Abstract
Photolysis of benzaldehyde (1; 90% 13 C=O) in cyclohexane-d 12 results in the formation of benzaldehyde-h and -d with emissive CIDNP for the 13 C=O function. This observation requires a secondary encounter of a free benzoyl radical with either phenylhydroxymethyl or cyclohexyl-d 11 radicals. Photolysis of deoxybenzoin (5; 99% 13 C=O) and p-chloro-5 (99% 13 C=O) in cyclohexane-d 12 also generates benzyldehyde-h and -d with the same emissive CIDNP for the 13 C=O function. These observations are rationalized in terms of a previously unreported primary intermolecular deuterium abstraction by photoexcited deoxybenzoin from the (deuterated) solvent. This assignment is supported by the significantly decreased measured lifetime of triplet deoxybenzoin in cyclohexane-h and -d (429 and 724 ns, respectively) compared to the lifetime in benzene (847 ns). © 1994, American Chemical Society. All rights reserved.