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Reduction of Substituted p-Benzoquinones by FeII Near Neutral pH

Permanent URL:
http://handle.nal.usda.gov/10113/36719
File:
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Abstract:
The oxidation of dihydroxyaromatics to benzoquinones by FeIII (hydr)oxides is important in respiratory electron shuttling by microorganisms and has been extensively studied. Prior publications have noted that the Gibbs Free Energy (ΔG) for the forward reaction is sensitive to dihydroxyaromatic structure, pH, and concentrations of reactants and products. Here, we address the back reaction, benzoquinone reduction by FeII. Rates markedly increase with increasing pH, in accord with increases in ΔG. Ring substituents that raise the potential of the p-benzoquinone/hydroquinone half reaction raise reaction rates: -OCH₃ < -CH₃ < -C₆H₅ < -H < -Cl. p-Naphthoquinone, with a reduction potential lower than the five substituted p-benzoquinones just listed, yields the lowest reaction rates. The complexity of the reaction is reflected in lag periods and less-pronounced S-shaped time course curves. Benzoquinone reduction by FeII may be an important link in networks of electron transport taking place in suboxic and anoxic environments.
Author(s):
Uchimiya, Minori , Stone, Alan T.
Subject(s):
benzoquinones , reduction , iron , pH , structure-activity relationships , naphthoquinones , electron transport chain
Format:
p. 173-188.
Note:
Includes references
Source:
Aquatic geochemistry 2010 Jan., v. 16, no. 1
Language:
English
Publisher:
Dordrecht : Springer Netherlands
Year:
2010
Collection:
Journal Articles, USDA Authors, Peer-Reviewed
Rights:
Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.