title: Mechanistic study of the oxidation of caffeic acid by digital simulation of cyclic voltammograms.
abstract: The oxidation mechanism of caffeic acid (CAF) has been studied by means of cyclic voltammetry with the plastic formed carbon or glassy carbon electrode. CAF gives a well-developed two-electron reversible wave in acidic media, whereas it shows an irreversible behavior, i.e., a decrease of the rereduction peak, in less acidic media, suggesting that the oxidation of CAF follows an irreversible chemical reaction(s). Digital simulation analyses based on different oxidation mechanisms have been performed for the voltammograms obtained with the GC electrode in 1:1 (v/v) water:ethanol solutions. The results clearly show that the seeming two-electron oxidation of CAF occurs stepwise via one-electron processes, each of which follows an irreversible chemical reaction. It has also been suggested that the semiquinone radical as an intermediate of the one-electron oxidation should play an important role in the oxidation reaction. Evaluations of the rate constants for the chemical reactions have further suggested that the chemical reactions are dimerization reactions.
authors.affiliation: Department of Chemistry, Faculty of Science, Kobe University, Nada, Kobe 657-8501, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Hotta
authors.forename: Masashi
authors.initials: M
authors.lastname: Ueda
authors.forename: Satomi
authors.initials: S
authors.lastname: Nagano
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Tsujino
authors.forename: Junko
authors.initials: J
authors.lastname: Koyama
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Osakai
mesh_terms: D002109:Caffeic Acids / Q000737:chemistry*; D003198:Computer Simulation; D004563:Electrochemistry / Q000379:methods*; D004566:Electrodes; D004579:Electron Transport; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D010084:Oxidation-Reduction; D011809:Quinones / Q000737:chemistry*; D012044:Regression Analysis
chemical_list: D002109:Caffeic Acids; D011809:Quinones