Spectra and structure of silicon containing compounds: XXIX. Conformational studies of methyl vinyl difluorosilane from temperature dependent FT-IR spectra of xenon and krypton solutions |
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| Affiliation: | 1. University of Campinas, FOP-UNICAMP, São Paulo, Brazil;2. Primary Care Postgraduate Program, State University of Montes Claros Unimontes, Minas Gerais, Brazil;3. José do Rosario Vellano University, Minas Gerais, Brazil;4. Center for Rehabilitation of Craniofacial Anomalies, University of Alfenas, Minas Gerais, Brazil;5. University of California, San Diego, La Jolla, CA, USA;6. Department of Pediatrics, Faculty of Medicine, Federal University of Minas Gerais (UFMG), Minas Gerais, Brazil;1. State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, Hubei, China;2. Chemical Engineering Department, Faculty of Engineering, Gadjah Mada University, Yogyakarta 55281, Indonesia;3. School of Material Science and Engineering, University of Jinan, Jinan 250022, Shandong, China;4. China-EU Institute for Clean and Renewable Energy, Huazhong University of Science and Technology, Wuhan 430074, Hubei, China |
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| Abstract: | Variable temperature (?55 to ?150°C) studies of the infrared spectra (3500–400 cm?1) of methyl vinyl difluorosilane, CH2CHSiF2CH3, dissolved in liquid xenon and krypton have been recorded. Utilizing three sets of conformer doublets due to the cis and gauche rotamers from the krypton solution and two pairs from the xenon solution, the enthalpy difference has been determined to be 67±7 cm?1 (0.80±0.09 kJ/mol) and 83±11 cm?1 (0.99±0.14 kJ/mol), respectively, with the gauche conformer the more stable form. However, in the crystalline solid only the cis conformer is present. Ab initio calculations have been carried out with several different basis sets up to MP2/6-311+G(2d,2p) with full electron correlation by the perturbation method from which the conformational stabilities have been determined. With the largest basis set MP2/6-311+G(2d,2p), the cis conformer is predicted to be the more stable conformer by 10 cm?1 which is inconsistent with the experimental results; however, this value is so small that the ab initio prediction cannot be relied on to give the correct conformer stability. The spectroscopic and theoretical results are compared to the corresponding quantities for some similar molecules. |
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