Electrochemistry of Alloxan and Its N-Methyl Derivatives in Aqueous Solution

Abstract
Alloxan, methyl‐ and dimethyl alloxan in aqueous solutions are reduced by way of three processes. The first cathodic wave (wave Ia), appears between pH 0–8 and is a kinetically controlled two‐electron, one‐proton reduction to the respective dialuric acid anion. Dehydration of the reducible carbonyl site is the kinetic factor. A second pH independent kinetically controlled reduction wave (wave Ib) is observed for 1.0 mM solutions of methyl‐ and dimethyl alloxan and for 10.0 mM solutions of alloxan between pH 0–3. The process involved is the transfer of two electrons to protonated alloxan molecules, again producing the dialuric acid anion. Wave II , detected only in the limited pH range of ca. 4.7–5.9, is a virtually pH independent, two‐electron reduction of the hydrated form of alloxan to the dialuric acid dianion as the potential controlling process. This study indicates that wave II is not due to the further reduction of dialuric acid. Evidence is also given which refutes the view that alloxantin exists to a large degree in aqueous solutions.