Decay kinetics of aryloxy and semiquinone radicals in the presence of copper ions

Khudyakov, I. V.; Кузьмин, В. А.; Emanuel, N.M.

doi:10.1002/kin.550101002

Cited by 14 publications

(2 citation statements)

References 11 publications

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“…On the other hand, to get good agreement with the experimental data concerning the consumption of BC, R-TOH, and oxygen, the rate constant k 21 should be at least 5 × 10 7 M -1 s -1 . Such a high value seems to be quite reasonable in view of the strong exothermicity of reaction 21 and also by comparison with the rate constants for the similar dismutation reactions of catechol (3.9 × 10 8 M -1 s -1 ) 33 and of 2,6-dimethylhydroquinone (3.0 × 10 8 M -1 s -1 ). 34 It can be therefore concluded that reaction 21, being so fast to overwhelm reaction -20, i.e., the hydrogen transfer from R-TOH to the semiquinone radical, represents the driving force of the regeneration process that makes the recycling of R-tocopherol practically irreversible under typical autoxidation conditions.…”

Section: Resultssupporting

confidence: 59%

A Quantitative Approach to the Recycling of α-Tocopherol by Coantioxidants

et al. 2002

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A systematic investigation is reported on the regeneration of alpha-tocopherol (alpha-TOH) in homogeneous solution by coantioxidants in order to better understand the mechanism and the factors responsible for the effectiveness of this process. The current availability of thermochemical data concerning the reactants involved in the regeneration reactions, as well as a large number of the kinetic constants for the various reactions involved, allowed us to rationalize the experimental observations collected so far. Three limiting cases have been considered. The first case is that of a coantioxidant irreversibly regenerating alpha-TOH, where the effectiveness of the recycling process depends on the magnitude of the rate constant k(r). The second case is that of a coantioxidant reversibly recycling alpha-TOH, where regeneration can only be observed if the bond dissociation enthalpy value of the coantioxidant is lower or at least close to that of the O-H bond of alpha-tocopherol. The third case is that of a catechol derivative (chosen as a model compound for polyphenolic antioxidants), where recycling of alpha-TOH is feasible even though the BDE value is significantly higher than that of vitamin E. In this case, the driving force for the recycling process is the removal of the semiquinone radical from the catechol derivative by the alpha-tocopheroxyl radical, which makes the regeneration of alpha-TOH practically irreversible.

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Section: Resultssupporting

confidence: 59%

A Quantitative Approach to the Recycling of α-Tocopherol by Coantioxidants

et al. 2002

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“…tivatorb). What connection, if any, components I1 and I11 may have with the free radical species at the one-electron oxidation step, namely, pbenzosemiquinone and its anion as well as the complex of this anion with cupric ion (9), is presently unknown.…”

Section: Discussionmentioning

confidence: 99%

High-Performance Liquid Chromatography of Preparations of Ribonucleic Acid Inactivator(s) from Cupric Ion and Hydroquinone Before and After Treatment with Histidine

Dubes

Masoud

Al-Moslih

1983

Journal of Pharmaceutical Sciences

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Analysis of Radicals byEPR

Walton

2012

Encyclopedia of Radicals in Chemistry, Biology and Materials

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This article explains why electron paramagnetic resonance (EPR) spectroscopy is one of the most versatile and useful techniques for investigating free radicals. Easy to use EPR tools are expounded for organic chemists to exploit in researching the structures and reactivities of radicals and as a resource for synthetic planning. The article provides key references and introduces the literature on the EPR spectra of a wide range of organic radicals in solution. How EPR spectra result from molecules containing one unpaired electron (UPE) is explained and basic theory is presented for isotropic conditions. A correlation chart enables g ‐factors, which are key spectral parameters, to be used in determining which element is the principal site of the UPE. Methods of analysing complex EPR spectra and obtaining hyperfine splittings (hfs) are described. How geometries around the central atoms of radicals, and conformations about neighboring bonds, can be deduced from EPR data is explained. Modern ab initio methods of computing EPR parameters are briefly sketched. Features of the EPR spectra of model radicals centered on elements from groups 13, 14, 15, and 16 of the periodic table are surveyed. EPR methods for concentration measurements and for studying radical kinetics in time‐resolved and steady‐state modes are set out. Derivations from EPR spectral data of thermodynamic parameters such as radical enthalpies of formation and bond dissociation enthalpies are also explained.

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Decay kinetics of aryloxy and semiquinone radicals in the presence of copper ions

Cited by 14 publications

References 11 publications

A Quantitative Approach to the Recycling of α-Tocopherol by Coantioxidants

A Quantitative Approach to the Recycling of α-Tocopherol by Coantioxidants

High-Performance Liquid Chromatography of Preparations of Ribonucleic Acid Inactivator(s) from Cupric Ion and Hydroquinone Before and After Treatment with Histidine

Analysis of Radicals byEPR

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