Chapter - II

FTIR AND FT-RAMAN SPECTRA, ASSIGNMENT AND ANALYSIS

OF N-(PHENYL)- AND N-(CHLORO SUBSTITUTED PHENYL)-292-

DICHLOROACETAMIDES

INTRODUCTIOK

N-phenyl acetamide (Acetanilide) is an organic solid in which two close chams

of hydrogen bonded amide groups run through the crystal. It is an interesting system

because the nearly planar amide groups display bond distances, which are close to those

found in polypeptides. Since the physical properties of hydrogen bonded amide systems

are very sensitive to bond distances, we expect N-phenyl acetamide and its derivatives

to be useful model system in the search for new physical features of extended

polypeptides and perhaps even natural proteins.

Spectroscopic and crystal structural studies give valuable informations on bond

properties. Amides are of fundamental chemical interest as conjugation between

nitrogen lone-pair electrons and the carbonyl rc-bond results in distinct physical and

chemical properties. The amide moiety is an important constituent of many biologically

significant compounds. Therefore, an understanding of the forination, properties and

reactions of ainides is central to future developments in such areas as polypeptides and

protein chemistry.

As a result of hybridisation, the C-N bond in amides possesses considerable

double bond character. Also we may expect to find restricted rotation about this bond

and a planar configuration for the amide group. This planar structure has been

confirmed by measurement with X-rays and polarised radiation in the solid state. The

X-ray data have suggested that the trans- configuration is the most stable and it has been

shown that protein chains involve this structure.

Many imides. hydroxainic acids and hydrazides exhibit pharmacological

activity, which has further stimulated recent interest in their chemistry. Further many

acetanilides exhibit fungicidal; herbicidal and pharmacological activities. Naick

reported the synthesis of acetonitrile by dehydration of acetamide on an active ZnO

catalyst [ I] and compared with zeolite catalysts. The choloroacetanilde herbicide

alachlor is one of the most extensively used of all the agro chemicals. 2-chloro-2',6'-

diethyl acetaliilide and 2-hydroxy-2',6'-diethyl acetanilide are conventional metabolites

of the chloroacetanilide herbicide alachlor [2]. N-phenyl acetamide is used in medicine

under the name antifebrin, as a febrifuge. It is a useful intermediate in various reactions

of aniline in which it is desirable to protect the amino group. The acetamido

(-NHCOCH;) group is predominantly p-orienting.

The electrochemical behaviour of propanil and related N-subs~ituted amides,

such as acetanilide and N,N-dipl~eiiyl acetamide was studied by cyclic and square wave

voltainetry using a glassy carbon electrode [3]. Anilide herbicides are promising weed

control agents for a wide variety of economically importanl crops including rice, cotton,

potatoes and corns. Among the attractive features of these herbicides are their

effectiveness selectivity and low mammalian toxicity [4,5]. Propanil (3,4-

dichloropropioanilide) is a selective contact anilide herbicide recommended for post-

emergence use in rice. It is commonly used for the control of broad leveled and grass

weeds and is the only active substance in the phyto-pharmaceutical products.

Single crystal Raman, far infrared and inelastic neutron scattering (INS) spectra

of acetanilide in the low frequency region were obtained as a function of temperature

[6]. More than expected number of observed bands in the low frequency region was

assigned to the low frequency internal modes that exhibits anamolus frequency shift and

line narrowing behaviour upon cooling.

On the basis of temperature dependence infrared and Raman specrra, Herrebout

et al. [7] sho~rn that the effects of temperature on the structure and the changes in the

strength of the hydrogen bonding within a structure elucidated a lot of complexity of the

solid state vibrational spectra of N-methylacetamide.

The experimental and theoretical work about crystalline acetanilide has been

focused the 'anomalous' temperature dependent infrared absorption and Raman peaks at

about 1650 cm-' and the multi-band structure in the N-H stretching region. Rarnan

experiments have been performed on specifically deuterated acetaililide single crystal in

the low freq~~eilcy (phonon) and C=O stretching [8].

The unusual temperature dependence of the amide-I region in the IR spectrum

of the acetanilide has been attributed to a self-trapped Davydov-like soliton. Johnson et

al. [9] studied the temperature dependence o l the single crystal Railla11 scattering, from

acetanilide and its N-D and "c-0 substituted analogs in the phonon acd internal mode

regions. The results provided strong evidence that the unusual temperature dependence

of the amide-I mode in the Raman spectra is caused by temperature tuning of Fermi

resonance.

The vibrational spectra and normal vibrations of trichloroacetamide has been

investigated by Sree Ramulu et al. [lo] and the nature of the absorption bands in

relation to the mixing of vibrational frequencies were discussed.

Carzri et al. [ l l ] investigated the infrared absorption and Raman scattering on

crystalline acetanilide at lorn temperature. Equilibrium properties and spectroscopic

data ruled out explanations based on convelltiollal assignment, crystal defects, Fermi

resonance and upon frozen kinetics between two different subsystems; but a soliton

model, siillilar to that proposed by Davydov for a-helix in proteins was in agreement

with the experimental data.

Vibrational spectra of soine halogen substituted acetanlides have been analysed

by Krishnamoorthy et al. [12-151. The temperature dependence of the Raman scattering

from a single crystal of acetanilide and fully deuterated acetanilide in the low frequency

(phonon) and C=O stretching regions was studied [ I 61. The observed normal behaviour

of the frequency shift of the C=O stretching 111odes in deuterated acetanilide, raises

questions concerning several theoretical nlodels proposed to explain the peculiar

behaviour with temperature of the A], stretching nlodes observed in acetanilide.

The spectral investigation of tertiary amides and related systems has been

reported [I 7,181. The Rainan and infrared spectra of N,N-diethyl formamide, N,N-

diethyl acetamide and N,N-diethy1 chloroacetamide were measured and the fundamental

modes are assigned on the basis of norn~al coordinate analysis using modified valance

force field by Sudarshan et al. [19].

Localised excitations, to localised modes in alkali halides, and to localised

excitonic states are postulated for a set of internal vibrational modes in hydrogen

bonded molecular crystals of acetanilide [201 and described the characteristics of the IR

and Raman peaks associated with those localised states. The theory of self-trapping of

amide-I vibrational energy in crystalline acetanilide was studied and the spectrum of

stationary, self-trapped (soliton) solutions was deterrnilled and tested for dynamic

stability [2 11.

Tenznbaum et al. [22] developed a new model to study the molecular dynamics

of the acetanilide crystal by computer simulation. Low frequency oscillations of the

molecules as a whole were considered with high frequency vibrations of the amide

involved in hydrogen bonding. The N-(substituted phenyl)-2,2~2-trichloroacetan~ides

have been synthesised and their infrared and Ranla11 spectra were measured. The inter

correlations of infrared C=O and N-H frequencies have been analysed [23].

