Trace crossings in cyclic voltammetry and electrochemic electrochemical inducement of chemical reactions: Aromatic nucleophilic substitution

Crossing of anodic and cathodic traces is frequently observed on cyclic voltammograms featuring the electrochemical induction of a chemical reaction in the case where the product standard potential is positive to the reactant reduction potential. The theory of this phenomenon has been established in the contaxt of aromatic nucleophilic substitution. The reaction of potassium diethyl phosphite on 4-chlorobenzonitrile in liquid ammonia was investigated as an example illustrating this type of phenomenon and its interpretation. The simulation of the experimental voltammograms demonstrates the proposed mechanistic and kinetic model and allows the rate constants of the various steps to be determined. Much higher rate constants can thus been attained than by the standard application of electrochemical techniques (the gain may reach five or six orders of magnitude). A procedure is derived from these observations and then a rationalization for inducing chemical reactions with a very low electricity consumption as opposed to that which occurs when the electrode potential is settled at the level of the reactant wave.