physical Chemistry A vol 101 no 20 pp 3823ndash38311997

[34] S Gunasekaran R Arun Balaji S Kumaresan G Anandand S Srinivasan ldquoExperimental and theoretical investigationsof spectroscopic properties of N-acetyl-5-methoxytryptaminerdquoCanadian Journal of Analytical Sciences and Spectroscopy vol53 no 4 pp 149ndash162 2008

[35] P Hohenberg and W Kohn ldquoInhomogeneous electron gasrdquoPhysical Review vol 136 no 3 pp B864ndashB871 1964

[36] R G Pearson ldquoAbsolute electronegativity and absolute hard-ness of Lewis acids and basesrdquo Journal of the American ChemicalSociety vol 107 no 24 pp 6801ndash6806 1985

[37] D Avci Y Atalay M Sekerci and M Dincer ldquoMolecular struc-ture and vibrational and chemical shift assignments of 3-(2-Hydroxyphenyl)-4-phenyl-1H-124-triazole-5-(4H)-thione byDFT and ab initio HF calculationsrdquo Spectrochimica Acta A vol73 no 1 pp 212ndash217 2009

[38] H O Kalinowski S Berger and S Braun Carbon13 NMRSpectroscopy John Wiley amp Sons Chichester UK 1988

[39] K Pihlaja and E Kleinpeter Carbon-13 NMR Chemical Shiftsin Structural and Sterochemical Analysis VCH PublishersDeerfield Beach Fla USA 1994

[40] P S Kalsi Spectroscopy of Organic Compounds New AgeInternational 2004

[41] A F Parsons Keynotes in Organic Chemistry Blackwell Pub-lishing Oxford UK 2003

[42] M A Palafox ldquoScaling factors for the prediction of vibrationalspectra I benzenemoleculerdquo International Journal of QuantumChemistry vol 77 no 3 pp 661ndash684 2000

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Page 14: Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. · Molecular Structure, NMR, HOMO, LUMO, ... ects of carbonyl and methyl substitutions

14 Journal of Spectroscopy

Table 9 Atomic charges for optimized geometry of O-Anisic acid(OAA) and Anisic acid (AA) obtained by B3LYP6-31Glowastlowast densityfunctional calculations

Atomsa MullikenOAA AA

C1 00018 00373C2 03297 minus01002

C3 minus01368 minus01219

C4 minus00836 03612

C5 minus00943 minus01394

C6 minus01061 minus01118

C7 05570 05445O8 minus04650 minus04848

O9 minus05104 minus05064

H10 03198 03217O11 (H11) minus04841 01203C12 (H12) minus00837 01021H13 (O13) 01064 minus05111

H14 (C14) 01352 minus00831

H15 01211 01099H16 00913 01302H17 00929 01246H18 00886 00913H19 01200 01155aThe atoms indicated in the parenthesis belong to AA

Table 10Natural atomic charges ofO-Anisic acid (OAA) andAnisicacid (AA) calculations performed at the B3LYP6-31Glowastlowast level oftheory

Atomsa OAA AAC1 minus02176 minus02053

C2 03724 minus01746

C3 minus03284 minus02801

C4 minus01952 03443

C5 minus02720 minus03289

C6 minus01806 minus01748

C7 08091 08139O8 minus05861 minus06102

O9 minus07295 minus07217

H10 05047 05050O11 (H11) minus04921 02634C12 (H12) minus03307 02544H13 (O13) 02070 minus05119

H14 (C14) 02390 minus03300

H15 02070 02090H16 02443 02352H17 02426 02090H18 02439 02449H19 02621 02585aThe atoms indicated in the parenthesis belong to AAFor numbering of atoms refer to Figures 1(a) and 1(b)

that orbital 40 is the HOMO and orbital 41 is the LUMO forOAA and AA respectively

Many organic molecules that contain conjugated 120587 elec-trons are characterized as hyperpolarisabilities and are ana-lyzed by means of vibrational spectroscopy The analysis

Table 11 Calculated quantum chemical parameters ofO-Anisic acid(OAA) and Anisic acid (AA) derivatives

Parameters OAA AA119864HOMO minus0227 minus0231

119864LUMO minus0041 minus0036

Δ119864 0186 0195120594 0134 0133Η 0093 0097Σ 10752 10256

Table 12 Calculated 13C NMR chemical shifts (ppm) of O-Anisicacid (OAA) and Anisic acid (AA)

Carbona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAC1 11782 12315 10447 12620C2 15848 13146 14696 13936C3 11204 11384 9681 12272C4 13517 16297 11926 17125C5 12191 11384 10447 11047C6 13347 13146 12019 13751C7 16634 16714 14609 17174C12 (C14) 5674 5544 4322 5549aThe atoms indicated in the parenthesis belong to AA

Table 13 Experimental and calculated 1H NMR chemical shifts(ppm) of O-Anisic acid (OAA) and Anisic acid (AA)

Protona Exp B3LYP6-31Glowastlowast

OAA AA OAA AAH10 1030 13 11 11H13 H14 H15 (H11) 4066 7914 3932 8405H16 (H12) 708 7027 6831 7147H17 (H15 H16 H17) 756 3836 7570 3824H18 710 7027 7069 6673H19 813 7914 3932 8217aThe atoms indicated in the parenthesis belong to AA

of the wave function indicates that the electron absorptioncorresponds to the transition from the ground state to thefirst excited state and is mainly described by the one-electronexcitation from the HOMO to the LUMO The HOMO of 120587nature (ie aromatic ring) is delocalized over the whole CndashC bond By contrast the LUMO is located over the aromaticring Consequently the HOMO-LUMO transition implies anelectron density transfer toCOOHandOCH

3group from the

aromatic ringThe theoretical basis for the new quantities lies in the

density functional formalism [35] Since molecular orbital(MO) theory is by far the most widely used by chemistsit is important to place 120594 and 120578 in a MO framework Ithas already been shown [36] that the MO theory of thechemical bond contains the values of 120594 and 120578 for the bondingfragments Hard molecules have a large HOMO-LUMO gapand soft molecules have a small HOMO-LUMO gap A small

Journal of Spectroscopy 15

HOMO

(a)

LUMO

(b)

Figure 6 Contour surfaces of frontier molecular orbitals of O-Anisic acid

HOMO

(a)

LUMO

(b)

Figure 7 Contour surfaces of frontier molecular orbitals of Anisic acid

HOMO-LUMO gap automatically means small excitationenergies to the manifold of excited states Therefore softmolecules with a small gap will be more polarizable thanhard molecules High polarizability was the most character-istic property attributed to soft acids and bases Energy gapsshould be small for best bonding or bothmolecules should besoft

In the present study the title compound AA is dynam-ically more stable due to the large energy gap OAA is asoft molecule due to small energy gap The Contour surfacesof the frontier molecular orbitals are sketched in Figures 6and 7

51 NMR Spectra DFT methods treat the electronic energyas a function of the electron density of all electrons simul-taneously and thus include electron correlation effect [37]In this study molecular structure of the OAA and AA wasoptimized by using B3LYP method in conjunction with 6-31Glowastlowast 13C and 1H chemical shift calculations of the titlecompounds have been made by using GIAO method andsame basis set The isotropic shielding values were usedto calculate the isotropic chemical shifts 120575 with respect totetramethylsilane (TMS) The isotropic chemical shifts arefrequently used as an aid in identification of reactive ionicspecies The B3LYP method allows calculating the shielding

16 Journal of Spectroscopy

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 150

140

130

120

110

100

90110 120 130 140 150 160 170

(a)

70 75 80 85 90 95 100 1056

7

8

9

10

11

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

(b)

Figure 8 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for O-Anisic acid

constants with the proper accuracy and the GIAOmethod isone of the most common approaches for calculating nuclearmagnetic shielding tensors

Theoretical and experimental chemical shifts of OAA andAA in 1H and 13C NMR spectra are gathered in Tables 12and 13 The range of the 13C NMR chemical shifts for atypical organic molecules usually is gt100 ppm [38 39] andthe accuracy ensures reliable interpretation of spectroscopicparameters In the present study the 13C NMR chemicalshifts in the ring are gt100 ppm as they would be expectedThe 13C chemical shifts carbonyl carbons vary from 150 to220 ppm This depends on the decrease in electron donatingor shielding ability of the attached atoms [40] The C=Ogroups of carboxylic acids and derivatives are in the range of150ndash185 ppm [29]