Laser Raman and FTIR spectra of p-nitroacetanilide were recorded and the

observed bands are assigned assuming the molecules belong to the Cs point group [24].

FT-NIR spectra have been measured for N-methylacetamide in pure liquid form and in

CCll solutions [XI. Infrared study of din~ethylacetamide in CHClslCC14 solutions has

been carried out [26] and the behaviour of C=O stretching mode vs. mole% CHC131CC14

can be explained on the basis of the bulk dielectric effect of the solvent system and the

existence of hydrogen bonded complexes between solute and solvent, and between

solvent n~olecules.

A new investigation of the temperature dependence of the far-infrared spectra of

acetanilide and its isotopomers have been presented by Spire et al. [27] and they

concluded that no significant change of their integrated intensity was observed when

reducing the temperature for the four bands at 3 1, 42, 64 and 80 cm". The temperature

induced frequency shift values and other properties of these bands are consistent with

the assign~nents as anharmonic lattice phonons.

The problem of the anomalous peak at 1650 cm-' in the amide-I spectrum of

acetanilide [ l l ] and some of its deuterated derivatives [28] has attracted many

experinlental and theoretical studies. Possible explanations for this unconventional IR

and Raman band have been niuch debated. The first proposed theoretical model was a

self trapped localised state created thro~lgh co~pliiig of amide-I quanta with optical

phonons and some times labeled as a 'Davydov soliton' [29] or a 'vibrational polaron'

[30]. This nonlinear excitation, if exists, sho~lld bc able to translate along the lattice

without energy dissipation and may be ~nvolved in some biological process involvillg

energy transfer.

A theoretical research [3 11 was made for effects of Raman scattering caused by

the soliton excitation occurring in the acetanilide molecular crystals on the basis of

vibrational mode of amide-I. The energy gap between the soliton state and the vibron

state has been found by partial diagoizalised method in second quantised representation.

The differential cross section of the Raman scattering, arising from the soliton

excitation, has also been obtained.

Many researches have been carried out in the nonlinear properties of molecular

crystals of acetanilide. Acetanilide is an interesting system because the nearly planar

amide-I group display bond distances, whicl~ is close to those found in polypeptide.

Since the physical properties of such hydrogen bonded amide-I system are very

sensitive to bond distances, the study of acetanilide revealed some new phenomenon

[32-361.

Kalosakas et al. [37] analysed the possibility of the observation of polaron

cormal modes at the far-infrared spectrum of acetanilide and related organics by using a

stationary and norillal mode analysis of the semi classical Holstein model in order to

convert the lour frequency linear polaron modes to low lying far-infrared lines of the

acetanilide spectrum.

The quantum vibrational spectra of molecular chains in acetanilide %ere

calculated by the discrete nonlinear Schrodinger equation by Pang and Xen [38].

Nielsen 1391 studied the isotopically substituted hydrogen bonded amides using NIR

and considered as nlodel systeins for hydrogen bonding in real proteins. He pointed out

that the energy to break a specific hydrogen bond depends on the presence of other

hydrogen bonds in the system. The Raman spectrum was influenced by a coupling

between vibrational modes in hydrogen bonded systeins and said that the modes are

collective and the collectivity may be related to the cooperative effect [40,41] in

hydrogen bonded systems.

As amides are the simplest model for peptides, their exact structure has been the

subject of many experimental and theoretical studies. Further, many acetanilide

derivatives exhibit fungicidal, herbicidal and pharinacological activities. A systematic

study on the vibrational spectra of simple primary, secondary and tertiary arnides

received considerable attention in the spectroscopic literature in view of their obvious

importance to biological systems. Despite the wide use of the N-phenyl acetamide

family of nlolecules in various applications, their spectroscopic properties are not

received n~uch attention. Studies of intermolecular associations, dichroic absorption,

band contour of the vapour spectra, measurements of integrated intensities of the

absorption bands and normal coordinate analysis give information regarding the nature

of the functional groups, orbital interactions and mixing of skeletal frequencies.

While acetanilide itself has been the subject of spectroscopic study of some

workers, the vibrational spectroscopic analysis of acetanilide derivatives particularly the

N-phenyl- and N-(chloro substituted pheny1)-2,2-dichloroacetamides have not been

studied. Therefore, we are interested in the spectroscopic studies of amides in their

state. Although there are reports on infrared and Raman studies of anilines,

amides, N-phenylclzloroacetanlides, N-methylacetamides and N-phenyl-2,2,2-

trichloroacetamides. no reports are available on substituted N-phenyl-2,2-

dichloroacetamides and its (cllloro substituted pllenyl) derivatives. We have prepared

some N-(pheny1)- and N-(chloro substituted phenyl)-2,2-dichloroacetanlides of the

configuration X,C6Hj.PNHCO-CHC12 (where, X = Cl and y = 1 , 2 and 3) and reported

the FTIR and FT-Rainan spectra of the compounds. The experimental and theoretical

investigation of N-(chloro substituted pheny1)-2,2-dichloroacetamides have been carried

out in order to understand the effect of the halogen substitution on the characteristic

frequencies of the amide group for the first time in the present worlc. The main purpose

of the present investigation is to synthesis some substituted N-(pheny1)-2,2-

dichloroacetamides, to record the FTIR and FT-Raman spectra, to assign the various

fundamental inodes precisely, to analyse the fundamental vibrations completely, to

show how the ainide bond (-NHCO-) parameters vary with the substitution of the

chlorine atom in the phenyl group and to analyse the mixing of different normal modes

with the help of potential energy distribution calculated through nornlal coordinate

analysis. Thus. in the present investigation, owing to the importance of halogen

substituted N-phenyl acetamides, we have undertaken an extensive spectroscopic

study of N-phenyl-2,2-dichloroacetamide and N-(chloro substituted pheny1)-2,2-

dichloroacetamides containing various number of chlorine atoms by recording their

FTIR and FT-Raman spectra and subjecting them to normal coordinate analysis, in an

effort to provide a possible explanations for our observations.

EXPERIMENTAL

The compounds under investigation namely, ~-~hen~l-2,2-dichloroacetamide

and K-(chloro substituted pheny1)-2,2-dichloroacetanlides were prepared from the

respective cl~loroanilines, dichloroacetic acid and phosphorus oxychloride based on the

reported procedure [23,42]. The pure samples of aniline, chloroanilines (2-

chloroaniline, 4-chloroaniline, 2,3-dichloroaniline, 2,4-dichloroaniline, 2,3,4-

trichloroaniline and 2,4.6-trichloroaniline); dichloroacetic acid and phosphorus

oxychloride were purchased from MIS. Aldrich chemicals, U.S.A, with stated purity and

are used as such without further purification. All other chelnicals employed are of A.R

grade.

