Oxidation chemistry of adenine and hydroxyadenines at pyrolytic graphite electrodes

The electrochemical oxidation of adenine and hydroxyadenines has been studied in aqueous solutions in the pH range 3.0–11.2 using a pyrolytic graphite electrode. The initial course of the electrode reaction has been deduced to involve a 2e, 2H+ reaction to give 2- and not 8-hydroxyadenine, further oxidation of which gives 2,8-dihydroxyadenine and then diimine species which undergo a series of chemical reactions to give different products. The major products of oxidation at pH 3.0 {urea, alloxan [2,4,5,6(1H,3H)-pyrimidinetetrone] and parabanic acid (imidazolidinetrione)} and at pH 7.0 [allantoin (5-ureidohydantoin)] have been isolated using HPLC and column chromatography and their structures elucidated by spectroscopic techniques. The probable EC mechanisms for their formation have also been suggested.