Dissociation energies of O-H and N-H bonds in hybrid antioxidants

The dissociation energies of O-H and N-H bonds have been determined for ten aminophenoltype (HOArAmH) hybrid antioxidants. The bond dissociation energies D _O-H and D _N-H have been estimated from experimental kinetic data (rate constants of the reactions of peroxyl radicals with these antioxidants and their alkyl-substituted derivatives) by the intersecting-parabolas method. Kinetic data for the reactions of peroxyl radicals with HOArAmH, ROArAmH, and HOArAmR compounds were used. The following D _O-H and D _N-H values (kJ/mol) were obtained: for 4-hydroxydiphenylamine, D _O-H = 338.8 and D _N-H = 355.9; for 4-hydroxyphenyl-2-naphthylamine, D _O-H = 335.4 and D _N-H = 353.6; for 6-hydroxy-1,2-dihydro-2,2,4-tri-methylquinoline, D _O-H = 338.0 and D _N-H = 348.2; for 9-hydroxy-1,2-dihydro-2,3,4-trimethylquinoline, D _O-H = 329.7 and D _N-H = 383.3; for 6-hydroxy-1,2,3,4-tetrahydro-2,2,4-trimethylquinoline, D _O-H = 324.4 and D _N-H = 345.3; for 8-hydroxy-1,2,3,4-tetrahydro-2,2,4-trimethylquinoline, D _O-H = 329.4 and D _N-H = 380.6; for 5-hydroxyimidazole, D _O-H = 356.4 and D _N-H = 368.4; for 5-hydroxy-2-methylimidazole, D _O-H = 351.3 and D _N-H = 362.6; for 5-hydroxy-4,6-dimethylimidazole, D _O-H = 346.7 and D _N-H = 357.3; for 5-hydroxy-2,4,6-trimethylimidazole, D _O-H = 347.7 and D _N-H = 358.7.