Hydrogens bonded to an aromatic ring are stronglydeshielded and absorb downfieldWhen the120587-electrons enterthe magnetic field they circulate around the ring to generatea ring current This produces a small induced magnetic fieldthat reinforces the applied field outside the ring resultingin aromatic protons being deshielded [41] A related effectis observed for carboxylic acids For these compoundscirculation of electrons in the double bonds produces inducedmagnetic field These are responsible for the high chemicalshift values of acid protons (H10) Carboxylic acids asstable hydrogen-bonded dimers in nonpolar solvents even athigh dilution The carboxylic proton therefore absorbs in acharacteristically narrow range 132 to 100 and is affectedonly slightly by concentration [29]

In a methyl group a proton is covalently bonded tocarbon oxygen or other atoms by a sigma bond Whenplaced in a strong magnetic field the electrons of the sigmabond circulate to generate a small magnetic field whichopposes the applied field A nearby electronegative atomwithdraws electron density from the neighbourhood of theproton so that a smaller applied field is needed to cause thespin state of the proton to flip The signal for a deshielded

Table 14 Theoretically computed energies (au) zero-point vibra-tional energies (kcalmolminus1) rotational constants (GHz) entropies(calmolminus1 Kminus1) nuclear repulsion energy (Hartrees) and dipolemoment (Debye) for OAA and AA

Parameters B3LYP6-31Glowastlowast

OAA AAZero-point energy 9306056 9314966

Rotational constants139942 344405114384 056752063193 048875

EntropyTotal 99243 97126Translational 40967 40967Rotational 30142 30199Vibrational 28134 25960Dipole moment 24181 35822Nuclear repulsion energy 592968293 573992628

proton (1 surrounded by less electron density) is observed tobe more downfield than the signals for protons that are notdeshielded by electronegative atoms [40] The chemical shiftvalue of C7 (OAA and AA) has bigger value than the othercarbons due to the electronegative property of oxygen atom

The linear correlations between calculated and experi-mental data of 13CNMRand 1HNMRspectra are determinedas 09 and 10 for OAA and 09 and 09 for AA respectivelyThere is an excellent linear relationship between experimentaland computed results which are shown in Figures 8 and 9

6 Thermodynamic Properties

Several calculated thermodynamical parameters are pre-sented in Table 14 for OAA andAA respectively Scale factorshave been recommended [42] for an accurate prediction in

Journal of Spectroscopy 17

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 180

170

160

150

140

130

120

110110

120 130 140 150 160 170

(a)

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

11

10

9

8

7

7 8 9 10 11 12 13

(b)

Figure 9 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for Anisic acid

determining the zero-point vibration energies (ZPVE) andthe entropy 119878vib(119879) The total energies and the change inthe total entropy at room temperature using B3LYP6-31Glowastlowastmethod are presented

7 Conclusion

Attempts have been made in the present work for the molec-ular parameters and frequency assignments for the com-pounds OAA and AA from the FTIR and FT-Raman spectraThe equilibrium geometries and harmonic and anharmonicfrequencies for the title compounds were determined andanalyzed at DFT level of theory utilizing 6-31Glowastlowast basis setThe assignments of most of the fundamentals of the titlecompounds provided in this work are quite comparableThe excellent agreement of the calculated and observedvibrational spectra reveals the advantages of a smaller basisset for quantum chemical calculations HOMO and LUMOenergy gap explains the eventual charge transfer interactionstaking place within the molecule The experimental andtheoretical investigation of the title compounds have beenperformed successfully by using 1H and 13C NMR Thevarious modes of vibrations were unambiguously assignedon the basis of the result of the PED output obtainedfrom normal coordinate analysis These studies confirm thepresence of COOH and OCH

3group Dimeric molecules are

held together by hydrogen bridges between carbonyl groupsThe obtained data and simulations both show the way to thecharacterization of the molecules and help in spectra studiesin the future

References

[1] GMelentyeva and LAntonovaPharmaceutical ChemistryMirPublishers Moscow Russia 1988

[2] ldquoo-Anisic acid(579-75-9) catalog of chemical suppliersrdquo httpwwwchemexpercomchemicalssuppliercas579-75-9html

[3] B A Hess Jr L J Schaad P Carsky and R Zaharaduick ldquoAbinitio calculations of vibrational spectra and their use in theidentification of unusual moleculesrdquo Chemical Reviews vol 86no 4 pp 709ndash730 1986

[4] P Pulay X Zhou and G Forgarasi in Recent Experimental andComputational Advances in Molecular Spectroscopy R Faustoand R Fransto Eds vol 406 ofNATOASI Series p 99 KluwerDordrecht Netherlands 1993

[5] P Pulay G Fogarasi G Pongor J E Boggs and A VarghaldquoCombination of theoretical ab initio and experimental infor-mation to obtain reliable harmonic force constants ScaledQuantum Mechanical (SQM) force fields for glyoxal acroleinbutadiene formaldehyde and ethylenerdquo Journal of the Ameri-can Chemical Society vol 105 no 24 pp 7037ndash7047 1983

[6] C E Blom and C Altona ldquoApplication of self-consistent-fieldab initio calculations to organic moleculesrdquo Molecular Physicsvol 31 no 5 pp 1377ndash1391 1976

[7] G Fogarasi and P Pulay in Vibrational Spectra and Structure JR Durig Ed vol 14 Elsevier Amsterdam Netherlands 1985

[8] G Fogarasi ldquoRecent developments in the method of SQM forcefields with application to 1-methyladeninerdquo Spectrochimica ActaA vol 53 no 8 pp 1211ndash1224 1997

[9] G R deMare N Yu Panchenko andW Ch Bock ldquoAnMP26-31GlowastMP26-31Glowast vibrational analysis of s-trans- and s-cis-acryloyl fluoride CH2=CH-CF=Ordquo The Journal of PhysicalChemistry vol 98 no 5 pp 1416ndash1420 1994

[10] G Pongor P Pulay G Fogarasi and J E Boggs ldquoTheoreticalprediction of vibrational spectra 1 The in-plane force fieldand vibrational spectra of pyridinerdquo Journal of the AmericanChemical Society vol 106 no 10 pp 2765ndash2769 1984

[11] Y Yamakitu and M Tasumi ldquoVibrational analyses of p-benzoquinodimethane and p-benzoquinone based on ab initioHartree-Fock and second-order Moller-Plesset calculationsrdquoThe Journal of Physical Chemistry vol 99 no 21 pp 8524ndash85341995

18 Journal of Spectroscopy

[12] M Karabacak A Coruh and M Kurt ldquoFT-IR FT-RamanNMR spectra and molecular structure investigation of 23-dibromo-N-methylmaleimide a combined experimental andtheoretical studyrdquo Journal of Molecular Structure vol 892 no1ndash3 pp 125ndash131 2008

[13] M S Masoud M K Awad M A Shaker and M M T El-Tahawy ldquoThe role of structural chemistry in the inhibitiveperformance of some aminopyrimidines on the corrosion ofsteelrdquo Corrosion Science vol 52 no 7 pp 2387ndash2396 2010

[14] M J Frisch G W Trucks H B Schlegel et al Gaussian 03Revision B4 Gaussian Inc Pittsburgh Pa USA 2003

[15] P L Polavarapu ldquoAb initio vibrational Raman and Ramanoptical activity spectrardquo Journal of Physical Chemistry vol 94no 21 pp 8106ndash8112 1990

[16] G Keresztury S Holly J Varga G Besenyei A Wang andJ R Durig ldquoVibrational spectra of monothiocarbamates-IIIR and Raman spectra vibrational assignment conforma-tional analysis and ab initio calculations of S-methyl-NN-dimethylthiocarbamaterdquo Spectrochimica Acta A vol 49 no 13-14 pp 2007ndash2017 1993

[17] G Keresztury ldquoRaman spectroscopy theoryrdquo in Handbook ofVibrational Spectroscopy J M Chalmers and P R Griffths Edsvol 1 p 71 John Wiley and Sons 2002

[18] R G Parr R A Donnelly M Levy and W E Palke ldquoElec-tronegativity the density functional viewpointrdquo The Journal ofChemical Physics vol 68 no 8 pp 3801ndash3807 1977

[19] R G Parr and R G Pearson ldquoAbsolute hardness companionparameter to absolute electronegativityrdquo Journal of theAmericanChemical Society vol 105 no 26 pp 7512ndash7516 1983

