The electrochemical oxidation of diethylstilbestrol (DES) in acetonitrile

The electro-oxidation of the former drug diethylstilbestrol (DES) was examined in detail by means of cyclic voltammetry (CV) and controlled potential electrolysis (CPE) techniques. Analogous to the electrochemistry of the structurally-related compound bisphenol A (BPA), DES undergoes two successive oxidation processes at ca. 0.64 and 0.81 vs. (Fc/Fc⁺)/V at glassy carbon electrodes in acetonitrile. The former anodic process was determined to involve up to four moles of electrons, whereas the latter anodic peak was assigned as the oxidation of a secondary product formed after the initial oxidation of DES. Results from variable voltammetric scan rate experiments showed that the secondary process can be outrun at high scan rates, while simultaneously detecting a new reduction wave (at ca. 0.50 vs. (Fc/Fc⁺)/V). Additionally, at fast scan rates, this reduction process was found to be chemically reversible; whereby a corresponding anodic peak was recorded at ca. 0.53 vs. (Fc/Fc⁺)/V on the second cycle. Following a similar mechanistic pathway as BPA, under prolonged periods of time (e.g. slow scan rates), DES is proposed to undergo an overall four-electron oxidation, whereas at fast scan rates the oxidation of DES was found to only involve two electrons. The CV data were modeled using digital simulations that allowed an estimation of the electrochemical and kinetic parameters associated with the electrode reactions.