Absolute rate constants for hydrocarbon autoxidation. V. The hydroperoxy radical in chain propagation and termination

Howard, J. A.; Ingold, K. U.

doi:10.1139/v67-131

Cited by 112 publications

(71 citation statements)

References 32 publications

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“…lo3 M-' S -' at 65") has been obtained for zinc ditolyldithiophosphate (40). rather than by an alkylperoxy radical (25). Our results suggest that the HOO' radical is trapped about ten times more readily.…”

Section: Kinetics Of Inhibitionmentioning

confidence: 59%

Metal Complexes as Antioxidants. I. The Reaction of Zinc Dialkyldithiophosphates and Related Compounds with Peroxy Radicals

Howard¹,

Ohkatsu²,

Chenier³

et al. 1973

Can. J. Chem.

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The kinetics of the inhibition of the autoxidation of several hydrocarbons by a number of zinc dialkyldithiophosphates and by zinc isopropylxanthate and zinc diethyldithiocarbamate have been studied at 30' and at 50'. The oxidations were generally auto-retarding but initial rate measurements showed that these compounds trapped peroxy radicals and allowed rate constants for this process to be calculated. Rate constants for the reaction of t-butylperoxy radicals with these compounds have been measured by a kinetic e.p.r. method in the temperature range 0' to -90'. Extrapolation of the e.p.r. data to the temperatures of the inhibition studies showed that the various experimental procedures yielded results in satisfactory agreement with one another.It is suggested that the reaction of peroxy radicals with zinc complexes involves reaction at the metal center either by an electron transfer or an SH2 process.Les cinetiques d'inhibition de I'auto-oxydation de plusieurs hydrocarbures par un certain nombre de phosphates de dialkyldithio zinc, d'isopropylxanthate de zinc et de diethyldithiocarbamate de zinc, ont etC CtudiCes h 30'et a 50'. Les oxydations sont generalement auto-retardees rnais les mesures de vitesse initiale montrent que ces composes piegent les radicaux peroxy et permettent ainsi le calcul des constantes de vitesse pour ce processus. Les constantes de vitesse pour la reaction des radicaux I-butylperoxy sur ces composes ont kt6 mesurees par une methode cinetique r.p.e. dans I'intervalle de temperature de 0' a -90'.L'extrapolation des donnees r.p.e. aux temperatures d'etude de I'inhibition montre que tous les divers procedes experimentaux donnent des resultats en accord satisfaisant.On a suggCrC que la reaction des radicaux peroxy sur les co~nplexes de zinc implique une reaction sur le centre metallique soit par un transfert d'electron soit par un processus SH2.

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Section: Kinetics Of Inhibitionmentioning

confidence: 59%

Metal Complexes as Antioxidants. I. The Reaction of Zinc Dialkyldithiophosphates and Related Compounds with Peroxy Radicals

Howard¹,

Ohkatsu²,

Chenier³

et al. 1973

Can. J. Chem.

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“…are the chain propagating and terminating peroxy species in this substrate (12), are more reactive than alkylperoxy radicals towards the nickel conlplexes.…”

Section: Inllibitecl A~rfoxiclafiorzsmentioning

confidence: 93%

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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“…There is no contamination of other peroxides in the assay of the sample. t-BuOOH was estimated by iodometric method 33 .…”

Section: Methodsmentioning

confidence: 99%

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2015

IJPSR

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ABSTRACT:The rates of oxidation of uracil and chlorogenic acid (CGA) by tertbutoxyl radicals have been studied by measuring the absorbance of uracil at 258 nm and CGA at 328 nm spectrophotometrically. tert-butoxyl radicals are generated by the photolysis of tert-butyl hydroperoxide in presence of tert-butyl alcohol to scavenge  OH radicals. The rates and the quantum yields () of oxidation of CGA by t-BuO  radicals have been determined in the absence and presence of varying concentrations of uracil. An increase in the concentration of uracil has been found to decrease the rate of oxidation of CGA suggesting that uracil and CGA compete for t-BuO  radicals. Using competitive kinetic studies, the rate constant for the reaction of t-BuO  radical with uracil has been found to be 4.43 10 8 dm 3 mol -1 s -1 . The quantum yields ( expt ) have been calculated from the experimentally determined rates of oxidation of CGA under different experimental conditions. Assuming that CGA acts as a scavenger of t-BuO  radicals only, the quantum yields ( cal ) have been theoretically calculated.  expt and  cal values suggest that CGA not only protects uracil from t-BuO  radicals but also repairs uracil radicals formed by the reaction of uracil with t-BuO  radicals.

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Absolute rate constants for hydrocarbon autoxidation. V. The hydroperoxy radical in chain propagation and termination

Cited by 112 publications

References 32 publications

Metal Complexes as Antioxidants. I. The Reaction of Zinc Dialkyldithiophosphates and Related Compounds with Peroxy Radicals

Metal Complexes as Antioxidants. I. The Reaction of Zinc Dialkyldithiophosphates and Related Compounds with Peroxy Radicals

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

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