[20] R G Pearson ldquoAbsolute electronegativity and hardness appli-cation to inorganic chemistryrdquo Inorganic Chemistry vol 27 no4 pp 734ndash740 1988

[21] P Geerlings F De Proft and W Langenaeker ldquoConceptualdensity functional theoryrdquo Chemical Reviews vol 103 no 5 pp1793ndash1873 2003

[22] R Ditchfield ldquoMolecular orbital theory of magnetic shieldingand magnetic susceptibilityrdquo Journal of Physical Chemistry vol56 no 11 article 5688 4 pages 1972

[23] KWolinski J F Hilton and P Pulay ldquoEfficient implementationof the gauge-independent atomic orbital method for NMRchemical shift calculationsrdquo Journal of the American ChemicalSociety vol 112 no 23 pp 8251ndash8260 1990

[24] M Kurt M Yurdakul and S Yurdakul ldquoMolecular structureand vibrational spectra of 3-chloro-4-methyl aniline by densityfunctional theory and ab initio Hartree-Fock calculationsrdquoJournal of Molecular Structure vol 711 no 1ndash3 pp 25ndash32 2004

[25] D Steele and D H Whiffen ldquoThe vibration frequencies ofpentafluorobenzenerdquo Spectrochimica Acta vol 16 no 3 pp368ndash375 1960

[26] D N Sathyanarayanan Vibrational Spectroscopy Theory andApplication New Age International publishers New DelhiIndia 1996

[27] L D S YadavOrganic Spectroscopy Springer NewDelhi India2004

[28] J Mohan Organic Spectroscopy Principles and ApplicationsNarosa Publishing House New Delhi 2nd edition 2009

[29] R M Silverstein G C Bassler and T C Morrill SpectrometricIdentification of Organic Compounds John Wiley amp Sons NewYork NY USA 1981

[30] G Socrates Infrared Characteristic Group Frequencies WileyNew York NY USA 1980

[31] R S Mulliken ldquoElectronic population analysis on LCAO-MOmolecular wave functionsrdquoThe Journal of Chemical Physics vol23 no 10 pp 1833ndash1840 1955

[32] K Fukuli T Yonezawa and H Shingu ldquoA molecular orbitaltheory of reactivity in aromatic hydrocarbonsrdquo Journal ofPhysical Chemistry vol 20 no 4 article 722 4 pages 1952

[33] C H Choi and M Kertesz ldquoConformational information fromvibrational spectra of styrene trans-stilbene and cis-stilbenerdquoJournal of Physical Chemistry A vol 101 no 20 pp 3823ndash38311997

[34] S Gunasekaran R Arun Balaji S Kumaresan G Anandand S Srinivasan ldquoExperimental and theoretical investigationsof spectroscopic properties of N-acetyl-5-methoxytryptaminerdquoCanadian Journal of Analytical Sciences and Spectroscopy vol53 no 4 pp 149ndash162 2008

[35] P Hohenberg and W Kohn ldquoInhomogeneous electron gasrdquoPhysical Review vol 136 no 3 pp B864ndashB871 1964

[36] R G Pearson ldquoAbsolute electronegativity and absolute hard-ness of Lewis acids and basesrdquo Journal of the American ChemicalSociety vol 107 no 24 pp 6801ndash6806 1985

[37] D Avci Y Atalay M Sekerci and M Dincer ldquoMolecular struc-ture and vibrational and chemical shift assignments of 3-(2-Hydroxyphenyl)-4-phenyl-1H-124-triazole-5-(4H)-thione byDFT and ab initio HF calculationsrdquo Spectrochimica Acta A vol73 no 1 pp 212ndash217 2009

[38] H O Kalinowski S Berger and S Braun Carbon13 NMRSpectroscopy John Wiley amp Sons Chichester UK 1988

[39] K Pihlaja and E Kleinpeter Carbon-13 NMR Chemical Shiftsin Structural and Sterochemical Analysis VCH PublishersDeerfield Beach Fla USA 1994

[40] P S Kalsi Spectroscopy of Organic Compounds New AgeInternational 2004

[41] A F Parsons Keynotes in Organic Chemistry Blackwell Pub-lishing Oxford UK 2003

[42] M A Palafox ldquoScaling factors for the prediction of vibrationalspectra I benzenemoleculerdquo International Journal of QuantumChemistry vol 77 no 3 pp 661ndash684 2000

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Page 15: Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. · Molecular Structure, NMR, HOMO, LUMO, ... ects of carbonyl and methyl substitutions

Journal of Spectroscopy 15

HOMO

(a)

LUMO

(b)

Figure 6 Contour surfaces of frontier molecular orbitals of O-Anisic acid

HOMO

(a)

LUMO

(b)

Figure 7 Contour surfaces of frontier molecular orbitals of Anisic acid

HOMO-LUMO gap automatically means small excitationenergies to the manifold of excited states Therefore softmolecules with a small gap will be more polarizable thanhard molecules High polarizability was the most character-istic property attributed to soft acids and bases Energy gapsshould be small for best bonding or bothmolecules should besoft

In the present study the title compound AA is dynam-ically more stable due to the large energy gap OAA is asoft molecule due to small energy gap The Contour surfacesof the frontier molecular orbitals are sketched in Figures 6and 7

51 NMR Spectra DFT methods treat the electronic energyas a function of the electron density of all electrons simul-taneously and thus include electron correlation effect [37]In this study molecular structure of the OAA and AA wasoptimized by using B3LYP method in conjunction with 6-31Glowastlowast 13C and 1H chemical shift calculations of the titlecompounds have been made by using GIAO method andsame basis set The isotropic shielding values were usedto calculate the isotropic chemical shifts 120575 with respect totetramethylsilane (TMS) The isotropic chemical shifts arefrequently used as an aid in identification of reactive ionicspecies The B3LYP method allows calculating the shielding

16 Journal of Spectroscopy

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 150

140

130

120

110

100

90110 120 130 140 150 160 170

(a)

70 75 80 85 90 95 100 1056

7

8

9

10

11

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

(b)

Figure 8 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for O-Anisic acid

constants with the proper accuracy and the GIAOmethod isone of the most common approaches for calculating nuclearmagnetic shielding tensors

Theoretical and experimental chemical shifts of OAA andAA in 1H and 13C NMR spectra are gathered in Tables 12and 13 The range of the 13C NMR chemical shifts for atypical organic molecules usually is gt100 ppm [38 39] andthe accuracy ensures reliable interpretation of spectroscopicparameters In the present study the 13C NMR chemicalshifts in the ring are gt100 ppm as they would be expectedThe 13C chemical shifts carbonyl carbons vary from 150 to220 ppm This depends on the decrease in electron donatingor shielding ability of the attached atoms [40] The C=Ogroups of carboxylic acids and derivatives are in the range of150ndash185 ppm [29]

Hydrogens bonded to an aromatic ring are stronglydeshielded and absorb downfieldWhen the120587-electrons enterthe magnetic field they circulate around the ring to generatea ring current This produces a small induced magnetic fieldthat reinforces the applied field outside the ring resultingin aromatic protons being deshielded [41] A related effectis observed for carboxylic acids For these compoundscirculation of electrons in the double bonds produces inducedmagnetic field These are responsible for the high chemicalshift values of acid protons (H10) Carboxylic acids asstable hydrogen-bonded dimers in nonpolar solvents even athigh dilution The carboxylic proton therefore absorbs in acharacteristically narrow range 132 to 100 and is affectedonly slightly by concentration [29]

In a methyl group a proton is covalently bonded tocarbon oxygen or other atoms by a sigma bond Whenplaced in a strong magnetic field the electrons of the sigmabond circulate to generate a small magnetic field whichopposes the applied field A nearby electronegative atomwithdraws electron density from the neighbourhood of theproton so that a smaller applied field is needed to cause thespin state of the proton to flip The signal for a deshielded

Table 14 Theoretically computed energies (au) zero-point vibra-tional energies (kcalmolminus1) rotational constants (GHz) entropies(calmolminus1 Kminus1) nuclear repulsion energy (Hartrees) and dipolemoment (Debye) for OAA and AA

Parameters B3LYP6-31Glowastlowast

OAA AAZero-point energy 9306056 9314966

Rotational constants139942 344405114384 056752063193 048875

EntropyTotal 99243 97126Translational 40967 40967Rotational 30142 30199Vibrational 28134 25960Dipole moment 24181 35822Nuclear repulsion energy 592968293 573992628

proton (1 surrounded by less electron density) is observed tobe more downfield than the signals for protons that are notdeshielded by electronegative atoms [40] The chemical shiftvalue of C7 (OAA and AA) has bigger value than the othercarbons due to the electronegative property of oxygen atom

