Bishui, B M

Sirkar, S C

English

IACS Institutional Repository

12 ON THE RAMAN SPECTRA AT LOW TEMPERATURES.' BENZENE DERIVATIVES By S. c. SIRKAR* AND B. M. BISHUI ABSTRACT The Raman spectra of Imll.ylamint', benzyl alcohol and benzovl chloride have been investigated in the solid ~tate at about- 170"<-' and in the liquid state a~ the room temperature. The p')Iarisation of the Raman lincs of all these liqnids has also been studied. From the observ~d depolarisation of some of ~e Raman lines it has been conduded that the molecnlt:s of these three compounds in the li4luid state POHSCSS a plant' of symmetry. In the ('ase of benzyl amine in the solid state sOme of the Raman lines undf'rgo changes in frequency and intensity aud some new I1I1er, appear in the low frequency region, and it is concluded that in the liquid state the molecl1les are only I()f)sely associated, but in tbe so.lid state they arc strongly associated amI form polymeric groups, In the case of benzyl alcobol and benzoyl chloride such Raman lines ill the low frequency region appear even in the liquid state and no appreciable cll:mges in the frequencies of the other prominent Raman lines take place with the solidification of the liquids at the low temperature. It is concluded from these facts that even in tht, liquid state the molecules of tlwsc two compounds exist as polymers It ,vas observed by Mizushirna and Morino (1938) alld by the present authors (1943, 1945, 1946) that thl' Ramall spectra of some aliphatic com-pounds undergo some changes when these compounds arc solidified at low ternperatUl-es. As pointed out previously by the present authors (1945), the explanation offered by the previous workers regarding such changes in the lines due to intramolecular vibratlOIlS is not quite satisfactory. As regards the origin of the new Ra11lan lilies, wh.ich appear in the low frequency region in the Ramall spectra of many aliphatic and aromatic compott11l1s, the view is held by many workers that these hues arc due to lattice oscillatiOlls in whicb only intermolecular electrostatic field takes part. Sirkar (1937), howeverT l'oiutec1 out SOHH: difficulty in such an interpretation, becau~e ill the case of centrosymmdrical molecules the intensity of the lines due to such intermolecular oscillations is expected to be negligible. He put forward the view that some secondary bonds may be formed he tween neighhouring molecules to form small polymeric groups, and the oscillations of constituent single molecules against each otlIer in such groups may give rise to Raman lines in the low. frequency region Experimental results regarding such new line;, in the case of Jifferent types of molecules may be helpful in understanding the true origin of such lmes and therefore, a programme has been undertaken to study the Raman spectra of a large number of aromatic and aliphatic compounds in the solid state at low temperatures. The present investigation deals with such spectra of three benzene derivatives, each having an aliphatic side chain. The substances studied in the present invel>tigation are benzylamine, benzyl alcohol and benzoyl chloride. Liquids from KaJdbaum's original packing were used after being redistilled in vacuum. The technique * Fellow of the Indian Physical Society 114 s. C. Szrk,ar and B. M. B~shui Benzylamine. The Raman spectrum of benzylamine was studied formerly by Dadieu and Kohlrausch (1930) and by Reitz and Stockmair (1935)· The results obtained by the latter authors are more recent and have been included in Table J, These results agree fairly well with those obtained by the l!resent authors, which are given in column 2 of Table I, but there are some minor discrepancies. The weak lines 579 em-I, 895 em-I, II76 em-I, 2973 em-1 and 3385 cm- I observed by them have not been observed by the present authors. Also the frequencies of some the of the lines reported by them are a little lower than those observed in the present investigation. The lines 175 cm- I, 628 