Dichloroacetic acid (0.1 inol) and phosphorus oxychloride (0.1 mol) were mixed

together slowly with stirring to obtain a clear mixture. To this, anilinelrespective

chloroanilines (0.1 mol) was slowly added with constant stirring. After all the

aniline/chloroanilil~es has been added the stirring was continued for '/z hour and allowed

to stand at room temperature. Then the mixture was slowly warmed (70°C) to expel the

hydrochloric acid formed. Then cold water was added dropwise under ice-cold

conditions to hydrolyse the excess phosphorus oxychloride present. Then the

hydrochloric acid was removed by treating it with excess of 2N sodium hydroxide

solution, thereby the crude N-(pheny1)- and K-(chloro substituted pheny1)-2,2-

dichloroacetanlides were precipitated. allowed to stand for 15 minutes. Then the

products were filtered, washed thoroughly with cold water until free from the base and

dried. The crude samples were recrystallised from ethanol several times. The melting

points of the recrystallised samples were determined. All the melting points determined

are uncorrected. The purity of the compounds was confirmed by chemical analysis for

C, H and N. The compounds prepared, the melting point (m.p) and the elemental

analysis of the compounds are presented in Table 1

Table 1

Melting points and elemental analysis of the compounds studied:

S1. Name of the compound Melting % Found/(Calculated) No point

("c> C H N 1 N-phenyl-2,2-dichloroaceta~nide 109 47.01 3.42 6.81

2 N-(2-chloropheny1)-2,2-

dici~loroacetamide

3 N-(4-chloropheny1)-2,2-

dicl~loroacetamide

4 N-(2,3-dichloropheny1)-2,2-

dichloroacetamide

5 N-(2,4-dichloropheny1)-2,2-

dichloroacetamide

6 N-(2,3,4-trichloropheny1)-2,2-

dichloroacetamide

7 N-(2,4,6-trichloropheny1)-2,2-

dichloroacetamide (3 1.24) (1.3 1) (4.56)

The FTIR spectra of all the compounds were recorded in a Bruker IFS 66V

spectrometer in the range of 4000 to 400 cm-'. The spectral resolution was k 2cm-l.

The FT-Raman spectra of these compounds were also recorded in the same instrument

with FRA 106 Raman module equipped with Nd:YAG laser source operating at

1.064pm line with 200 m W power. The spectra were recorded with a scanning speed of

30 cm"min-' of spectral width 2 cm-'. The frequencies of all sharp bands are accurate

to ? 1 cnl- ' .

NORMAL COORDINATE ANALYSIS

The general molecular structure of the compounds under investigation is

represented i11 Fig. 1

(i) NPA XI , X2, X3, X4, XS = H (ii) 2CPA XI = Cl and Xz, X3, &, XS = H (iii) 4CPA X; = C1 and XI , Xz, Xq, X j = H (iv) 23CPA XI , X2 = C1 and X3, %, XS = H (v) 24CPA XI, X3 = C1 and Xl, &, XS = H (vi) 234CPA Xi, X', X3 = C1 and Xq, Xj = H (vii) 246CP.4 XI , X;, X5 = C1 and Xz, Xq = H

Fig. 1 Molecular Structure of N-(Pheny1)- and

N-(Chloro substituted Pheny1)-2,2-Dichloroacetamides

The geometry of the all the lnolecules under investigaticin is considered by

possessing Cs point group symmetry. The 5 1 fundai~lental vibrations of each compound

are distributed into the irreducible representatioils under Cs syillnletry as 36 in-plane

vibrations of a' species and 15 out of plane vibrations of a" species.

i.e., rvlb = 36a' + 15a"

All vibrations are active in both 1R and Raman.

Normal coordinate analysis provides a more quantitative description of the

vibrational modes. Owing to the complexity of the molecule (5 1 intramolecular

vibrations expected), a normal coordinate analysis is carried out to obtain a more

complete informations of the molecular rrlotions i~lvolved in the normal modes of N-

(pheny1)- and N-(chloro substituted pheny1)-2,2-d~chloroacetamides, and also for a

complete assignment of infrared and Raman spectra of these n~olecules. Wilson's FG

matrix method [43-451 was used for the normal coordinate analysis in which the normal

coordinates are defined with respect to a set of n~olecular internal coordinates. The

normal coordinate calculations were performed by utilising the program of Fuhrer et al.

[46] with suitable modifications for computing the G and F matrice:; and for adjusting a

set of independent force constants. The structural parameters necessary for these

compounds are talten from Sutton table [47] and structurally related similar molecules

The initial set of force constants were subsequently refined by the damped least square

technique. The simple general valance force field (SGVFF) was employed for both in-

plane and out of plane vibrations in order to find the potential energy distributions that

are characteristics of the force field. so as to avold any misassignment of frequencies,

due to any possible inadequacy of force constants. The potential energy was expressed

by SGVFF for the following reasons. (a) SGVFF has been shown to be very effective

in normal co-ordinate analysis (NCA) of benzene and its derivatives. (b) Valence force

constants can be transferred between the related molecules that are very useful in

normal co-ordinate analysis [48]. All the frequencies are assigned in terms of

fundamental, overtone and combination bands. To check whether the chosen set of

assignments contributes maximum to the potential energy associated with the normal

coordinates of the molecules, the potential energy distributions are calculated using the

final set of force constants. The potential energy distribution corresponding to each of

the observed frequencies shows the reliability and accuracy of the spectral analysis.

RESULTS .AND DISCUSSION

The observed vibrational assignments of the co~npounds are discussed in four

sections The first section deals with the vibrat~oiial characteristics of N-(pheny1)-2,2-

dichloroacetatntde (NI'A) wlule thc second section represents the vibrational

assignnlents and analysis of N-(2-chlorophenyl)-2,2-dichloroacetaride (2CPA) and N-

(4-chloropheny1)-2,2-dichloroacetsunide (4CPA). The vibrational analysis of N-(2,3-

dichloropheny1)-2,2-dichloroacetamide (23CPA) and N-(2,4-dichloropheny1)-2,2-

dichloroacetamide (24CPA) are discussed in the third section and in the final section,

we have presented the f~lndamental vibrational properties of N-(2,3,4-trichloropheny1)-

2,2-dichloroacetamide (234CPA) and N-(2,4,6-trichlorop11enyl)-2,2-dichloroacetamide

(246CPA).

SECTION - 1

N-(PHENYL)-2,2-DICHLOROACETAMIDE (NPA)

The FTIR and FT-Raman spectra of hi-(pheny1)-2,2-dichloroacetarnide (NPA)

are shown in Figs. 2 and 3. All the observed wavenulnbers are assigned in terms of

fundamentals, overtones and combination bands. The observed and calculated

frequencies along with their relative intensities, probable assignments and potential

energy distribution (PED) of NPA are su~ninerised in Table 2.

