Voltammetric Behavior of Trolox in Methanol and Ethanol Solutions

Abstract

Electrochemical oxidation of trolox on carbon electrodes was investigated by means of some voltammetric techniques in methanol and ethanol solutions in the presence of an excess of acid or base. The oxidation occurs according to EEC mechanism, i.e. in two quasireversible one-electron steps yielding the corresponding phenoxyl radical and, subsequently, phenoxonium cation. Phenoxonium ion decays because of a pseudo-first order follow-up chemical reaction with nucleophiles. The electrochemical behavior of trolox is strongly influenced by the surrounding environmental conditions. In acidic solutions, a single two-electron anodic wave was observed. The presence of a strong base drastically improves the stability of the intermediate, phenoxyl radical. Under these conditions, the twoelectron wave was found to split into its one-electron components over a range of scan rates. The resolution is much distinct in ethanol. Simulations with DigiSim software were used to fit the cyclic voltammograms in order to estimate thermodynamic and kinetic data for the reaction mechanism studied.

Catalytic radical reduction in aqueous solution via oxidation of biologically-relevant alcohols

“…However, in methanol (MeOH) or ethanol (EtOH) solutions, these processes converge into a single 2e – oxidation. 38 Subsequent hydrolysis of TrO + can then cleave the tertiary carbon–oxonium bond, which renders the 2e – oxidation of Trolox irreversible.…”

“…vs. Trolox) and was consistent with the ability of Trolox to serve as a non-catalytic 2e – reductant in EtOH solution. 38 …”

Prepeak of trolox caused by theophylline and its application to the determination of theophylline in rat plasma

“…The prepeak potential was about +0.75 V vs. Ag/AgCl. The oxidation mechanism of TrOH was explained in that the first electron transfer was accompanied by deprotonation to give a phenoxy radical, from which the loss of the second electron leads to the forming of a phenoxonium ion [44]. The occurrence of the prepeak is considered in terms of the acceleration of the first electron transfer reaction of TrOH.…”

“…Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid, TrOH), a water-soluble derivative of a-TOH, has also been used in place of a-TOH [43]. If theophylline causes a prepeak of TrOH or a-TOH, theophylline would be detected at less positive potential compared with direct electrolysis, since the oxidation potentials of TrOH [44][45][46] and a-TOH [47,48] are more negative than that of theophylline. Thus, in the present study, we examined the characteristics of the prepeak of TrOH, and developed a novel HPLC-ECD based on the voltammetric oxidation of TrOH for determining theophylline in plasma.…”

Eletroquímica computacional - princípios e diretrizes para utilização

“…[33][34][35][36][37][38][39][40][41][42][43] Um texto abrangente, com foco na simulação de mecanismos de reação, foi publicado por Gosser. 44 …”