Secondary hydrogen isotope effect for the transition from olefin to free radical
✍ Scribed by Richard W. Henderson; William A. Pryor
- Publisher
- John Wiley and Sons
- Year
- 1972
- Tongue
- English
- Weight
- 279 KB
- Volume
- 4
- Category
- Article
- ISSN
- 0538-8066
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✦ Synopsis
Secondary kinetic isotope effects occur in radical additions to deuterated olefins. Substitution of a deuterium at a carbon undergoing an sp2 to sp3 hybridization-change during reaction, Cg in eq. ( I ) , leads to an
The effect at a carbon going from a n olefinic to a radical center, C, in eq. (I), generally has been assumed to be negligible, since a nominal sp2 hybridization is maintained throughout reaction. Using new, sensitive instrumentation for radioactivity determination and a recently developed quench correction technique, we now find that there is a small, normal isotope effect ( k H / k T > 1) associated with a change from olefin to radical. Specifically, when R . is the polystyryl radical, X is phenyl, and the a-C bears a tritium, k H / k T = 1.04. This result is discussed in relation to recent data on cyXoaddition reactions.