VOBRAU0OMAL SPECTRA AND ANALYSIS SOME DO-FLUOR0...

CHAPTER - 3

VOBRAU0OMAL SPECTRA AND ANALYSIS

OF SOME DO-FLUOR0 PHENOLS

74

VIBRATIONAL SPECTRA AND ANALYSIS OF SOME

DI-FLUORO PHENOLS

INTRODUCTION

Phenols are organic compounds that contain a hydroxyl group (-OH)

bound directly to a carbon atom in the benzene ring. Unlike nonnal alcohols,

phenols are acidic because of the influence of the aromatic ring. Phenols are

made by fusing a sulphonic acid with sodium hydroxide to form the sodium

salt of the phenol. The free phenol is liberated by adding sulphuric acid. It is

used as anti-bacterial and anti-septic and also for the treatment of surgical

instruments and bandaging materials [I].

Halogination of phenol derivatives produces active substances with

substantially high anti-microbial effect. The degree of dissociation of

haloginated phenol derivatives increases with the number of halogen atoms.

The combination of akylation and halogenations, in particular the later

produces phenolic rnicrobicides which are used as active disinfectants and for

the preservation of materials. Chlorophenol is an important group of industrial

chemical which got variety of uses ranging from preparation of preservatives to

insecticides. But they show high oral toxicity and were almost not biologically

degradable [2 ] .

7 5

However, with few exceptions. organic fluorine compounds which

are physiologically inert, display insignificant toxicity. This is a consequence

of the chemical stability of the C - F bond and the increased stability of

hydrogen and halogen bonds attached to a fluorinated carbon atom [3]. Low

toxicity is an important factor in many applications like agricultural chemicals,

pharmaceuticals, biocides, and dyes. Due to low toxicity and wide ranging

applications of fluorine derivatives of phenol, we conducted a through

vibrational analysis of four di-fluoro phenol compounds in order to understand

the molecular dynamics of phenol derivatives as a whole.

The vibrational spectra of phenol and phenol-OD were studied by

Evans [4]. He reported the Raman specixa (liquid phase) with depolarization

measurements and infrared spectra (vapour, solution, liquid and solid phase) in

the 300 - 3800 cm-' region for phenol and phenol - OD. A complete

vibrational assignment for phenol was proposed and a value of 3.37 Kcal/mole

was determined for the barrier to internal rotation about the C- 0 bond.

Thermodynamic functions for phenol as an ideal vapour at 1 atm. pressure was

calculated.

Hidalgo et al. [5] studied the infra red absorption spectra of phenol

and three diphenols namely Procatechine, Resoreine, Hydroquinone. They

investigated the said compounds in the frequency range 2 and 40 pm (5000 -

250 cm-I). The spectra obtained for the solids in KBr disks in mulls and as

frozen melts were compared. An attempt was made to assign the measured

frequencies to different modes of vibrations of these molecules. The

7 6

fundamental vibrations of the phenol and diphenols were also compared with

that of the benzene vibrations.

Green et a1 [6] reported the complete assignment of fifteen mono

substituted phenols. They presented the Infrared spectra (in the region 3650 -

50 cml) and Rarnan spectra for the compounds o-, m- or p- XC6H40H (X =

CH3, F, C1, Br, I). The infrared spectra were recorded for the above compounds

as dilute solution, and in carbon tetrachloride, carbon disulfide and

cyclohexane. The Raman spectra were recorded for the liquid states of the

compounds and the Raman data were used for identifying several of the

fundamentals relating to the aromatic ring. All the fundamental frequencies

have been assigned properly in this work.

A complete vibrational study of three dimethyl phenols and three

dichlorophenols was reported by Green et a1 [7]. In this paper the results of the

vibrational spectra of the six dimethylphenols (xylenols) and of 2,6-, 2,5- and

3,4- dichlorophenol were presented. Infrared spectra, in the region 3650 - 50

crn", of these compounds as solid, liquid and saturated solution were recorded,

together with the Raman spectra of dimethyl compounds as liquids or saturated

solutions. The interpretations were made utilizing the results of previous

studies of several tri-substituted benzenes and mono substituted phenols. With

the aid of these and of additional infrared spectra of the o-deutrated derivatives

of the four of the compounds, the majority of all the compounds located

without ambiguity. The doubts in the assignment of the OH-in plane, 6(OH),

and out-of-plane (torsional), y(OH) and bending vibrations were settled by

proper assignments. '

Laser Rarnan spectra of 2,4- dibromophenols and 2,2'-

dibromophenols was reported by Mohan [8]. The spectra were recorded in the

region 200 to 4000 cm-' on a carry model 82 grating spectrophotorneter with an

Argon Laser source. The observed frequencies have been assigned to the

various modes of vibrations in terms of fundamentals assuming Cs and C2,

point group symmetry. The assignments made were cross checked with the

literature values of similar compounds and found to be agreeing well with the

earlier works.

