SPECTRA AND STRUCTURE OF SILICON-CONTAINING COMPOUNDS .21. INFRARED AND RAMAN-SPECTRA, CONFORMATIONAL STABILITY, AB-INITIO CALCULATIONS ANDVIBRATIONAL ASSIGNMENTS FOR CHLORODIMETHYLMETHOXYSILANE

The Raman (50 to 3200 cm(-1)) and infrared (50 to 3500 cm(-1)) spec tr a of chlorodimethylmethoxysilane, Cl(CH3)(2)SiOCH3, in the vapor and s olid phases have been recorded. Raman spectra of the liquid including depolarization ratios have also been recorded. Optimized geometries an d conformational stabilities have been obtained from ab initio calcula tions utilizing the RHF/3-21G and RHF/6-31G* basis sets. The calculat ions from both of these basis sets indicated the gauche conformer to b e significantly more stable than the trans conformer. Since the gauche has twice the multiplicity of the trans form it is unlikely that the trans conformer will be detected in the fluid phases at room temperatu re. This is supported by the fact that no infrared or Raman bands were found to vanish in the spectra of the crystalline solid. The vibratio nal frequencies have been calculated using appropriate scaling factors , and the vibrational spectra are interpreted in detail. The results h ave been compared with those obtained for some related molecules.