CONTRIBUTION TO THE ELUCIDATION OF THE REDOX BEHAVIOR OF CAMPHORQUINONE .2. VOLTAMMETRIC STUDY OF THE RATE-CONTROLLED ADSORPTION-DESORPTIONOF THE PRODUCT OF THE ELECTRODE-REACTION ON A MERCURY-ELECTRODE

The electroreduction of camphorquinone, CQ, at a mercury electrode was studied by linear-sweep cyclic voltammetry in buffered aqueous soluti ons. A pre-peak system was observed al CQ concentrations above 5 x 10( -4) M. The influence of pH, CQ concentration and scan rate on these pe aks was studied. The experimental results can be justified only if the peaks are caused by the strong product adsorption at the electrode. A t low scan rate values and high concentrations the behaviour can be ex plained if the adsorption is in equilibrium. In the rest of cases the process is controlled by the adsorption-desorption rate, even though s ome deviations from theoretical predictions are observed. Such deviati ons can be ascribed to the occurrence of side interactions between ads orbed molecules. The adsorption of CQ itself and the complexity of the reduction mechanism complicates the analysis of the adsorption-desorp tion pre-peak system.