The near Ultraviolet absorption spectrum of o-aminophenol [9] were

studied by Sharma et a1 in the vapour phase using a Hilger hydrogen lamp as

the source of continuum. Two systems of discrete absorption bands were

observed and reported by them. The first system of bands in the region 3020 -

2905 A were interpreted with four ground state and eight excited state

fundamentals. The second system in the region 2770 - 2610 A has been

interpreted with one ground state (294 cm-') and seven excited state

fundamentals.

Dwivedi et a1 [lo] recorded and analysed the Infrared absorption

spectra of 2,4 - dibromo phenols and 2,6-dibrmophenols. They recorded the

spectra in the region 200 - 4000 cm-' taking the samples as dilute solutions.

The spectra were analysed assuming Cs symmetry for 2,4 - dibromophenol and

7 8

C2v symmetry for 2,6-dibrmophenol. The observed fundamental vibrations

have been approximately assigned to the normal modes of vibrations of the

molecules under study. In making the assignments the authors had used the

data from the related molecules such as dibrmobenzene, bromophenol, and

dichlorophenol.

Mallick et a1 1111 studied the Infrared, Rarnan and ultraviolet spectra

of 2-bromo-4-chloro phenol and 2-chloro-4- bromo phenol. They analysed the

vibrational spectra of both the compounds and carried out assignments for the

fundamental vibrational frequencies assuming Cs point group symmetry. In the

ultraviolet absorption spectra of both the compounds, two systems of bands

corresponding to l ~ b and l ~ a of benzene was observed. They carried

successful assignments of the UV spectra in comparison with that of the

vibrational spectra.

The Infrared spectra of 2,3,4- and 2,3,6-Trichlorophenols have been

reported by Tripathi et a1 [12]. He had obtained the IR spectra using Beckman

IR-12 spectrophotometer in nujol mull using KBr optics in the region 200 -

4000 cm-l. The complete vibrational analysis has been proposed in terms of

fundamentals, combinations and overtones. The probable modes of vibrations

for most of the fundamentals are also discussed. He has compared the

vibrations of trichlorophenols with that of benzene and dichlorophenols taken

from literatures.

Suraj La1 Srivastava [13] reported the vibrational spectra of 2,3-, 2,4-

and 2,5- dichlorophenols. The infrared spectra of all the three compounds were

recorded in the region 400 - 3800 cm-' in nujol mull phase on UR-10 Carl

Zeiss spectrophotometer, using interchangeable optics. Talung OH group as a

single mass point, the molecules are assumed to posses Cs point group

symmetry. The observed bands were analysed in terms of fundamentals, their

combinations and overtones. The probable modes of vibration of these

fundamentals were also discussed. Baruah et al [14] reported the near

Ultraviolet absorption spectrum of 2,4-dimethylphenol vapour.

Sanyal et a1 [17] analysed the near ultraviolet and infrared absorption

spectra of 3,5- Dichlorophenol. The discrete band system, of 3,5-diclorophenol,

an analogue of the electronically forbidden transition 1 ~ 2 u , t l ~ l g , of

benzene has been investigated in the region 2880 - 2640 A. Altogether 72

bands have been measured and the (0,O) band of the system were fixed at

35437 cm-l. The remaining band was explained in terms of three ground state

and six excited state frequencies. The infrared absorption spectrum of this

molecule has also been investigated in the frequency range 4000 - 300 cm-I.

The LR spectrum of the sample was recorded in the form of fine suspension in

Nujol mull. The observed IR vibrations were assigned to the fundamental

modes of molecular vibrations of the sample. Correlations of the Ultraviolet

frequencies were also presented with the infrared data. Kailash Chandra 1161

reported the electronic spectra of para-bromophenol.

The a* t n system in the electronic absorption spectra of some di-

substituted phenols was studied by Navati et al [17] [18]. These authors studied

the vapour phase electronic spectra of 2,4-, 2,5-, 3,4-, 3,5 - difluorophenols in

the region h = 2870 - 2470 A and given probable assignments of the observed

frequencies. M.S.Navati and M.A.Shashidhar reported the vibrational analysis

of 2,4-, 2,5-, 3,4-, 3,5 - difluoro phenols. They have also given the patial IR

and Raman data along with the electronic absorption spectral data and partially

assigned the frequencies to the vibrational modes of the compounds [19]. They

have not given a complete IR and Raman data's and their assignments also

were partial.

Literature survey shows that chloro-substituted phenol attracted a

large number of researchers than any other substituted phenols. This may be

due their wide-ranging applications in agricultural chemicals, pharmaceuticals,

biocides and dyes [2] . But only little work is found on the study of other

halogen substituted phenols like bromo-, fluoro- and iodo-phenols. Thus it is

felt that a complete vibrational analysis of four difluorophenols viz. 2,3 -

difluorophenols (2,3-DFP), 2,4 - difluorophenols (2,4-DFP), 2,4 -

difluorophenols (2,s-DFP), and 3,5 - difluorophenols (3,5-DFP) could add a

information in the understanding of the molecular dynamics of fluoro-phenols.

