Pulse Radiolytic Polarography: The Kinetics of the Oxidation of the Ethanol Radical at the Mercury Electrode

Abstract

Abstract The ethanol radical was produced in N 2 O saturated, 2 · 10 −3 molar aqueous ethanol solutions by a 20 ns pulse of high energy electrons. The anodic current of the radical was recorded as a function of time at various potentials of the mercury electrode and at various p H‐values of the solution. The concentration of the radical in the bulk of solution as a function of time was simultaneously recorded by optical measurements. Analysis of the data shows that the electrode process is reversible in the 10 −5 s range at p H > 12, i.e. when the base form of the radical is mainly present. Transfer rate constants of more than 1.0 cm s −1 are calculated. Below p H = 12, the electrode process becomes more irreversible with decreasing p H. The kinetics of the oxidation of the acid form of the radical is strongly influenced by its adsorption at the mercury electrode. The influence of electrochemically inactive adsorbed solutes is also investigated: Adsorbed sulfate ions strongly decrease the anodic current at potentials more positive than ‐ 0.5 V. Fluorid ions exert a less pronounced effect. Adsorbed alcohol molecules have a promoting effect on the oxidation of the ethanol radical.