Conformational stabilities, ab initio calculations and structural parameters for 2-chloroethyl silane and 2-chloroethyl trifluorosilane
作者:Gamil A. Guirgis、Yasser E. Nashed、Peter Klaeboe、James R. Durig
DOI:10.1016/s0022-2860(98)00768-6
日期:1999.5
The infrared spectra of gaseous and solid 2-chloroethyl silane, ClCH(2)CH(2)SiH(3) and 2-chloroethyl trifluorosilane, ClCH(2)CH(2)SiF(3), was recorded. Additionally, the variable temperature infrared spectra of the sample dissolved in liquid xenon was obtained. Both the trans and gauche conformers are present in the fluid phases. For 2-chloroethyl silane only the trans conformer is present in the solid form but for the 2-chloroethyl trifluorosilane molecule the gauche rotamer is the more stable form in the solid. The enthalpy difference between the two conformers for 2-chloroethyl silane was determined to be 181 +/- 12 cm(-1) (2.17 +/- 0.14 kJ/mol) and for 2-chloroethyl trifluorosilane 55 +/- 11 cm(-1) (658 +/- 132 J/mol) with the trans conformers more stable for both molecules. Ab initio calculations were carried out at the RHF/6-31G* and MP2/6-31G*levels for both molecules from which structural parameters and conformational stabilities were determined. The predicted conformational stabilities are consistent with the experimental results. (C) 1999 Elsevier Science B.V. All rights reserved.