1. A product study of 1-adamantyl and 1-bicyclo[2.2.2]octyl radicals in hydrocarbon solvents. An unusually large hydrogen isotope effect
- Author
-
Jack W. Timberlake, Alan E. Luedtke, Paul S. Engel, Woo Ki Chae, Edward S. Lewis, Gregor E. Marschke, and Sharon A. Baughman
- Subjects
Steric effects ,Cyclohexane ,Hydrogen ,Radical ,chemistry.chemical_element ,General Chemistry ,Hydrogen atom abstraction ,Photochemistry ,Biochemistry ,Catalysis ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,Deuterium ,Kinetic isotope effect ,Benzene - Abstract
1-Adamantyl (ada.) and 1-bicyclo(2.2.2)octyl (bo.) radicals have been generated by photolysis of the corresponding azoalkanes in various hydrocarbon solvents. Both radicals abstract hydrogen readily from saturated hydrocarbons and they add to aromatic rings much faster than tert-butyl. does. Despite its reactivity, ada. is remarkably selective in hydrogen atom abstraction, preferring a benzylic hydrogen 25:1 over a cyclohexane hydrogen. The effect of solvent viscosity indicates that formation of the radical dimers biada and bibo occurs in the solvent cage. The most striking result of this work is a deuterium isotope effect of 25 for hydrogen transfer from cyclohexane to ada. at 65/sup 0/C. Steric compression in the transition state is postulated to cause an unusually large tunnel correction and hence a large k/sub H//k/sub D/. 6 tables.
- Published
- 1983