Decomposition of N-methyl-N-nitrosotoluene-p-sulphonamide in basic media: hydrolysis and transnitrosation reactions

Abstract

The decomposition of N-methyl-N-nitrosotoluene-p-sulphonamide (MNTS) has been studied in basic and neutral water–alcohol mixtures. In alkaline media and when OH^– was the nucleophile, the known hydrolysis reaction in which OH^– attacks the SO₂ group was observed; this reaction was first order in both OH^– and MNTS. In the presence of ammonia, hydroxylamine, hydrazine, or primary, secondary or tertiary amines, a transnitrosation reaction took place in which the additional nucleophiles attacked the nitrogen atom of the MNTS NO group; this reaction was first order in both MNTS and free amine. In particular, MNTS proved to be as efficient as some alkyl nitrites for the nitrosation of secondary amines in neutral or alkaline media, in which conventional nitrosating agents do not exist. Similar reaction rates were observed for the more basic tertiary amines (which gave NO₂^– among the final products). Primary amines underwent rather slower reactions, with the exception of hydroxylamine and hydrazine, the nucleophilic nature of which is increased by the α effect. We discuss the relative reactivities of the various amines in terms of their basicity and vertical ionization potentials, and we report the effect of the proportion of alcohol in the medium on the rates of both hydrolysis and transnitrosation reactions.