Chapter 3

Vibrational Spectra and Assignment of Cyclohexanone Oxime

CHAPTER - 3

INTRODUCTION

Cyclohexanone is a colorless, mobile liquid with an odor similar to that of

pepper mint and acetone. It was first prepared by the dry distillation of calclum

pimelate and later by Bouveault by the catalytic dehydrogenation of

cyclohexanol. It is used chiefly as a chemical intermediate and as a solvent for

resins, lacquers, dyes and insecticides.

The most important use of cyclohexanone is as a chemical ~ntermediate in

nylon manufacture : 97% of all cyclohexanone output is used either to make

caprolactam for nylon-6 or adipic acid for nylon-66. In the caprolactam process

cyclohexanone is converted to cyclohexanone oxime (mp, 89-90°C), which is

rearranged with sulfuric acid to E-caprolactam (mp, 69°C). The overall efficiency

is > 97%. In the production of adipic acid, cyclohexanone is oxidized w~th nitric

acid m the presence of catalysts. Cyclohexanone is also used as a solvent and

thinner for lacquers, especially those containing nitrocellulose or vinyl chloride

polymer and copolymers and as a general solvent for synthetic resins and

polymers. Cyclohexanone is an excellent solvent for insecticides and many other

similar materials. Cyclohexanone is used as a building block in the synthesis of

many organic compounds, such as pharmaceuticals, insecticides, and herbicides.

Cyclohexanone is used in the manufacture of magnetic and video tapes.

Cyclohcxmone oxime with molecular formula CJi,,NO the derivative of

cyclohexanone is a white crystalline solid that can be crystallized as prisms from

hydroarbom solvents. It has melting point 90.S°C and boiling point 204OC.

sublimes at room temperature. It is probably combustible. This chemical

compound is stable under normal laboratory conditions. This compound is the

most important commercial derivative of cyclohexanone.

It can be prepared by warming cyclohexanone with an aqueous mixture

of hydroxylamine hydrochloride and sodium bicarbonate. Large commercial

quantities of cyclohexanone oxime are used as the intermediate in the

preparation of caprolactam which is used to form nylon. This compound is used

as a drug (therapeutic agent). The oxime undergoes a Beckmann rearrangement

in the presence of sulfuric acid to give caprolactam. The cyclohexanone oxime

can also be reduced to a mixture of cyclohexylamine and dicyclohexylamine or

it can be hydrolyzed to cyclohexanone.

NMR spectra of some oximes were measured at natural isotopic

abundance in pyridine and acetonitrile solutions (I). The temperature

dependence of the FT-IR spectra of absorbed cyclohexanone oxime was studied

on pentasil zeolite (2). Thennodynamic properties like heat capacities of

crystalline and liquid cyclohexanone oxime were measured by vacuum adiabatic

calorimehy (6 - 300 K) and by the triple heat bridge method (300-450 K) (3). The

mrrangement of cyclohexanone oxime to e-caprolactam was investigated over

heterogeneous catalysts (4).

Jain and Sharma reported the mechanism of reaction of impurities such

as cyclohexanol, cyclohexanone, aniline and cyclohexanone oxime, during the

course of polymerisation of caprolactam. This ~ndicates that cyclohexanone

oxime's application in the manufacture of nylon (5). A simplified industrial

route for the synthesis of cyclohexanone oxime an intermediate in the

caprolactam process is described by Rofia (6). This chemical compound was

employed as an oxidant in redox polymerisation (7). Talukdar, Wong and Mathur

reported the use of solar energy for the photonltrosafion of cyclohexane for the

production of cyclohexanone oxlme hydrochloride, an intermediate for the

manufacture of caprolactam (8).

However, so far no work is reported on vibrat~onal spectra and analysis of

cyclohexanone oxime. The aim of the present work is to obtain all the vibrational

frequencies and to propose assignments for cyclohexanone oxime. Hence the

present investigation has been attempted for the first time to get more information

on the fundamental vibrations as well as to assign all of them using the normal

coordinate analysis through FT-Infrared and FT-Raman spectroscopy.

3.1 EXPERIMENTAL DETAILS

The FTIR spectrum of cyclohexanone oxime is recorded on Brucker

IFS 66V FTIR spectrometer in the region 4000-200 cm-I. The FT Raman

spectnun of the same compound is also recorded on the same instrument with

FRA 106 Raman mod& equipped with Nd : YAG laser source opelilting at

1.06 pn l i e with a scanning speed of 30 cm.' min-' of spectral width 20 cm-'.

