pH法测定若干金属离子与天门冬酰胺络合反应的热力学参数

THE DETERMINATION OF THERMODYNAMIC PARAMETERS ASSOCIATED WITH THE FORMATION OF SOME METAL-ASPARAGINE COMPLEXES

本文在不同温度和离子强度为0.1的条件下,以pH电位法分别测定了Co^(2+)、Ni^(2+)、Cu^(2+)、Zn^(2+)、Cd^(2+)与天门冬酰胺形成1:2络合物时的平衡常数。在所有测定的温度范围内,吉氏自由能变化的递变顺序为Cu^(2+)<Ni^(2+)<Zn^(2+)<Co^(2+)<Cd^(2+)。以温度系数法计算了有关络合反应的焓和墙的变化,并据此对反应的动力问题进行了讨论。

Equilibrium constants for the formation of Co^(2+),Ni^(2+),Cu^(2+),Zn^(2+) and Cd^(2+)bis-complexes of asparagine have been determined potentiometrically at an ionic strength of 0.1 and at 10°,15°,20°,25°,30℃.At all the temperatures studied,the Gibbs free energy changes increase in the Order Cu^(2+)<Ni^(2+)<Zn^(2+)<Co^(2+)<Cd^(2+).The enthalpy and entropy changes for the bis-species are calculated from the temperature coefficient data.The primary driving force favoring the formation of the corresponding complexes in solution has been discussed.