Photochemical nitration by tetranitromethane .38. Nitration of tris(4-bromophenyl)amine, a compound corresponding to a stable radical cation

The photochemical reaction between tris(4-bromophenyl)amine (TBPA) and tetranitromethane in dichloromethane or acetonitrile gave almost exclusively the nitro-debromination product, 4-nitrophenylbis (4'-bromophenyl) amine (1). In the presence of trifluoroacetic acid, the 2-nitro-substitution product, 4-bromo-2-nitrophenylbis (4'-bromophenyl) amine (3) also appeared, together with further brominated TBPAs (4). Preparative and kinetic studies of the individual reactions involved, viz. the TBPA-NO2, TBPA(.+)-NO2 and TBPA(.+)-trinitromethanide ion reactions, indicated that the simple regiochemistry of the photochemical reaction is due to an addition-elimination mechanism, in which the initial attack of trinitromethanide ion occurs at the carbon ipso to the nitrogen function.