and T = 25°C. The rate constants of oxidation in aqueous solvent, k, were obtained from the extrapolation of the linear plots of the specific rate constants k vs. % H2O plots at each pH value. A linear relationship between k and 1/[H+] was observed for both flavonoids with k = k1Ka1/[H+], where Ka1 was the first acid dissociation constant on the catechol ring and k1 is the rate constant of the oxidation
在pH 5.5-7.5,μ= 0.10 M [(n -Bu)4 N]的各种比例的CH 3 OH / H 2 O混合溶剂中,已进行了dpph •自由基还原
邻苯二酚和
儿茶素的动力学研究。ClO 4,T= 25℃。在
水性溶剂中,氧化速率常数ķ,从该特定速率常数的线性曲线的外推得到ķ与%H 2 ö地块在每一pH值。对于k = k 1 K的两种类
黄酮,在k和1 / [H + ]之间观察到线性关系。A1 / [H + ],其中ķ A1是
儿茶酚环上的第一酸解离常数和ķ 1是mononegative物种HX的氧化速率常数- 。从曲线的斜率获得的k 1的值是
邻苯二酚和
儿茶素的(8.2±0.2)×10 5和(6.1±0.1)×10 5 M -1 s -1。根据Marcus理论对外层电子转移反应的反应分析得出的值为3.7×10 3 M -1 s -1dpph • / dpphH对的自交换速率常数。©2011 Wiley