Conformational rivalry of geminal substituents in silacyclohexane derivatives: 1-Phenyl vs. 1-OR,R=H or Me |
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| Authors: | Tran Dinh Phien Liubov E Kuzmina Elena N Suslova Bagrat A Shainyan Sergey A Shlykov |
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| Institution: | 1. Institute of Research and Development, Duy Tan University, 03 Quang Trung, Da Nang, Viet Nam;2. Ivanovo State University of Chemistry and Technology, Sheremetievskiy Ave., 7, Ivanovo, 153000, Russian Federation;3. A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Division of the Russian Academy of Sciences, 1 Favorsky Street, 664033, Irkutsk, Russian Federation |
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| Abstract: | Molecular structure and conformational equilibria of 1-methoxy- 1 and 1-hydroxy-1-phenylsilacyclohexanes 2 were studied by quantum chemical (QC) calculations and combined gas electron diffraction/mass spectrometry (GED/MS). Both molecules may exist in 5 or 6 forms, differing from each other by the substituents' position: (i) axial or equatorial and (ii) rotational orientation relative to the six-membered ring frame. The contribution of axial forms of both compounds varies from 35 to 60% depending on the theoretical method applied. From the GED data, the summarized molar fractions of the conformers were found to be Phax:Pheq = 70(15):30(20) and 50(20):50(20)% which corresponds to ΔG = Gax–Geq = ?0.55(46) and 0.00(56) kcal/mol, for compound 1 and 2, respectively. The concentration of the Phax forms of 1-phenyl-1-(X)-silacyclohexanes (X = H, HO, Me, MeO and Me2N) increases with the size of the second substituent at the silicon atom: 38(10)<50(20)<58(15)<70(15) <80(15)%. |
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| Keywords: | Corresponding author 1-Methoxy-1-phenyl-1-silacyclohexane 1-Hydroxy-1-phenyl-1-silacyclohexane Conformational analysis Gas phase electron diffraction Quantum chemical calculations |
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