The linear correlations between calculated and experi-mental data of 13CNMRand 1HNMRspectra are determinedas 09 and 10 for OAA and 09 and 09 for AA respectivelyThere is an excellent linear relationship between experimentaland computed results which are shown in Figures 8 and 9

6 Thermodynamic Properties

Several calculated thermodynamical parameters are pre-sented in Table 14 for OAA andAA respectively Scale factorshave been recommended [42] for an accurate prediction in

Journal of Spectroscopy 17

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 180

170

160

150

140

130

120

110110

120 130 140 150 160 170

(a)

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

11

10

9

8

7

7 8 9 10 11 12 13

(b)

Figure 9 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for Anisic acid

determining the zero-point vibration energies (ZPVE) andthe entropy 119878vib(119879) The total energies and the change inthe total entropy at room temperature using B3LYP6-31Glowastlowastmethod are presented

7 Conclusion

Attempts have been made in the present work for the molec-ular parameters and frequency assignments for the com-pounds OAA and AA from the FTIR and FT-Raman spectraThe equilibrium geometries and harmonic and anharmonicfrequencies for the title compounds were determined andanalyzed at DFT level of theory utilizing 6-31Glowastlowast basis setThe assignments of most of the fundamentals of the titlecompounds provided in this work are quite comparableThe excellent agreement of the calculated and observedvibrational spectra reveals the advantages of a smaller basisset for quantum chemical calculations HOMO and LUMOenergy gap explains the eventual charge transfer interactionstaking place within the molecule The experimental andtheoretical investigation of the title compounds have beenperformed successfully by using 1H and 13C NMR Thevarious modes of vibrations were unambiguously assignedon the basis of the result of the PED output obtainedfrom normal coordinate analysis These studies confirm thepresence of COOH and OCH

3group Dimeric molecules are

held together by hydrogen bridges between carbonyl groupsThe obtained data and simulations both show the way to thecharacterization of the molecules and help in spectra studiesin the future

References

[1] GMelentyeva and LAntonovaPharmaceutical ChemistryMirPublishers Moscow Russia 1988

[2] ldquoo-Anisic acid(579-75-9) catalog of chemical suppliersrdquo httpwwwchemexpercomchemicalssuppliercas579-75-9html

[3] B A Hess Jr L J Schaad P Carsky and R Zaharaduick ldquoAbinitio calculations of vibrational spectra and their use in theidentification of unusual moleculesrdquo Chemical Reviews vol 86no 4 pp 709ndash730 1986

[4] P Pulay X Zhou and G Forgarasi in Recent Experimental andComputational Advances in Molecular Spectroscopy R Faustoand R Fransto Eds vol 406 ofNATOASI Series p 99 KluwerDordrecht Netherlands 1993

[5] P Pulay G Fogarasi G Pongor J E Boggs and A VarghaldquoCombination of theoretical ab initio and experimental infor-mation to obtain reliable harmonic force constants ScaledQuantum Mechanical (SQM) force fields for glyoxal acroleinbutadiene formaldehyde and ethylenerdquo Journal of the Ameri-can Chemical Society vol 105 no 24 pp 7037ndash7047 1983

[6] C E Blom and C Altona ldquoApplication of self-consistent-fieldab initio calculations to organic moleculesrdquo Molecular Physicsvol 31 no 5 pp 1377ndash1391 1976

[7] G Fogarasi and P Pulay in Vibrational Spectra and Structure JR Durig Ed vol 14 Elsevier Amsterdam Netherlands 1985

[8] G Fogarasi ldquoRecent developments in the method of SQM forcefields with application to 1-methyladeninerdquo Spectrochimica ActaA vol 53 no 8 pp 1211ndash1224 1997

[9] G R deMare N Yu Panchenko andW Ch Bock ldquoAnMP26-31GlowastMP26-31Glowast vibrational analysis of s-trans- and s-cis-acryloyl fluoride CH2=CH-CF=Ordquo The Journal of PhysicalChemistry vol 98 no 5 pp 1416ndash1420 1994

[10] G Pongor P Pulay G Fogarasi and J E Boggs ldquoTheoreticalprediction of vibrational spectra 1 The in-plane force fieldand vibrational spectra of pyridinerdquo Journal of the AmericanChemical Society vol 106 no 10 pp 2765ndash2769 1984

[11] Y Yamakitu and M Tasumi ldquoVibrational analyses of p-benzoquinodimethane and p-benzoquinone based on ab initioHartree-Fock and second-order Moller-Plesset calculationsrdquoThe Journal of Physical Chemistry vol 99 no 21 pp 8524ndash85341995

18 Journal of Spectroscopy

[12] M Karabacak A Coruh and M Kurt ldquoFT-IR FT-RamanNMR spectra and molecular structure investigation of 23-dibromo-N-methylmaleimide a combined experimental andtheoretical studyrdquo Journal of Molecular Structure vol 892 no1ndash3 pp 125ndash131 2008

[13] M S Masoud M K Awad M A Shaker and M M T El-Tahawy ldquoThe role of structural chemistry in the inhibitiveperformance of some aminopyrimidines on the corrosion ofsteelrdquo Corrosion Science vol 52 no 7 pp 2387ndash2396 2010

[14] M J Frisch G W Trucks H B Schlegel et al Gaussian 03Revision B4 Gaussian Inc Pittsburgh Pa USA 2003

[15] P L Polavarapu ldquoAb initio vibrational Raman and Ramanoptical activity spectrardquo Journal of Physical Chemistry vol 94no 21 pp 8106ndash8112 1990

[16] G Keresztury S Holly J Varga G Besenyei A Wang andJ R Durig ldquoVibrational spectra of monothiocarbamates-IIIR and Raman spectra vibrational assignment conforma-tional analysis and ab initio calculations of S-methyl-NN-dimethylthiocarbamaterdquo Spectrochimica Acta A vol 49 no 13-14 pp 2007ndash2017 1993

[17] G Keresztury ldquoRaman spectroscopy theoryrdquo in Handbook ofVibrational Spectroscopy J M Chalmers and P R Griffths Edsvol 1 p 71 John Wiley and Sons 2002

[18] R G Parr R A Donnelly M Levy and W E Palke ldquoElec-tronegativity the density functional viewpointrdquo The Journal ofChemical Physics vol 68 no 8 pp 3801ndash3807 1977

[19] R G Parr and R G Pearson ldquoAbsolute hardness companionparameter to absolute electronegativityrdquo Journal of theAmericanChemical Society vol 105 no 26 pp 7512ndash7516 1983

[20] R G Pearson ldquoAbsolute electronegativity and hardness appli-cation to inorganic chemistryrdquo Inorganic Chemistry vol 27 no4 pp 734ndash740 1988

[21] P Geerlings F De Proft and W Langenaeker ldquoConceptualdensity functional theoryrdquo Chemical Reviews vol 103 no 5 pp1793ndash1873 2003

[22] R Ditchfield ldquoMolecular orbital theory of magnetic shieldingand magnetic susceptibilityrdquo Journal of Physical Chemistry vol56 no 11 article 5688 4 pages 1972

[23] KWolinski J F Hilton and P Pulay ldquoEfficient implementationof the gauge-independent atomic orbital method for NMRchemical shift calculationsrdquo Journal of the American ChemicalSociety vol 112 no 23 pp 8251ndash8260 1990

[24] M Kurt M Yurdakul and S Yurdakul ldquoMolecular structureand vibrational spectra of 3-chloro-4-methyl aniline by densityfunctional theory and ab initio Hartree-Fock calculationsrdquoJournal of Molecular Structure vol 711 no 1ndash3 pp 25ndash32 2004

[25] D Steele and D H Whiffen ldquoThe vibration frequencies ofpentafluorobenzenerdquo Spectrochimica Acta vol 16 no 3 pp368ndash375 1960

[26] D N Sathyanarayanan Vibrational Spectroscopy Theory andApplication New Age International publishers New DelhiIndia 1996

[27] L D S YadavOrganic Spectroscopy Springer NewDelhi India2004

[28] J Mohan Organic Spectroscopy Principles and ApplicationsNarosa Publishing House New Delhi 2nd edition 2009

[29] R M Silverstein G C Bassler and T C Morrill SpectrometricIdentification of Organic Compounds John Wiley amp Sons NewYork NY USA 1981

