The reductive halogenation of aromatic azo compounds

Abstract

The conversion of compounds of the type Ar-N=N-Y into p-X-ArNHNHY by the reaction with hydrogen halides has been re-examined and has been found to be not as general a reaction as expected. The most likely mechanism is one involving nucleophilic addition of halide ion to the aromatic nucleus at the position para to the azo group, this being facilitated by the strong -R character of the -N=N-YH+ substituent. This addition is made essentially irreversible by a series of prototropic shifts resulting in the formation of a stable hydrazo compound.