Theoretical and Experimental Investigation on the Oxidation of Gallic Acid by Sulfate Radical Anions

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• 作者：Paula Caregnato ; Pedro M. David Gara ; Gabriela N. Bosio ; Mó ; nica C. Gonzalez ; Nino Russo ; Marí ; a del Carmen Michelini ; Daniel O. Má ; rtire
• 刊名：Journal of Physical Chemistry A
• 出版年：2008
• 出版时间：February 14, 2008
• 年：2008
• 卷：112
• 期：6
• 页码：1188 - 1194
• 全文大小：316K
• 年卷期：v.112,no.6(February 14, 2008)
• ISSN：1520-5215

文摘

By monitoring the decay of SO₄^- after flash photolysis of aqueous solutions of S₂O₈^2- at different pH values,the kinetics of the reaction of SO₄^- radicals with gallic acid and the gallate ion was investigated. Thebimolecular rate constants for the reactions of the sulfate radicals with gallic acid and the gallate ion werefound to be (6.3 ± 0.7) × 10⁸ and (2.9 ± 0.2) × 10⁹ M^-1 s^-1, respectively. On the basis of the oxygen-independent second-order decay kinetics and on their absorption spectra, the organic radicals formed asintermediates of these reactions were assigned to the corresponding phenoxyl radicals. DFT calculations inthe gas phase and aqueous solution support formation of the phenoxyl radicals by H abstraction from thephenols to the sulfate radical anion. The observed recombination of the phenoxyl radicals of gallic acid toyield substituted biphenyls and quinones is also supported by the calculations. HPLC/MS product analysisshowed formation of one of the predicted quinones.