CARBON VIBRATIONS

The carbon-carbon stretching modes of the phenyl group are expected in the

range from 1650 to 1400 cm-I. Benzene has two degenerate modes at 1596 cm-I (e2,)

and 1485 cm-I (el,,). Similarly the frequency of two non-degenerate modes observed at

1310 cnl-' (bz,,) and 995 cm-' (a,,) in benzene. The actual position of these mode are

determined not so much by the nature of the substituents but by the form of substitution

around the ring [49]. Under Cs symmetry, in the case of NPA molecule, the C=C

stretching bands appeared at 1601. 1499, 1485 cm-I in the infrared and the

corresponding Raman frequencies are observed at 1599, 1492, 1479 cm-I. The C-C

stretching modes are assigned to the bands at 1447, 1388, 1344 cm-' in the IR while the

respective Rainan bands are observed at 1443, 1396, 1355 cm-I. These frequencies

appear in the respective range and the PED confirms this results and further shows that

these modes are pure.

The in-plane carbon bending vibrations are obtained from the non-degenerate

band at 1010 cm-' (bl,,) and degenerate modes 606 cm-' (el,) of benzene. Likewise, the

CCC out of plane bending modes are defined with reference to 703 cm-' (bag) and

degenerate 404 cm-' (el,) modes of benzene. I11 the present work the bands occurring at

616, 540, 505 cm-' in the IR and 625, 539, 51 1 cm-I in the Raman are assigned to the

CCC in-plane bending of NPA The CCC out of plane bending 111odes of NPA under

Cs symmetry is attributed to the Raman frequencies observed at 384 and 345 crn-I. The

CCC in-plane bending vibrations are described as mixed modes as there are about 20%

PED contribution mainly from C-H in-plane bending and out of plane bending

vibrations, respectively. The C-N in-plane and out of plane bending modes also

coupled with some percentage of carbon-carbon bending vibrations.

In benzene the ring breathing (a',) mode and the CCC trigonai bending (b,,)

vibrations exhibit the characteristic frequencies at 995 and 1010 crn-I respectively. In

NPA the ring breathing mode is observed at 861 cm'l in the IR and 870 cm-' in Ramm

while the CCC trigonai bending is seen at 1001 and 998 cm-' in the IR and Raman

respectively The NCA predlcts that these are very pure modes since their PED

contr~bution are almost 100%.

C-H VIBRATIONS

The aromatic C-H stretching vibratloils are normally found between 3100 and

3000 cm-I. In thls region the bands are not affected appreciably by the nature of

substituents. The aromatic C-H stretching frecluencles arise from the modes observed

at 3062 (al,), 3047 (e?,), 3060 (b,,,) and 3080 (e lu) cm-I of benzene and its derivatives.

In NPA, the phenyl C-H stretching modes are observed at 3086, 3048, 3013 and 2998

cm-' in the IR and at 3087, 3063, 3020 and 2997 cm-' in Raman spectra. The alkyl C-H

stretching is observed in the region 3000-2850 cni-' Thus the frequency at 2900 ern-'

in the IR and Ralnan is attributed to the C-H stretching of -CHC12 group. The PED

contribution of the aroinatic stretching modes indicates that these are also highly pure

modes as carbon-carbon stretch~ng, while the C-H stretching in -CI-TCI2 group is mixed

with the C-C1 stretching by 15%.

The aromatlc C-H in-plane bendlng modes of benzene and its derivatives are

observed in the region 1300-1000 cm-I. Studies on the spectra of benzene shows that

there are two degenerate ez, (1 178 cnl-l'l and el, (1 037 ctn-I) and two non-degenerate bz,

(1 152 cm") and az, (1 340 cm-l) vibratioils involving the C-H in-plane bending. These

modes are observed in NPA at 1289, 1241, 11 77, 1075 and 1029 cm-' in the IR and, the

corresponding frequencies are obtained in the Ranla11 at 1292, 1079 and 1033 cm-' . The

C-H out of plane bending mode of benzene derivatives are observed in the region

950 to 600 cm-'. The C-H out of plane bending results from b2, (985 cm*'), ei, (970

cm-I), el, (850 cm-') and az, (671 cm-I) modes of benzene. In the present case these

bands are occurred in the s a ~ d region and are presented in Table 2. The alkyl C-H

in-plane bending is assigned to the mode at 1305 cm" and the corresponding out of

plane vibration is ascribed to the medium mtensity band at 12 17 cmV1 in the IR and the

Raman counterpart is observed at 1222 cm-I. The aromatic C-H in-plane and out of

plane bending vibrations have substantial contribution from the rins CCC in-plane and

out of plane bending, respectively. The alkyl C-H in-plane and out of plane bending

modes are significantly overlapped with C-CI in-plane and out of plane bending modes

respectively.

AMIDE GROUP VIBRATIONS

The characteristic vibrations of the alnide (-CONH-) group in N-(pheny1)- and

N-(chloro substituted pheny1)-2,2-dichloroacetamides, and the principal associated

frequencies are classified as follows: -

(i) Arnide-I band of all amides occurring in the range 1680-1630 cm-I, which

involves mainly the C=O stretching vibration. For N-phenyl acetamide the

corresponding frequency may rise upto 1700 cm-'.

(ii) Amide-I1 band is found in the region 1570-1 520 cm-' corresponding mainly

to N-H in-plane bending vibrarions.

(iii) Ainide-I11 band around 1300 cm-I, containing the C-N stretching mode.

(iv) Amide-IV, corresponding to the in-plane bending vibration of C=O appears

between 855 and 760 cm".

(v) Amide-V mode in the region 800-645 cm-I belongs to the out of plane

bending of N-H bond.

(vi) Amide-VI, the out of plane bending of C=O bond which occur in 6 10-5 15

c111.I region.

(vii) In the high frequency region between 3300-3000 cm-I, wealdmedium bands

arising from the Fermi resonance between N-H stretching and the amide-I

overtone and, other combinatioll and overtone bands.

Following these criteria we made the assignment of all frequencies in the FTIR

and FT-Raman spectra of N-(pheny1)- and N-(chloro substituted pheny1)-2,2-

dichloroacetamides.

A characteristic feature of the ainide group in amide is the amide-I band. This

mode is observed as an IR absorption peak at about 1680 cm" in N-phenyl acetamide.

In the case of N-phenyl acetamide the amide-I band is raised due to the delocalisat~on of

the nitrogen lone pair electrons. In N-phenyl acetamide structure there is competition

between the phenyl ring and the C=O for the lone pair of electroi~s of the nitrogen.

Simple secondary amides absorbs near 1640 cm". Amide-I band, the C=O stretching

mode is the strongest band in the infrared spectrum and appears with diminished

intensity in the Raman spectrum. Hence the IR band observed at 1672 cm-' is assigned

to the amide-I band of NPA molecule. The Raman counterpart is obtained at 1680 cm".