Hence in the present investigation the FTIR and FT Raman spectra of all the

four compounds mentioned above were recorded and an assignment of the

observed frequencies to the fundamental vibrational modes of the molecules

have been presented. In addition normal coordinate analyses of the compounds

Flg 3-9: Molecular Structure ol2,3-Dl-Fluoro Phenol

Flg 3-10: Molecular Str U C ~ U ~ Q of 2,rbDI-flu or^ phenol

Flg 3-1 1 : Molecular Structure of 2,SDI-Fluoro Phenol

Flg 3-12: Molecular Structure ol3,S.DI-Fluoro Phenol

under study were also made in order to provide a theoretical explanation to the

forces that holds the molecular field of difluorophenols.

EXPERIMENTAL DETAILS

The samples of the compounds under study were obtained in

spectroscopic grade from Aldrich Chemical Co. USA, and were used for

recording the spectra. Three of the four compounds 2,3-DFP, 2,5-DFP and 3,5-

DFP were in solid form and the compound, 2,4-DFP was in the liquid form.

Thus the FT Infrared Spectra were recorded for the solid samples in Nujol Mull

and the compound 2,4-DFP being in liquid form was used as such. The FTJR

spectra were recorded in on Bruker IFS 66V FTIR spectrometer in the region

4000 - 400 cm-'. The FT-Raman spectra of all the four compounds were also

recorded in the same instrument with FRA 106 Raman module equipped with

Nd:YAG laser source giving output at 10.6 pm lime with 200-rnw power. A

scanning speed of 30 cml mid1 of spectral width 2.0 cm-'was used to record

the spectra. The frequencies for all sharp bands were accurate to i 1 cnil The

FTIR spectra of 2,3- DFP, 2,4-DFP, 2,5-DFP, and 3,5-DFP is given in the

figure- 3-1 to 3-4 and the FT Raman spectra of the compounds are given in the

figure-3-5 to 3-8 respectively. The geometrical structure of the molecules is

shown in the figure-3-9 to 3-12 respectively along with the ball and stick figure

of the respective molecules.

NORMAL COORDINATE ANALYSIS

To present a complete plcture of the molecular forces holding the

dichloro phenols and phenolic compounds on the whole a normal cool-dmate

analysis was carned out. The normal coordinate analysis also prov~ded support

to the assignments of the observed frequencies to the fundamental vibrational

modes of the molecules under study. If the -OH group is considered as point

mass and as the -F substituents remain coplanar then the compounds 2,3- DFP,

2,4-DFP, 2,5-DFP may be considered as belonging to the Cs point group.

Because of the syrnmetncal nature of the -F subshtuents around the ring, the

compound 3,5-DFP could be considered to come under C2v point group. Total

of 30 fundamental vibrahons in each case will then be divided into the

vibrational species as under [22]:

Cs Point Group r = 21 A' + 9 A"

C2v Point group r = l lA l + 3A2 + 6B1 + 10B2

where A', A", A1, A2, B1 and B2 have their usual meaning. In addition there

will be three more vibrations due to OH group. All the vibrations are allowed

in the IR as well as in the Raman spectra except the A2 vibration in C2v point

group, which is forbidden in the IR spectrum but appears weakly in the Raman

spectrum.

Wilson's FG-Matrix method [21] was used for the normal coordinate

analysis using the observed vibrational frequencies. In the present work to

83

study the vibrational frequencies of dichlo~ophenol colnputel plogiam for

normal coordinate calculations developed by Fuhler et a1 [22] were suitably

modified and used. The internal coord~nates for the out-of-plane bending

vibrations are defined in accordance with the recommendations of IUPAC. The

structural parameters employed in the present work were taken from the

literatures: C-C = 1.401 A, C-H = 1.103 A, C-OH = 1.357 A, 0-H = 0.973 A, C-F = 1.351 and all the ring angles are 120". These values are cross-checked

with molecular modeling program [24]. The Simple General Valence Force

Field (SGVFF) was shown to be very effective in the normal coordinate

analysis [23] and thus the SGVFF is employed in the present work to express

the potential energy. It was also shown that the valence force constants could

be transfenred between the related molecules for carrying out the normal

coordinate analysis efficiently.

The initial set of valence force constants with a few off-diagonal

constants were transferred from related molecules. A zero-order calculation

with the transferred force constants was performed and except for

deformational modes and low frequency modes, the result showed a reasonable

agreement between the calculated and observed frequencies. The initial set of

force constants were subsequently refined by the least square technique. The

calculated frequencies from the final set of force constants gives a good

agreement with the observed frequencies and are given in the table - 3-1 to 3-4.

