| DOI | Trouver le DOI : https://doi.org/10.1021/jo00122a026 |
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| Auteur | Rechercher : Bowry, V.W.1; Rechercher : Ingold, K. U.1 |
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| Affiliation | - Conseil national de recherches du Canada. Institut Steacie des sciences moléculaires du CNRC
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| Format | Texte, Article |
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| Sujet | alpha tocopherol; radical; autooxidation; lipid peroxidation; reaction analysis |
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| Résumé | Rate constants which have been reported for the bimolecular self-reaction of α-tocopheroxyl radicals vary by about 5 orders of magnitude. We have found that the observed bimolecular rate constant can vary by about a factor of 7 during a single, but typical experiment, e.g., in chlorobenzene at 37 °C from ca. 7 x 103 M-1 s-1 initially to ca. 1 x 103 M-1 s-1 finally. The overall reaction involves a disproportionation with the transfer of a hydrogen atom from the 5-methyl group of one radical to the phenoxyl oxygen atom of the other radical forming α-tocopherol and an o-quinone methide. In the slow regime (which corresponds to the true reaction of two α-tocopheroxyl radicals) this disproportionation has a deuterium kinetic isotope effect of 3.7. The bizarre kinetic behavior observed with α-tocopheroxyl radicals has been traced to a very minor impurity which will be present in any normal sample of α-tocopherol. The impurity in question is a bisphenol in which two α-tocopherol moieties have become linked through their 5-methyl carbon atoms. This bisphenol is a "natural" impurity in α-tocopherol since it will be formed upon exposure of α-tocopherol to air. The coupling of two o-quinone methide molecules yields a spiro-dimer which is then reduced to the bisphenol, probably by unoxidized α-tocopherol. © 1995 American Chemical Society. |
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| Date de publication | 1995 |
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| Dans | |
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| Langue | anglais |
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| Publications évaluées par des pairs | Oui |
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| Numéro NPARC | 21276588 |
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| Exporter la notice | Exporter en format RIS |
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| Signaler une correction | Signaler une correction (s'ouvre dans un nouvel onglet) |
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| Identificateur de l’enregistrement | f3fd8f98-d046-410e-b73a-fdbb456970d9 |
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| Enregistrement créé | 2015-10-13 |
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| Enregistrement modifié | 2020-04-29 |
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