Denitrosation of nitrosamines—a quantitative study. Reactions of N-methyl-N-nitrosoaniline, N-nitrosoproline, dimethylnitrosamine and N-nitrososarcosine

Abstract

Rate measurements are reported for the denitrosation of N-methyl-N-nitrosoaniline (NMNA), N-nitrosoproline (NPr), dimethylnitrosamine (DMN), N-nitrososarcosine (NS) and N-nitrosopyrrolidine (NPy), in acid solution in the presence of nucleophilic catalysts in the following solvent systems: water, ethanol, various aqueous acetic acid solutions (up to 80% acetic acid) and acetonitrile. The reactivity sequence generally is found to be NMNA > NPr =ca. NS DMN =ca. NPy. The most reactive solvent system is 80% acetic acid–water containing bromide ion (or thiourea) as a nucleophilic catalyst. The results, together with some earlier work in water, are discussed (a) in terms of the changing relative reactivities of the nucleophiles as the polarity of the solvent is changed, and (b) in terms of the electron-withdrawing properties of any substituents which can effect both the protonation equilibria and also the rate constant for nucleophilic attack of the protonated form of the nitrosamine.