Reactions of the phthalimide N-oxyl radical (PINO) with activated phenols: The contribution of π-stacking interactions to hydrogen atom transfer rates

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DOIResolve DOI: http://doi.org/10.1021/jo302483s
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TypeArticle
Journal titleJournal of Organic Chemistry
ISSN0022-3263
Volume78
Issue3
Pages10261037; # of pages: 12
Subject2 ,4 ,6-trimethylphenol; Aromatic rings; Degree of Charge Transfer; Deuterium kinetic isotope effect; Hammett correlation; Hydrogen transfer; Hydrogen-atom transfer; Laser flash photolysis; Marcus cross-relations; N-oxyl radicals; Phenolic antioxidant; Phthalimide; Radical scavenging; Solvent effects; Stacking interaction; Theoretical calculations; Charge transfer; Deuterium; Free radical reactions; Hydrogen; Kinetics; Rate constants; Phenols; 2,2,5,7,8 pentamethylchroman 6 ol derivative; 2,6 di tert butyl 4 substituted phenol derivative; 2,6-dimethylphenol derivative; antioxidant; deuterium; hydrogen; phenol derivative; phthalimide derivative; phthalimide n oxyl radical; radical; scavenger; unclassified drug; article; chemical interaction; chemical structure; photolysis; transport kinetics
AbstractThe kinetics of reactions of the phthalimide N-oxyl radical (PINO) with a series of activated phenols (2,2,5,7,8-pentamethylchroman-6-ol (PMC), 2,6-dimethyl- and 2,6-di-tert-butyl-4-substituted phenols) were investigated by laser flash photolysis in CH3CN and PhCl in order to establish if the reactions with PINO can provide a useful tool for evaluating the radical scavenging ability of phenolic antioxidants. On the basis of the small values of deuterium kinetic isotope effects, the relatively high and negative ρ values in the Hammett correlations and the results of theoretical calculations, we suggest that these reactions proceed by a hydrogen atom transfer (HAT) mechanism having a significant degree of charge transfer resulting from a π-stacked conformation between PINO and the aromatic ring of the phenols. Kinetic solvent effects were analyzed in detail for the hydrogen transfer from 2,4,6-trimethylphenol to PINO and the data obtained are in accordance with the Snelgrove-Ingold equation for HAT. Experimental rate constants for the reactions of PINO with activated phenols are in accordance with those predicted by applying the Marcus cross relation. © 2013 American Chemical Society.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC); National Institute for Nanotechnology (NINT-INNT)
Peer reviewedYes
NPARC number21269680
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Record identifier2be74efe-8693-4e05-a8cf-7aded57725ab
Record created2013-12-13
Record modified2016-05-09
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