Photolysis of Benztriazole in Alcoholic Glass at 77 K

Article abstract of DOI:10.1021/j100291a023

The photolysis of benztriazole (1) in alcoholic glass at 254 nm has been studied by UV absorption, emission, IR, and mass spectroscopies.Bond scission of the N-NH bond of 1 originates from the S₁(?,?^*) state to give the azo compound 2, having an absorption band at 423 nm and an IR absorption band at 2070 cm^-1.This yellow azo intermediate is decomposed thermally or photochemically.Iminocyclohexadienylidene (3) with resonance structures of a carbene (3a) and a biradical (3b) may be produced as a colorless second intermediate.On the basis of reaction product analysis from the rigid-phase photolysis of 1 at 77 K compared to those in liquid solution and gas-phase photolyses, the reaction paths of 3 to yield aniline, o-anisidine, o-ethoxyaniline, and 1-cyanocyclopentadiene are discussed in terms of the spin states of 3.