The rate constants for the reaction of primary alkyl radicals with substituted phenolic compounds have been measured in benzene or toluene at room temperature by using the radical clock technique. With three representative phenols, containing in the ortho positions substituents of different size, the kinetics of the hydrogen transfer to alkyl radicals was studied at different temperatures to obtain the
The Oxidative Solvolysis of Durohydroquinone Monobenzoates. A Study of the Mechanism
作者:Makoto Takagi、Masato Tazaki、Tsutomu Matsuda
DOI:10.1246/bcsj.50.2704
日期:1977.10
by a kinetic study in an acetonitrile solution. The relation between the mode of oxidation, whether it is a one-electron or two-electron process, and the activation of the acyl group was explicitly discussed in terms of the mechanism. Two-electron oxidation is suggested to offer a better chance for acyl activation. Some generalization of the mechanism is made for other oxidation-induced acyl, phosphoryl
Bond dissociation energies (BDE) of several phenolic compounds have been determined by studying the equilibration of couples of phenols and of the corresponding phenoxyl radicals by means of EPR spectroscopy. Measurements were carried out in highly concentrated solutions submitted to continuous photolysis in the presence of di-tert-butyl peroxide. Since under this experimental condition the decay of the phenoxyl radicals was slower than the hydrogen transfer reaction from phenols to phenoxyls, equilibrium concentrations of the two radicals were actually measured. Due to the fact that the radical species are continuously generated in solution, phenols giving short-lived phenoxyl radicals could also be investigated by this method. All of the examined phenols are characterized by O-H bonds weaker than that of the parent compound, PhOH, and their BDE values can be calculated to a good approximation by an additive rule using fixed contributions for the various substituents. Only in the case of the sterically crowded 4-methoxytetramethylphenol (5b), where the p-methoxy substituent is compelled to stay out of the plane of the aromatic ring, is the experimental BDE remarkably different from the calculated value.
Iodine oxidation of .alpha.-tocopherol and its model compound in alkaline methanol: unexpected isomerization of the product quinone monoketals
作者:Kanji Omura
DOI:10.1021/jo00269a043
日期:1989.4
Autoxidation of biological molecules. 1. Antioxidant activity of vitamin E and related chain-breaking phenolic antioxidants in vitro