Effectiveness of phenol antioxidants and the properties of quinolide peroxides

Roginskii, V.A.; Dubinskii, V. Z.; Shlyapnikova, I.A.; Miller, V.B.

doi:10.1016/0014-3057(77)90178-1

Cited by 30 publications

(5 citation statements)

References 22 publications

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“…A cyclohexadienone is very likely to be responsible for this absorbance. 17 The decay of cyclohexadienones generated from the phenoxyl radicals (1-15) has also been studied. Since the 4-hydroperoxycyclohexa-2,5-dien-1 -one is considered to be sta-ble17•30 in these time regions, the absorbance appears to derive from the 6-hydroperoxycyclohexa-2,4-dien-1 -one.…”

Section: Resultsmentioning

confidence: 99%

Free radical combination reactions involving phenoxyl radicals

Jönsson¹,

Lind²,

Reitberger³

et al. 1993

J. Phys. Chem.

121

112

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Section: Resultsmentioning

confidence: 99%

Free radical combination reactions involving phenoxyl radicals

Jönsson¹,

Lind²,

Reitberger³

et al. 1993

J. Phys. Chem.

121

112

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“…Meanwhile, f was not affected by styrene concentration, either in experiments (within the range from 2 to 8 M) or in simulations (not shown). The conclusion that reaction (5) rather than (4) predominates may also be made by using the analytical approach [16]. The contribution of reaction (4) …”

Section: Competition Between Reactions (4) and (5)mentioning

confidence: 99%

Substituted p‐hydroquinones as a chain‐breaking antioxidant during the oxidation of styrene

Loshadkin

Roginsky

Плисс

2002

Int J of Chemical Kinetics

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ABSTRACT:The technique based on monitoring oxygen consumption was applied to test 13 substituted p-hydroquinones (QH 2 ) as a chain-breaking antioxidant during the oxidation of styrene initiated by 2,2 -azobis(2,4-dimethylvaleronitrile) at 37 • C. The methodology originally developed to test monophenolic antioxidants was modified to fit it to specific features of oxidative transformation of QH 2 . Chain-breaking capability of QH 2 was characterized by two parameters: the rate constant k 1 for reaction of QH 2 with the peroxy radical LO 2 · : (1) QH 2 + LO 2 · → QH · + LOOH and the stoichiometric factor of inhibition, f , which shows how many kinetic chains may be terminated by one molecule of QH 2 . Rate constants k 1 × 10 5 (in M −1 s −1 ) were found to be 5.54 (nonsubstituted QH 2 ); 7.13 (Me-QH 2 ); 13.1 (Et-QH 2 ); 12.0 (tBu-QH 2 ); 15.6 (2,6-Me 2 -QH 2 ); 18.8 (2,3-Me 2 -QH 2 ); 17.1 (2,5-Me 2 -QH 2 ); 13.7 (2,6-(MeO) 2 -QH 2 ); 4.70 (2,6-Ph 2 -QH 2 ); 0.90 (2,5-Cl 2 -QH 2 ); 23.2 (Me 3 -QH 2 ); 4.40 (2,3-(MeO) 2 -5-Me-QH 2 ). Parameter f never exceeds 2; for the majority of QH 2 , f was found to be visibly less than 2, decreasing when the rate of initiation decreased. Both experimental data and results of computer kinetic simulations suggest that, contrary to monophenolic antioxidants, the main path of QH · transformation is the self-disproportionation rather than recombination of QH · with LO 2 · . Most likely, f is commonly lower than 2 because of the reaction of QH · with molecular oxygen. The latter may result in faster depletion of QH 2 and the increase in the rate of inhibited oxidation.

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“…There is, however, no information on g-values or on mechanisms of inhibition for these antioxidants at elevated temperatures (up to 190°C). Based on limited data available in the literature for temperatures up to 140°C [18][19][20], it should be expected that QOOR formed during inhibition with MPH and the corresponding compounds, Q'OOR and Q'(OOR)2, formed during inhibition with BPH would, under our conditions, decompose and contribute to formation of free radicals. This should then lead to n-values lower than those obtained at low temperatures.…”

Section: Stoichiometric Factorsmentioning

confidence: 99%

Initiation in hydrocarbon autoxidation at elevated temperatures

Jensen

Korček

Zinbo

et al. 1990

Int J of Chemical Kinetics

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Kinetic and mechanistic investigations of liquid phase autcxidation of hexadecane at 120 to 190°C have shown that, in the early stages of oxidation, the initiation process involves homolytic decomposition of hydroperoxides. The values of a composite first order rate constant for this decomposition, k l , have been determined in stirred flow reactor experiments from the rate of formation of termination products and in batch reactor studies using inhibitor methods.Arrhenius parameters derived from these studies (log (A/s-') = 8.5 and E, = 26 kcal mol-') allow calculation of k l as a function of temperature. This permits determination of the rate of initiation as a function of hydroperoxide concentration and facilitates determination of absolute rate constants for other oxidation reactions occurring in this system.

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Effectiveness of phenol antioxidants and the properties of quinolide peroxides

Cited by 30 publications

References 22 publications

Free radical combination reactions involving phenoxyl radicals

Free radical combination reactions involving phenoxyl radicals

Substituted p‐hydroquinones as a chain‐breaking antioxidant during the oxidation of styrene

Initiation in hydrocarbon autoxidation at elevated temperatures

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