Ga. Guirgis et al., RAMAN AND INFRARED-SPECTRA, CONFORMATIONAL STABILITY, AB-INITIO CALCULATIONS AND VIBRATIONAL ASSIGNMENTS FOR CHLOROMETHYL METHYL SILANE, Journal of molecular structure, 446(1-2), 1998, pp. 15-39
The infrared (3500 to 30 cm(-1)) spectra of gaseous and solid and the
Raman (3500 to 10 cm(-1)) spectra of the liquid with quantitative depo
larization ratios and solid chloromethyl methyl silane, ClCH2SiH2CH3,
have been recorded. Similar data have also been recorded for the Si-d(
2) isotopomer. These data indicate that two conformers are present in
the fluid states but only one conformer is present in the annealed cry
stalline state. The mid-infrared spectra of the sample dissolved in li
quified xenon as a function of temperature (-100 to -70 degrees C) hav
e been recorded. Utilizing conformer pairs at 738 (gauche), 685 (gauch
e), and 700 (trans) cm(-1) the enthalpy difference has been determined
to be 180 +/- 18 cm(-1) (515 +/- 51 cal mol(-1)) with the gauche conf
ormer the more stable species. However, in the spectrum of the solid,
the trans conformer is the stable rotamer remaining after the sample i
s well annealed. Utilizing the Si-H stretching frequencies from the in
frared spectrum of the ClCH2SiHDCH3 isotopomer, the two Si-H bond dist
ances are calculated to be 1.482 and 1.487 Angstrom for the gauche con
former. The optimized geometries, conformational stabilities, harmonic
force fields, infrared intensities, Raman activities, depolarization
ratios, and vibrational frequencies are reported for both conformers f
rom RHF/6-31G and/or MP2/6-31G* ab initio calculations. The gauche co
nformer is predicted to be the more stable rotamer from both ab initio
calculations in agreement with the experimental results. The other ca
lculated quantities are compared to the experimentally determined valu
es where applicable as well as with some corresponding results for som
e similar molecules. (C) 1998 Elsevier Science B.V.