[30] G Socrates Infrared Characteristic Group Frequencies WileyNew York NY USA 1980

[31] R S Mulliken ldquoElectronic population analysis on LCAO-MOmolecular wave functionsrdquoThe Journal of Chemical Physics vol23 no 10 pp 1833ndash1840 1955

[32] K Fukuli T Yonezawa and H Shingu ldquoA molecular orbitaltheory of reactivity in aromatic hydrocarbonsrdquo Journal ofPhysical Chemistry vol 20 no 4 article 722 4 pages 1952

[33] C H Choi and M Kertesz ldquoConformational information fromvibrational spectra of styrene trans-stilbene and cis-stilbenerdquoJournal of Physical Chemistry A vol 101 no 20 pp 3823ndash38311997

[34] S Gunasekaran R Arun Balaji S Kumaresan G Anandand S Srinivasan ldquoExperimental and theoretical investigationsof spectroscopic properties of N-acetyl-5-methoxytryptaminerdquoCanadian Journal of Analytical Sciences and Spectroscopy vol53 no 4 pp 149ndash162 2008

[35] P Hohenberg and W Kohn ldquoInhomogeneous electron gasrdquoPhysical Review vol 136 no 3 pp B864ndashB871 1964

[36] R G Pearson ldquoAbsolute electronegativity and absolute hard-ness of Lewis acids and basesrdquo Journal of the American ChemicalSociety vol 107 no 24 pp 6801ndash6806 1985

[37] D Avci Y Atalay M Sekerci and M Dincer ldquoMolecular struc-ture and vibrational and chemical shift assignments of 3-(2-Hydroxyphenyl)-4-phenyl-1H-124-triazole-5-(4H)-thione byDFT and ab initio HF calculationsrdquo Spectrochimica Acta A vol73 no 1 pp 212ndash217 2009

[38] H O Kalinowski S Berger and S Braun Carbon13 NMRSpectroscopy John Wiley amp Sons Chichester UK 1988

[39] K Pihlaja and E Kleinpeter Carbon-13 NMR Chemical Shiftsin Structural and Sterochemical Analysis VCH PublishersDeerfield Beach Fla USA 1994

[40] P S Kalsi Spectroscopy of Organic Compounds New AgeInternational 2004

[41] A F Parsons Keynotes in Organic Chemistry Blackwell Pub-lishing Oxford UK 2003

[42] M A Palafox ldquoScaling factors for the prediction of vibrationalspectra I benzenemoleculerdquo International Journal of QuantumChemistry vol 77 no 3 pp 661ndash684 2000

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Page 16: Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. · Molecular Structure, NMR, HOMO, LUMO, ... ects of carbonyl and methyl substitutions

16 Journal of Spectroscopy

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 150

140

130

120

110

100

90110 120 130 140 150 160 170

(a)

70 75 80 85 90 95 100 1056

7

8

9

10

11

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

(b)

Figure 8 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for O-Anisic acid

constants with the proper accuracy and the GIAOmethod isone of the most common approaches for calculating nuclearmagnetic shielding tensors

Theoretical and experimental chemical shifts of OAA andAA in 1H and 13C NMR spectra are gathered in Tables 12and 13 The range of the 13C NMR chemical shifts for atypical organic molecules usually is gt100 ppm [38 39] andthe accuracy ensures reliable interpretation of spectroscopicparameters In the present study the 13C NMR chemicalshifts in the ring are gt100 ppm as they would be expectedThe 13C chemical shifts carbonyl carbons vary from 150 to220 ppm This depends on the decrease in electron donatingor shielding ability of the attached atoms [40] The C=Ogroups of carboxylic acids and derivatives are in the range of150ndash185 ppm [29]

Hydrogens bonded to an aromatic ring are stronglydeshielded and absorb downfieldWhen the120587-electrons enterthe magnetic field they circulate around the ring to generatea ring current This produces a small induced magnetic fieldthat reinforces the applied field outside the ring resultingin aromatic protons being deshielded [41] A related effectis observed for carboxylic acids For these compoundscirculation of electrons in the double bonds produces inducedmagnetic field These are responsible for the high chemicalshift values of acid protons (H10) Carboxylic acids asstable hydrogen-bonded dimers in nonpolar solvents even athigh dilution The carboxylic proton therefore absorbs in acharacteristically narrow range 132 to 100 and is affectedonly slightly by concentration [29]

In a methyl group a proton is covalently bonded tocarbon oxygen or other atoms by a sigma bond Whenplaced in a strong magnetic field the electrons of the sigmabond circulate to generate a small magnetic field whichopposes the applied field A nearby electronegative atomwithdraws electron density from the neighbourhood of theproton so that a smaller applied field is needed to cause thespin state of the proton to flip The signal for a deshielded

Table 14 Theoretically computed energies (au) zero-point vibra-tional energies (kcalmolminus1) rotational constants (GHz) entropies(calmolminus1 Kminus1) nuclear repulsion energy (Hartrees) and dipolemoment (Debye) for OAA and AA

Parameters B3LYP6-31Glowastlowast

OAA AAZero-point energy 9306056 9314966

Rotational constants139942 344405114384 056752063193 048875

EntropyTotal 99243 97126Translational 40967 40967Rotational 30142 30199Vibrational 28134 25960Dipole moment 24181 35822Nuclear repulsion energy 592968293 573992628

proton (1 surrounded by less electron density) is observed tobe more downfield than the signals for protons that are notdeshielded by electronegative atoms [40] The chemical shiftvalue of C7 (OAA and AA) has bigger value than the othercarbons due to the electronegative property of oxygen atom

The linear correlations between calculated and experi-mental data of 13CNMRand 1HNMRspectra are determinedas 09 and 10 for OAA and 09 and 09 for AA respectivelyThere is an excellent linear relationship between experimentaland computed results which are shown in Figures 8 and 9

6 Thermodynamic Properties

Several calculated thermodynamical parameters are pre-sented in Table 14 for OAA andAA respectively Scale factorshave been recommended [42] for an accurate prediction in

Journal of Spectroscopy 17

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 180

170

160

150

140

130

120

110110

120 130 140 150 160 170

(a)

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

11

10

9

8

7

7 8 9 10 11 12 13

(b)

Figure 9 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for Anisic acid

determining the zero-point vibration energies (ZPVE) andthe entropy 119878vib(119879) The total energies and the change inthe total entropy at room temperature using B3LYP6-31Glowastlowastmethod are presented

7 Conclusion

Attempts have been made in the present work for the molec-ular parameters and frequency assignments for the com-pounds OAA and AA from the FTIR and FT-Raman spectraThe equilibrium geometries and harmonic and anharmonicfrequencies for the title compounds were determined andanalyzed at DFT level of theory utilizing 6-31Glowastlowast basis setThe assignments of most of the fundamentals of the titlecompounds provided in this work are quite comparableThe excellent agreement of the calculated and observedvibrational spectra reveals the advantages of a smaller basisset for quantum chemical calculations HOMO and LUMOenergy gap explains the eventual charge transfer interactionstaking place within the molecule The experimental andtheoretical investigation of the title compounds have beenperformed successfully by using 1H and 13C NMR Thevarious modes of vibrations were unambiguously assignedon the basis of the result of the PED output obtainedfrom normal coordinate analysis These studies confirm thepresence of COOH and OCH

3group Dimeric molecules are

held together by hydrogen bridges between carbonyl groupsThe obtained data and simulations both show the way to thecharacterization of the molecules and help in spectra studiesin the future

References

[1] GMelentyeva and LAntonovaPharmaceutical ChemistryMirPublishers Moscow Russia 1988

[2] ldquoo-Anisic acid(579-75-9) catalog of chemical suppliersrdquo httpwwwchemexpercomchemicalssuppliercas579-75-9html

[3] B A Hess Jr L J Schaad P Carsky and R Zaharaduick ldquoAbinitio calculations of vibrational spectra and their use in theidentification of unusual moleculesrdquo Chemical Reviews vol 86no 4 pp 709ndash730 1986

[4] P Pulay X Zhou and G Forgarasi in Recent Experimental andComputational Advances in Molecular Spectroscopy R Faustoand R Fransto Eds vol 406 ofNATOASI Series p 99 KluwerDordrecht Netherlands 1993

