The halogenation of aromatics: Part VI. Types of reactions occurring in the gas‐phase halogenation of benzene derivatives

Abstract A series of chlorinations of benzene derivatives C6H5X showed that three main reaction types may be distinguished, viz. a) substitutions into the nucleus with retention of X (X = C6H5‐O, Cl, F, CN, CCl3, COCl, COOCH3), b) substitution within the group X (X = alkyl, CHO, probably OCH3) and c) exchange of X for Cl (X = NO2, CHO, Br, probably Cl). Bromination of chlorobenzene led to bromobenzene and bromochlorobenzenes as well as to dibromobenzenes and dichlorobenzenes. Isomer distributions in the latter two dihalides were slightly different from those found in the bromination of bromobenzene and chlorination of chlorobenzene, respectively. Some of the mechanisms involved are briefly discussed.