The fiquencics for all sharp bands w a e accurate to f 1 cm.'. The structure of

the compound is shown in Fig.3.1. The recorded specbum of cyclohexanone

oxime is shown in Fig.3.2.

3.2 THEORETICAL CONSIDERATIONS

The molecular symmetry of the molecule helps to determine and classify

the actual number of fundamental vibrations of the system. The observed

spectrum is explained on the basis of C, point group symmetry. The 5 1 optically

active fundamental vibrations are distributed as T,,b = 35a' (in-plane) + 16a"

(out-of-plane).

All the modes are active in both Raman and Infrared. Assignments have

been made on the basis of relative intensities, magnitudes of the frequencies and

polarisation of the Raman limes. The vibrational assignments are discussed in

terms of the potential energy distribution which was obtained from the evaluated

constants.

3.3 NORMAL CO-ORDINATE ANALYSIS

The normal coordinate calculations have been performed to obtain

v~brational fiquencles and the potential energy distribution for the various

modes. In the normal coordinate analysis, the potential energy distribution plays

an important role for the characterisation of the relative contributions from each

internal coordinates to the total potential energy associated with particular normal

coordinate of the molkule.

NOH

Fig.3.1 Structure of CYCLOHEXANONE OXIME

WAVENUMBER (cm' )

FIG.3.2. FTIR AND FTR SPECTRA OF Cyclohexanone oxime

The normal coordinate analysis is necessary for complete assignment of

the vibrational firquencies of larger polyatomic molecules and for a quantitative

description of the vibrations. The values of bond-length and bond-angles have

been taken h m allied molecules and Sutton table (9). Internal co-ordinates for

the out-of-plane torsional vibmtions are defined as mcoaunended by IUPAC. The

simple valence force field has been adopted for both in-plane and outsf-plane

vibmtions. The normal coordinate calculations have been performed using the

program of Fuhrer et aL, (10). The initial set of force constants have been taken

from the related molecules.

3.4 POTENTIAL ENERGY DISTRIBUTION

To check whether the chosen set of assignments contribute maximum to

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

potential energy distribution (PED) has been calculated using the relation

F,~L2,k

PED = - L

where F,, are the force constants defined by damped least square technique, L,,

the normalised amplitude of the associated element (i,k) and hi the eigen value

~mresponding to the vibrational frequency of the element k. The PED

Contribution comeqm~ding to each of the observed f-uencies over 10% are

alone listed in the present work.

3.5 RESULTS AND DISCUSSION

The observed frequencies along with their rtlative intensities of

cyclohexanone oxirne and probable assignments are presented in Table 3.1. The

assignment of fkequcncies is made as follows.

Stretching vibrations

C-H Stretching

In large numbered rings such as cyclohexane, the C-H stretching

absorptions are usually observed below 3000 cm". In the present case, the

absorption band observed at 2843,2889,2925 and 2977 cm" in the IR spectrum

and 2831, 2857, 2900, 2938, 2962, and 2988 cm-' in the Raman spectrum are

assigned to the C-H stretching present in the cyclohexane ring. The weak and

strong wave numbers correspond to symmetric and antisymmetric vibrations of

the C-H bond. The calculated wave numbers agree with the observed frequencies.

The present conclasion is in agreement with the literature values 111-141.

The PED calculation for C-H stretching indicates that all are pure modes

except at the calculated tkquency, at 2890 cm-I and 2849 cm" which are the

mixed modes with little contributions due to C-C stretching.

0-H stretching

In the the 0-H stretching band is of medium to strong intensity

although it may be broad. H o d e r , in in spectra, the band is

g 4 y weak The O-H &etching of the cyclohcxa~~ne oxime is assigned to

3 187cm-' which agrees with the calculated frequency at 3 18 1 cm-' [I 5-2 1 ]

C=N Stretching

For oximes, the C=N stretching band occurs in the region 1690-1 620 cm*' .

In the present case, it is assigned to strong infrared at 1669 cm" which agrees

with the calculated frequency at 1664 cm" and literature value [22].

