Variable scan rate cyclic voltammetry and theoretical studies on tocopherol (vitamin E) model compounds.
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.
Yao
Wei Wei
WW
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore.
Peng
Hong Mei
HM
Webster
Richard D
RD
Gill
Peter M W
PM
D003198:Computer Simulation; D004563:Electrochemistry; D008956:Models, Chemical; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D013237:Stereoisomerism; D024505:Tocopherols / Q000737:chemistry*
D024505:Tocopherols