The kinetics of the reaction of 2,4-dinitrochlorobenzene with aniline have been studied in toluene and in toluene–methanol binary solvents and compared with the reactions in benzene and chloroform. The reactions in aprotic solvents exhibit a rate dependence that is third-order in amine consistent with aggregates of the aniline acting as the nucleophile. Molecular complexes between the aniline and the substrate were also detected spectrophotometrically. Additionally, an inhibitory effect of toluene complexes was observed, which is similar to the previously reported effect of benzene in the reaction of the same substrate with n-butylamine. The reaction in the presence of pyridine shows an amine dependence which indicates formation of ‘mixed aggregates’ between aniline and pyridine. All the above results, as well as recently reported studies of other reactions different from S_NAr, are fully interpreted within the ‘dimer nucleophile’ mechanism.