The NCA shows that the amide-I band is to be pure even though it has mixed with the

amide-I11 mode by 1 1% as well as 10% of C-C stretching.

The N-H in-plane bending and the C-K stretching vibrations are known as

amide-I1 and amide-I11 bands, respectively. The amide-I1 band is often intense, almost

as intense as the C=O stretch itself. The N-H in-plane bending sometimes gives rise to

an overtone band at about twice the bending fundamental at around 1500 cm-I. The

arnide-I1 band of NPA appeared as a very strong band at 1555 cm" in the IR and strong

mode at 1568 cm-' in Raman spectra. The arnide-I11 band is strong in both IR and

Raman spectra of NPA observed at 1344 cnl-' in the IR and 1355 cm*' in Raman.

Though we assigned this frequency also to C-C stretching, the NCA predicts that the

potential energy contribution of C-N stretching is very high and exhibits pure in nature.

The amide-I1 band of NPA mixes with the C-N in-plane bending to a considerable

amount and the CCC in-plane bending also contributi~lg by 10%.

The C=O in-plane bending is called the amide-IV band. In NPA molecule it is

assigned to the very strong IR band at 81 1 cm-' and in Rarnan spectra at 81 0 cm-I. The

amide-V band is known as N-H out of plane bending vibration. This mode gives rise to

a medium to weak band. In NPA this mode is assigned to the wavenumber 7 12 and 7 15

cm-I in the IR and Rainan spectra, respectively. The C=O out of plane bending, amide-

VI band of NPA which occur at 558 CIII-' in IR. The corresponding Raman frequency is

observed at 568 cm-I. The an~ide-IV and amide-V bands have significant contributions

from C-N and C-C in-plane and out of plane bending respectively. The N-H out of

plane bending mode overlap with the ring CCC out of plane bending by 16%.

N-H STRETCHING

Secondary amides are the most corninon and important type of amide contains

only one N-H stretching band in the infrared spectrun~. This band appears between

3370 and 3 170 cm-l. The exact location of the N-H stretching mode depends upon the

other groups adjacent to the -CONH- skeleton. In more concentrated solution and in

solid samples, the free N-H band is replaced by a multiple bands in the 3330-3060 cm"

region. Thus the very strong band observed at 3270 cm" in IR and in the Rarnan at

3275 cm-' is attributed to the N-H stretching of NPA molecule. The NCA shows that

this is an absolute Inode

C-C1 VIBRATIONS

The C-C1 absorpdon is observed in the broad region between 850 and 550 cm-I.

When several chlorine atoms are attached to one carbon atom, the band is usually more

intense and at high frequency end of the assigned limits. In view of this, the very strong

band in IR at 759 cm-I having a strong Raman counterpart at 760 cm-' is assigned to the

asymmetric stretching. The synllnetric CC12 stretching in NPA is observed at 667 crn-I

in IR and at 672 cm-' in Raman. The in-plane CClz deformation and rocking vibrations

are obtained at a low frequency region of the Raman spectra corresponding to 297 and

195 cni-I, respectively. The out of plane CC12 wagging and twisting modes are assigned

to the Rarnan frequencies of 238 and 253 cm-' respectively. These assignments are in

good agreement with the literature [50] . From the PED we observed that the

asymmetric CClz stretching moderately overlapped with the C-C stretch and C-H in-

plane bending modes where as the symmetric CC12 stretching is mixed with the C-C

aqd C-H stretching mode. CC12 wagging and twisting vibrations effectively mixed

with each other and also the in-plane C-H and C-C bending vibrations contributed to

CC12 deformation and rocking modes.

SECTION - 2

N-(2-CHLOROPHENYL)-272-DICHLOItiOACETAAMIDE (2CPA) AND

N-(J-CNLOROPHENYL)-2,2-DICHLOIiOACETAMI13E (4CPA)

The FTIR and FT-Raman spectra of N-(2-chlorophenyl)-2,2-dichloroacetamide

(2CPA) and N-(4-chlorophenyl)-2,2-dichloroacetam1de (4CPA) are presented in Figs.

4-7. The theoretical and observed wavenumbers of the fundamental vibrations of both

the compounds along with their relative intensities and potential energy distribution of

the individual mode is presented in Table 3. The correlation of the amide (-CONH-)

group vibrational frequencies are summerised in Table 6.

AMIDE GROUP VIBRATIONS

The N-H stretching frequency of 2CPA is found at 3255 cm-I in the IR and

3253 cm-' in Raman. For JCPA, the bands at 3277 cm-' in the IR and 3269 cm-' in

Raman are assigned to the N-H stretching vibration. By con~parison, we observed that

the N-H stretching of 2CPA is lowered by 20 cm-' than that of NPA while there is 110

change in this frequency of 4CPA. I11 N-phenyl acetainide, the C=O and N-H bonds

inay be either cis or trans to each other. But the dipole ~noment measurements

demonstrated the trans conformer is the predominant and stable. Infrared spectroscopy

is one of the most widely used methods to study the nature and dynamics of hydrogen

bonded systems. A molecule exhibiting hydrogen bonding alters its infrared frequency

in a highly dramatic fashion. Clear manifestations of hydrogen bonding are large

frequency shift and band broadening of the dollars hydrogen stretching vibration.

The influence of a ring substituent on N-H stretching frequency of these

compounds under investigation may be the resultant of steric, direct field effect,

6 3

hydrogen bonding and bond polarisation effects. I11 an ortho-chloro, bromo or nitro

substituted N-phenyl acetamide n~olecules, the forination of intra~nolecular hydrogen

bond is further favoured the trans conformation.

The lllesomeric and inductive effects of para substituents have little influence on

the N-H stretching vibrations of these amides and it is reason,~ble to assume the

polarisation interactions of an ortho substituent, likewise have little effect on the N-H

stretching frequency [ j l ] . The steric effect of ol-tho substituent must be considered in

conjunction with the conformations. The increase in N-H stretching frequency may be

expected in introduction of an ortho methyl or t-butyl group into the phenyl ring of N-

phenyl acetamide. It is not due to the direct field effect but because of the steric

interactions.

Likewise the other ortho substituents chloro. bromo, nitro, methoxy groups may

produce increase in N-H stretching frequency of N-phenyl acetamide by exerting steric

compression on the N-H bond, but in addition, these substituents exerts intramolecular

hydrogen bonding and also an appreciable direct field effects.

In 2CPA the expected lowering of N-H stretching frequency is observed. This

lowering of N-H frequency in 2CPA than that of NPA shows the presence of strong

intramolecular hydrogen bonding between the chlorine atom connected at the ortho

position and the hydrogen of the amide group. The intramolecular hydrogen bonding is

considered to be the predominant effect than the steric factor. Steric compressions and

the direct field effects exerted by ortho substituents may offset the depression.

