On energetics of proton and electron transfer of selected phenol derivatives: Theoretical investigation of radical and oxonium cations

In this paper, the systematic theoretical study of phenol and 36 compounds representing various ortho, meta and para-substituted (R-PhOH) phenols is presented. The hydroxyl group acidity is a characteristic feature of phenol which can be modified using substitution of phenyl ring. The proton-coupled electron transfer was investigated for parent neutral phenols, R-PhOH, their cation radicals, R-PhOH+center dot, and oxonium cations, R-PhOH2+. Density functional theory calculations were combined with solvent continuum model for water and dimethyl sulfoxide environment. For aqueous solution, the Pourbaix diagrams (electrochemical potential vs. pH) were constructed from the theoretically predicted acidity constants and electrochemical standard potentials. From the thermodynamic point of view, the obtained theoretical results allow the estimation of the thermodynamically preferred process and alternative reaction pathways of phenolic derivatives in very acidic media.