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本文在总离子强度I=1.00mol·dm~(-3)、[Cu~(2+)]》[H_2A]、[H~+]》[H_2A]、无氧及无缓冲剂存在的条件下,研究Cu(Ⅱ)氧化抗坏血酸(H_2A)的动力学和机理。发现Cu(Ⅱ)与H_2A不发生配位反应,但在Cl~-存在的情况下,确有Cu(Ⅱ)的H_2A配合物生成。Cu(Ⅱ)氧化H_2A反应的速率方程为r={a+b[Cl~-]}[Cu~(2+)]{[H~+]+K_a}~(-1),25℃时a和b值分别为4.08×10~(-4)s~(-1)和0.555dm~3·s~(-1)·mol~(-1)。Cu(Ⅱ)氧化H_2A反应的表观活化能为68.1kJ·mol~(-1)。根据动力学结果,提出了反应机理,并给出了配合物ClCuHA的结构形式。
In this paper, under the conditions of total ionic strength I = 1.00mol · dm -3, [Cu 2+] [H 2 A], [H ~ +] "[H 2 A], oxygen free and no buffer The kinetics and mechanism of oxidation of ascorbic acid (H 2 A) by Cu (Ⅱ) were studied. It was found that there was no coordination reaction between Cu (Ⅱ) and H_2A, but there was indeed Cu (Ⅱ) H_2A complex in the presence of Cl ~ -. The rate equation for the oxidation of H 2 A with Cu (Ⅱ) is r = {a + b [Cl ~ -]} [Cu ~ (2 +)] {[H ~ +] + K_a} And b values were 4.08 × 10 -4 s -1 and 0.555 dm -3 · s -1 · mol -1, respectively. The apparent activation energy of oxidation of H 2 A by Cu (Ⅱ) was 68.1 kJ · mol -1. According to the kinetic results, the reaction mechanism was proposed and the structure of the complex ClCuHA was given.