Table of Contents
International Journal of Chemical Physics
Volume 2015, Article ID 835707, 13 pages
http://dx.doi.org/10.1155/2015/835707
Research Article

Proton-Coupled Electron Transfer in the Reaction of 3,4-Dihydroxyphenylpyruvic Acid with Reactive Species in Various Media

1Department of Physics, Faculty of Science, The University of Ngaoundere, P.O. Box 454, Ngaoundere, Cameroon
2Laboratoire de Spectroscopie Atomique, Moléculaire et Applications, Faculté des Sciences de Tunis, Université de Tunis El Manar, Campus Universitaire, 1060 Tunis, Tunisia
3University of Maroua, P.O. Box, 46 Maroua, Cameroon
4Fundamental Physics Lab, Graduate Training Unit in Physics and Engineering Sciences, Faculty of Science, University of Douala, P.O. Box 24157, Douala, Cameroon

Received 26 August 2014; Revised 21 December 2014; Accepted 22 December 2014

Academic Editor: Franck Rabilloud

Copyright © 2015 J. J. Fifen et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The distinction of concerted proton-coupled electron transfer (CPCET) from sequential one as well as proton transfer-electron transfer (PT-ET) from electron transfer-proton transfer (ET-PT) in the O–H bond cleavage reactions in various media has always been a difficult task. In this work, the activation barrier of the CPCET mechanism, its rate constants, and reaction free energies related to ET-PT and PT-ET involving coreactive species were presented as good parameters to attempt the problem. DFT calculations were carried out studying the described pathways subsequent to the scavenging of and by the 3,4-DHPPA in various media. The solvation was described in a hybrid manner using IEF-PCM model conjointly with a model that takes into account some solute-solvent interactions. As a result, we found that the scavenging of hydroxyl radical by 3,4-DHPPA is thermodynamically governed by a one-step hydrogen atom transfer (CPCET) from the acid to the radical in all media. In kinetic viewpoint, CPCET still dominates in the vacuum and in nonpolar solvents, but in polar solvents it could compete strongly with the ET-PT mechanism so that the latter could slightly dominate.