Dissociation energies of O-H, N-H, and S-H bonds in sulfur-containing antioxidants

The dissociation energies of O-H bonds (D (O-H)) of 48 phenol sulfides and N-H bonds (D (N-H)) of five amino sulfides were determined from experimental data. The dissociation energies of the bonds were estimated by the method of crossing parabolas from the kinetic data (the rate constants of reactions of peroxyl radicals with these antioxidants). The O-H, S-H, and N-H bond dissociation energies were determined for three hybrid antioxidants (two hydroxythiophenols and one aminophenol): D (O-H) = 335.9 kJ mol(-1) and D (S-H) = 340.8 kJ mol(-1) for 2-hydroxy-3,5-bis-(1'-phenylethyl)thiophenol, D (O-H) = 337.7 kJ mol(-1) and D (S-H) = 344.2 kJ mol(-1) for 3,5-bis-(1'-phenylethyl)-4-hydroxythiophenol, and D (O-H) = 338.6 kJ mol(-1) and D (N-H) = 366.2 kJ mol(-1) for 1-(N-phenylamino)-2-thiol-3-thio-(3',5'-bis-di-tert-butyl-4'-hydroxyphenyl)-propane.