THE PREPEAK METHOD TO DETERMINE RATE CONSTANTS OF RAPID REACTIONS FOLLOWING CHARGE-TRANSFER AT ELECTRODES

Theoretical data are presented for the determination of second-order rate constants of reactions of electrode-generated intermediates with reactants in limiting concentrations for three common reaction mechanisms. The method is applicable to second-order reactions with rate constants ranging from about 10(6) M(-1) S-1 up to the diffusion-controlled limit. In cases where heterogeneous charge transfer kinetics contribute to the response, calculations must be carried out taking into account the heterogeneous rate constant. The kinetic method is demonstrated using the proton transfer reaction between a radical cation and pyridine, with a rate constant of 2.3 x 10(8) M(-1) s(-1). The method is potentially applicable to a wide range of reactions of electrode-generated intermediates.