Publication costs assisted by the XJ. S. Army Natick LaboratoriesThe absorption spectra, extinction coefficients, decay kinetics, and dissociation constants of the ketyl radicals and the radical anions of 2-, 3-, and 4-benzoylpyridines have been observed and determined. These radicals were produced from the reaction with hydrated electrons in aqueous 1.0 M iert-butyl alcohol, using the technique of pulse radiolysis. The ketyl radicals have high extinction coefficients and absorption bands in the visible and uv regions. The pAa's are 12.3 ± 0.2, 9.2 ± 0.2, and 12.0 ± 0.2 for 2-, 3-, and 4-benzoylpyridine, respectively. A second dissociation constant of the ketyl radicals for the corresponding benzoylpyridinium ions is observed with pAa's of 3.1 ± 0.1, 4.1 ± 0.2, and 4.2 ± 0.2, respectively. Identical spectra were observed from the reaction of acetone ketyl radicals (CHOjCOH with these benzoylpyridines (BP), indicating a quantitative electron transfer to form the corresponding ketyl radicals. The rate constants of reactions of (CEUhóOH radicals with BP were found to be dependent on the pAa of the BP. The ketyl radical and radical anions of 3-benzoyl-V-methylpyridinium ion were found to be distinctly different from those of 3-BP and a pAa = 5.9 ± 0.2 was determined. The absorption spectra of the H atom adducts to benzoylpyridinium ions were also determined and are compared with those of the ketyl radicals. Analogies between the photochemistry and radiation chemistry of benzoylpyridines and benzophenone are discussed.

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Cyclohexen (I) führt bei der radikalischen Addition (photochemisch oder über Redox‐Transfer) von Brom‐dichlornitromethan (II) zu den beiden Addukten (III) und (IV).