PHOTOSOLVOLYSIS OF 3,4-DICHLOROANILINE IN WATER - EVIDENCE FOR AN ARYL CATION INTERMEDIATE

Irradiation of 3,4-dichloroaniline in water (λ > 290nm) gave 2-chloro-5-aminophenol with a conversion of 78±5%. The photolysis quantum yield at 313 nm of 0.052±0.003 was unaffected by cyanide (0.35 M) or pH changes between 4 and 12. A MO calculation indicated a large excited singlet state shift in electron density to the carbon undergoing substitution. The reaction is suggested to proceed through an aryl cation intermediate produced by heterolytic cleavage of the meta carbon-chlorine bond. Reaction from the triplet state is not considered likely since neither oxygen nor sorbic alcohol affected the quantum yield. © 1979.