停止-流动分光光度法研究铕(II)与二甲酚橙快速电子转移反应动力学

用停止-流动分光光度法研究了Eu~(2+)与二甲酚橙(XO)间快速电子转移反应的动力学规律。求得了速控步骤的动力学参数。如反应级数(n=2)、几个不同温度下的速率常数(k_(278 K)=5.7×10~8 L·mol~-·s~(-1), k_(s38 K)=1.01×10~9 L·mol~(-1)·s~(-1))、活化能(E=7.6×10~3 J·mol~(-1)), 以及指前因子(A=1.5×10~(10) L·mol~(-1)·s~(-1)), 并判断出其为溶液中扩散控制型反应。根据实验现象与测试结果, 提出了Eu~(2+)与XO的反应分别在Eu~(2+)相对过量和在XO过量时的反应机理, 并判断了各反应步骤速率常数之间的相对关系。

Studies on Kinetics of the Electron Transfer Reaction Between Eu(II) and Xylenol Orange by Stop-Flow Method

The kinetics and mechanism of the reaction between Eu~(2+) and Xylenol orange (XO) in aqueous solution has been studied by means of stop-flow spectrophotometric method. The kinetic parameters of the rate-controlling step, i,e, reaction order (n=2), rate constant at various temperatures (k_(278 K)=5.7×10~8 L·mol~(-1)·s~(-1), k_(338 K)=1.01×10~9 L·mol~(-1)·s~(-1)…), activation energy (E=7.6×10~3 J·mol~(-1)) and preexponential factor (A=1.5×10~(10) L·mol~(-1)·s~(-1)) have been determined. It has been established that the electron transfer reaction between Eu~(2+) and XO is a diffusion controlled reaction.The possible mechanisms of the reaction between Eu~(2+) and XO both in the presence of excess XO and Eu~(2+) also have been suggested. The relation between the rate constants of each step were estimated.