Vibrational assignments and torsional barrier heights of some methylsilylchlorides

The infrared spectra of gaseous chloromethyl-, dichloromethyl-, and methyldichlorosilane have been obtained from 4000 to 33 cm−1 and the far infrared spectrum of gaseous methylchlorosilane has been recorded from 350 to 33 cm−1. The far infrared spectrum of the low temperature solids (−190°C) have also been recorded from 350 to 33 cm−1. The Raman spectra of the liquids have been measured, with quantitative depolarization ratios, from 4000 to 100 cm−1. Assignments for all of the fundamentals for each of the molecules are proposed on the basis of depolarization ratios, band contours, and group frequencies. The bands corresponding to the torsional modes are assigned as appearing at 172, 177, 175, and 184 cm−1 in the infrared spectra of the solids and give corresponding barriers of 3.00, 3.69, 2.25 and 2.09 kcal/mole for chloromethyl-, dichloromethyl-, metylchloro-, and methyldichlorosilane, respectively. The results are discussed in terms of present theory.