Absolute rate constants for hydrocarbon oxidation. VIII. The reactions of cumylperoxy radicals

Howard, J. A.; Ingold, K. U.; Symonds, M.C.R.

doi:10.1139/v68-165

Cited by 104 publications

(58 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The propagation rate constant is a factor of 10 lower than the values found for the secondary peroxy radicals. This result is in agreement with our earlier conclusions that tertiary peroxy radicals are less reactive than secondary peroxy radicals in chain propagation (9,12). The propagation and termination rate constants for the oxidation of tetralin in the presence of three secondary ether hydroperoxides (Table 111) are similar to one another and to the values found for tetralin alone or in-the presence of tetralin hydroperoxide.…”

Section: Resultssupporting

confidence: 91%

Absolute rate constants for hydrocarbon autoxidation. XVII. The oxidation of some cyclic ethers

Howard¹,

Ingold²

1969

Can. J. Chem.

Self Cite

View full text Add to dashboard Cite

The propagation and termination rate constants have been determined for the autoxidation of 1,4-dioxan, tetrahydropyran, tetrahydrofuran, 2,s-dimethyltetrahydrofuran, and phthalan. The rate constants for a-hydrogen atom abstraction from sonle of the ethers by the tetralylperoxy radical and from tetralin by some ether peroxy radicals have been measured and compared. The chain transfer rate constants have been estimated for the reaction of the c~~mylperoxy radical with a-hydroperoxytetrahydrofuran, a-hydroperoxytetrahydropyran, and a-ethoxyethyl hydroperoxide.

show abstract

Section: Resultssupporting

confidence: 91%

Absolute rate constants for hydrocarbon autoxidation. XVII. The oxidation of some cyclic ethers

Howard¹,

Ingold²

1969

Can. J. Chem.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Subsequently, the peroxyl radical abstracts a hydrogen atom from the lipid in a reaction classified as an atom transfer reaction (eq 6). This hydrogen atom transfer occurs in a selective manner, preferring the most weakly bound hydrogen atom, as demonstrated by the large kinetic deuterium isotope effect (Howard et al 1968;Ingold 1969). Furthermore, this reaction is the rate-limiting step in the autoxidation sequence and it produces a lipid hydroperoxide and a new L• radical.…”

Section: Figurementioning

confidence: 97%

Autoxidation of Conjugated Linoleic Acid Methyl Ester in the Presence of α‐Tocopherol: The Hydroperoxide Pathway

Pajunen

Johansson

Hase

et al. 2008

Lipids

View full text Add to dashboard Cite

The autoxidation of conjugated linoleic acid (CLA) is poorly understood in spite of increasing interest in the beneficial biological properties of CLA and growing consumption of CLA-rich foods. In this thesis, the autoxidation reactions of the two major CLA isomers, 9-cis,11-transoctadecadienoic acid and 10-trans,12-cis-octadecadienoic acid, are investigated. The results contribute to an understanding of the early stages of the autoxidation of CLA methyl ester, and provide for the first time a means of producing and separating intact CLA methyl ester hydroperoxides as well as basic knowledge on lipid hydroperoxides and their hydroxy derivatives.Conjugated diene allylic monohydroperoxides were discovered as primary autoxidation products formed during autoxidation of CLA methyl esters in the presence and absence oftocopherol. This established that one of the autoxidation pathways of CLA methyl ester is the hydroperoxide pathway.Hydroperoxides were produced from the two major CLA methyl esters by taking advantage of the effect of -tocopherol to promote hydroperoxide formation. The hydroperoxides were analysed and separated first as methyl hydroxyoctadecadienoates and then as intact hydroperoxides by HPLC. The isolated products were characterized by UV, GC-MS, and NMR techniques. In the presence of a high amount of -tocopherol, the autoxidation of CLA methyl ester yields six kinetically-controlled conjugated diene monohydroperoxides and is diastereoselective in favour of one particular geometric isomer as a pair of enantiomers. The primary autoxidation products produced from the two major CLA isomers include new positional isomers of conjugated diene monohydroperoxides, the 8-, 10-, 12-, and 14-hydroperoxyoctadecadienoates. Furthermore, two of these new positional isomers have an unusual structure for a cis,trans lipid hydroperoxide where the allylic methine carbon is adjacent to the cis instead of the usual trans double bond.The 1 H and 13 C NMR spectra of nine isomeric methyl hydroxyoctadecadienoates and of ten isomeric methyl hydroperoxyoctadecadienoates including the unusual cis,trans hydroperoxides, i.e. Me 8-OOH-9c,11t and Me 14-OOH-10t,12c, were fully assigned with the aid of 2D NMR spectroscopy. The assigned NMR data enabled determination of the effects of the hydroxyl and hydroperoxyl groups on the carbon chemical shifts of CLA isomers, identification of diagnostic signals, and determination of chemical shift differences of the olefinic resonances that may help with the assignment of structure to as yet unknown lipid hydroperoxides either as hydroxy derivatives or as intact hydroperoxides.A mechanism for the hydroperoxide pathway of CLA autoxidation in the presence of a high amount of -tocopherol was proposed based on the characterized primary products, their relative distribution, and theoretical calculations. This is an important step forward in CLA research, where exact mechanisms for the autoxidation of CLA have not been presented before. Knowledge of these hydroperoxide formation steps is of cr...