The amide-I band of 2CPA is found at 1678 crn-' in IR and 1685 cm-' in Raman

while in 4CPA the corresponding frequencies are observed at 1676 and 1682 cm-'. The

increase in wavenumber of C=O stretching in 2CPA and 4CPA than that of NPA

molecule reveals that the substitution of chlorine in the phenyl ring makes the molecule

effect~vely compete with the carbonyl oxygen for the electrons of the nitrogen, thus

increasing the force constants of the C=O bond.

The frequencies observed at 1545 and 1555 cm-' In IR are ascribed to the an~ide-

I1 band of 2CPA and 4CP.4, respectively. The corresponding Raman counterpart

obtained at 1551 and 1558 cm-'. The C-Ii stretching modes of 2CPA is assigned at

1340 and 1346 cm-' in IR and Raman spectra. The strong fundamental modes observed

at 1338 and 1350 cm-' in IR and Raman 1s attributed to C-N stretching of 4CPA. The

amide-IV, C=O in-plane bending of 2CPA is found at 807 cm-' in IR and 804 cm*' in

Rarnan. The fundamental modes 801 and 800 c111-' are attributed to the C=O in-plane

bending of 4CPA molecule. The ainide-V, the N-H out of plane bending is observed at

739, 742 cm-I in 2CPA and at 745, 749 cm-' In 4CPA. The C=O out of plane bending

of 2CPA is seen at 574 cm-I in IR, the corresponding frequency of 4CPA is observed at

574 and 584 cm-I in IR and Raman spectra.

The other amide group vibrations of 2CPA and 4CPA molecules exhibit their

characteristics in a similar fashion. When compared these modes of 2CPA and 4CPA

with that of the amide group frequencies of NPA molecule, no appreciable changes in

the magnitude of these modes are observed except the N-H out of plane bending mode.

The amide-V, mode of 2CPA and 4CPA is shifted to higher frequency by 30 cm-I than

in NPA. The PED calculations determ~ile that the anlide-I, amide-11, amide-IV and

amide-VI bands possessing the character of C-N and C-C vibrations. The amide-111

and amide-V bands are significantly overlapped with the N-M stretching and CCC out

of plane bending vibrations.

CARBON VIBRATIONS

The frequency of e2, degenerate pair in benzene is fiiirly insensitive to

substitution. Similarly the frequency of el, vibrations pair is also not very sensitive to

substitution, although heavy halogens cause undoubtedly diininish the frequency [52].

The C=C stretching of 2CPA is found in the IR spectrum at 1593, 1500, 1475 cm" and

at 1591, 1499, 1471 cm-'in Raman. Similarly the very strong lines observed in the

infrared spectrum of 4CPA at 16 17, 1492 cm-I and in the Raman at 1600, 1501, 1472

cm-' are ascribed to the C=C stretching modes. The C-C illodes of 2CPA and 4CPA

are given Table 3. These are all considered to be absolute modes according to the

normal coordinate analysis.

C-H VIBRATIONS

The C-H present in the phenyl ring of 2CPA gives bands at 3 104, 3052, 301 1

ern-I in JR and at 3100, 3086, 3045, 3009 cm-' in Raman. In 4CPA these modes are

obtained as strong bands in IR at 3106 and 3094 cm'l while in Raman these are

observed at 3104, 3091, 3057 and 3000 cm-'. The alkyl C-H stretching frequency of

2CPA and 4CPA is observed at 2889, 2891 cm-' in IR and 2892,2886 cm-' in Rarnan,

respectively. All other in-plane and out of plane bending vibrations of C-H mode is

presented in Table 3.

C-Cl VIBRATIONS

Three frequencies are expected in the region S00-550 em-', whose origin can be

attributed to the stretching vibrations of CC12 group and the phenyl (3-C1 bond. The

asymmetric stretching mode of CC12 in 2CPA is observed at 760 cm-' in IR and 779

66

cm.' in Raman. Strong infrared band at 655 crn-' and medium Raman band at 657 cm"

are ascribed to the syinlnetric CC12 stretching mode of 2CPA. In 4CPA the bands at

767. 770 cm-' and 640, 648 cm-' are attributed to the asy~nrnetric and symmetric CClz

stretching vibrations, respectively. The phenyl C-C1 stretching mode of 2CPA is

observed as a medium band at 684 cm-' in IR and 687 cm-' in R a m a ~ , whereas in 4CPA

it is found only in Rainan at 690 cm-'. The strong Raman bands at 341 and 339 cmsl are

ass~gned to the C-C1 in-plane bending whereas the out of plane bending is assigned to

the medium bands observed at 222 and 219 cln-' in Raman for 2CPA and 4CPA

respectively. The other vibrations of CC12 like deformation, rocking, wagging and

twisting modes of 2CPA and 4CPA are observed in the similar region as in the case of

NPA molecule and are presented in Table 3. The contribution of the corresponding

C-C1 vibi%tions observed about 70% and hence these modes are also pure modes. In

the low frequency region of the infrared and Raman spectra of 2CPA and 4CPA mainly

the C-C1 in-plane and out of plane bending modes are extensively mixed with other

modes.

SECTION - 3

N-(2,3-DICHLOR0PHENYL)-2,2-DICHLOROACETAIDE (23CPA)

AND IV-(2,4-DICHLOR0PHENYL)-2,2-DICHLOROACETAMIDE (24CPA)

The FTIR and FT-Raman spectra of N-(2,3-dichloropheny1)-2,2-

dichloroacetamide (23CPA) and N-(2,4-dichloropheny1)-2,2-dichloroacetamide

(24CPA) are shown in Figs. 8-1 1. The vibrational assignments of these compounds are

made on the basis of observed frequencies and their relative intensities in FTIR and FT-

Raman spectra together and potential energy distribution of the fundamental frequencies

calculated from the normal coordinate analysis are presented in Table 4.

N-H STRETCHING

The strong IR band observed at 321 8 cm-' and a weak Raman band at 3215 cm-'

is assigned to the N-H stretching mode of 23CPA. In 24CPA the N-H stretching mode

is attributed to the medium band at 3 199 cnl-' in infrared and 3210 cm" in Rarnan. The

N-H stretching of 24CPA is shifted to lower frequency by 15 cm-I when compared to

23CPA. The N-H stretching frequency of 23CPA and 24CPA molecules are

significantly lowered than the monocl~loro substituted compounds and NPA by around

50 cm-' confirm the presence of intramolecular hydrogen bonding.

AMIDE GROUP VIBRATIONS

The C=O stretching of 23CPA and 24CYA are observed at 1684, 1682 cm-' in

infrared and 1680, 1685 cm-' in Raman spectra respectively. The amide-11, amide-111,

amide-IV and amide-VI vibrations of 23CPA and 21CPA are observed as almost equal

in magnitudes and also not deviated much from the corresponding frequencies of

NPA. The N-H out of plane bending of 23CPA and 24CPA produce significant

frequency shift from that of NPA. It has 14% contribution from CCC out of plane

bending vibrations.

