Theoretical calculation of substituent effects on the O-H bond strength of phenolic antioxidants related to vitamin E

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DOIResolve DOI: http://doi.org/10.1021/ja963378z
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TypeArticle
Journal titleJournal of the American Chemical Society
ISSN0002-7863
Volume119
Issue18
Pages42454252; # of pages: 8
Subjectalpha tocopherol; antioxidant; article; conformation; degradation; dissociation constant; hydrogen bond; ionic strength; nonhuman; polarization; reaction analysis; vitamin metabolism; X ray analysis
AbstractCalculations on phenol and a large number of phenols substituted with methyl, methoxyl, and amino groups have yielded reliable gas-phase O-H bond dissociation energies, BDE(ArO-H)(gas). Geometries for the phenol, ArOH, and aryloxyl radical, ArO, were optimized at the (semiempirical) AM1 level followed by single point density functional theory (DFT) calculations using a 6-31G basis set supplemented with p-functions on the hydrogen atom and the B3LYP density functional. This gave BDE(PhO-H)(gas) = 86.46 kcal/mol, which is in good agreement with the experimental value of 87.3 ± 1.5 kcal/mol. All but one of the compounds and conformations examined had weaker O-H BDE's than phenol, the exception being o-methoxyphenol with the O-H group pointing toward this substituent (BDE = 87.8 kcal/mol). Where comparison was possible, calculated differences in O-H BDE's were in excellent agreement with experiment (better than 1 kcal/mol). A simple group additivity scheme also gave excellent agreement with calculated BDE (ArO-H)(gas) values. Some potential new leads to phenolic antioxidants more active than vitamin E have been uncovered.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC)
Peer reviewedYes
NPARC number21276739
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Record identifier6f96eacf-923b-4aab-a931-b7125aa91dcf
Record created2015-10-13
Record modified2016-05-09
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