Electrochemical Oxidation of Guanine at the Pyrolytic Graphite Electrode

The electrochemical oxidation of guanine at the pyrolytic graphite electrode was investigated by linear and cyclic scan voltammetry between p H 0–12.5 and by controlled electrode potential electrolysis in aqueous 1M acetic acid solution. Guanine is oxidized by an initial potential determining attack at the double bond followed by a further oxidation of the double bond to give 2‐amino‐6,8‐dioxypurine ‐4,5‐diol which, being unstable, undergoes further reaction by two routes: ( a ) further electrochemical oxidation to parabanic acid, guanidine, and carbon dioxide; and ( b ) hydrolysis to oxalyl guanidine and carbon dioxide. The exact nature of intermediate species in the electro‐oxidation of guanine and uric acid were more thoroughly established by extensive use of fast sweep cyclic voltammetry. In particular it appears that in ammonia buffers at moderately high p H, the intermediate is a 4,5‐diamine rather than a 4,5‐diol.