show abstract

“…2,36,37). It is perhaps worth noting that alkyl radicals also abstract hydrogen more rapidly from alkanals than from benzaldehyde (35).…”

Section: Propagationmentioning

confidence: 99%

Absolute rate constants for hydrocarbon autoxidation. XIII. Aldehydes: photo-oxidation, co-oxidation, and inhibition

Заиков¹,

Howard²,

Ingold³

1969

Can. J. Chem.

Self Cite

View full text Add to dashboard Cite

The oxidations of acetaldehyde, heptanal, octanal, cyclohexanecarboxaldehyde, pivaldehyde, and benzaldehyde in chlorobenzene at 0 "C have been studied. These aldehydes oxidize at similar rates under similar conditions because there are compensating changes in the rate constants for chain propagation (k,) and chain termination (2k,). The termination rate constants increase from -7 x lo6 M-I S-I f or pivaldehyde and cyclohexanecarboxaldehyde to -2 x lo9 M-' s-' f or benzaldehyde. The propagation rate constants increase from -1 x lo3 M-'s-' for pivaldehyde to -1 x lo4 M-l s-' f ox benzaldehyde.The rate of oxidation of the aldehydes was decreased by the addition of 1,4-cyclohexadiene, tetralin, tetralin hydroperoxide, cumene, cumene hydroperoxide, t-butyl hydroperoxide, and 2,6-di-t-butyl-4-methylphenol. As a result of product analysis and absolute rate constant measurements, it is concluded that the peroxy radicals derived from aldehydes are considerably more reactive in hydrogen atom abstraction from hydrocarbons than are the peroxy radicals derived from the hydrocarbons. In the abstraction from cyclohexadiene, the acylperoxy radicals appear to be from 15 to 70 times as reactive, and the benzoylperoxy radicals about 8W900 times as reactive, as the hydroperoxy radical. The differences in reactivity are very much less pronounced in the abstraction from 2,6-di-t-butyl-4-methylphenol.The great ease of oxidation of all aldehydes, and particularly benzaldehyde, is due at least in part to the high reactivity of the peroxy radicals formed in these reactions.

show abstract

Absolute rate constants for hydrocarbon oxidation. VIII. The reactions of cumylperoxy radicals

Cited by 104 publications

References 19 publications

Absolute rate constants for hydrocarbon autoxidation. XVII. The oxidation of some cyclic ethers

Absolute rate constants for hydrocarbon autoxidation. XVII. The oxidation of some cyclic ethers

Autoxidation of Conjugated Linoleic Acid Methyl Ester in the Presence of α‐Tocopherol: The Hydroperoxide Pathway

Absolute rate constants for hydrocarbon autoxidation. XIII. Aldehydes: photo-oxidation, co-oxidation, and inhibition

Contact Info

Product

Resources

About