ELECTROCHEMICALLY INDUCED AROMATIC NUCLEOPHILIC-SUBSTITUTION IN LIQUID-AMMONIA - COMPETITION WITH ELECTRON-TRANSFER

Electrochemical inducement of aromatic nucleophilic substitution of ArX compounds is investigated for a number of substrate and nucleophile systems in liquid ammonia. Electron transfer to the Ar-radical resulting from the initial reductive cleavage is essentially the only reaction competing with substitution. The competition occurs under two different regimes involving either homogeneous or heterogeneous electron transfer leading to different kinds of kinetic control. Cyclic voltammetry is used both for a rapid estimate of the nucleophile reactivity and for a quantitative determination of the rate constants of the nucleophile addition on Ar-. The method is also applied to the determination of the kinetic stabilities of the substrate anion radicals which is not possible through the standard application of electrochemical techniques. The agreement of the predicted kinetics with the experimental data both under homogeneous and heterogeneous electron transfer conditions provides further support for the SRN1 mechanism. © 1979, American Chemical Society. All rights reserved.