Nitrosation, diazotisation, and deamination. Part XIII. Substituent effects of the nitrosation of anilinium ions

Abstract

The rate of diazotisation of aniline in 3M-perchloric acid is accelerated by m- and p-methyl and -methoxy-groups and retarded by chlorine atoms in the meta- and para-positions: the strongest acceleration is given by the m-methoxy-group. Similar results are reported for the effect of three substituents on the nitrosation of N-methylaniline under the same conditions. The substituent effects of p-methyl and p-chloro-substituents are not very sensitive to an increase in the acidity of the medium. The substituent effects are shown to be inconsistent with reaction through the free amine and are interpreted in terms of an initial attack of the nitrosating agent on the aromatic ring of the protonated amine followed by proton loss from the –NRH₂+ group and migration of the nitrosating agent to this group.