C-Cl VIBRATIONS

The C-C1 stretching of 23CPA and 24CPA are found in the expected range.

The frequencies seen at 694 cm" in infrared and 715, 689 cm" in Rarnan are ascribed to

the C-Cl stretching in 23CPA while in 24CPA ~t is observed at 707, 692 cm-I in IR and

704 cm-' in Raman. respectively. The CC12 asymmetric and symmetric stretching

frequencies of 23CPA and 24CPA does not show any variation from that of the

corresponding frequencies in NPA. The CClz wagging mode significantly overlap with

CC12 twisting mode and vice versa. Similarly the aroiuatic C-CI out of plane bending

modes also have more than 30% CCC out of plane bending contribution. The NCA

shows that C-N, N-C and CCC out of plane bending vibrations strongly coupled with

other modes and the original character of the respective nlode is only about 50%.

SECTION - 4

N-(2,3,4-TRICHL0ROPHENYL)-2,2-DICHLOROACETAMIDE (234CPA) AND

N-(2,4,6-TRECHLOR0PHENYL)-2,2-DICHLOROACETAIIDE (246CPA)

The Figs. 12-15 represents the FTIR and FT-Ra~nan spectra of 234CPA and

246CPA. The observed and calculated vibrational frequencies, the assignments of

different vibrational fundaineiltal modes and the potential energy contribution of the

individual modes are given in Table 5. The results presented in Table 5 are self

explanatory. Hence the discussion is confined iuainly to the vibrations having their

origin in -CONH- moiety and carbon vibrations. The C=C stretching modes of

234CPA are observed in IR at 153 1 and 1445 cm" while in Raman these are ascribed to

the frequencies 1535, 1449 and 1429 cmT'. In 246CPA the C=C fundamental modes are

assigned to the frequencies of 1532, 1453, 1432 cm" in IR and the Raman counterpart

at 1535, 1447 and 1430 cm-'. Similarly the C-C stretching modes of 234CPA are

obtained at 1 393, 1 37 1 , 1330 cm-' in the infrared, the corresponding Ranlan frequencies

are assigned at 1389, 1368, 1328 cm-'. In 246CPA these modes-are observed at 1392,

1374, 1332 and 1398, 1368, 133 1 cm" in the i~ifrared and Raman spectra respectively.

Although the carbon-carbon vibrations are considered to be fairly insensitive to the

substitutions in the phenyl ring these cause decrease in frequency by heavy halogen

substitution. In the cases of 234CPA and 246CPA the frequency of carbon-carbon

stretching shifted to lower frequency side when compared to other compounds studied

in the present work. That is. the carbon-carbon stretching modes vary from 1601 to

1325 cm-' in the infrared of NPA while in Raman from 1599 to 1355 cmml. But in the

case of 234CPA and 246CPA the range of these modes are obtained between 153 1 and

1272 and. 1532-1254 cine' in the infrared, respectively. Similar trends are also noticed

in the RanIan spectra of 234CPA and 246CPA. Thus, the vibrational bands

corresponding to the ez, mode of benzene and its derivatives, which appears at 1596

cm-', and the el, n~ode at 1485 cm-I are lowered in these chloro substituted N-phenyl

acetamide and is very significantly pronounced in 234CPA and 246CPA.

The aromatic C-H stretching illodes of 234CPA are obtained at 3069 and 3017

cm-' in IR and, 3075 and 3025 cnl-' in Raman. I,ikewise, the strong modes present at

3077, 3030 and 3073, 3029 cm-' are assigned to the C-H stretching modes in 246CPA.

AMIDE GROUP VIBRATIONS

The ainide group vibrational frequencies of 234CPA and 246CPA are found

very close to each other and there is no difference in their magnitudes. The 234CPA

and 246CPA shows very strong C=O absorption frequencies at 1688 and 1689 cm-'

respectively in the infrared. The correspondiiig Rainan bands are seen at 1685 and 1687

cm-I. The amide-I inode of the parent coinpound NP.4 is found at 1672 cm-' in the

infrared and 1680 cm-' in Raman. The comparison clearly shows a slight increase in

amide-I frequency of 234CPA and 246CPA Sinlllarly the other frequencies relating to

arnide-11, arnide-111, amide-IV and amlde-VI band does not show any appreciable

variation when compared to NPA molec~lie and others. But the correlation of amide-V

band of 234CPA and 246CPA with that of NPA clearly indicates that the frequencies

are increased very significantly by about 40-50 cin-' with that of NF'A.

3-H STRETCHING

The K-H stretching frequency of 234CPA is assigned to a very strong IR mode

at 3219 cm" and the same is observed at 321 1 cm*' in 246CPA. The frequencies at

3217 cnl-' and 3219 cm-I in Raman belongs to 234CPA and 246CPA respectively. As

explained earlier the N-H stretching frequency is more influenced by the presence of

intramolecular hydrogen bonding in ortho-chloro substituted co~npounds and found that

the depression in magnitude of N-H stretclling is more in the cases of 234CPA and

246CPA.

POTENTIAL ENERGY DISTRIBUTION

To check whether the chosen set of assignnlents contribute the most to the

potential energy associated with normal coordinates of the molecules, the potential

energy distribution (PED) has been calculated using the relation

F!, LI, PED = -- where PED is the contribution of the it" symmetry coordinate to the potential energy of

the vibrations whose frequency is vk. F,, is the force constant evaluated by the damped

least square technique, Llk is the normalised amplitude of the associated element (i,k)

2 2 2 and hb the eigen value corresponding to ~ h c vlblat~onal frcqucncy k (h~=4n c va ). The

PED contribution corresponding to each of the observed frequencies are listed in

Tables.

From the complete vibrational analysis of the FTIR and FT-Raman spectra of

NPA, 2CPA, 4CPA, 23CPA, 24CPA, 234CPA and 246CPA n~olecules the following

observatioils are made:

(i) Although the phenyl ring skeletal carbo11-carbon stretching is insensitive to

substitution, we found the substitution of cl~lorine atom in the ling diminished the

carbon-carbon stretching frequencies particularly in the case of 234CPA and 246CPA

but not much influenced in other compounds.

(ii) The comparison of amide group frequencies of the compounds under

investigation shows that the presence of intramolecular hydrogen bonding between the

chlorine atoll1 and amide hydrogen specifically in the ortho-chloro substituted

con~pounds like 2CPA, 23CPA, 24CPA, 234CPA and 246CPA. This is confirmed

from the observed N-H stretching frequencies and found lowering in magnitudes of

these vibrations in the case of ortho-chloro substituted compounds than that of WPt.1.

The depressions in N-H stretching frequencies relative to NPA are not quantitative

indications of the strength of intramolecular hydrogen bonding. The intramoiecular

hydrogen bonding is not favoured in the para cholro substituted molecule 4CPA.

