Antioxidant Activities of Dihydric Phenol Derivatives for the Autoxidation of Tetralin

Abstract

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 (Rinh) were 1.1—1.6 × 10−6, 3.0—3.8 × 10−6, and 13.3—18.4 × 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.

Phenols as Antioxidants

“…Yamamura and coworkers used an oxygen absorption method to study the effects of a series of 46 dihydric phenols on inhibition of azo-initiated oxidation of tetralin 160 . They reported activities in terms of the stoichiometric factor, n, and the rate of oxygen absorption, R inh , during induction periods.…”

“…The antioxidant properties of 1,4-hydroquinones has been reexamined by several groups more recently. Yamamura and coworkers 160 found that these hydroquinones were less effective in reducing oxygen uptake than catechols (by about one-half) and the stoichiometric factors of hydroquinones ranged (0.6-1.1) to about half that of the catechols. It is interesting to note that they attributed the higher activity of catechols, compared to hydroquinones, to the increased stability of the derived phenoxyl radicals due to the intramolecular hydrogen bond.…”

Hydroarylation of Styrenes with Electron-Rich Arenes Over Acidic Ion-Exchange Resins

“…OH HO 1 H NMR (400 MHz, DMSO-d6) δ = 9.14 (s, 1H), 9.00 (s, 1H), 7.22 (q, J=7.4, 4H), 7.11 (t, J=6.7, 1H), 6.86 (d, J=8.4, 1H), 6.25 (s, 1H), 6.18 (d, J=8.4, 1H), 4.32 (q, J=7.2, 1H), 1.45 (d, J=7.2, 3H). 13 C NMR (100 MHz, DMSO-d6) δ =156.22, 155.10, 147.12, 127.…”

“…13 C NMR (100 MHz, DMSO-d6) δ =156.22, 155.10, 147.12, 127. 96 1 H NMR (400 MHz, DMSO-d6) δ = 8.94 (s, 2H), 7.17 (m, 10H), 6.88 (d, J=4.9, 1H), 6.27 (s, 1H), 4.29 (q, J=7.2, 2H), 1.44 (m, 6H). 13 C NMR (100 MHz, DMSO-d6) δ =153.…”

Applications of bismuth(iii) compounds in organic synthesis

“…Many functionalized hydroxyquinones are of interest because of their applications as antioxidants. 59 Hence their synthesis has received considerable attention. One of the earliest methods developed for their synthesis is the Thiele-Winter acetoxylation, which utilizes sulfuric acid as a catalyst.…”