The rotated disk electrode (RDE) has unique advantages for studying chemical reactions interposed between successive electron transfers (so-called ECE reactions). A simple modification of previously described digital simulation techniques allows various chemical kinetic complications to be introduced into the basic RDE hydrodynamic equations. These calculations have been applied experimentally to the important class of ECE reactions involving dimerization of cation radicals. The anodic oxidation of several substituted triphenylamines and their subsequent dimerization to tetraphenylbenzidines was studied at a platinum RDE. Second-order rate constants for dimerization in the range 103-104 1. mol-1 sec-1 were readily uncovered.
Digital simulation has proven to be a useful approach to electrochemical problems involving complex geometries. This method was used to take into account the contributions of cylindrical diffusion to diffusion processes at finite planar disk electrodes. The current-time relationship for diffusion-controlled electrolysis at a planar disk electrode with radius R was found to be it1/2 = (nFACD1/2/ir1/2)jl + 1.92(Dt//i2)1/2¡. For chronopotentiometry the transition time, r, was found to be given by ir1/2 = (nFACD1/2 7 1/2/2)|1 + 0.72 // 2)1/2|. The chronoamperometric working curves for the first-order ECE
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