Differentiation of excited-state and biradical processes. Photochemistry of phenyl alkyl ketones in the presence of oxygen
The photochemistry of butyrophenone, valerophenone, ..gamma..-methylvalerophenone, and ..gamma..-phenylbutyrophenone was examined in the presence of oxygen. The use of triplet quenchers to tune the triplet lifetime to a conveniently short value allows the differentiation of triplet state and biradical reactions. Typically oxygen quenches the triplet state with rate constants of approximately 4 x 10/sup 9/ M/sup -1/ s/sup -1/ and interacts with the biradicals with k/sub 8/ approximately 7 x 10/sup 9/ M/sup -1/ s/sup -1/. The interaction results in the formation of an intermediate which has as its main decay path the fragmentation to acetophenone, olefin and the regeneration of oxygen. About 75% of these intermediates decay giving type II products, while the other 25% yields a hydroperoxide. The ratio of products is probably controlled by spin statistical factors. Previous reports indicating that oxygen has no effect on the Norrish type II reaction are incorrect. 7 figures.
- Research Organization:
- Univ. of Notre Dame, IN
- OSTI ID:
- 6740848
- Journal Information:
- J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 100:14; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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