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Ab Initio Calculations of the Potential Surface for Rearrangement of 2,2,3,3-Tetrafluoromethylenecyclopropane to 1-(Difluoromethylene)-2,2-difluorocyclopropane.
- Source :
-
Journal of the American Chemical Society . 12/27/2006, Vol. 128 Issue 51, p16676-16683. 8p. 1 Diagram, 1 Chart. - Publication Year :
- 2006
-
Abstract
- (4/4)CASSCF and CASPT2 calculations have been performed to understand the reason that addition of a second pair of geminal fluorines to methylenecyclopropane lowers the barrier to rearrangement by 6.7 kcal/mol more than addition of the first pair. Our calculations duplicate this experimental finding by Dolbier and co-workers. Our computational results confirm Dolbier's conjecture, that the non-additive lowering of Ea for the rearrangement of 2,2,3,3-tetrafluoromethylenecyclopropane (9) to 1-(difluoromethylene)-2,2-difluorocyclopropane (11) is due to destabilization of 9 by the presence of the vicinal CF2 groups in this fluorocarbon. In the course of exploring the potential energy surface for the rearrangement of 9, we have located a bond-stretch isomer (21)) that differs from 9 by inversion of both CF2 groups. The enthalpy of 20 is computed to be 21.9 kcal/mol higher than that of 9, but direct interconversion of these two ‘bond-stretch invertomers’ requires passage over a TS whose enthalpy is calculated to be 11.7 kcal/mol higher than that of 20. [ABSTRACT FROM AUTHOR]
- Subjects :
- *THERMODYNAMICS
*PHYSICS
*QUANTUM chemistry
*CHEMICAL bonds
*ENTHALPY
Subjects
Details
- Language :
- English
- ISSN :
- 00027863
- Volume :
- 128
- Issue :
- 51
- Database :
- Academic Search Index
- Journal :
- Journal of the American Chemical Society
- Publication Type :
- Academic Journal
- Accession number :
- 23659571
- Full Text :
- https://doi.org/10.1021/ja065963y