Photochemistry of N-nitrosamines in neutral media

N-Nitrosamines have long been held to be photostable in solution in absence of acid, although a few reports to the contrary have been published. This paper reports a study of the photolysis of N-nitrosopiperidine and N-nitrosodiisopropylamine in aprotic and protic solvents. It is shown that the cleavage of the N-N bond is a very facile process. In the absence of radical scavengers, however, reformation of the nitrosamines is very rapid, giving little or no net photolysis. In the presence of scavengers, photolysis proceeds with high efficiency to give non-nitrosamine products. When the trapping agent is oxygen, the net reaction is photo-oxygenation to the corresponding nitramine. The nitramine, in turn, is photolabile and undergoes photolysis to give cleavage products. The formation of the nitramine proceeds through the initial photochemical cleavage of the nitrosamine to the aminyl radical and nitric oxide, followed by the oxidation of the nitric oxide to nitrogen dioxide and the recombination of the latter with the aminyl radical. These results have some important implications for the destruction of nitrosamine wastes.