PHOTOCHEMISTRY OF SUBSTITUTED CYCLIC ENONES .7. FLASH-PHOTOLYSIS OF 3-PHENYLCYCLOPENT-2-ENONES AND 3-PHENYLCYCLOHEX-2-ENONE

The spectra and lifetime of the triplet states of 3-phenylcyclopent-2- enone, 3-phenyl-5-(prop-2-enyl)-cyclopent-2-enone, and 3-phenylcyclohex-2-enone have been measured by laser flash photolysis (λexc 308 nm). The lifetimes of the triplet state of the 3-phenyl-substituted enones are considerably longer than those reported for the unsubstituted cyclo-enones. Rate constants for the quenching of these triplet states by oxygen, (Z)- and (E)-1-phenylprop-1-ene, (Z)- and (E)-penta-1,3-diene, cyclohexene, and 2,3-dimethylbutene are recorded.