Solvent effects on extraction of potassium picrate with benzo-18-crown-6. A new equation for the determination of ion-pair formation of crown ether-metal salt complexes in water |
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Authors: | Yasuyuki Takeda Hiroyasu Sato Shin Sato |
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Affiliation: | (1) Department of Chemistry, Faculty of Science, Chiba University, Yayoi-cho, Inage-ku, 263 Chiba, Japan |
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Abstract: | In order to determine the ion-pair formation constant of a crown ether-metal salt 1:1:1 complex in water, an equation is derived from regular solution theory and its predictions are verified experimentally by the solvent extraction method using benzo-18-crown-6 (B18C6), potassium picrate (KA), and various diluents of low dielectric constant. The distribution constants of B18C6 itself and the overall extraction constants of KA with B18C6 were determined at 25±0.2°C. The distribution constants of the neutral K(B18C6)A complex were calculated from these data. The literature value for the complex-formation constant of K(B18C6)+ in water and the ion-pair formation constant (KK(B18C6)A) for K(B18C6)A in water determined in this study were log KK(B18C6)A=3.12±0.23 at 25°C). The distribution behavior of B18C6 and K(B18C6)A is explained in terms of regular solution theory. The molar volumes V (cm3·mol–1) and solubility parameters (cal1/2-cm–3/2) are as follows: VB18C6=249±36; VK(B18C6)A=407±56; B18C6 = 11.5 ± 0.5; and K(B18C6)A = 11.5 ± 0.5. |
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Keywords: | Solvent extraction ion-pair formation constant in water solvent effects regular solution theory molar volume solubility parameter benzo-18-crown-6 potassium picrate |
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