Alternating current polarography with multi-step charge transfer

A theory is presented for the a.c. polarographic wave arising from a two-step charge transfer process in which rate control is exerted by diffusion and charge transfer. Predictions of the theory are examined in detail. It is found that: (a) conditions for pure diffusion control depend markedly on the relative values of the standard potentials associated with the two charge transfer steps; (b) many features potentially useful in mechanistic diagnosis are predicted for the a.c. polarographic read-out and ambiguity between single-step and two-step mechanisms is highly unlikely; (c) as one would expect, relative and absolute values of the rate and thermodynamic parameters associated with the charge transfer steps have a profound influence on the predicted a.c. polarographic-behavior; (d) despite the complexities and variety of behavior predicted, simple rationalization of many of the predictions is possible; (e) the problem of evaluating rate parameters from experimental data appears amenable to solution.