Cyclic alpha-acetoxynitrosamines: Mechanisms of decomposition and stability of alpha-hydroxynitrosamine and nitrosiminium ion reactive intermediates

A study of the kinetics and mechanism of the decay of alpha-acetoxy-N-nitro sopyrrolidine and alpha-acetoxy-N-nitrosopiperidine are reported. The compo unds differ in reactivity by more than 2 orders of magnitude at physiologic al pH. On the basis of thermodynamic parameters, common ion inhibition and azide ion trapping experiments, both compounds appear to decompose under th ese conditions by the formation of N-nitrosiminium ion intermediates; The d ifferences in reactivity are rationalized on the basis of results from an a b initio study, described in the accompanying paper. The first direct study of the kinetics of decay of cyclic alpha-hydroxynitrosamines of nitrosopip eridine and nitrosopyrrolidine and a third compound, 2-hydroxy-2-methylnitr osopyrrolidine is also summarized. These prove to be highly unstable reacti ve intermediates, in contrast to what might be expected on the basis of ear lier reports concerning cyclic alpha-hydroxynitrosamines.