As another proof of H2 evolution, the basicity of the reaction was probed; if proton reduction took place, a basic environment would result and facilitate base-mediated side reactions. The reduction of 1 was therefore interrupted to study a possible side reaction occurring on base-sensitive methyl ester. Indeed, transesterification product 46 was observed under DC conditions, whereas no such product was observed under rAP conditions. Consistent with these findings are literature reports of CO2 or CO reduction using pulsed potential instead of DC that produce less H2. Collectively, these experiments support the mechanism summarized in Figure .