Hydrogen Donating Solvent Participation in the Photochemistry of Benzaldehyde and Deoxybenzoin: A 13C CIDNP Study

Article abstract of DOI:10.1021/jo00084a030

Photolysis of Benzaldehyde (1; 90percent (13)C=O) in cyclohexane-d12 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 the free benzoyl radical with either phenylhydroxymethyl or cyclohexyl-d11 radicals.Photolysis of deoxybenzoin (5; 99percent (13)C=O) and p-chloro-5 (99percent (13)C=O) in cyclohexane-d12 also generates benzaldehyde-h and -d with the same emissive CIDNP for the (13)C=O function.These observations are rationalized in terms of 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).