Anomalous influence of adsorbed higher aliphatic alcohols on electroreduction of nitromethane and 1-nitrohexane on mercury electrodes

The electroreduction of nitromethane and 1-nitrohexane in both the absence and in the presence of n-octanol and n-decanol was studied. It was found th at, under comparable conditions at smaller concentrations of inhibitors, ni tromethane is inhibited more strongly than 1-nitrohexane by the n-alcohol a dsorbed monolayer on the mercury electrodes. This was explained by the larg er affinity of nitrohexane to the alcohol-rich surface phase and of nitrome thane to the aqueous solution phase. Through the increased affinity of both reactants to the electrode surface phase at the inhibitor concentration, c /c(s), exceeding 0.6, the independence of the electroreduction rate constan t of both reactants was explained. When the bulk concentration of inhibitor s approached saturation even the increase of the rate constant was observed . The change of the solvent composition, from pure water to 10 vol.% ethano l, increases the inhibition by increasing the affinity of the reactant to t he solution phase.