Arrhenius Parameters for Reaction of the <i>tert</i>-Butylperoxy and 2-Ethyl-2-propylperoxy Radicals with some Nonhindered Phenols, Aromatic Amines, and Thiophenols

Chenier, J. H. B.; Furimsky, Edward; Howard, J. A.

doi:10.1139/v74-550

Cited by 57 publications

(44 citation statements)

References 8 publications

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“…Rates of decay of 4 were found to obey the rate expression where k, is the rate constant for reaction [8]. Absolute values of k, from 173-233 K are given in Table 5.…”

Section: Tert-butylperoxyl4mentioning

confidence: 97%

“…Stoichiometric factors n , i.e., the number of radicals destroyed by each molecule of VO(acac),, were determined by the esr titration method described previously (8).…”

Section: Kinetic Proceduresmentioning

confidence: 99%

“…indicating that reaction [8] has a normal A-factor and is fast because of a low activation energy. A solution of azocumene (25 mM) and VO(acac), (50 mM) in chlorobenzene absorbed oxygen at an initial rate of 2.7 x M s-' at 323 K, slightly faster than the rate in the absence of VO(acac), (1.6…”

Section: Tert-butylperoxyl4mentioning

confidence: 99%

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A kinetic electron spin resonance study of the reaction of some oxy radicals with vanadyl acetylacetonate

Howard¹,

Tait²,

Yamada³

et al. 1981

Can. J. Chem.

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. Can. J . Chem. 59, 2184Chem. 59, (1981.Reactions of phenoxyl, iminoxyl, nitroxyl, peroxyl, and alkoxyl radicals with VO(acac), in solution have been studied by kinetic esr spectroscopy. Rates of reaction are first-order with respect to each reactant and radical reactivity increases in the order galvinoxyli 2,4,6-tri-tert-butylphenoxyl< di(l-adamanty1)methylene-iminoxyl< tert-butylperoxyl. Rates of reaction are retarded by pyridine and accelerated by methanol and there is an isotope effect on the rate when the hydroxyl proton of C H 3 0 H is replaced by deuterium. Vanadium-5 I nmr spectroscopy has demonstrated that several vanadium(V) products are formed while conventional product studies have indicated that, in the case of phenoxyl and alkoxyl, the radical is reduced almost exclusively to the parent phenol and alcohol and that VO(acac), is eventually regenerated in substantial yields. The net reaction is, therefore, catalytic reduction of the radical. Variable temperature esr studies have shown that phenoxyl and iminoxyl radicals and VO(acac), exist in equilibrium with diamagnetic reaction products. Utilisant la spectroscopie de rpe cinktique, on a etudie les reactions des radicaux phenoxyle, iminoxyle, nitroxyle, peroxyle et alkoxyle avec le VO(acac), en solution. Les vitesses de reaction sont du premier ordre par rapport a chaque rkactifet la reactivite des radicaux augmente dans I'ordre suivant: galvinoxyle < tri-tert-butyl-2,4,6 phenoxyle < di(adamanty1-1) methylhe iminoxyle < tert-butylperoxyle. Les vitesses de reaction sont ralenties par la pyridine et accelCrees par le methanol et le remplacement du proton hydroxylique du C H 3 0 H par un deuterium provoque un effet isotopique cinttique. La spectroscopie de rmn du vanadium-51 a demontre qu'il se forme plusieurs produits du vanadium(V) tandis que des etudes conventionnelles des produits indiquent que, dans le cas du phenoxyle et de I'alkoxyle, le radical est presqu'exclusivement reduit en phenol apparente et en alcool alors que le compose VO(acac), est regenere avec des rendements qui sont eventuellement substantiels. La reaction globale est cependant une reduction catalytique du radical. Des etudes de rpe ti temperature variable rtvelent que les radicaux phenoxyle et iminoxyle et le VO(acac), existent en equilibre avec des produits de reaction diamagnetiques.[Traduit par le journal] Introduction to give a vanadium(V)-ROOH complex which is ~t is well known that oxidation of olefins, Sul-followed by nucleophilic attack at the "activated" phides, sulphoxides, and amines by alkyl hydro--0-0-bond of the hydroperoxide by the peroxides (ROOH) is catalyzed by vanadyl acetyl-nucleo~hile. acetonate, VO(acac), (1).Although these oxidations are heterolytic there is some evidence that free-radicals are produced by

