Inactivation of biologically active N-methyl-N-nitroso compounds in aqueous solution: effect of various conditions of pH and illumination

The rates of decomposition of N-methyl-N′-nitro-N-nitrosoguanidine (NG), N-methyl-N-nitroso-p-toluenesulfonamide (MNTS), N-methyl-N-nitrosourea, and N-methyl-N-nitrosourethane in dilute aqueous solutions at pH levels ranging from 2 to 9 are tabulated. There are considerable differences in the breakdown rates of these compounds. At low pH, MNTS is destroyed several times faster than any of the other compounds, while at pH 7, MNTS is about 100 times as stable as methylnitrosourea. Rates of photochemical destruction of NG and MNTS are also given. Some of the breakdown products have been identified. These data are used to provide tentative explanations for some apparently anomalous biological results.