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Issue 3, 2017
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QSARs for phenols and phenolates: oxidation potential as a predictor of reaction rate constants with photochemically produced oxidants

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Abstract

Quantitative structure–activity relationships (QSARs) for prediction of the reaction rate constants of phenols and phenolates with three photochemically produced oxidants, singlet oxygen, carbonate radical, and triplet excited state sensitizers/organic matter, are developed. The predictive variable is the one-electron oxidation potential (E1), which is calculated for each species using density functional theory. The reaction rate constants are obtained from the literature, and for singlet oxygen, are augmented with new experimental data. Calculated E1 values have a mean unsigned error compared to literature values of 0.04–0.06 V. For singlet oxygen, a single linear QSAR that includes both phenols and phenolates is developed that predicts experimental rate constants, on average, to within a factor of three. Predictions for only 6 out of 87 compounds are off by more than a factor of 10. A more limited data set for carbonate radical reactions with phenols and phenolates also gives a single linear QSAR with prediction of rate constant being accurate to within a factor of three. The data for the reactions of phenols with triplet state sensitizers demonstrate that two sensitizers, 2-acetonaphthone and methylene blue, most closely predict the reactivity trend of triplet excited state organic matter with phenols. Using sensitizers with stronger reduction potentials could lead to overestimation of rate constants and thus underestimation of phenolic pollutant persistence.

Graphical abstract: QSARs for phenols and phenolates: oxidation potential as a predictor of reaction rate constants with photochemically produced oxidants

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Publication details

The article was received on 20 Oct 2016, accepted on 29 Nov 2016, published on 01 Dec 2016 and first published online on 01 Dec 2016


Article type: Paper
DOI: 10.1039/C6EM00580B
Citation: Environ. Sci.: Processes Impacts, 2017,19, 324-338
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    QSARs for phenols and phenolates: oxidation potential as a predictor of reaction rate constants with photochemically produced oxidants

    W. A. Arnold, Y. Oueis, M. O'Connor, J. E. Rinaman, M. G. Taggart, R. E. McCarthy, K. A. Foster and D. E. Latch, Environ. Sci.: Processes Impacts, 2017, 19, 324
    DOI: 10.1039/C6EM00580B

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