To check whether the chosen frequency contribute maximum to the potential

energy associated with normal co-ordinate of the molecules, the potential

energy distribution has been calculated. The highest PED contributions

84

col~esponding to each of the observed frequencies are alone listed in the tables.

The close agreement between the observed and calculated frequencies confirms

the validity of the present assignment.

VIBRATIONAL ASSIGNMENTS

The assignments were made on the basis of relative intensities of the

bands and magnitudes of the frequencies and assignments of molecules of

similar structure proposed by earlier workers. The vibrations of the molecule

under study are generally divided into two groups: (1) skeletal vibrations i.e.

the vibrations associated with the ring and (2) group vibrations due to the

substituents. Apart from assignments to fundamental vibrations attempt was

also made to assign the overtone and combination bands. Some of the

assignments are discussed in the following paragraphs. The assignments

pertaining to overtones and combination bands of the samples are not discussed

but are given in the Table -3-1 to 3-4.

SKELETAL VIBRATIONS

Carbon Virations

The characteristic skeletal stretching modes of carbon-cdon bond in

benzene v(C-C) give rise to two doubly degenerate vibrations eZg (1596 cm-l)

and e2, (1485 cm-l) and two non-degenerate mode b2, (1310 cm-') and a lg

(995 cml) [25]. The doubly degenerate vibration split up into two components

under reduced symmetry. In the case of di-substituted benzenes, it has been

suggested by Randle and Whiffin [26] that the components of doubly

8 5

degenerate vibrations appear in the range 1430 - 1630 cm-'. In the same line of

thought, the fundamentals at 1330, 1479, 1483, 1511, 1525 and 1626 cml in

2,3 DFP have been assigned to C - C stretching frequencies corresponding to

these modes of benzene. This assignment is quite in line with that of tri-

substituted benzenes [27]. Similarly, for the compounds 2,4-DFP the

frequencies assigned to the above modes are 1310, 1450, 1508, 1545, 1605 and

1790 cm". For the 2.5-DFP, the frequencies 1308, 1342, 1450, 1506, 1580 and

1607 cm-' and for the compound 3,5 DFP, the frequencies 1354, 1445, 1470,

1508, 1604 and 1625 were assigned to the modes discussed above. In all the

above compounds the C - C stretching frequencies are almost equal. This is

mainly because the actual positions are determined not so much by the nature

of substituents but by the form of substitution around the ring [28].

In the benzene the fundamentals alg (992 mi1) and blU (1010 cm-')

represent the ring breathing mode and carbon triogonal mode. Under the Cs

point group both the vibrations will have the same symmetry species A'. As the

energies of these vibrations are very close, there is an appreciable interaction

between three vibrations and consequently their energies will be modified [29].

The ring breathing vibrations of 2,3-DFP is assigned to 914 cm-'. In 2,4-DFP,

2,5-DFP and 3,5-DFP, it is assigned to 971, 969 and 925 cm-' respectively. The

trigonal vibrational mode are observed at 1055, 1054, 1075, 1117 cm-' in the

four molecules respectively. This assignment is in accordance with that of

Mecke & Rosmy [30] and Srivastava [13].

86

The in-plane carbon bending vibrations are derived from non-

degenerate b lu (1010 cm-') and degenerate e?, (606 cm' ) modes of benzene. -a

The e2, (606 cm-') degenerate frequency splits into two totally symmetric b

vibrations under Cs symmetry [30]. The frequencies observed at 521 & 572

cm-' in 2,3-DFP, 609 & 733 cm-' in 2,4-DFP and 618 & 625 cm-' in 2,5-DFP

are assigned to the degenerate frequencies corresponding e2, (606 cml) mode 0

of benzene.

The degenerate in-plane ring deformation e2, mode of benzene splits b

up into two components under C2" symmetry. In para di-substituted benzenes,

the higher cdmponent corrzsponding to e2, (608 cm-') of benzene appears 0

generally around 630 cm-' because the contribution of the atoms placed at the

para position is negligible. In the present case, the molecule 3,5-DFP is a tri-

substituted benzene, fluorine atoms in the 3 & 5 positions take part in

vibrations. Thus the higher component in the present case will also be a mass

dependent quantity and may decrease in magnitude while the lower component

may reduce appreciably because all the three substituents in this case will take

part in the vibration [15]. Thus, the infrared bands appearing at 615 and

599 cm-' in the spectrum of 3,5-DFP were assigned as the components of

e2g (608 cm-') mode of benzene.

