Photoreactions of Nitroso Compounds in Solution. XX. Photoreduction, Photoelimination, and Photoaddition of Nitrosamines

It has been established that alkylnitrosamines undergo photoreduction in methanol solutions in the presence of an acid to give the parent amine, formaldehyde, and N-aminoformamide. Where it is possible, an exchange reaction between the δ-hydrogen and the nitroso group is also observed during this photolysis. However, photoelimination also occurs in competition with photoreduction, the extent of which is dependent on the rates of the two photoprocesses. In aqueous solutions, N-nitrosamines predominantly undergo photoelimination. Those nitrosamines that undergo rapid photoelimination or photoreduction do not efficiently add to olefins photolytically. Conversely if photoaddition is retarded, a nitrosamine takes elimination or reduction pathways. Excitation of n → π* or π → π* transition band of N-nitrosamines gives virtually the same photoreaction patterns. Minor differences in the photoproducts are attributed to other secondary reactions.