The Inhibited Autoxidation of Styrene: Part Iii. The Relative Inhibiting Efficiencies of Ortho-Alkyl Phenols

The reaction of tert-butylperoxy radicals with some 2,6-di-iert-butyl-4-substituted phenols, a-naphthol, a-naphthylamine, and N-phenyl-a-naphthylaniine has been studied by following the change in radical concentration with time sing an e.p.r. spectrometer. Rates of radical decay were first-order in both reactants and were not influenced by the presence of teri-butyl hydroperoxide.Absolute values of the second-order rate constants were measured from -35 t o -100" and the preexponential factors and activation energies fell in the range lo4-lo5 M -' s -l and 0.5-1.0 kcal niol-l. Rate constants for deuterated phenols (OD) and aromatic amines (ND) were an order of magnitude lower than for the corresponding light compounds.There was no evidence for q u a n t~~m mechanical t~~n n e l i n g in these hydrogen atom transfer reactions and it would appear that the activation parameters are low because reaction initially involves the forniation of a hydrogen bonded peroxy radical -phenol (or aromatic anline) complex, followed by the transfer of a hydrogen atom within the coniplex.. . Can. J. Chem. 51, 3738 (1973)

Section: 6-di-tert-butyl-4-s~bstit~1te~i Pl~enolsmentioning

confidence: 99%

Arrhenius Parameters for Reaction of tert-Butylperoxy Radicals with some Hindered Phenols and Aromatic Amines

Howard¹,

Furimsky²

1973

“…The effect of alkyl groups at ortho positions of the OH groups on its antioxidant activity has been studied by many authors. For example, Howard and Ingold (9) have reported the antioxidant activity of alkyl phenols depends on the position of substituents. They also reported that the steric effects due to ortho alkyl substituents are important.…”

Section: Resultsmentioning

confidence: 99%

Comparison of heteroatom-bridged analogues of methylenebisphenols for antioxidant activities

Nishiyama¹,

Kagimasa²,

Yamada³

1994

A series of methylenebisphenols, thiobisphenols, oxybisphenols, and iminobisphenols were evaluated as antioxidants for tetralin at 60 °C by means of an oxygen-obsorption method. It was found that replacement of the bridged methylene group of methylenebisphenols by a nitrogen atom showed considerably better antioxidant effects. The antioxidant effects of these compounds were influenced by the positions of the phenolic hydroxyl groups in their molecules.

“…The kinetics for the inhibition of styrene autoxidation by 2,4,6-tri-t-butylphenol have been described previously (2). Over a wide range of reactant concentrations, the rate of the inhibited oxidation can be represented by (2) where R H represents the styrene, I Z the initiator, and AH the phenol.…”

Section: Styrenementioning

confidence: 99%

“…Over a wide range of reactant concentrations, the rate of the inhibited oxidation can be represented by (2) where R H represents the styrene, I Z the initiator, and AH the phenol. The inhibited rates in the presence of Hz0 and DzO gave a deuterium isotope effect PD20/PH20 = 10.5, i.e., ( k 6 )~~/ ( k 6 ) .…”

Section: Styrenementioning

confidence: 99%

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THE INHIBITION OF AUTOXIDATION BY 2,4,6-TRI-tert-BUTYL SUBSTITUTED PHENOL, ANILINE, AND THIOPHENOL

Gardner¹,

Howard²,

Ingold³

1964

Self Cite

The reactions of peroxy radicals with 2,4,6-tri-t-butyl substituted phenol, aniline, and thiophenol have been examined by a kinetic method. The primary process involves abstraction of the hydrogen atom attached to the functional group, since all three compounds show fairly large isotope effects when this hydrogen is replaced by deuterium. The phenol and aniline react with about two peroxy radicals per molecule. In contrast, the thiophenol reacts with only a single peroxy radical. ,