Study of Competitive Chelating Reaction between Lanthanum and Tribromoarsenazo in the Medium of Weak Acid by Capillary Zone Electrophoresis

Two kinds of metal chelates of rare earth elements reacted with tribrimoarsenazo formed under the condition of critic acid were observed by simultaneous technique of capillary electrophoresisphotothermal interference spectrometry. The tendency of the conversion between these chelates as functions of the mole ratio of the reagent and the metal, pH value and the elapsing time was investigated. Kinetic equation of competitive chelating reaction between the TBA-La (Ⅲ) and La (Ⅲ) -critic acid were established. It was found that the competitive chelating reaction follows secondorder kinetics, for this second-order reaction, k=5.55 L·mol-1·S-1.

镧与二溴一氯偶氮胂配位反应动力学及机理研究

本文提纯了二澳一氯偶氮肿(DBCA),纯度达97%以上。测定了镧与DBCA(以H_6R表示,下同)的配应比为La^(3+)(H_2O)_6:H_6R=1:3。用停流分光光度法研究了镧与DBCA配位反应的动力学。获得经验速率方程为R=k[La^(3+)(H_2O)_6][H_6R]~2[H_3^+O]^(-1),实验活化能为54.26KJ·mol^(-1),活化焓为51.82KJ·mol^(-1),活化熵为-86.55J·K^(-1)。拟定了反应机理,由此机理导出的速率方程与经验速率方程相吻合。最后讨论了配合物的几何构型和反应模式。