Synthesis and mutagenicity of 3-halogenated and 3,3',5,5'-tetrahalogenated benzidines

3-Fluorobenzidine (FBz), 3-chlorobenzidine (ClBz), 3-bromobenzidine (BrBz), 3,3',5,5'-tetrafluorobenzidine (F4Bz), and 3,3',5,5'-tetrachlorobenzidine (Cl4Bz) were synthesized and tested for their ability to revert Salmonella typhimurium. F4Bz was the only compound to show direct-acting mutagenicity and was equally potent in strain TA98 and the acetylase-deficient strain TA98/1,8-DNP6. In the presence of hamster liver S9, all compounds except Cl4Bz were mutagenic. The relative mutagenicities in TA98 were FBz greater than ClBz greater than BrBz greater than F4Bz greater than Bz greater than Cl4Bz = 0. In TA98/1,8-DNP6 the trend was F4Bz approximately BrBz approximately ClBz greater than FBz greater than Bz greater than Cl4Bz = 0.