Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. ·...
Transcript of Research Article Molecular Structure, NMR, HOMO, LUMO, and Vibrational … · 2019. 7. 31. ·...
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
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Carbohydrate Chemistry
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Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Quantum Chemistry
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CatalystsJournal of
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
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CatalystsJournal of
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
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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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
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
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CatalystsJournal of
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
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CatalystsJournal of
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
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Carbohydrate Chemistry
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Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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CatalystsJournal of
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
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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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Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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CatalystsJournal of
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
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
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
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Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Journal of
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Analytical ChemistryInternational Journal of
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Quantum Chemistry
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Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
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
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Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
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Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
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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
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
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
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
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
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
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
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
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
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
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