ROLE OF PROTON-TRANSFER IN THE ELECTROCHEMICAL REDUCTION-MECHANISM OFSALICYLIDENEANILINE

The electrochemical reduction mechanism of salicylideneaniline has bee n investigated by cyclic voltammetry, controlled potential electrolysi s and coulometry. The main reduction product, characterised by HPLC, I R,H-1 NMR and X-ray diffractometry, is an anionic dimer, present in tw o diastereoisomeric forms, together with the conjugate base of the sub strate. The latter stems from an intermolecular proton transfer from t he substrate to a basic reduction intermediate. Kinetic analysis of th e voltammetric results has allowed the electrode reaction mechanism to be fully characterised, showing in particular that the rate-determini ng step is the coupling between two anionic radicals, promoted by intr amolecular H-bridging. (C) 1997 Elsevier Science S.A.