Binding thermodynamic constants of alkaline earth metal ions with 18-crown-6 studied by microcalorimetry

被引：3

作者：

Liu Peng ^{[1
]}

Li Xi ^{[1
]}

Pan Mu ^{[2
]}

机构：

[1] Wuhan Univ Technol, Dept Appl Chem, Sch Sci, Wuhan 430070, Peoples R China

[2] Wuhan Univ Technol, State Key Lab Adv Technol Mat Synth & Proc, Wuhan 430070, Peoples R China

来源：

ACTA PHYSICO-CHIMICA SINICA | 2008年 / 24卷 / 01期

关键词：

microcalorimetry; titration; crown ester; binding constant; enthalpy-driven;

D O I：

10.3866/PKU.WHXB20080129

中图分类号：

O64 [物理化学（理论化学）、化学物理学];

学科分类号：

070304 ; 081704 ;

摘要：

The binding of alkaline earth metal ions with 18-crown-6 was studied by microcalorimetry. Equilibrium constant and changes of enthalpy, entropy, Gibbs free energy can be obtained from titration analysis. In the process of binding, the free metal ions bind to oxygen atom of 18-crown-6 by static force. The binding causes both energy and entropy in system to decrease, so reaction process was accompanied by release of heat and reduction of freedom. Having the similar size to ion radii (138 pm) of Ba2+, the cycle of 18-crown-6 can surround Ba2+ tightly. Metal ions with a smaller size have a weaker force to bind oxygen atom because of size effect. From Be2+, Mg2+, Ca2+, Sr2+ to Ba2+, more heat releases and equilibrium constant increases in the process of the binding reaction.

引用

页码：161 / 164

页数：4

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