Mohan, S

Sundaraganesan, N

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Indian J. Phys. 6 8 B (1). 87-91 (1994)U P  B- an intem ational journalVibrational spectra and normal coordinate analysis o f N-methylthiopropionamideN Sundaraganesan and S MohanR am an School o f  Physics, Pondicherry  U niversity . Pondicherry-605 014, India Received 17 June 1993, accepted 26 November 1993A b s tr a c t  : The Ram an spectnun o f  N -m ethylth iopropionam ide w as recorded in th e  reg ion  1 0 0 -4 0 0 0  cm ~ ^ . T he  in fra red  sp e c tra  o f  N -m eth y lth io p ro p io n am id e  and  N -d eu te ra ted  N  - m ethylthiopropionam ide and  their solutions in chloroform  w ere also  recorded in the range 400 0  -  180cm ~^. N orm al coord inate  treatm ent o f  both N -m ethylth iopropionam ide and N -deuterated  N -  m ethylthiopropionam ide w as canned out using  general quadratic  valence force field  and the force constan ts w ere refined by the dam ped least squares m ethod. T he potential energy distributions in sym m etry  coo rd ina tes are  d iscussed  in  re la tion  to  th e  m ix ing  o f  skeletal freq u en c ies fo r N - m ethylthiopropionam ide and the nature o f  absorption band is investigated.V ib ra tional spec troscopy  has p roved  to  be  o f  m uch  help  in e luc idating  the  struc tu re  o f  am ides. Infrared  and R am an spectra  stud ies o f  d ichroism , band  co n to u r studies and norm al coordinate analysis o f  sim ple prim ary, secondary and tertiary am ides and thioam ides and o f  th e ir deu terated  sp ec ie s  en ab led  vario u s w o rk ers  to  assign  th e  sk e le ta l freq u en c ie s and  to  investigate the nature o f  am ide 1. am ide II and the am ide III absorption bands.In th is context, the  v ibrational spectra  o f  N -m ethylth iopropionam ide have been th e  ob jec t o f  m uch interest. IR  and R am an spectra  w ith ten tative assignm ents w ere reported  by  V enkata  R am iah  and  U sha B ai [1]. H ow ever, the  IR data  w as lim ited  to  4 0 0  cm  , and R am an sp ec tru m  w as lim ited  b e tw een  2 0 0 -1 6 0 0  c m ^ .  T h e  no rm al c o o rd in a te  trea tm e n t o f  N -  m ethylthiopropionam ide w as carried out by  R am an R ao et al [2]. bu t there is no report on  the  ou t - o f-p lan e  v ib ra tio n s o f  bo th  N -m eth y lth io p ro p io n am id e  and  N -deu tera ted  N -m eth y lth io p ro  - pionam ide.K e y w o r d s  : V ibrational spectra. N -m ethylthiopropionam ide, N -deuteiated thiopropionam ide, vibrational assignm entP A C S  N o s . : 33 .10 . G x . 33 .20 .-t, 78 .30 .-jAs there are several discrepancies in the assignments proposed in the above investigations [1*2], an attempt has been made to reinvestigate the Raman and infrared spectra by including both in-plane and out-of-plane vibrations. In the present work, we report a complete infrared and Raman data along with the results of normal coordinate analysis taking into account the internal modes of the CH3 and CH2 groups. ^  lACSN  Sundaraganesan and S  Mohani 5s — U5— CM m *riCO </3 C/3 C/5^ ^ m „^  ^  On Ch 00 00O'i  i  i  iO ' O n ^  ON ONCO OQ _  P^^  CO oo ^^  oo CO CO§ "  = 2. ^  o  CO - r* ~•- fM fO O nNOS I  s  IfC>  ^ CO «6 =  ^ r5fi to" o3 j2 s  i  3=: " 3i l l s I si  ~  i  Sl i s l  S 3 8 ? S Sdt = s  2t c:) »L  sfi £  5 y  o  .1S8 & yX & y  5  S  i  I  I" I" ^X a:t)a: XuJ5£  -It  Sa d&X 3t  ?I Ii 1  I% Xdo IJ8% Xo#IX I  ?: ut  ?= t)p CO> CO> s .f I ?S'*'§ ' S! ' F: s?a 2 CO cn§  §  §  I  »  »S  ?  ^  o  VO Sjq R R S S SCO>s  s^ >^i  I  i  ^?  