Some New Details of the Copper-Hydrogen Peroxide Interaction

Abstract

The addition of neocuproine (NC) or bathocuproinedisulphonate at the end of the autooxidation of CuIin phosphate buffer, pH 7.4, regenerates almost entirely the O2consumed. Other chelating agents assayed, includingo-phenanthroline, cannot replace NC in promoting the O2formation. O2is also produced by adding NC to a mixture of CuIIand H2O2. Concomitant with the O2evolution, the typical absorbance of the (NC)2CuIcomplex appears to account for the complete reduction of CuIIto CuI. It is concluded that the addition of H2O2with CuIIproduces the equilibrium CuII(O2H)−↔ CuI•O2H. Addition of NC shifts the equilibrium to the right side by binding CuI. The released O2•−then reacts with the remaining CuIIyielding, in the presence of NC, the net reaction of 4 NC + 2 CuII+ H2O2→ 2 (NC)2CuI+ O2+ 2 H+. O2is also released in the absence of added NC provided the H2O2concentration is increased. In these conditions the CuII(O2H)−complex undergoes other reactions leading to the copper-catalysed decomposition of H2O2.