Redox reactions of vitamin E in 1,2-dichloroethane with oxidants in water at the water/1,2-dichloroethane interface

摘要

The oxidation of ot-tocopherol (vitamin E), a-TOH, in 1,2-dichloroethane, DCE, by NO or Mn04 in water (pH = 1-9), W, at the W/DCE interface was investigated by voltammetry for charge (ion or electron) transfer at the interface of two immiscible electrolyte solutions, VCTIES, and controlled potential difference electrolysis at the interface. A positive current wave due to the interfacial redox reaction producing atocopherone cation a-TO . and H' in DCE was observed by VCTIES. The H . transferred to W, and a part of a-TO. was converted to a-tocopheryl quinone, a-TQ by the hydrolysis with the water dissolved in DCE. Even when the potential difference at the interface, E, was in the range where any faradaic current was not observed by VCTIES, the interfacial reaction proceeded and gave a-TQ in DCE. The reduction products of NO or Mn04 in W at E in both ranges were N20 or Mn2+ and Mn02 , respectively. When the oxidant in W was Mn04 and E was available for the transfer of Mn04 to DCE, the redox reaction between MnO, and a-TOH in DCE proceeded in addition to the interfacial redox reaction. ce-Tocopherol spiro-dimer, a-TD, a-TQ and Mn0 2 were produced by the reaction in DCE. The oxidation reaction of ot- TOH at the W/DCE interface was compared with that at a platinum electrode in the bulk of DCE.