铜(Ⅱ)的EDTA螯合物对抗坏血酸氧化的催化作用

本文研究Cu-EDTA催化抗坏血酸被氧氧化反应。发现Cu-EDTA的催化作用随条件而异,在碱性条件下,Cu-EDTA没有催化作用;在酸性条件下,有催化作用,这时真正起催化作用的不是与Cu-EDTA成平衡的游离铜离子,而是Cu-EDTA本身。在pH 3.5,温度为25℃时,抗坏血酸和过氧化氢的浓度出现振荡。根据实验结果,提出了体系中可能发生的主要反应。

THE CATALYTIC OXIDATION OF ASCORBIC ACID BY Cu (Ⅱ)-EDTA CHELATE

The kinetics of catalytic oxidation of ascorbic acid by Cu(Ⅱ)-EDTA chelate has been studied. The catalytic activity of this chelate was found to change with pH. Cu (Ⅱ)-EDTA chelate showed no catalytic activity at pH 8.8, but at pH 3.5, obvious catalytic activity was observed. The catalytic activity was not attributed to the dissociated cupric ions, but to the chelate itself. The concentration of ascorbic acid and intermediate hydrogen peroxide has oscillatory behavior during the oxidation of ascorbic acid at pH 3.5. The main reactions taken place in the system of Cu(Ⅱ)-EDTA-ascorbic acid-O₂ were proposed.