Mechanistic study of the oxidation of L-ascorbic acid by chloranil at the nitrobenzene vertical bar water interface

The redox reaction between L-ascorbic acid in water and chloranil in nitrob enzene has been studied by means of polarography with an ascending water el ectrode as well as cyclic voltammetry with a stationary interface. Through accurate measurement of the limiting currents, it has been suggested that t he redox reaction should be a two-electron reaction rather than a one-elect ron reaction described previously. A spectrophotometric technique has also been used to observe that the redox reaction proceeds spontaneously under c ertain conditions even without electrochemical control. Based on these find ings, it has been concluded that the present heterogeneous charge transfer reaction is the ion transfer of chloranil semiquinone radical, which is dri ven by the homogeneous electron transfer between ascorbic acid and chlorani l in the aqueous phase. (C) 2000 Elsevier Science S.A. All rights reserved.