Assessment of the importance of changes in ground-state energies on the bond dissociation enthalpies of the O-H bonds in phenols and the S-H bonds in thiophenols

Analyses of homolytic bond dissociation enthalpies (BDEs) of O-H bonds in phenols and S-H bonds in thiophenols show that M- and P-electron withdrawing substituents decrease the ground-state energies, which increases BDEs in the order S-H < N-H < O-H. Paradonor groups stabilize the radicals to decrease BDEs of the acidic H-A bonds. Oxidation potentials of various O-, M- and P-substituted thiophenols exhibit a linear relationship with their pKHA.+ values.