Thermodynamic study on solvent extraction of 18-crown-6-alkali metal ion complexes and tetraalkylammonium ions with picrate anions into benzene.
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概要
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Enthalpy and entropy changes for ion-pair extractions of tetraalkylammonium ions (Me<SUB>4</SUB>N<SUP>+</SUP>, Et<SUB>4</SUB>N<SUP>+</SUP>, <I>n</I>-Pr<SUB>4</SUB>N<SUP>+</SUP>, <I>n</I>-Bu<SUB>4</SUB>N<SUP>+</SUP>) with picrate anions, overall extractions of alkali metal (Na, K, Rb, Cs) picrates with 18-crown-6 (18C6), and distribution of 18C6 itself were determined between benzene and water, Me, Et, <I>n</I>-Pr, and <I>n</I>-Bu denoting methyl, ethyl, propyl, and butyl groups, respectively. All the extracted 18C6 complexes were 1:1:1 complexes (alkali metal ion: 18C6: picrate anion). The values of enthalpy and entropy changes are negative for overall extractions of all the alkali metal picrates with 18C6. Plots of thermodynamic quantities for ion-pair extractions of R<SUB>4</SUB>NA vs. the number of carbon atoms of R<SUB>4</SUB>N<SUP>+</SUP> show a linear relationship, R<SUB>4</SUB>N<SUP>+</SUP> and A<SUP>−</SUP> being tetraalkylammonium ion and picrate anion, respectively. Enthalpy and entropy changes were calculated for ion-pair extractions of 18C6–alkali metal ion complexes with picrate anions. The thermodynamic parameters for ion-pair extractions of 18C6–alkali metal picrate complexes were compared with those of R<SUB>4</SUB>NA, and were discussed in detail from the standpoint of molecular grounds. It was found from these data that the 18C6–K<SUP>+</SUP> complex acts as a structure breaker in water.
- 公益社団法人 日本化学会の論文