[5] P Pulay G Fogarasi G Pongor J E Boggs and A VarghaldquoCombination of theoretical ab initio and experimental infor-mation to obtain reliable harmonic force constants ScaledQuantum Mechanical (SQM) force fields for glyoxal acroleinbutadiene formaldehyde and ethylenerdquo Journal of the Ameri-can Chemical Society vol 105 no 24 pp 7037ndash7047 1983

[6] C E Blom and C Altona ldquoApplication of self-consistent-fieldab initio calculations to organic moleculesrdquo Molecular Physicsvol 31 no 5 pp 1377ndash1391 1976

[7] G Fogarasi and P Pulay in Vibrational Spectra and Structure JR Durig Ed vol 14 Elsevier Amsterdam Netherlands 1985

[8] G Fogarasi ldquoRecent developments in the method of SQM forcefields with application to 1-methyladeninerdquo Spectrochimica ActaA vol 53 no 8 pp 1211ndash1224 1997

[9] G R deMare N Yu Panchenko andW Ch Bock ldquoAnMP26-31GlowastMP26-31Glowast vibrational analysis of s-trans- and s-cis-acryloyl fluoride CH2=CH-CF=Ordquo The Journal of PhysicalChemistry vol 98 no 5 pp 1416ndash1420 1994

[10] G Pongor P Pulay G Fogarasi and J E Boggs ldquoTheoreticalprediction of vibrational spectra 1 The in-plane force fieldand vibrational spectra of pyridinerdquo Journal of the AmericanChemical Society vol 106 no 10 pp 2765ndash2769 1984

[11] Y Yamakitu and M Tasumi ldquoVibrational analyses of p-benzoquinodimethane and p-benzoquinone based on ab initioHartree-Fock and second-order Moller-Plesset calculationsrdquoThe Journal of Physical Chemistry vol 99 no 21 pp 8524ndash85341995

18 Journal of Spectroscopy

[12] M Karabacak A Coruh and M Kurt ldquoFT-IR FT-RamanNMR spectra and molecular structure investigation of 23-dibromo-N-methylmaleimide a combined experimental andtheoretical studyrdquo Journal of Molecular Structure vol 892 no1ndash3 pp 125ndash131 2008

[13] M S Masoud M K Awad M A Shaker and M M T El-Tahawy ldquoThe role of structural chemistry in the inhibitiveperformance of some aminopyrimidines on the corrosion ofsteelrdquo Corrosion Science vol 52 no 7 pp 2387ndash2396 2010

[14] M J Frisch G W Trucks H B Schlegel et al Gaussian 03Revision B4 Gaussian Inc Pittsburgh Pa USA 2003

[15] P L Polavarapu ldquoAb initio vibrational Raman and Ramanoptical activity spectrardquo Journal of Physical Chemistry vol 94no 21 pp 8106ndash8112 1990

[16] G Keresztury S Holly J Varga G Besenyei A Wang andJ R Durig ldquoVibrational spectra of monothiocarbamates-IIIR and Raman spectra vibrational assignment conforma-tional analysis and ab initio calculations of S-methyl-NN-dimethylthiocarbamaterdquo Spectrochimica Acta A vol 49 no 13-14 pp 2007ndash2017 1993

[17] G Keresztury ldquoRaman spectroscopy theoryrdquo in Handbook ofVibrational Spectroscopy J M Chalmers and P R Griffths Edsvol 1 p 71 John Wiley and Sons 2002

[18] R G Parr R A Donnelly M Levy and W E Palke ldquoElec-tronegativity the density functional viewpointrdquo The Journal ofChemical Physics vol 68 no 8 pp 3801ndash3807 1977

[19] R G Parr and R G Pearson ldquoAbsolute hardness companionparameter to absolute electronegativityrdquo Journal of theAmericanChemical Society vol 105 no 26 pp 7512ndash7516 1983

[20] R G Pearson ldquoAbsolute electronegativity and hardness appli-cation to inorganic chemistryrdquo Inorganic Chemistry vol 27 no4 pp 734ndash740 1988

[21] P Geerlings F De Proft and W Langenaeker ldquoConceptualdensity functional theoryrdquo Chemical Reviews vol 103 no 5 pp1793ndash1873 2003

[22] R Ditchfield ldquoMolecular orbital theory of magnetic shieldingand magnetic susceptibilityrdquo Journal of Physical Chemistry vol56 no 11 article 5688 4 pages 1972

[23] KWolinski J F Hilton and P Pulay ldquoEfficient implementationof the gauge-independent atomic orbital method for NMRchemical shift calculationsrdquo Journal of the American ChemicalSociety vol 112 no 23 pp 8251ndash8260 1990

[24] M Kurt M Yurdakul and S Yurdakul ldquoMolecular structureand vibrational spectra of 3-chloro-4-methyl aniline by densityfunctional theory and ab initio Hartree-Fock calculationsrdquoJournal of Molecular Structure vol 711 no 1ndash3 pp 25ndash32 2004

[25] D Steele and D H Whiffen ldquoThe vibration frequencies ofpentafluorobenzenerdquo Spectrochimica Acta vol 16 no 3 pp368ndash375 1960

[26] D N Sathyanarayanan Vibrational Spectroscopy Theory andApplication New Age International publishers New DelhiIndia 1996

[27] L D S YadavOrganic Spectroscopy Springer NewDelhi India2004

[28] J Mohan Organic Spectroscopy Principles and ApplicationsNarosa Publishing House New Delhi 2nd edition 2009

[29] R M Silverstein G C Bassler and T C Morrill SpectrometricIdentification of Organic Compounds John Wiley amp Sons NewYork NY USA 1981

[30] G Socrates Infrared Characteristic Group Frequencies WileyNew York NY USA 1980

[31] R S Mulliken ldquoElectronic population analysis on LCAO-MOmolecular wave functionsrdquoThe Journal of Chemical Physics vol23 no 10 pp 1833ndash1840 1955

[32] K Fukuli T Yonezawa and H Shingu ldquoA molecular orbitaltheory of reactivity in aromatic hydrocarbonsrdquo Journal ofPhysical Chemistry vol 20 no 4 article 722 4 pages 1952

[33] C H Choi and M Kertesz ldquoConformational information fromvibrational spectra of styrene trans-stilbene and cis-stilbenerdquoJournal of Physical Chemistry A vol 101 no 20 pp 3823ndash38311997

[34] S Gunasekaran R Arun Balaji S Kumaresan G Anandand S Srinivasan ldquoExperimental and theoretical investigationsof spectroscopic properties of N-acetyl-5-methoxytryptaminerdquoCanadian Journal of Analytical Sciences and Spectroscopy vol53 no 4 pp 149ndash162 2008

[35] P Hohenberg and W Kohn ldquoInhomogeneous electron gasrdquoPhysical Review vol 136 no 3 pp B864ndashB871 1964

[36] R G Pearson ldquoAbsolute electronegativity and absolute hard-ness of Lewis acids and basesrdquo Journal of the American ChemicalSociety vol 107 no 24 pp 6801ndash6806 1985

[37] D Avci Y Atalay M Sekerci and M Dincer ldquoMolecular struc-ture and vibrational and chemical shift assignments of 3-(2-Hydroxyphenyl)-4-phenyl-1H-124-triazole-5-(4H)-thione byDFT and ab initio HF calculationsrdquo Spectrochimica Acta A vol73 no 1 pp 212ndash217 2009

[38] H O Kalinowski S Berger and S Braun Carbon13 NMRSpectroscopy John Wiley amp Sons Chichester UK 1988

[39] K Pihlaja and E Kleinpeter Carbon-13 NMR Chemical Shiftsin Structural and Sterochemical Analysis VCH PublishersDeerfield Beach Fla USA 1994

[40] P S Kalsi Spectroscopy of Organic Compounds New AgeInternational 2004

[41] A F Parsons Keynotes in Organic Chemistry Blackwell Pub-lishing Oxford UK 2003

[42] M A Palafox ldquoScaling factors for the prediction of vibrationalspectra I benzenemoleculerdquo International Journal of QuantumChemistry vol 77 no 3 pp 661ndash684 2000

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Page 17: Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. · Molecular Structure, NMR, HOMO, LUMO, ... ects of carbonyl and methyl substitutions

Journal of Spectroscopy 17

Calculated 13C NMR chemical shifts (ppm)

Expe

rimen

tal1

3C

NM

R ch

emic

al sh

ifts (

ppm

) 180

170

160

150

140

130

120

110110

120 130 140 150 160 170

(a)

Calculated 1H NMR chemical shifts (ppm)

Expe

rimen

tal1

H N

MR

chem

ical

shift

s (pp

m)

