| Abstrakt: |
In order to determine the ion-pair formation constant of a crown ether–metal salt complex (1 : 1 : 1) in water, an equation is derived from the regular solution theory. Then, the theoretical predictions are verified experimentally by solvent extraction with 15-crown-5 (15C5), sodium picrate (NaA), and various organic solvents of low dielectric constant. The partition constants of 15C5 and the actual overall extraction constants of NaA with 15C5 were determined at 25 ± 0.2 °C. The partition constants of the Na(15C5)A complex are calculated from these data, the literature value for the complex-formation constant of Na(15C5)+in water, and the ion-pair formation constant (KNa(15C5)A) in water determined in this study (log KNa(15C5)A= 4.09 ± 0.23 at 25 °C). The distribution behavior of 15C5 and Na(15C5)A is explained by the regular solution theory. The obtained molar volumes V/cm3mol-1and solubility parameters d/cal1/2cm-3/2are as follows; V15C5= 189 ± 34, VNa(15C5)A= 215 ± 46, d15C5= 12.0 ± 0.1, and dNa(15C5)A= 12.0 ± 0.1. |