The carbon out-of-plane vibrations are represented by the non-

degenerate b2 (703 cm-') and degenerate e2u (404 cm-') modes of benzene. g

The non-degenerate mode is found to be constant in substituted benzenes [32]

and in the present work, it falls at 506 c n ~ ' in 2,3-DFP cm", 580 crn-' in

2,4-DFP, 599 cm-' in 2.5-DFP and 567 cm-' in 3,5-DFP. The degenerate mode

, gets split up in all the compounds under study and seems to appear at e2b

4922 & 428 cm-' in 2,3-DFP, 557 & 505 cm-' in 2,4-DFP, 525 & 468 cm' in

2,5-DFP and 506 & 529 cm-l in 3,s-DFP. This assignment is in line with the

Dwivedi [lo], Mohan & Payami [3 11.

C - H Vibrations

The tri-substituted benzenes, which form the subject of the recent

investigation, give rise to three C-H stretchings, three C-H in-plane

deformations and three C-H out-of plane deformations. In aromatic

compounds, C-H stretching frequencies appears in the frequency range 3000 -

3 100 cm-' [33]. The aromatic C-H stsetchings is usually a band' of medium to

weak intensity. In view of this, the three infrared bands at 3040, 3060 & 3090

cm-l in 2.3-DFP, 3040, 3063 & 3082 cml in 2,4-DFP, 3045,3066 & 31 19 cm-I

in 2,5-DFP and 3005, 3020 & 3040 cml in 3,5-DFP were assigned to the C-H

stsetchings. In this region the bands are not appreciably affected by the nature

of the substituents. These assignments were found to be in line with Tripathi

et a1 [12], Srivastva [13] and Sanyal & Pandey [15].

The three in-plane C-H bending vibrations appear in the range 1000 -

1300 cml in the substituted benzenes and the three out-of-plane bending

vibrations occurs in the frequency range 750 - 1000 cm-' [34]. All these

frequencies are identified in the spectra of the samples taken for the study and

are in the expected frequency region and they are tabulated in the table- 2.1 to

table-2.4. They are in agreement with the literature values [14,15,17, 201

GROUP VIBRATIONS

0 - H Vibrations

Studies on the vibrational spectra of phenol and substituted phenols

[6, 30, 351 suggest that the 0-H valence stretching vibrations of the hydroxyl

group lies in the region 3300 - 3500 cm-'. On the basis of the available data

this vibration, in the present investigation, has been assigned to the 3373, 3383,

3395 and 3395 cm-' in the four samples of 2,3-DFP, 2,4-DFP, 2,5-DFP and

3,5-DFP respectively.

Kletz and Prize [36] pointed out that in substituted phenols a strong

band appears around 1300 cm-'. They suggested that it corresponds to the

valence vibration of the OH group in the aromatic ring and the 0-H

deformation mode has been suggested to lie near 1200 cm-'. This assignment

was also found support from Mecke and Rossmy [37]. Kletz and Price argued

that C-0 or C-OH stretching mode in phenols absorbs at higher frequencies

under the influence of the aromatic ring. There are therefore, possibilities of

coupling between the 0-H and C-OH frequency or between the C-OH

frequency and the aromatic ring vibrations. Mecke and Rossmy [37] have

accordingly assigned the higher of the two main frequencies of phenol to C-OH

stretching mode. They considered that the band at 1180cm-' possess strongest

OH character. This idea is also supported by the assignment made by

Srivastava [15] for dichlorophenols. In the present analysis C-OH stretching

89

mode is assigned to the 1306, 1290, 1275, and 1267 cm-' in the four

compounds respectively.

The bands in the region 200 - 400 cm-I are difficult to assign as most

of them are got interaction from other bands, as shown by PED calculations.

The bands at 168 cml in 2,3-DFP, 168 cm-' in 2,4-DFP, 177 cmW1 in 2,5-DFP

and 220 cm-' in 3,5-DFP are assigned as out-of-plane (0-H) deformation. This

assignments got support from Jakobsen's assignments [38] made for p-cresol.

The weak band at 292 cm-' in 2,3-DFP, 280 cm-' in 2,4-DFP, 285 cm-I in 2,5-

DFP and 352 cm-' in 3,5-DFP are assigned as (C-OH) in-plane bending. The

above-observed bands are assigned in view of the assignment by Tripathi et a1

[14] for trichlorophenols.

C-F Vibrations

The bands at 1278 & 1249 cm-l in 2,3-DFP, 1263 & 1229 cm-' in

2,4-DFP, 1183 & 1233 cml in 2,5-DFP and 1208 & 1242 cm' in 3,5-DFP are

assigned to the C-F stretching modes. This is in accordance with the

assignments made by Diwidi and Sharma [35] for fluoro-bromotoluenes and

Varsanyi [27] for o, p, & m-fluorobenzenes. The C-F in-plane bending

vibrations are assigned too the vibrational frequencies observed at 355 & 313

cm-* in 2,3-DFP, 354 & 423 cm-' in 2,4-DFP, 390 & 315 cm-' in 2,5-DFP and

428 & 458 cm-' in 3,5-DFP. The C-F out-of-plane bending frequencies are

identified in the Rarnan bands at 183 & 272 cml in 2,3-DFP, 27 1 & 221 cm-' in

2,4-DFP, 247 & 254 cm-' in 2,5-DFP and 275 & 265 cm-' in 3,5-DFP. The

9 0

assignments for both the in-plane and out-of plane C-F deformations are

agreeing well with the assignments made by the Navati et al. [20].