11

10

9

8

7

7 8 9 10 11 12 13

(b)

Figure 9 Plot of the calculated versus the experimental 13C NMR and 1H NMR chemical shifts (ppm) for Anisic acid

determining the zero-point vibration energies (ZPVE) andthe entropy 119878vib(119879) The total energies and the change inthe total entropy at room temperature using B3LYP6-31Glowastlowastmethod are presented

7 Conclusion

Attempts have been made in the present work for the molec-ular parameters and frequency assignments for the com-pounds OAA and AA from the FTIR and FT-Raman spectraThe equilibrium geometries and harmonic and anharmonicfrequencies for the title compounds were determined andanalyzed at DFT level of theory utilizing 6-31Glowastlowast basis setThe assignments of most of the fundamentals of the titlecompounds provided in this work are quite comparableThe excellent agreement of the calculated and observedvibrational spectra reveals the advantages of a smaller basisset for quantum chemical calculations HOMO and LUMOenergy gap explains the eventual charge transfer interactionstaking place within the molecule The experimental andtheoretical investigation of the title compounds have beenperformed successfully by using 1H and 13C NMR Thevarious modes of vibrations were unambiguously assignedon the basis of the result of the PED output obtainedfrom normal coordinate analysis These studies confirm thepresence of COOH and OCH

3group Dimeric molecules are

held together by hydrogen bridges between carbonyl groupsThe obtained data and simulations both show the way to thecharacterization of the molecules and help in spectra studiesin the future

References

[1] GMelentyeva and LAntonovaPharmaceutical ChemistryMirPublishers Moscow Russia 1988

[2] ldquoo-Anisic acid(579-75-9) catalog of chemical suppliersrdquo httpwwwchemexpercomchemicalssuppliercas579-75-9html

[3] B A Hess Jr L J Schaad P Carsky and R Zaharaduick ldquoAbinitio calculations of vibrational spectra and their use in theidentification of unusual moleculesrdquo Chemical Reviews vol 86no 4 pp 709ndash730 1986

[4] P Pulay X Zhou and G Forgarasi in Recent Experimental andComputational Advances in Molecular Spectroscopy R Faustoand R Fransto Eds vol 406 ofNATOASI Series p 99 KluwerDordrecht Netherlands 1993

[5] P Pulay G Fogarasi G Pongor J E Boggs and A VarghaldquoCombination of theoretical ab initio and experimental infor-mation to obtain reliable harmonic force constants ScaledQuantum Mechanical (SQM) force fields for glyoxal acroleinbutadiene formaldehyde and ethylenerdquo Journal of the Ameri-can Chemical Society vol 105 no 24 pp 7037ndash7047 1983

[6] C E Blom and C Altona ldquoApplication of self-consistent-fieldab initio calculations to organic moleculesrdquo Molecular Physicsvol 31 no 5 pp 1377ndash1391 1976

[7] G Fogarasi and P Pulay in Vibrational Spectra and Structure JR Durig Ed vol 14 Elsevier Amsterdam Netherlands 1985

[8] G Fogarasi ldquoRecent developments in the method of SQM forcefields with application to 1-methyladeninerdquo Spectrochimica ActaA vol 53 no 8 pp 1211ndash1224 1997

[9] G R deMare N Yu Panchenko andW Ch Bock ldquoAnMP26-31GlowastMP26-31Glowast vibrational analysis of s-trans- and s-cis-acryloyl fluoride CH2=CH-CF=Ordquo The Journal of PhysicalChemistry vol 98 no 5 pp 1416ndash1420 1994

[10] G Pongor P Pulay G Fogarasi and J E Boggs ldquoTheoreticalprediction of vibrational spectra 1 The in-plane force fieldand vibrational spectra of pyridinerdquo Journal of the AmericanChemical Society vol 106 no 10 pp 2765ndash2769 1984

[11] Y Yamakitu and M Tasumi ldquoVibrational analyses of p-benzoquinodimethane and p-benzoquinone based on ab initioHartree-Fock and second-order Moller-Plesset calculationsrdquoThe Journal of Physical Chemistry vol 99 no 21 pp 8524ndash85341995

18 Journal of Spectroscopy

[12] M Karabacak A Coruh and M Kurt ldquoFT-IR FT-RamanNMR spectra and molecular structure investigation of 23-dibromo-N-methylmaleimide a combined experimental andtheoretical studyrdquo Journal of Molecular Structure vol 892 no1ndash3 pp 125ndash131 2008

[13] M S Masoud M K Awad M A Shaker and M M T El-Tahawy ldquoThe role of structural chemistry in the inhibitiveperformance of some aminopyrimidines on the corrosion ofsteelrdquo Corrosion Science vol 52 no 7 pp 2387ndash2396 2010

[14] M J Frisch G W Trucks H B Schlegel et al Gaussian 03Revision B4 Gaussian Inc Pittsburgh Pa USA 2003

[15] P L Polavarapu ldquoAb initio vibrational Raman and Ramanoptical activity spectrardquo Journal of Physical Chemistry vol 94no 21 pp 8106ndash8112 1990

[16] G Keresztury S Holly J Varga G Besenyei A Wang andJ R Durig ldquoVibrational spectra of monothiocarbamates-IIIR and Raman spectra vibrational assignment conforma-tional analysis and ab initio calculations of S-methyl-NN-dimethylthiocarbamaterdquo Spectrochimica Acta A vol 49 no 13-14 pp 2007ndash2017 1993

[17] G Keresztury ldquoRaman spectroscopy theoryrdquo in Handbook ofVibrational Spectroscopy J M Chalmers and P R Griffths Edsvol 1 p 71 John Wiley and Sons 2002

[18] R G Parr R A Donnelly M Levy and W E Palke ldquoElec-tronegativity the density functional viewpointrdquo The Journal ofChemical Physics vol 68 no 8 pp 3801ndash3807 1977

[19] R G Parr and R G Pearson ldquoAbsolute hardness companionparameter to absolute electronegativityrdquo Journal of theAmericanChemical Society vol 105 no 26 pp 7512ndash7516 1983

[20] R G Pearson ldquoAbsolute electronegativity and hardness appli-cation to inorganic chemistryrdquo Inorganic Chemistry vol 27 no4 pp 734ndash740 1988

[21] P Geerlings F De Proft and W Langenaeker ldquoConceptualdensity functional theoryrdquo Chemical Reviews vol 103 no 5 pp1793ndash1873 2003

[22] R Ditchfield ldquoMolecular orbital theory of magnetic shieldingand magnetic susceptibilityrdquo Journal of Physical Chemistry vol56 no 11 article 5688 4 pages 1972

[23] KWolinski J F Hilton and P Pulay ldquoEfficient implementationof the gauge-independent atomic orbital method for NMRchemical shift calculationsrdquo Journal of the American ChemicalSociety vol 112 no 23 pp 8251ndash8260 1990

[24] M Kurt M Yurdakul and S Yurdakul ldquoMolecular structureand vibrational spectra of 3-chloro-4-methyl aniline by densityfunctional theory and ab initio Hartree-Fock calculationsrdquoJournal of Molecular Structure vol 711 no 1ndash3 pp 25ndash32 2004

[25] D Steele and D H Whiffen ldquoThe vibration frequencies ofpentafluorobenzenerdquo Spectrochimica Acta vol 16 no 3 pp368ndash375 1960

[26] D N Sathyanarayanan Vibrational Spectroscopy Theory andApplication New Age International publishers New DelhiIndia 1996

[27] L D S YadavOrganic Spectroscopy Springer NewDelhi India2004

[28] J Mohan Organic Spectroscopy Principles and ApplicationsNarosa Publishing House New Delhi 2nd edition 2009

[29] R M Silverstein G C Bassler and T C Morrill SpectrometricIdentification of Organic Compounds John Wiley amp Sons NewYork NY USA 1981

[30] G Socrates Infrared Characteristic Group Frequencies WileyNew York NY USA 1980

[31] R S Mulliken ldquoElectronic population analysis on LCAO-MOmolecular wave functionsrdquoThe Journal of Chemical Physics vol23 no 10 pp 1833ndash1840 1955

[32] K Fukuli T Yonezawa and H Shingu ldquoA molecular orbitaltheory of reactivity in aromatic hydrocarbonsrdquo Journal ofPhysical Chemistry vol 20 no 4 article 722 4 pages 1952

