Electrochemical reduction and consumption of 4-phenyl-3-buten-2-one

• We investigate the electroreduction of BDA and ZnCl2 using the mercury electrode.
• The Zn2+ reduction in the presence of BDA proceeds in two steps.
• Two steps correspond to zinc and the first step of BDA reduction.
• The BDA undergoes a 16% mineralization during 60 minutes of electrolysis with 0.3 A.

When benzylideneacetone (BDA), a commonly used brightener in the zinc plating process, is added to a solution containing Zn2+ ions in aqueous 0.5 M KCl and 0.1 M H3BO3, the zinc electroreduction potential shifts towards negative values by about 0.24 V to -1.28 V vs. SCE. Two stages are observed during the reduction of Zn2+ to zinc at -1.28 V in the presence of BDA. Besides Zn2+ reduction, the BDA, itself, is reduced in two steps at the mercury electrode. The BDA is reduced at a potential of -1.12 V versus saturated calomel electrode (SCE) for the first step, the formation of 4-phenyl-2-butanone and at -1.32 V vs. SCE for the second step, the formation of 4-phenyl-2-butanol. It was found that, Zn2+ ions do not form complexes with BDA in the substrate's concentrations used in the present study. The mineralization of the solution, which is the loss of organic compounds from solution, occurs during BDA electrolysis and is due to the rapid decomposition of BDA. The mineralization obtained after 60 minutes with current density of 0.015 A per square centimeter results in 16% loss of carbon content.