Vibrational assignments and torsional barrier heights of the dimethylhalosilanes

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Abstract
The infrared and Raman spectra of dimethylfluoro-, dimethylbromo-, dimethyliodo-, and dimethyldiiodosilane have been recorded from 4000 to 33 cm−1 and assignments are proposed for all the fundamental vibrations. The far infrared spectra and low frequency Raman spectra were recorded from 350 to 33 cm−1 for dimethyldifluoro-, dimethylchloro-, dimethyldichloro-, dimethyldibromo-, and dimethylsilane. The methyl torsional modes are assigned at 189, 156, 192, 173, 160, 178, 170, and 152 cm−1 for dimethylfluoro-, dimethyldifluoro-, dimethylchloro-, dimethylbromo-, dimethyldibromo-, dimethyliodo-, dimethyldiiodo-, and dimethylsilane, with corresponding barriers to internal rotation of 2.39, 1.70, 2.56, 2.07, 1.81, 2.18, 2.02, and 1.51 kcal/mole, respectively.