SfO  CM1 ^ CO> i COCO O I i i i i •Q» I i IVibrational spectra and normal coordinate analysis etc 292r3O?:ubOcPUa: a:8GO>aS2  n: D: p: ^ 5^8  = S ^ ^*— ^   04 r4 r4oo ON ^  00 ^  cnS 2  g  K S |  §f II III P  ^f f i I's ic s a R n ^ N  n « j 2 ‘ J ‘ & 1G O G O C O M I O M C O  C O G O ^ ^ ^ * ^ * ^P ! 9 S ; s : 8 ; s ^® S 3  -S' -T!* -Pi-ft -rS^S § | 5 S 6 g g tCO « o o r - ^. ^  ^  CH2 ?3 ^  3  3§ fJ jS  !2boI I  ^? Vt b•IfI l l s<2•8zV•Sb  b  b  e  ^b i  b  2  ^!£J ms^  PI  ICOsCMJCOnCOs^•8uIbIbuIbIbR? I § Io  2^:sJItuI 1 U 2O. O. JT*6  5  I  i: « : « j«Sa n  ijCO> 1 s s S 1 >1 o s«o«r>B 1 8COS sI  > > ^ ^ ^^ m r- lo o  ONi i I i s i 2? sI  §i•< <90 N  Sundaraganesan and S  Mohancs CM CM CM CMa:a: aa H  aa3 3+ + Inaa i'i'ai’iS I fJ |  J J  s 'Br- »n «o mm ■^ m m rfo  cN m oo+ + + +CM CM CM CM'r^  'Tn 'g ia ® <1 2i  «i l y gn <N + +a^7s I a**u CM CM CM/~ vfC> CM5 "7^a 3g'W g g3 s3i «N7>, CM CM CNJ a a Xu>• 3 53 g5  2  o= = I §ZiSs»  »  >S 9  ^s  SIsO 100s' § Sm , ^  m''j' &V:§I■pSs  z  >g  9  ia»-•I§Vibrational spectra and normal coordinate analysis etc 91Pure chemicals of N-methylthiopropionamide (NMTP) obtained from Bharathidasan University was used as such without further purification, to record Raman and infrared spectra. The laser Raman spectrum of NMTP was recorded using 488 nm line of At* for excitation in the region 100-4000 cm"^  in Cary Model grating spectrophotometer with a 4 W Ar+ laser. The infrared spectrum of NMTP and N-deuterated NMTP and their solutions in chloroform were recorded using Perkin Elmer 983G double beam grating spectrophotometer. N-deuteration was achieved by repeated exchanges with D2O. The removal of D 2O was carried out at room temperature in order to minimize a possible sample deterioration which was reported in literature [3]. Experiments carried out under the same conditions used for the deuterium exchange, but using normal water as solvent, did not reveal detectable sample changes.In order to ascertain the amount of mixing among the normal modes and to obtain a more accurate description of the fundamental vibrations of NMTP and N-deuterated NMTP, a normal coordinate analysis was undertaken. The calculations were performed using Wilson's FG matrix method with the computer programs developed by Schachtschneider [4],The molecular skeleton is planar to a good approximation and therefore a Q  symmetry can be assumed. This results in 39 fundamental vibrations which span the irreducible representations as 24A' (in-plane) and 15A " (out-of-plane) vibrations. All the fundamental modes are active in both Raman and infrared spectra. The bond lengths used in the present investigation are C-N = 1.36 A; C = S = 1.71 A; N-C = 1.47 A; C-C = 1.54 A; C-H = 1.09 A and N-H = 1.02 A. These values are taken from similar related system in reference to the title molecule.The observed and calculated frequencies, potential energy distributions (PED) in symmetry coordinates for NMTP and N-deuterated NMTP are shown in Table 1. PED in symmetry coordinates is obtained by using the formula f„/.  ^/  A*. PED contributions below 10% are not shown in the table.R e f e r e n c e s[1] K Venkata Ramiah and P Usha Bai 1973 Curr Set. 42  5 1[2] G Ramana Rao, V Balasubramanian and K Venkata Ramiah 1978 Indian J. Pure Appi Phys, 16 6 5 7[3] R A  Kydd and A  R C Dunham 1983 J. Molec. Struct. 69  79[4] J H Schachtschneider 1969 Technical Report (Shell Development Co. Emeryville, CA USA)

Vibrational Spectra and Normal Coordinate Analysis of N-Methylthiopropionamide

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Vibrational Spectra and Normal Coordinate Analysis of N-Methylthiopropionamide

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