CONCLUSION

The present investigation analyzed thoroughly the vibrational spectra

of four difluorophenols viz. 2,3-DFP, 2,4-DFP, 2,5-DFP and 3,5-DFP . Some

of the assignments, which were doubted in the earlier works, were reassigned

properly without ambiguity. Nolmal coordinate analysis was carried for the

first time for all the four compounds and the results were found interesting. The

PED calculated to check the colrectness of the chosen set of assignments reveal

the purity of the mode.

(Ole) 33NVlLI WSN VUL

TABLE- 3.1

OBSERVED AND CALCULATED FREQUENCIES AND POTENTIAL ENERGY DISTRIBUTION FOR 2,3 - DIFULORO PHENOL

PED %

87 VOH

91 VCH

86 VCH

88 VCH

91 vcc

8 1 vcc 74 vcc 79 vcc

84 vcc 88 vcc 68 ~ c . 0 ~ +14 vcc

88 VCF

81 VCE

74 PCH t. 16 PCcC 80 PcH 94 Pccc

* a2 .1 u - cn

- A' A ' - A' A' -

- - - - - - - - -

A' - A' A' A' A' A' A' A' A' A' A' A'

Wave number (cm-')

3370 3088 3055 3033

1621

1522 1510 1478 1470 1328 1309 1274 1241 1 170 1 140 1056

Assignments

(2 x 1330) + 914 0-H stretching C - H stretching C - H stretching C- H sttetching (2 x 1150) + 700 1306 t 1626 1278 + 1626 1249 t 1626 2 x 1278 1182 t1249 2 x 1150 1014 + 914 2 x 1014 (2 x 428) t 810 C = C stretching 2 x 770 C = C stretching C = C stretching C - C stretching C - C stretchg C - C stretchg C-OH stretching C-F stretching C-F stretching C-H in-plane bending C-H in-plane bending C-C-C trigonal bending

Observed Wave Number &

Rel. Intensit Infrared

cm-'

3576m 3373 s, Br

3060m 3040 m 2998m 2933 w 2900 vw 2877 w 2 5 5 1 ~ ~ 2442 vw 2305 vw 1 9 1 2 ~ 1 8 1 7 ~ ~ 1675m 1626 s 1567 w 1525vs 1511vs 1483vs 1479 vs 1330 s 1306 s 1278 s 1249m 1 182 s 1150 m 1055111

R:man . em-'

- -

3090 s -

3040 w - -

-

- - - - - - - 1624 w - - - - -

1332 m 1311 m 1280 w - 1 171 w 1155 vw 1057s

Notations: vw - very weak, w - weak, m - medium, s - strong, vs - very strong, sh - shoulder, br - broad, v - stretching, P - in-plane bending, q - out- of-plane bending, p - rocking, 6 - scissoring, o - wagging, z - torsion.

vl w .- u w

A'

A'

A

A

A

A'

A'

A ' -

A"

A"

A"

A ' -

A ' -

A ' -

* A"

A"

Wave

(cm-')

101 1

9 12

860

819

774

699

575

520

508

491

420

352

3 10

288

264

170

148

Observed WaveNumber&

Assignments

C-H in-plane bending

C-C-C rlng breathmg

C-H out-of-plane bending


C-H out-of-plane bendmg

C-C-C in-plane bending



C-C-C out-of-plane bendlng

C-C-C out-of-plane bending


C-F in-plane bending


C-OH in-plane bending

C-F out-of-plane bending


C-OH out-of-plane bending

Rel. Infrared

cm-'

1014vs

914w

867 w

815m

770s

700 s

572w

506 w

492 vw

428 vw

-

-

-

PED %

81 PCH 92 Pccc

74 q c ~

61 ~ C H + 14 ~ C C C

60 ~ C H + 26 ~ C C C

69 pccc

74 PCCC 8 1 PCCC 64 q c c ~

59 qc-c

5 1 ~ C C C + 19 ~ C H

64 PCF 71 PCF 49 P c - o K t l O pccc

54 qc-

50 ~ C F

46qc.013 +26 ~ C C C

Intensit R a i a n

cm-'

-

-

-

824s

775 w

698 vs

577 m

521 m

506 m

490 w

425 w

355 vw

313 m

292 w

272 s

183 w

168 vw

OBSERVED AND CALCULATED FWQUENCIES AND POTENTIAL ENERGY DISTRIBUTION FOR 2,4 - DIFLUORO PHENOL

m a, o

2

- - A' A'- A' A' - - - - - - - - A' A' A' A' A' A' A' A' A' A' A' A' A' A' A"

