Product distribution in preparative scale electrolysis: Part VI. Competition between dimerization and first-order deactivation

The dependence of product distribution from the various experimental parameters (rates, concentration diffusion layer thickness, current density) is analyzed for a reaction scheme involving the competition between dimerization and first-order deactivation of the intermediate resulting from the first electron uptake (or removal). Two cases are considered, corresponding to the product of the first-order deactivation being either electroinactive or undergoing a further electron transfer at the electrode or in the solution. It is shown that the dimer yield is not very sensitive to the further fate of the deactivation product. It is in all cases a function of the competition parameter σ=k₁k₂^?3/2D^1/2 c⁰ δ^?1 in potentiostatic conditions and σ^Δ=k₁k₂^?3/2D^?1/2(i⁰/FS) in galvanostatic conditions (k₁, k₂ rate constants of the dimerization and deactivation reactions respectively; D diffusion coefficient; c⁰ concentration of substrate; δ diffusion layer thickness; (i⁰/S) current density). The reduction of CO₂ in DMF with competitive formation of oxalate and formate is taken as an example illustrating the theoretical analysis.