cm - I, 1458 em-I, 1590 cm-1 and 1605 cm-1 are fouud ill the present investigation to be totally depolarised, This fact suggests that the molecule has a symmetry element which is most probably a plane of symmetry passing through the plane of Lhe benzene ring, The carbon and nitrogen atoms in the CH 2 NH 2 group then also lie in this plane, and two of the four hydrogen atoms are above and the other two below this plane. No other alternative symmetry clement of the single molecule is more probable than this plane of symmetry. In the solid state at about - 1700 C the substance yields two new Raman lines at 92 cm-I and 124 cm- I re::>pectively and some of the prominent Raman lines of the single molecule undergo changes in frequency and intensity at thi:s low temperature, Thus the band at 175 cm- I is split up into two lines at 160 cm- I and 207 cm- 1 alld the lines 786 em-I, 1207 cm- I , 1590 em-I, 1605 cm- 1 and 2935 cm- 1 shift to 774, II38, 1584, 1596 and 2901 cm-1 respectively at the low temperature. Also the relative intensities of the lines 1590 cm -1 and 1605 C111- 1 are reversed in the solid state. The line 3063 cm- I , which has a diffuse wing in the lower frequency side in the liquid state, becomes sharper and is accompanied by a faint component at 3050 cm-I in the solid state at the low temperature. As the Rayleigh line due to the liquid at the r00111 temperature is accompanied by a wing extending upto about 125 cm- I from its centre it is difficult to say whether the lines 92 cm-1 and 124 cm-1 observed in the solid state are also present in the spectrum due to the liquid. It is doubtful whether any intramolecular vibration of the single molecule can have such low frequencies. The diminution in the frequencies of the prominent Raman lines with th~ solidification of the liquid at the low temperature suggests that the molecules become strongly associated in the latter c:ase and the new lines 92 em-I and 124 cm-1 may be due to vibrations of such groups of associated molecules. The fact that the C-H frequencies are lowered in the solid state shows that the association takes place through the hydrogen atoms of the molecules. Benzyl alcohol. The Raman spectrum of this liquid was studied pre-viously by Dadieu and Kohlrauscb (I929). Howlett (193I) and Reitz and Stockmair 11935}. The results reported by the last two authors be'ing comparatively recent have been included in Table II. A comparison of the data given in the first two columns of Table II shows that the weak lines Raman Spectra at Low Temperatures 115 s8scm-1,900cm- l , II76cm- l , 1358 CIII- 1 and 34J4Cm-1 have not been obsel'ved by the present authors. Also the frequencies of some of the hydrogen lines, e.g., 2870 em-I. 2923 cm-1 and 2975 cm-1 reported by them are much lower than those observed in the present investigation. The second and third columns of ,Table II show that with the solidi-fication of the liquid at the low tem(>Crature the wing accompanying the Rayleigh line disappears and a line at 9il cm-1 is observed. It is not unlikely that this line may be present also in tile Raman spectrum due to the liquid, but being masked by the intense willg,lwhich extends upto 120 cm-1 from the centre of the Rayleigh line, it can ndt be detected. Fox and Martin (x940) concluded from the results of investfgatioll of the absorption spectrum of benzyl alcohol in the near infra-red region at the room temperature that the molecules are present even in the dilute solution of the liquid as dimers and in the concentrated solution there ii an equilihrium between dimers and tetramers. Although these conclusions were drawn from the observed struc-ture of the band at 2.75/'0, the Raman lines 91 em- 1 and ISS em-I, which correspond to bands in the extreme infra-red region, may also, be due oscilla-tions in such dimers and polymers. In the solid state also probably the molecules exist as dimers and polymers, and therefore only the rotational wing is absent and the lines 91 