氧化还原
化学
电子顺磁共振
没食子酸
聚合
无机化学
激进的
金属
羧酸盐
光化学
有机化学
抗氧化剂
聚合物
物理
核磁共振
作者
Joyce Ferreira Severino,B. A. Goodman,Thomas G. Reichenauer,Katharina F. Pirker
标识
DOI:10.3109/10715762.2010.515220
摘要
Interactions between transition metal ions and polyphenols can result in complexation, redox or polymerization, but the relative importance of these reactions is unclear. The present paper reports results from the reaction of gallic acid (GA) with Cu(II) using electron paramagnetic resonance (EPR) and UV/visible spectroscopy for various relative concentrations and pH values. Reduction of Cu(II) by GA does not occur under strongly acidic or strongly alkaline conditions. Di- or polymerization reactions between Cu(II) and carboxylate groups of GA dominate the results at acidic pH, whereas mononuclear complexes increase in importance at higher pH and GA concentrations. There was no evidence for any redox reaction between Cu(II) and GA and free radical formation from GA at high pH was shown to be the consequence of auto-oxidation, which was inhibited by Cu(II). Serious questions are thus raised about the existence of the frequently assumed redox reactions between Cu(II) and polyphenols.
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