2 x 1229 + 1196 2 x 1790 O-H stretching C - H stretching C - H stretching C - H stretching 1310 + 1605 1290 -t 1605 1229+ 1605 1310 + 1450 1054 + 1605 1054 + 1290 2 x 1054 733 + 1100 C = C stretching C = C stretching C = C stretching C - C stretching ,

C - C stretching C - C stretching C - OH stretching C-I? stretching C-F stretching C-H in-plane bending C-H in-plane bending C-H in-plane bending C-C-C triogonal bending C-C-C ring breathing C-H out-of-plane bending

-

84 VOH

89 VCH

92 VCH

80 VCH

-

- -

88 vcc 81 vcc 74 vcc 89 vcc

91 vcc 80 vcc 70 vc.0~ + 22 vcc 81 VCF

80 VCF

74 Pca 79 PCH 66 Pca + 20 PC( 88 PCCC 92 Bccc 72 ~ C H

Calculated Wave

number (cm-')

-

3381 3080 3060 3032

-

1784 1601 1541 1502 1441 1308 1281 1260 1221 1186 1155 1095 1051 970 921

Observed Wave

Rel. Infrared

cm-'

3 6 5 0 ~ 3567 w 3383 s, br

3 0 6 3 ~ 3 0 4 0 ~ 2 9 7 0 ~ 2896 w 2825 vw 2767 vw 2 6 5 8 ~ 2342 w 2092 w 1 8 3 3 ~ 1790vw 1605s 1545s,sh 1508 vs 1450s 1310s 1290s 1263 m 1229w 1196m 1160vs 1100s 1 0 5 4 ~ 971 vs 9 2 5 ~ ~

Number & Intensity

Raman cm-'

- - -

3082 s -

- - - - - - - - - -

1607m - - -

1308w 1285111 1262 w 1226w 1195w 1161w 1094w - 967 m -

I I Observed I Y. I Wave N~tnber &

Notations: vw - very weak, w - weak, m - medium, s - strong, vs - very strong, sh - shoulder, br - broad, v - stretching, P - in-plane bending, 7 - out- of-plane bending, p - rocking, 6 - scissoring, o - wagging, z - torsion.

Calculated Wave

number (cm-')

851

8 1 1

790

729

6 17

571

550

499 -

41 6

350 -

271

I ;'" /"t-of-plane bending 1 52 TCF 1 -OH out-of-plane bending 6 q C - O ~ +30 qccc

Assignments

C- H out-of-plane bending C-H out-of-plane bending






C-C-C out-of-plane bending 271+221



2x168

C-OH in-plane bending -F out-of-plane bending

FED %

69 ~ C H

50 VCH

66 Pccc + 20 PCH 74 Pccc

80 Pccc

54 qccc

49 ~ C C C + 26 ~ C H

58 qccc -

66 PCF 54 PCF

49 PC-OH +32 bccc

50 VCF

OBSERVED AND CALCULATED FREQUENCIES AND POTENTIAL ENERGY DISTRIBUTION FOR 2,5 - DIFLUORO PHENOL

Assignments

2 ~ 1 2 3 3 + 1 1 8 3

2 x 1233 t- 1108

0-H stretching

C-Hstretching

C- H stretching C - H stretching

1233 + 1607 1308 + 1342

1108 + 1275

1108 + 729 C = C stretching

C = C stretching

2 x 770 C = C stretching

2 x 729

C - C stretching

C - C stretching

C-Cstretching

C-OH stretching

C-F stretching

C-Fstretching C-H in-plane bending

C-H in-plane bending C-H in-plane bending

C-C-C triogonal bending

C-C-C sing breathing

Calculated Wave

number (em-')

-

3391

3 114

3070

3040 -

1601

1575 -

1501 -

1450

1338

1305

1270

1228

1180

1165

1140

1101

1071

968

.- u a 3

- -

A'

A' A' A' - -

- -

-

A' A'- -

A' -

A' A'

A' A' A' A'

A ' - A' A' A'

A'

PED %

-

86 VOH

90 VCH

81 VCH

86 VCH

90 k c

87 vcc

71 vcc

82 vcc

74 vcc

90 vcc 7 4 ~ ~ - O H + 20 vcc

80 VCF

74 VCF

78 PCH 68 PCH 64 PCH f 32 Pccc

90 Pccc

92 PCCC

Observed Wave

Rel. Infrared

ern-'