em-land ISS cm- I due to vibrations in these polymers persist. It is significant that in thc case of benzyla1l1ine the band at 175 cm-1 splits up into two lincs at 160 (111-1 and 207 cm- 1 in the solid state , while in the case of benzylalcohol even the liquid at the room temperature yields two lines at 165 C1l1- 1 and :no cm- I • It is further observcd tbat tllt:-prominent Raman lines of benzyl alcohol do not undcrgo tilly appreciable change with the solidification of the liquid, while in the case of benzylatninc the lines undergo changes with the solidification. These fads clearly point out that in the case of benzyl alcohol the molcctlles are already strongly associated in the liquid state and the strcngth of the association does not further increase appreciably with the soiidification of the 'substance at the low temperature, while in the case of benzyl amine such association is not so strong in the liquid state, but it becomes much stronger in the solid state. Some of the Raman lines due to the liquid are observed in the present investigation to be totally depolarised, as can be seen from Table II. Hence the molecule possesses probably a plane of symmety, which is more probable than a two-fold axis of rotation. Benzoyl chloTide.-The data given in the first two columns of Table III show that some of the Raman lines due to tbis liquid at the room temperature observed by the present authors have not been observed by Thompson and Norris (936). The Raman spectrum of the liquid had also been studied, previously by Dadieu and Kohlrausch (1929), Mastsullo I and Han (1933), Thatte and Ganesan (r931) and Kohlrausch and Pongratz (1934), and the polarisation of the lines was studied by Simons (1932). The resu1ts obtained by Thompson and Norris being latest have been included in Table III. The--; 116 s. c. Sir~ar and B. M. Bishui lines observed by Kohlrauseh and Pongratz hut not observed by Thompson and Norris are 13I7 em-I, 2610 em-I, 2649 cm- I and 3012 cm- I . These lines have not been observed in the present investigation also. The line 846 em + I observed in the present investigation was not observed by Kohl. rauseh and Pongratz, but it was recorded as a line 840 cm-1 by Thompson and Norris, und the line I164 C111- 1 observed by the latter authors but not recorded by the former authors has not been observed in present invesigation. The line 20I cm- J observed in the present investigation and also hy Kohlrausch and Pongratz was not recorded by Thompson and Norris. It can be seen from the third column of Table II that no remarkable change takes place in the frequencies of the prominent Raman lines when the liquid is solidified at about -170°C. The line 98 cm-1 observed at the low temperature is probably also present in the Raman spectrum of the liquid, and is masked by the strong wing accompanyiug the Rayleigh line and extending upto about 120 cm-l from its centre. In this case also two lines at 161 cm-1 and 23 I cm-1 are yielded by the liquid at the rool1l temperature as in the case of benzyl alcohol. From these facts it may be concluded that just like the molecules of benzyl alcohol those of benzoyl chloride also are shongly asso-ciated to form polymeric groups in the liquid state. As in the previous cases some of the Raman lines due to the liquid are observed to be totally dePolarised both by the present authors and by Simons (J932). Hence the single molecule has a plane of symmetry. From the above discussions it can be concluded that the lines in low frequency region observed in the Raman spectra of these three benzene derivatives in the solid state at about - 170°C are not due to lattice oscillations in which only the intermolecular electrostatic field takes part, but they are due to vibrations in polymeric groups which arc present even in the liquid state in two of the derivatives and are formed in the solid state in the case of benzylamine. ACKNOWLEDGMENTS The investigation was carried out in the Palit Laboratory of the Physics Department, University College of Science, Calcutta. The authors are indebt-ed to Prof. M. N. Saha, F.R.S., for kindly providing all facilities for the investigation in the Palit Laboratory. / PHYSICS DIiI'AR~'MIINT, CALCUTTA VNIVItRSITV. 