Elucidating the Catalytic Role of Mg(II) in the Intramolecular Proton Transfer Reaction in Thymine

Abstract

In the framework of the reaction force analysis a study of the mechanism of the 1-3 intramolecular proton transfer in free and Mg (II) coordinated Thymine was done in terms of the reaction electronic flux and Wiberg bond orders. Profiles of these properties evidentiated differences between the proton transfer mechanisms induced by the presence of Mg(II) cation. A significative lowering in the activation energy put forward the catalytic effect of Mg. The reaction force analysis allows a precise identification of the catalytic effect thus uncovering the physical nature of activation energies. While in the free Thymine electronic polarization and transfer processes are present separately, in the Mg(II) coordinated Thymine both effects are observed simultaneously and are localized on the ring in the molecular topology. It is argued that the difference in the charge transfer mechanism leads to a more stable enol form in the Mg(II) coordinated Thymine. © 2012, Sociedad Química de México.