Photolysis of 5,5-dimethyl-4-phenyl-Δ-1,2,4-triazolin-3-one. Fragmentation to nitrogen, carbon monoxide, and isopropylidene phenyl amine

Abstract

Photolysis of 5,5-dimethyl-4-phenyl-Δ1-1,2,4-triazolin-3-one (2) produces the same products as thermolysis; namely, nitrogen, carbon monoxide, and isopropylidene phenyl amine (acetone anil). The quantum yield for direct photolysis of 2 in methanol with 313 nm light is 0.066. Sensitization with benzophenone in the same solvent, and quenching with 1,3-cyclohexadiene, revealed that photolysis of 2 involves a triplet excited state. The most likely photo processes are thought to involve initial cleavage of the C3—N4 bond or the C3—N2 bond (Norrish, type 1 cleavage).