Antioxidant activities of dihydric phenol derivatives for the autoxidation of tetralin

Article abstract of DOI:10.1246/bcsj.68.2955

The antioxidant activities of dihydric phenols, such as catechol, resorcinol, and hydroquinone, and their twenty-three alkyl and benzyl substituted derivatives were evaluated by means of an oxygen-absorption method at 60°C for determining the oxidation of tetralin. Catechols exhibited a much higher stoichiometric factor (2.0-2.3) compared with those of other compounds. The stoichiometric factors of hydroquinones (0.6-1.1) are almost half those of catechols, and are lower for the resorcinols (0.3-0.6). In addition, the rates of oxidation during the induction period (R(inh)) were 1.1-1.6 x 10^-6, 3.0-3.8 x 10^-6, and 13.3-18.4 x 10^-6 M min^-1 for catechols, hydroquinones, and resorcinols, respectively. According to these results, catechols and hydroquinones are efficient antioxidants, and their activities may be dependent on the stability of phenoxyl radicals as oxidation products due to the formation of the quinone structure. Furthermore, the stability of phenoxyl radicals derived from catechols is higher than that of those from hydroquinones. In spite of having two OH substituents, resorcinols behave as monohydric phenols in the reaction with peroxyl radicals.