Electrochemical Study of Pyridoxine (Vitamin B₆) in Acetonitrile

Cyclic voltammetry (CV) and controlled potential electrolysis (CPE) experiments revealed that at a Pt electrode, pyridoxine undergoes a one-electron chemically irreversible oxidation at approximately 0.50V versus Fc/Fc⁺, likely generating a dimeric product. Fouling of the electrode surface could be detected with repeated scans during CV and during preparative scale CPE oxidation experiments. These adsorption effects were overcome by performing bulk oxidation of pyridoxine with NOSbF₆ as a chemical oxidant. At Pt electrodes, a cathodic wave associated with the reduction of pyridoxine was detected at approximately -1.60V versus Fc/Fc⁺. The reduction process appeared to be chemically reversible on the shorter timeframe of CV, but not under the prolonged timescale of CPE. The reduction of pyridoxine involves a direct discharge of pyridoxine at the Pt surface, generating an oxide anion, which upon treatment with iodomethane yields N-methylated pyridoxine rather than its O-methylated analogue. Dual electrochemical behavior: In acetonitrile, pyridoxine can undergo both electrochemical oxidation and reduction independently, of which both processes involve one electron each. The oxidation process appears to be chemically irreversible and fouled the electrode, whereas the reduction process seems to be chemically reversible only for a short timeframe of seconds. The mechanisms of these processes were investigated (see picture).