92, VI'PER CIRCUI,AR ROAD, CAI,CUTTA. REFERENCES Dadieu A, and Kohlrausch, K. W. F. (1929). S. R. :g. in benzene derivatives. Monatsh, 83, M, 282 (1930) ; S. R. E. in organic substances Monatsh, 66,379. Fox, J. J. and Martin, A. E. (1940). Investigations an the Infra-red spectra. Trans. Farad.. Soc., 36, 867 • Howlett, L E. (1931). Raman effect in glycols .and nitriles. Canad. J. Res., I, Bo. Raman Spectra iit Low Temperatures 117 Kohlraus('h, K. W F. lind Pongratz, A. (1934/. S. H. E. in benzene tlt'ril'lItivE's, lVlell. Rer., 142, ,'iRB Matslll1o, K and Han, 1\ (H)331. Ramon effect ill bellzene derivatives Hull. Cllew. Soc. japan, 8. 333. Mizushima, S. and Morino, V. (19381. Roman spectra and molecular configurations of ' ethylene dibromide PrOt". Ind. -/cad. Sr. II, 8,3':;' Reitz. A. W. and Htock mair, V/. I J '35) Ramen sp('l'trn of benzene deri\'ati\'es, Wi,,". Ucr. 114, (66. Simons, L. ;193zl. 1'olaris1\tion of Raman lines of some organic suhstances. SO(, St. Finnira. Comm. Phys. Ma/ll, ,SS Sirkar, S. C. (1937\ On the intensities 01 Raman lines due to lattice osrilla.tions. Ind. J. Ph),s, 11.343· Sirl,er, S, C. and Bishlli, R M (19431. On' the Raman spectra of a few alkyl slllphides in the solid state, 1'1'0(, Nat Ins!. Sc mdia, 9,287. Sirkal', S. C. and Bishui. II. M. 1194,'i1. On the Raman spectra of ethylen(' dibromidc and dkhlorethyifne in the solid state Illd. I I'liys., 19, 24. Sirkar, S. C. awl Bisbui n. M. (1946). Oil the Raman spectra of a few aliphatk ketones in the solid state. llld. j. l'hys., 20, 35. Thatte, V. N. and Ganes'In, A. S. (293(1. Raman spectra of organic substances. 1'1111, Mag., 22, 823. Thumpson, D. n. and NOlTis, J. F. 119,,6), Raman spectra of benzene derivatives. jour. Amer. Clteln. Soc., 58, 1953; 59, 816. 'l'he following special publications of the Indian Association for the Cultivation of Science. 210, Bowbazar Street, Calcutta, are available at the prices shown against each of them :-N:J.. Subject Author III Methods in Scieutific Resean'h Sir E. J. Russell IV The Origin of the Planets Sir James H. Jeans V Separation of Isotopes Prof. F. W. Aston VI Garnets and their Role in Sir Lewis L. Fermor Nature. VII (I) The Royal Botanic Gardens. ••• Sir Arthur Hill Kew. VIII IX X (2) Studies in the Germination ... of Seeds. InteratomiC' Forces The Educational Aims and Practices of the California Institute of Technology " Prof. J. E. Lennard-Jolles R. A. Millikan Active Nitt:Jgen ... Prof. S. K. Mitra A New Theory Price Rs. A. P. 060 060 060 .2 8 0 180 180 060 280 .-\ discount of 25% is allowed to Booksellers aud Ageljts. Third page of cover do. do. do. do. Other pages do. do. RATES OF ADVERTISEMENTS Rs. 25. full page " IS. half page .. 8. quarter page .. 19. full page " II. half page " 6/8, quarter page Jaurnegs of the Future TO-day ~housanda of people traverse thitI vast land by rail. whethel it be for private or business reasons. With growmg national consciousness, the desire (0 see and I<now their I)wn great country will Impel many more to travel. Where thousands travel to-day. tens of thou, sands will (ravel to-morrow In this essential service as ill many other fields of industry and commerce, steel-the metal of strength-plays a conspicuous and vital pan. --YA,.A .,.EEL----------...... by The Tata Iron " S ••• l Co .• Ltd. H .... Sal .. offio.: IOllA, CU ... Sir •••• Calcutta. 4 

On the Raman Spectra at Low Temperatures Benzene Derivatives

http://arxiv.iacs.res.in:8080/jspui/bitstream/10821/1410/1/On%20the%20Raman%20Spectra%20at%20Low%20Tempera%20_By%20S.%20C.%20Sirkar%20%26%20B.%20M.%20Bishui.pdf

On the Raman Spectra at Low Temperatures Benzene Derivatives

Abstract

Similar works

Full text

Available Versions

IACS Institutional Repository