3658 w

3567m

3395s,br

3119m

3066 m 3045w -

2833 vw

2650 vw

2 3 8 0 ~ ~

1 8 3 7 ~ 1607 vs

1530 W , S ~ 1506vs

1465m

1450 s 1342 m,br

1308s

1275 m

1233 vs

1183m

1146 vs

1108 s

1075vw

969 vs

Number & Intensity

Raman c,,-i

-

-

-

3112w

3075 m 3044w

-

- -

1704w 1608 w

1580 w - - -

1455 w -

1310m 1274 w 1231 w

1181w

1170 m

1149 w

1105 m - 967 s

Notations: vw - very weak, w - weak, m - medium, s - strong, vs - very strong, sh - shoulder, br - broad, v - stretching, P - in-plane bending, 7 - out- of-plane bending, p - rocking, 6 - scissoring, o - wagging, z - torsion.

m a

'5 QJ

8

A'

A"

A"

A'

A'

A'

A"

A"

A"

A ' -

A ' -

A"

A"

A"

Calcupdted Wave

number (cm-')

840

800

771

725

690

6 18

6 10

591

526

460

392

307

280

248

23 1

169


Assignments





390+315












Rel. Infrared

cm-'.

842 w

808 s

770 s

729 s

625 m

6 18 w

-

525vw

468 w

A ' -

-

- -

PED %

74 q c ~

61 q c ~

59 q c ~ + 22 qccc

69 bccc

74 Pccc 66 Pccc + 14 PcH 56 qccc

49 ~ C C C

52 ~ C C C + 30 ~ C H

64 PCF 52 PCF 46 PC-OH f 29 Pccc

5 1 ~ C F

49 ~ C F

42 q c - ~ ~ t 32 qccc

Intensity Raman

cm-'

841 vw

-

778 vs

733 s

692w

-

609 rn

599 s

517s

459s

390 s

3 15 vw

285 vw

254 s

247 s

177 w

OBSERVED AND CALCULATED FREQUENCLES AND POTENTIAL ENERGY DISTRIBUTION FOR 3,5 - DIFLUORO PHENOL

.i Y .- u w

,P

-

Al

Al

B2

Al -

B2

A1

Bz

BZ

Al

Al -

B:!

Al

Al

A1

Bz

B2 -

B2

A1

C"lcdated Wave

number (cm-')

3392

3037

3016

3000

1620

1599

1501

1462

1450

1348

1260

123 8

1201

1190

1148

11 11

998

924


Assignments

2 x 1152 + 1267

0-H stretchmg

C - H stretching

C - H stretching

C - H stretching

1208 + 529

C = C stretching

C = C stretclung

C = C stretching

C - C stretchmg

C - C stretching

C-Cstretching

767 + 529

C - OH stretching

C - F stretching

C-Fstretching



C-C-C triogonal bending

2 x 529


C-C-C ring breathing

Rel. Infrared

cm-'

3580m

3395s

3040 m

3020 s

3005 m

1 7 4 2 ~

1625 vs -

1508m

1470s

1445 w

1354w

1 3 0 0 ~

1267w

1242w

1208vw

1180vw

1152 vs

11 17 s

1055m

995 s

925 vw

PED %

-

9 0 ~ 0 ~

8 6 % ~

~ O V C H

~ ~ V C H

8ovcc

88vcc

82vcc

74vcc

76vcc

8 % ~

6 9 ~ ~ - O H + 19vcc

79 VCF

70 VCF

~ O P C H

~ ~ P c H 94Pccc -

70 PCH + ~ ~ P C C C 9 1 Pccc

Intensit RaLan '

cm-'

-

-

3047 m

3026 w -

-

1622 w

1604 w -

-

1452 vw

1346w -

-

. -

1205vw -

1146 w

11 10 w -

1000 s

Notations: vw - very weak, w - weak, m - medium, s - strong, vs - very strong, sh - shoulder, br - broad, v - stretching, P - in-plane bending, q - out- of-plane bending, p - rocking, 6 - scissoring, w - wagging, .t - torsion.

8 '5 u 8

B1

B1

Al

B1

A1

B7

Az

B1

A2

A1

A1

B2

B1

A2

B1

Wave number (cm-')

890

83 8

761

670

608

590

560

530

500

452

421

350

268

258

208


Assignments




C - H out-of-plane bending












Rel. Infrared

cm-'

9 0 0 ~

842 s

767 vw

671 m

615vw

-

-

529 w

-

458 w, sh

428 s - - -

-

PED %

61 r l c ~

54 YCH

61 Pccc i- 26 PCH 71 WH

74 Pccc 56 Pccc

49 9ccc + 32 llcH

59 rlccc

51 rlccc

58 PCF 50 PCF 44 ljc-OH + 28

Pccc

46 rlcF

49 llcF

42 rlc-oH + 32 rlccc

Intensity Raman

cm-'

-

840 s

- - -

599 vs

562 w

532 vw

505 m

450 vw

420 vw

352 vw

275 s

265 s

220 w

REFERENCES

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