VIBRATIONAL-SPECTRA, NORMAL VIBRATIONS AND ROTATIONAL-ISOMERISM OF ALKYLSILANES .2. ETHYLMETHYLSILANE, DIETHYLSILANE, METHYLPROPYLSILANE AND THEIR SI-PERDEUTERIUM COMPOUNDS

The infrared and Raman spectra of ethylmethylsilane, diethylsilane, methylpropylsilane and their Si-perdeuterium compounds were measured for the liquid and crystalline solid states. The spectra were analysed on the basis of the normal coordinate treatment. The CSi stretching wavenumbers are correlated with the conformation of the (Si)CH2CH2(C) group. This correlation is in accord with that obtained for the CS stretching wavenumbers of alkyl sulphides. In the crystalline solid state, ethylmethylsilane takes the trans form and diethylsilane and methylpropylsilane take the trans-trans form. All the staggered conformers except the gauche-gauche' form of the latter two compounds were shown to coexist in the liquid state. The trans and gauche conformations about the (C)SiH2CH2(C) axis have similar stabilities to each other. © 1979.