The Raman spectra (3500 to 30 cm
–1) of allyltrifluorosilane, CH
2CHCH
2SiF
3, in the liquid with quantitative depolarization ratios and solid states, and the infrared spectra (3500 to 30 cm
–1) of the gas and solid have been recorded. Additionally, the mid-infrared spectra of the sample dissolved in liquified xenon as a function of temperature (–100° to –55°C) have been recorded. All of these data indicate there are two conformers, the more stable
gauche rotamer and a very small amount of the
cis conformer in the fluid states, but only the
gauche form remains in the polycrystalline solid. The variable temperature studies of the infrared spectrum of the xenon solution indicate a relatively large enthalpy difference of 354±30 cm
–1 (4.23±0.36 kJ/mol) between the conformers. The fundamental frequencies for the asymmetric (54 cm
–1) and SiF
3 (48 cm
–1) torsions for the
gauche conformer were observed in the far infrared spectrum, and from the SiF
3 torsional frequency the barrier to internal rotation is calculated to have a value of 525 cm
–1 (6.28 kJ/mol). A complete vibrational assignment is presented for the
gauche conformer that is consistent with the predicted wavenumbers utilizing the force constants from
ab initio MP2/6-31G* calculations. The optimized geometries, conformational stabilities, harmonic force fields, infrared intensities, Raman activities, depolarization ratios, and vibrational wavenumbers 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 appropriate as well as with corresponding results for some similar molecules.Taken in part from the dissertation of Y. E. Nashed, which will be submitted to the Department of Chemistry in partial fulfillment of the Ph.D. degree
相似文献