Electrochemically controlled chemically reversible transformation of α-tocopherol (Vitamin E) into its phenoxonium cation

alpha-Tocopherol (alpha-TOH) can be electrochemically oxidized in CH3CN containing Bu4NPF6 in a chemically reversible two-electron/one-proton (ECE) process to form the phenoxonium cation (alpha-TO+) that is stable for at least several hours at 243 K. In the presence of up to similar to1% CF3SO3H, alpha-TO+ exists in equilibrium with the alpha-tocopherol cation radical (alpha-TOH+.), whereas at concentrations between similar to1-3% CF3SO3H the electrochemical oxidation of alpha-TOH occurs by close to one-electron to form alpha-TOH+.. alpha-TOH+. can be further oxidized in a one-electron process to form the alpha-tocopherol dication (alpha-TOH2+). The identity and stability of the phenolic cationic compounds were determined by a combination of electrochemical (cyclic voltammetry and controlled potential electrolysis) and in situ spectroscopic (UV-vis-NIR, FTIR, EPR, and NMR) analysis.