Low-Frequency Vibrations of Some Organotrichlorosilanes

Abstract

The far infrared (33–500 cm⁻¹) spectra of a series of organotrichlorosilanes have been recorded. The Raman spectra (0–600 cm⁻¹) have also been measured and the relative intensity and depolarization values of lines are tabulated. The spectra have been interpreted in detail and some low-frequency “group frequencies” are proposed for the SiCl₃ moiety. The infrared (3200–33 cm⁻¹) and Raman (0–3200 cm⁻¹) spectra of α-chlorovinyltrichlorosilane have been recorded and a complete vibrational assignment is presented. Torsional oscillations of the SiCl₃ group were observed for two of the molecules; barriers of 1.7 kcal/mole and 2.7 kcal/mole were calculated for the motion around the C—Si bonds of the vinyltrichlorosilane and the ethyltrichlorosilane molecules, respectively. The results are briefly discussed. Thermodynamic properties have been calculated for the latter two molecules.