Vibrational spectra and structure of tricyclopropylsilane

Abstract

The Raman spectra of tricyclopropylsilane were recorded for the condensed phases of this molecule, and infrared spectra ( 4 O o O cm-') were obtained for all three states of this compound. In addition, a survey microwave spectrum of tricyclopropylsilane was recorded in the R-band region, and AM1 semi-empirical calculations were also undertaken for this molecule. Both the spectrwopic data and the theoretical results indicate that tricyclopropylsilane does not exhibit any low-energy structure having threefold symmetry. Instead, experimental evidence indicates the presence of at least two conformers of this molecule in the fluid phases, and only one of these conformers remains in the polycrystallie solid phase. The Raman and infrared spectra argue in favor of the fluid-phase tricyclopropylsilane conformers having the three cyclopropane rings arranged in a mixture of s-cis and gauche orientations relative to the S i -H bond. These conclusions appear to be corroborated by the AM1 calculations, which indicate that the cis-cis-gauche rotamer of tricyclopropylsilane is the lowest in energy, followed by the cis-gauchegauche and cis-gauche-gauche' conformations, which are virtually equal in energy.

The infrared spectrum of 2-methylaziridine from scaled abinitio force fields

“…A number of absorptions due to the cis invertomer could clearly be assigned (for a discussion, see ref. 20). In the present work, the gas phase and solution IR spectra are remea- Can Fig.…”