Electrochemical Oxidation of Adenine: Reaction Products and Mechanisms

The electrochemical oxidation of adenine (6‐aminopurine), which gives a single well‐defined voltammetric wave at the pyrolytic graphite electrode (PGE), was investigated by macroscale controlled electrode potential at the PGE in aqueous 1M acetic acid solution (pH 2.3) with exhaustive isolation, identification, and determination of reaction products and intermediates. The electrochemical oxidation of adenine appears to follow initially the same path as the enzymatic oxidation, but further oxidation and fragmentation of the purine ring system occur. Thus, adenine is oxidized in a process involving a total of 6 electrons per adenine molecule to give as the primary product a dicarbonium ion intermediate, which, being unstable, undergoes a further series of reactions: (a) electrochemical oxidation to parabanic acid (some of which is further hydrolyzed to oxaluric acid), urea, carbon dioxide, and ammonia; (b) electrochemical reduction to give ultimately 4‐aminopurpuric acid, carbon dioxide, and ammonia; and (c) hydrolysis to allantoin, carbon dioxide, and ammonia.