C-C Stretching

The skeletal vibration of alkane are often weak in inkxed and usually of

weak to medium intensity in Raman spectra. The C-C stretclung absotptions

occur in the region 1260-700 cm-'. Thus bands observed at 1225, 1214, 1138,

11 10, 1095 and 1088 cm-' are assigned to six C-C stretching vibrations and they

are in agreement with the calculated fi-equencies.

In plane and out of plane bendings

C-H bending

The C-H in plane bending vibration in cyclohexane rings is usually

observed in the region between 1000 - 1400 cm-' which is normally weak while

the C-H out of plane vibrations occuning between 700 - 1000 cm-' is normally

Strong. With this observation, the bands at 1239, 1250, 1264, 13 19, 133 1, 1339,

1350, 1436, 1458 and M80 cm-' are assigned to C-H in plane bending while the

bands observed at 482,656,794,838,850,868,900,919,93 1, and 950 cm-' are

assigned to GH out of plane bending vibrations. These bending vibrations due to

the C-H bond well agree with the calculated fresuencies as shown in table 3.1

and with the literature values [23,24].

Ring breathing

The CCC trigonal bending and CCC ring breathing vibrations are assigned

to 1019 and 995 cm-' respectively which agree with calculated values at

101 1 cm'l and 992 cm-'. This conclusion is in good agreement with the literahue

values [25].

Conclusion

A complete vibrational spectra and analysis is reported in the prtsent work

for the fitst time for Cyclohexanone oxime. The close agreement between the

obsewed and calculated frequencies confirm the validity of the present

assignment.

REFERENCES

Cerioni, Giovanni, Plumitallo, Antonio. Magn. Reson. Chem., 31, 320, (1993).

Sato, Hiroshi, Hirose, Kenichi; Nakamura, Yasuo Chem Lett., 12, (1987), (1993).

A.A Kozyso, G.Ya Kabo, Kruk. J. Chem. Thermo 24,883, (1992).

G.P Heilmann G., Dahlhoff W.F., Holderich, J. Catal, 186, 12, (1 999).

S.L. Jain, N.D. Sharma, Man-made Text Ind~a, 40.55, (1 997)

Roffia, Chim. Ind (Milan) 72,598, (1990).

D.V.P.R Varaprasad, V. Mahadevan, J. Polym. Sci., Part A Polym. Chem., 24,3279, (1986).

J. Talukdar, E.H.S. Wong, V.K. Mathur, Solar energy 47, 165, (1991).

L.E. Sutton, the interatomic bond distances and bond angles m molecules and ~ons, Londen Chem., Soc., London (1983).

H.Fuhrer, V.B.Kartha, K.L.Kidd, P.J.Krugdel and H.H.Manstch computer program for infi-ared and spectrometry, normal coordinate analysis, volume 5, National Research Council, Ottawa, Canada, 1976.

D.F.Eggers and W.E.Lingsen, Anal. Chern., 28, 1328, (1956).

W.Kemp. Organic spectroscopy, Macmillan Press Ltd., London (1991).

S.Periandy and S.Mohan, Asian J. Chem., 8,707, (1996).

S.Mohan and N.Sundaruganesan, Indian J. Phy, 66B, 213, (1992).

LMotoyama andC.H.J&, J. Phys. Chem., 70,3226, (1966).

J.H.Vmder Maas and E.T.G.Luk, Spectrochim Acta, 30A, 2005, (1974).

ULidk.1, Ann. N.Y. Acad. Sci., 69,70, (1957).

S.Siggia, et al., in Chemistry of the Hydroxyl Group, Part 1, S. Patai (4.) Interscience, London, 3 1 1, (1 97 1).

J.S.CookandI.H.Reece, Austral, J. Chem., 14,211, (1961).

R.Laenenet al., J. Phys. Chem. A , 103,10708, (1999).

A.S.Wexler, Appl. Spectrosc Rev., 1,29, (1968).

George Socrates hiked and Raman characteristic group frequencies tables & charts Third Edition John Wiley & Sons Ltd. (2001).

W.O.George and P.S.Mcmtyre, Infrared spectroscopy, edited by D.J.Mowthorpe, John Wiley & Sons, London, (1987).

S.Mohan, A.R.Prabakaran, J.Raman Spectrosc., 20,263, (1989).

S.Mohan, A.R.Prabakaran and F.Payam~, J. Raman Spectrosc., 20, 455, (1989).