کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5212816 | 1383134 | 2017 | 8 صفحه PDF | دانلود رایگان |
- 1-Methyl-1-phenylsilacyclohexane was studied by GED and quantum chemistry.
- The value ÎG for Phax-twist â Pheq-orth is 0.18-0.82Â kcal/mol from DFT, MP2.
- The ratio PhaxMeeq:PheqMeax is 58(15):42(15)% from GED data.
- The rotation of the methyl group influences on orientation of the phenyl ring.
- IR spectra proves the existence of both conformers in the liquid phase.
Conformational properties and molecular structure of 1-methyl-1-phenylsilacyclohexane 1 were studied by quantum chemical (QC) calculations, combined gas electron diffraction/mass spectrometry (GED/MS) and IR spectroscopy. Molecule 1 may exist in four forms that differ by axial or equatorial positions of the substituents and by relative orientation of the two rings. Two of these conformers were found to dominate in the gas phase: 1-Pheq-orth conformer with the phenyl ring plane bisecting the CSiC endocyclic angle, and 1-Phax-twist with the phenyl ring and the CSiC exocyclic angle oriented nearly perpendicularly to each other. From the GED data, the summarized molar fractions of the conformers were found to be Pheq:Phax = 42(15):58(15)% which corresponds to ÎG = Geq-Gax = 0.19(37) kcal/mol. Experimental and calculated IR spectra provides an evidence of existence of both conformers in the liquid phase. The QC calculations yielded the ÎG = G(Pheq-orth)-G(Phax-twist) values of 0.18-0.36 DFT and 0.82 MP2 kcal/mol.
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Journal: Tetrahedron - Volume 73, Issue 8, 23 February 2017, Pages 1127-1134