CONFORMATIONAL STABILITY, STRUCTURAL PARAMETERS, VIBRATIONAL FREQUENCIES, AND RAMAN AND INFRARED INTENSITIES OF ALLYLSILANE

The Raman spectra (3500 to 30 cm(-1)) of allylsilane, CH2CHCH2SiH3, in the liquid with quantitative depolarization ratios and solid states a nd the infrared spectra (3500 to 30 cm(-1)) of the gas and solid have been recorded. Similar data have also been recorded for the Si-d(3) is otopomer. Additionally, the mid-infrared spectra of the normal sample dissolved in liquified xenon as a function of temperature (-100 to -50 degrees C) have been recorded. All these data indicate there is a sin gle conformer, the gauche rotamer, in all three physical states. Utili zing the Si-H stretching frequencies from the infrared spectrum of the gaseous CH2CHCH2SiD2H isotopomer, the three Si-H band distances (r(0) ) are calculated to be 1.484 Angstrom for the gauche conformer. The ot her ro parameters are estimated from the previously reported rotationa l constants. The fundamental frequencies for the asymmetric (78 cm(-1) ) and SiH3 (137 cm(-1)) torsions were obtained from sum and difference bands with the SiH3 stretches. From the SiH3 torsional frequency the barrier to internal rotation is calculated to have a value of 731 cm(- 1) (8.74 kJ/mol). The optimized geometries, conformational stabilities , harmonic force fields, infrared intensities, Raman activities, depol arization ratios, and vibrational frequencies have been obtained from RHF/6-31G* and/or MP2/6-31G* ab initio calculations. These quantities are compared to the corresponding experimental quantities when appropr iate as well as with some corresponding results for some similar molec ules.