Peroxyl Radical Reactions in Water Solution: A Gym for Proton-Coupled Electron-Transfer Theories.
Chemistry
; 22(23): 7924-34, 2016 06 01.
Article
em En
| MEDLINE
| ID: mdl-27111024
ABSTRACT
The reactions of alkylperoxyl radicals with phenols have remained difficult to investigate in water. We describe herein a simple and reliable method based on the inhibited autoxidation of water/THF mixtures, which we calibrated against pulse radiolysis. With this method we measured the rate constants kinh for the reactions of 2-tetrahydrofuranylperoxyl radicals with reference compounds urate, ascorbate, ferrocenes, 2,2,5,7,8-pentamethyl-6-chromanol, Trolox, 6-hydroxy-2,5,7,8-tetramethylchroman-2-acetic acid, 2,6-di-tert-butyl-4-methoxyphenol, 4-methoxyphenol, catechol and 3,5-di-tert-butylcatechol. The role of pH was investigated the value of kinh for Trolox and 4-methoxyphenol increased 11- and 50-fold from pHâ
2.1 to 12, respectively, which indicate the occurrence of a SPLET-like mechanism. H(D) kinetic isotope effects combined with pH and solvent effects suggest that different types of proton-coupled electron transfer (PCET) mechanisms are involved in water less electron-rich phenols react at low pH by concerted electron-proton transfer (EPT) to the peroxyl radical, whereas more electron-rich phenols and phenoxide anions react by multi-site EPT in which water acts as proton relay.
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01-internacional
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MEDLINE
Idioma:
En
Ano de publicação:
2016
Tipo de documento:
Article