On the enthalpies of homolytic and heterolytic S-H bond cleavage in para and meta substituted thiophenols

In this article, we have studied para- and meta-substituted thiophenols in order to study the effect of various electron-donating and electron-withdrawing groups in the gas-phase and in the four solvents on the enthalpies of homolytic and heterolytic S-H bond cleavage. Reaction enthalpies related to hydrogen atom transfer (HAT), single electron transfer-proton transfer (SET-PT) mechanism and sequential proton loss electron transfer (SPLET) mechanisms were studied using B3LYP/6-311++G** method. Solvent contribution to the enthalpies was computed employing integral equation formalism IEF-PCM method. Obtained results were confronted with available experimental data. Besides, reaction enthalpies and substituent effects were compared with previously published data for phenols with identical group of substituents. In studied environments, thermodynamically favored reaction pathway was determined.