(iii) The amide-I, C=O stretching frequency is slightly shifted to higher

wavenumber in the cases of N-(chloro substituted pheny1)- compounds tkan that of N-

(pheny1)-2,2-diclhoroacetarnide (NPA). The magnitude of frequency variation is not

significantly influenced by the position and number of chlorine atoms present.

( iv) Tile comparison of other amide group fi-equencies of the compounds did not

show any appreciable variation ln the respective wave numbers. It has also been

observed that the anlide-V band, the N-H out of plane bending of M-(chloro substituted

pheny1)- compounds is shifted to higher frequency than the N-(pheny1)- 2,2-

diclhoroacetamide

(v) The FTIR and FT-Raman vibrational frequencies of the compounds under

Investigations revealed close similarities in the magnitudes of the frequencies of other

similar modes in spite of the fact that the substituents in the phenyl ring are at different

positions.

(vi) From the norlnal coordinate a~lalysis we observed that most of the vibrations

of the compouilds investigated are re~narkably pure inodes with most of them composed

of at least 70% of PED and above. Significant vibration interactions with other

fundalllentals are also observed, particularly in the low frequency region. The PED

confirin the reliability and precision of the assignlnenl and analysis of the vibrational

fundamental modes.

r- oo - 6 0 a 2 8 L a a eel rrr ro rc, N

- - $ 0 ,..-. T

7 Y

-1 - +

Z d

>" $ C C d- 00 t-

--. DO 00 C F: + 3 +-'

2 2 4 m .t;

5 L U

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-a -cd

... 2 > 3

m + !2 >

m In

M 5 3 c.l

2 c.l i/:

LCI z S z

TI- b

2

E 00

2

P 3

b

2

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C1 d r-4 T - t

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P - F 5

=i: 0

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3 h - - - E 0

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OD s . - -c $ D a,

8 - P C -

.d

3: 0

m r- 2

3 CP, t' 0 - E 'n r. 0 - E 0 P- o -

I I I

'a

w 00

2 X N

I I

m l' - CCI m

I

2

I I

an C - 0 i-

2 C w, y 2

i

+ c-4 C?

C S a ,-.. N CPI

r- C

G' z CPI

3 vr - N C?

Cr,

00 3

N M

b

=O E:

9 + t?

4.4 LC

M n

1 U

z 0 CCI

P S

00 t-. 0 m

V)

vr b 0 CPI

C 2= d 30 0 CCI

I

I

m

a" 573 vw 571 s 570 vw 567 s 563 C=O out of plane bending 4lycCo + 21ycc + 1 lycN

a' 551 vw 545 w 548 s 549 m 543 CN in-plane bending 5 3 s ~ ~ + 30P~1i

a" 455 vw 459 s --- 450 s 45 1 C-N out of plane bending1 5 1 ycu + 20yc=o + 1 ~ Y N t i

a" CC out of plane bending 3 8ycc + 26yc-c1+ 2 1 yc FI

a" 425 vw --- 434 s 427 s 428 CCC out of plane bending 44yccc + 21ycfl + 2 0 ~ ~ ~

--- 385 m --- 389 s 38 1 N - C ~ I I ~ out of plane bending/ 30yNc + 2 4 7 ~ ~ + 21 y ~ c

aft CCC out of plane bending 38yccc 4- 22yc~ 4 2 1 ycr I

a' --- 355 w --- 352 m 350 C-Cl in-plane bending 64Sc Cl + 2 J Pcc-c

a! --- 322 s --- 327 111 318 C-C1 in-planc bending ~ ~ P c - c I + 19Pccc

a! --- 293 s --- 297 s 295 CC'l? deformation 5 16~(.i2 + 20Pc H + I 1 PCC

--- 252 m --- 259 m 249 CC12 twisting

--- 237 w --- 240 w 23 8 CClz wagging

at' --- 212 111 --- 21 5 n~ 21 5 C-CI out of plane bending 44yc-CI+ 28yccc

a r t --- 192 m --- 197 w 19 1 C-C1 out of plane bending 5 6 ~ ~ ~ 1 2 + 2 ~ Y C C C

a' --- 173 w --- 175 w 174 CC12 rocking 68pcu2 + 2 1 6 ~ ~ 1 2

a vs, very strong; s, strong; m, medium; w, weak; vw, very weak, v, stretching; 6, deformation; 0, in-plane bending;

y. out of plane bending; p, rocking; w, wagging; and z, twisting/torsion

i $ z m C'?

I

I

3 0 r- C? C?

00 w v, i

X N . .. m r- I/i i

.A C\I

I I I

E In

2 C'?

I I I

tn

d C'? 3

r '?

2 . - C - 0 4

2 + II.

I: I

'4

In r. 0 m

r/.

C'? r-- 0 m

m t-- r- 0 r'?

%. IA I-- 0 r '?

9 0\ w 0 C?

(d

d w 2 + cc Q vi 3 . " N t. 2 + C'? r- m 3

8 I

3 0\ m 00 N

I I I

E r- \n 00 CI

0 L >

V) 00

2 - r: 0 V

2 W m

U

3

3

C? 'n 3

V) > 'n CCI 'n d

m > N CCI 'n d

E In m m - m > - CCI 'n - -m

;i ;i > 7-

0

=U r: - A 0 i

2 -L m

H U

w + 2

I I I

LC

m 'n St;

E m d 2

Y 'n d z 'm

;i ;i >

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r 1

St;

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2

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2

m m N z

t

-m

" ;i U 0 M i

f z (-1 a 0 r-

2 3 S D a C m - 2 . - 7 U

- t-. 3 - E 0\ r-- -

ili

m r- 3 ri

E ffi t-. - -

9 r- I= w

cd

93 0 C-H out of plane bending 5 1~ct1+ 24~ccc

867 s

829 s

796 s

778 111

759 I l l

Riilg breathing

C-0 in-plane bending

CC12 asynlnletric stretching

CCC in-plane bending

N-H out 01 plane bending1 CCC in-plane bending

C-C1 stretching

C-(11 stretching

CCI2 synin1etric stretching

C=O out of plane bending1 C-C in-plane bending

C-N in-plane bending

C-N out of plane bending1 CCC out of plane bending

---

a''

CCC out of plane bending

'L 0 C,

C1 - N

+ C L.,

c? i

w

to s . - g 9

2 .--. 9 C

. A

7 U

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3 r- r- C?

I I I

V)

w7 r- CCI

I

I

- (d

ii ii cl F ..-.. + - e cl 30 - + M

k LC 0 m

s 0 . - +a

m 2 d? -2 N - u u

N 0 r CI

3 C? 0 C?

I

I

E i

0 C ' l

I

I

-m

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29.

30.

31.

32.

? 'l JJ.

34.

35.

36.

37.

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