Nuclear Magnetic Resonance Spectroscopy. Conformational Properties of Substituted 1,1-Difluorocyclohexanes
Abstract
Rates of ring inversion and conformational equilibria of gem-fluorocyclohexanes carrying various substituents were determined by fluorine magnetic resonance spectroscopy. For 1 ,l-dilluorocyclohexane, 1,1,2,2-tetrafluorocyclohexane, 4-methyl-4-ethyl-l,l-difluorocyclohexan4e,,4 -dimethyl-l,l-difluorocyclohexanea,n d 4-chloro-1,l-difluorocyclohexane, the activation energies (E,) for ring inversion were found to fall between 8.0 and 11.2 kcal/mole. For 4-chloro-1 ,l-difluorocyclohexane, the difference in free energy for the conformation with chlorine equatorial and the conformation with chlorine axial was found to be -0.32 and -0.17 kcal/mole for solutions in propene and acetone, respectively, and practically independent of temperature. The corresponding free-energy difference for the conformations of 4-methyl-4-ethyl-1 ,l-difluorocyclohexane is - 0.10 kcal/mole. With 3-methyl-, 4-methyl-, and 4-t-butyl-substituted ll-difluorocyclohexanes the equilibria between the conformations is shifted so much in favor of one conformer that only qualitative conclusions could be drawn from the fluorine magnetic resonance spectra.
Additional Information
© 1967 American Chemical Society. Received August 8, 1966. Supported in part by the National Science Foundation.Additional details
- Eprint ID
- 61117
- DOI
- 10.1021/ja00977a018
- Resolver ID
- CaltechAUTHORS:20151014-144942097
- NSF
- Created
-
2015-10-15Created from EPrint's datestamp field
- Updated
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2021-11-10Created from EPrint's last_modified field
- Other Numbering System Name
- Caltech Gates and Crellin Laboratories of Chemistry
- Other Numbering System Identifier
- 3405