A novel oxidative degradation of N-nitrosamine via electron transfer

Anodic oxidation of N-nitrosamines derived from various secondary amines has been investigated by cyclic voltammetry and controlled-potential electrolysis at a glassy carbon electrode in acetonitrile. The nitrosamines give one, two, or three irreversible anodic peaks, depending upon the structure of the parent secondary amines. Electrolysis of simple dialkylnitrosamines gave the corresponding nitramines with coulometric n-values between 1 and 1.5, together with beta-ketonitrosamines in which the carbonyl group is on the same side as the nitroso-oxygen atom. With N-nitrosopiperidine (derived from a cyclic amine), N-nitropiperidine was formed in the same way, but the beta-oxidized nitrosamine was not detected in the solution from electrolysis. Added water (ca. 1%) in acetonitrile had essentially no effect on the electrochemistry of simple dialkylnitrosamines, whereas the first anodic peak of N-nitrosopiperidine was increased and the formation of N-nitropiperidine was inhibited in the macroscale electrolysis. In deoxygenated acetonitrile, the first anodic peaks of all the nitrosamines examined were enhanced and the other anodic peaks became obscure. Macroscale electroysis gave neither the nitramines nor the beta-ketonitrosamines and the coulometric n-value increased. It is suggested that unidentified oxidation processes produce electroactive species whose further oxidation results in various degradation products.