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Stability of carbon‐centered radicals: Effect of functional groups on the energetics of addition of molecular oxygen
Author(s) -
Wright James S.,
Shadnia Hooman,
Chepelev Leonid L.
Publication year - 2009
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.21124
Subject(s) - radical , bond dissociation energy , chemistry , dissociation (chemistry) , oxygen , density functional theory , computational chemistry , unpaired electron , carbon fibers , chemical physics , materials science , organic chemistry , composite number , composite material
In this paper we examine a series of hydrocarbons with structural features which cause a weakening of the CH bond. We use theoretical calculations to explore whether the carbon‐centered radicals R • which are created after breaking the bond can be stabilized enough so that they resist the addition of molecular oxygen, i.e. where the reaction R • + O 2 → ROO • becomes energetically unfavorable. Calculations using a B3LYP‐based method provide accurate bond dissociation enthalpies (BDEs) for RH and ROO • bonds, as well as Gibbs free energy changes for the addition reaction. The data show strong correlations between ROO • and RH BDEs for a wide variety of structures. They also show an equally strong correlation between the ROO • BDE and the unpaired spin density at the site of addition. Using these data we examine the major functional group categories proposed in several experimental studies, and assess their relative importance. Finally, we combine effects to try to optimize resistance to the addition of molecular oxygen, an important factor in designing carbon‐based antioxidants. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009