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Published August 1, 1972 | public
Journal Article

Nuclear Magnetic Resonance Spectroscopy. Conformational Equilibration of Cycloheptane and Cycloheptene Derivatives


A study of the temperature dependence of the ^(19)F nuclear magnetic resonance (nmr) spectra of 4,4-difluoro-1,1-dimethylcycloheptane has shown that, at low temperatures, this substance exists predominantly in the twist-chair conformation with the methyl groups on the axis carbon atom. 1 ,1-Difluoro-4,5-trans-dibromocycloheptane, at low temperatures, exists predominantly in two different Conformations with the fluorine atoms at the axis carbon atom. 5,5-Difluorocycloheptene, at low temperatures, exists in a single conformation best represented as the chair. Activation parameters have been obtained for the conformational equilibration of these derivatives. For 1,1- difluorocycloheptane, 1,1,3,3-tetrafluorocycloheptane, and 4,4-difluoro-1-tert-butylcycloheptane the conformational equilibria are still rapid on the nmr time scale at low temperatures and only qualitative conclusions can be drawn about their conformations.

Additional Information

© 1972 American Chemical Society. Received October 16, 1971. Work supported by the National Science Foundation. Presented in part at the 19th National Organic Chemistry Symposium of the American Chemical Society, Tempe, Arizona, June 17, 1965.

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October 24, 2023