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“…Rates of decay of 4 were found to obey the rate expression where k, is the rate constant for reaction [8]. Absolute values of k, from 173-233 K are given in Table 5.…”

Section: Tert-butylperoxyl4mentioning

confidence: 97%

“…Stoichiometric factors n , i.e., the number of radicals destroyed by each molecule of VO(acac),, were determined by the esr titration method described previously (8).…”

Section: Kinetic Proceduresmentioning

confidence: 99%

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A kinetic electron spin resonance study of the reaction of some oxy radicals with vanadyl acetylacetonate

Howard¹,

Tait²,

Yamada³

et al. 1981

Can. J. Chem.

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“…Elecrror~ Spill Resormrzce Sirrdies Reaction of the nickel complexes with [err-butylperoxy and 2-ethyl-2-propylperoxy radicals was studied kinetically by electron spin resonance spectroscopy (1,7,8). tert-Butylperoxy radicals were generated by photolysis of azoisobutane (0.02 M) in an oxveen saturated solvent…”

Section: Procedrlresmentioning

confidence: 99%

“…Stoichiometric factors were determined by titrating a known concentration of (CH3),COO' with a nickel complex at -90 "C using esr spectroscopy to monitor the peroxy radical concentration (8).…”

Section: "mentioning

confidence: 99%

Metal complexes as antioxidants. II. Reaction of nickel di-n-butyldithiocarbamate and nickel diisopropyldithiophosphate with alkylperoxy radicals

Howard¹,

Chenier²

1976

Can. J. Chem.

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Nickel di-n-butyldithiocarbamate and nickel diisopropyldithiophosphate inhibit the α,α′-azo-bis-isobutyronitrile initiated autoxidation of tetralin, styrene, and cyclohexa-1,4-diene by scavenging chain propagating alkylperoxy radicals. The rapid reaction of these complexes with alkylperoxy radicals has been confirmed by low temperature electron spin resonance studies. Kinetic data obtained by these two techniques are reported. Product studies suggest that alkylperoxy radicals (ROO•) are reduced by reaction with the nickel complex to the alcohol (ROH) while the nickel complex is oxidized to a Lewis acid.

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Antioxidants in Chemistry and Biology

Valgimigli

Pratt

2012

Encyclopedia of Radicals in Chemistry, Biology and Materials

109

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Antioxidants are omnipresent in nature and industry; they are used to slow down the autoxidative degradation of both organic tissues and petroleum‐derived products. Various mechanisms by which antioxidants can act are known, the most common of which are introduced here. Since autoxidation is a radical chain reaction, radical‐trapping antioxidants play a particularly important role; therefore, we will discuss these compounds in most detail. To introduce and develop central concepts relating to this topic, we present kinetic and thermodynamic data obtained for the reactions of phenols, the archetypical radical‐trapping antioxidants, with chain‐carrying peroxyl radicals, and describe the means to obtain these data. We then extend our discussion to other important classes of radical‐trapping antioxidants, beginning with the closely related polyphenols and newly developed pyridinol and pyrimidinol antioxidants, and then further to aromatic amines, organosulfur compounds, and their derivatives. We go on to touch upon the synergistic behavior in antioxidant combinations, and the effects of the medium on these interactions, and finally round things up with a few more important biological examples: ascorbate and β‐carotene. A few comments on the state of the field and areas requiring further research and development are included.

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Arrhenius Parameters for Reaction of the tert-Butylperoxy and 2-Ethyl-2-propylperoxy Radicals with some Nonhindered Phenols, Aromatic Amines, and Thiophenols

Cited by 57 publications

References 8 publications

A kinetic electron spin resonance study of the reaction of some oxy radicals with vanadyl acetylacetonate

A kinetic electron spin resonance study of the reaction of some oxy radicals with vanadyl acetylacetonate

Metal complexes as antioxidants. II. Reaction of nickel di-n-butyldithiocarbamate and nickel diisopropyldithiophosphate with alkylperoxy radicals

Antioxidants in Chemistry and Biology

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