title: Variable scan rate cyclic voltammetry and theoretical studies on tocopherol (vitamin E) model compounds.
abstract: Variable scan rate (0.1-500 V s(-1)) cyclic voltammetry experiments were performed on a series of model tocopherol (vitamin E) compounds with differing degrees of methyl substitution around the aromatic (phenolic) ring. alpha-Tocopherol, with a fully methylated aromatic ring, produced stable phenoxonium cations upon oxidation in CH3CN, and was modeled via an ECE mechanism (where "E" represents an electron transfer and "C" a chemical step). Compounds with less methyl substitution around the aromatic ring were more reactive following oxidation, and formed additional oxidation products (hemiketals and p-quinones), and were modeled according to a more complicated ECECC mechanism. The equilibrium and rate constants associated with the chemical steps were estimated by digital simulations of the variable scan rate data over a range of temperatures ( T = 253-313 K) in acetonitrile containing 0.5 M Bu4NPF6 as the supporting electrolyte. The relative lifetimes of the phenoxonium cations of tocol and the tocopherols were compared with theoretical results obtained from molecular orbital calculations.
authors.affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore.
authors.forename: Wei Wei
authors.initials: WW
authors.lastname: Yao
authors.forename: Hong Mei
authors.initials: HM
authors.lastname: Peng
authors.forename: Richard D
authors.initials: RD
authors.lastname: Webster
authors.forename: Peter M W
authors.initials: PM
authors.lastname: Gill
mesh_terms: D003198:Computer Simulation; D004563:Electrochemistry; D008956:Models, Chemical; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D013237:Stereoisomerism; D024505:Tocopherols / Q000737:chemistry*
chemical_list: D024505:Tocopherols