[33] C H Choi and M Kertesz ldquoConformational information fromvibrational spectra of styrene trans-stilbene and cis-stilbenerdquoJournal of Physical Chemistry A vol 101 no 20 pp 3823ndash38311997

[34] S Gunasekaran R Arun Balaji S Kumaresan G Anandand S Srinivasan ldquoExperimental and theoretical investigationsof spectroscopic properties of N-acetyl-5-methoxytryptaminerdquoCanadian Journal of Analytical Sciences and Spectroscopy vol53 no 4 pp 149ndash162 2008

[35] P Hohenberg and W Kohn ldquoInhomogeneous electron gasrdquoPhysical Review vol 136 no 3 pp B864ndashB871 1964

[36] R G Pearson ldquoAbsolute electronegativity and absolute hard-ness of Lewis acids and basesrdquo Journal of the American ChemicalSociety vol 107 no 24 pp 6801ndash6806 1985

[37] D Avci Y Atalay M Sekerci and M Dincer ldquoMolecular struc-ture and vibrational and chemical shift assignments of 3-(2-Hydroxyphenyl)-4-phenyl-1H-124-triazole-5-(4H)-thione byDFT and ab initio HF calculationsrdquo Spectrochimica Acta A vol73 no 1 pp 212ndash217 2009

[38] H O Kalinowski S Berger and S Braun Carbon13 NMRSpectroscopy John Wiley amp Sons Chichester UK 1988

[39] K Pihlaja and E Kleinpeter Carbon-13 NMR Chemical Shiftsin Structural and Sterochemical Analysis VCH PublishersDeerfield Beach Fla USA 1994

[40] P S Kalsi Spectroscopy of Organic Compounds New AgeInternational 2004

[41] A F Parsons Keynotes in Organic Chemistry Blackwell Pub-lishing Oxford UK 2003

[42] M A Palafox ldquoScaling factors for the prediction of vibrationalspectra I benzenemoleculerdquo International Journal of QuantumChemistry vol 77 no 3 pp 661ndash684 2000

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Page 18: Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. · Molecular Structure, NMR, HOMO, LUMO, ... ects of carbonyl and methyl substitutions

18 Journal of Spectroscopy

[12] M Karabacak A Coruh and M Kurt ldquoFT-IR FT-RamanNMR spectra and molecular structure investigation of 23-dibromo-N-methylmaleimide a combined experimental andtheoretical studyrdquo Journal of Molecular Structure vol 892 no1ndash3 pp 125ndash131 2008

[13] M S Masoud M K Awad M A Shaker and M M T El-Tahawy ldquoThe role of structural chemistry in the inhibitiveperformance of some aminopyrimidines on the corrosion ofsteelrdquo Corrosion Science vol 52 no 7 pp 2387ndash2396 2010

[14] M J Frisch G W Trucks H B Schlegel et al Gaussian 03Revision B4 Gaussian Inc Pittsburgh Pa USA 2003

[15] P L Polavarapu ldquoAb initio vibrational Raman and Ramanoptical activity spectrardquo Journal of Physical Chemistry vol 94no 21 pp 8106ndash8112 1990

[16] G Keresztury S Holly J Varga G Besenyei A Wang andJ R Durig ldquoVibrational spectra of monothiocarbamates-IIIR and Raman spectra vibrational assignment conforma-tional analysis and ab initio calculations of S-methyl-NN-dimethylthiocarbamaterdquo Spectrochimica Acta A vol 49 no 13-14 pp 2007ndash2017 1993

[17] G Keresztury ldquoRaman spectroscopy theoryrdquo in Handbook ofVibrational Spectroscopy J M Chalmers and P R Griffths Edsvol 1 p 71 John Wiley and Sons 2002

[18] R G Parr R A Donnelly M Levy and W E Palke ldquoElec-tronegativity the density functional viewpointrdquo The Journal ofChemical Physics vol 68 no 8 pp 3801ndash3807 1977

[19] R G Parr and R G Pearson ldquoAbsolute hardness companionparameter to absolute electronegativityrdquo Journal of theAmericanChemical Society vol 105 no 26 pp 7512ndash7516 1983

[20] R G Pearson ldquoAbsolute electronegativity and hardness appli-cation to inorganic chemistryrdquo Inorganic Chemistry vol 27 no4 pp 734ndash740 1988

[21] P Geerlings F De Proft and W Langenaeker ldquoConceptualdensity functional theoryrdquo Chemical Reviews vol 103 no 5 pp1793ndash1873 2003

[22] R Ditchfield ldquoMolecular orbital theory of magnetic shieldingand magnetic susceptibilityrdquo Journal of Physical Chemistry vol56 no 11 article 5688 4 pages 1972

[23] KWolinski J F Hilton and P Pulay ldquoEfficient implementationof the gauge-independent atomic orbital method for NMRchemical shift calculationsrdquo Journal of the American ChemicalSociety vol 112 no 23 pp 8251ndash8260 1990

[24] M Kurt M Yurdakul and S Yurdakul ldquoMolecular structureand vibrational spectra of 3-chloro-4-methyl aniline by densityfunctional theory and ab initio Hartree-Fock calculationsrdquoJournal of Molecular Structure vol 711 no 1ndash3 pp 25ndash32 2004

[25] D Steele and D H Whiffen ldquoThe vibration frequencies ofpentafluorobenzenerdquo Spectrochimica Acta vol 16 no 3 pp368ndash375 1960

[26] D N Sathyanarayanan Vibrational Spectroscopy Theory andApplication New Age International publishers New DelhiIndia 1996

[27] L D S YadavOrganic Spectroscopy Springer NewDelhi India2004

[28] J Mohan Organic Spectroscopy Principles and ApplicationsNarosa Publishing House New Delhi 2nd edition 2009

[29] R M Silverstein G C Bassler and T C Morrill SpectrometricIdentification of Organic Compounds John Wiley amp Sons NewYork NY USA 1981

[30] G Socrates Infrared Characteristic Group Frequencies WileyNew York NY USA 1980

[31] R S Mulliken ldquoElectronic population analysis on LCAO-MOmolecular wave functionsrdquoThe Journal of Chemical Physics vol23 no 10 pp 1833ndash1840 1955

[32] K Fukuli T Yonezawa and H Shingu ldquoA molecular orbitaltheory of reactivity in aromatic hydrocarbonsrdquo Journal ofPhysical Chemistry vol 20 no 4 article 722 4 pages 1952

[33] C H Choi and M Kertesz ldquoConformational information fromvibrational spectra of styrene trans-stilbene and cis-stilbenerdquoJournal of Physical Chemistry A vol 101 no 20 pp 3823ndash38311997

[34] S Gunasekaran R Arun Balaji S Kumaresan G Anandand S Srinivasan ldquoExperimental and theoretical investigationsof spectroscopic properties of N-acetyl-5-methoxytryptaminerdquoCanadian Journal of Analytical Sciences and Spectroscopy vol53 no 4 pp 149ndash162 2008

[35] P Hohenberg and W Kohn ldquoInhomogeneous electron gasrdquoPhysical Review vol 136 no 3 pp B864ndashB871 1964

[36] R G Pearson ldquoAbsolute electronegativity and absolute hard-ness of Lewis acids and basesrdquo Journal of the American ChemicalSociety vol 107 no 24 pp 6801ndash6806 1985

[37] D Avci Y Atalay M Sekerci and M Dincer ldquoMolecular struc-ture and vibrational and chemical shift assignments of 3-(2-Hydroxyphenyl)-4-phenyl-1H-124-triazole-5-(4H)-thione byDFT and ab initio HF calculationsrdquo Spectrochimica Acta A vol73 no 1 pp 212ndash217 2009

[38] H O Kalinowski S Berger and S Braun Carbon13 NMRSpectroscopy John Wiley amp Sons Chichester UK 1988

[39] K Pihlaja and E Kleinpeter Carbon-13 NMR Chemical Shiftsin Structural and Sterochemical Analysis VCH PublishersDeerfield Beach Fla USA 1994

[40] P S Kalsi Spectroscopy of Organic Compounds New AgeInternational 2004

[41] A F Parsons Keynotes in Organic Chemistry Blackwell Pub-lishing Oxford UK 2003

[42] M A Palafox ldquoScaling factors for the prediction of vibrationalspectra I benzenemoleculerdquo International Journal of QuantumChemistry vol 77 no 3 pp 661ndash684 2000

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Page 19: Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. · Molecular Structure, NMR, HOMO, LUMO, ... ects of carbonyl and methyl substitutions

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of