Mechanisms of decomposition of alpha-hydroxydialkylnitrosamines in aqueous solution

A study of the decomposition of alpha-hydroxydialkylnitrosamines in aqueous 9% acetonitrile, with an ionic strength of 1 M (NaClO(4)), at 25 degrees C is reported. Plots of the logarithm of the buffer-independent rate constant, k(o), against pH are concave up and indicate a three-term rate law for the solvent reaction, including acid (k(H+)-, base (k(OH))-, and pH-independent (k(HOH)) terms. Secondary alpha-deuterium isotope effects for compound 1a, (N-nitrosomethylamino)phenylmethanol, are as follows: k(alpha)(H)/k(alpha)(D) = 1.12 +/- 0.03 and 1.19 +/- 0.02 for k(H+) and k(OH), respectively. General acid (k(HA)) and general base (k(A-) catalysis by more acidic carboxylic acid buffers is also observed. Structure reactivity and other parameters obtained in this study, and their changes with substrate and catalyst structure, permit the assignment of mechanisms for the k(H+) k(OH), k(HA), and k(A-) processes.