Conformational analysis—XXI : H NMR Conformational Study of Alkyl-Substituted 2-Oxo-1,3,2-Dioxathianes |
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Authors: | Tertu Virtanen Hannu Nikander Kalevi Pihlaja Erkki Rahkamaa |
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Affiliation: | Department of Chemistry, University of Turku, SF-20500 Turku 50, Finland;Department of Chemistry, University of Helsinki, SF-00100 Helsinki 10, Finland |
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Abstract: | 2-Oxo-1,3,2-dioxathiane and all methyl- and several alkyl-substituted 2-oxo-1,3,2-dioxathianes were prepared for a 1H NMR conformational study. The conformational energy of the axial SO group in CCl4, - ΔGθSO = 14.8±0.3kJ mol?1, was determined by chemical equilibration of the epimeric cis-4,6-dimethyl derivatives and it was found to decrease with the increasing solvent polarity. The conformational equilibria of alkyl-substituted derivatives were solved and the proportions of the conformers estimated using 1H NMR chemical shifts, vicinal coupling constants and in three cases also dipole moments. The configurational interactions in the C4C5C6 moiety are close to the corresponding values of 1,3-dioxanes. |
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