Extraction of Alkali Metal (Li, Na, K) Picrates with Benzo-15-crown-5 into Various Organic Solvents. Elucidation of Fundamental Equilibria Determining the Extraction-ability and -selectivity

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• 作者：Takeda ; Yasuyuki ; Hashimoto ; Kunio ; Yoshiyama ; Daisuke ; Katsuta ; Shoichi
• 关键词：alkali metal picrates ; benzo ; 15 ; crown ; 5 ; complexes ; distribution constants ; effect of a benzo group ; extractability ; fundamental equilibria ; ion ; pair formation constants in water ; molar volumes ; regular solution theory ; selectivity ; solubility
• 刊名：Journal of Inclusion Phenomena and Molecular Recognition inChemistry
• 出版时间：2002
• 出版年：2002
• 期刊代码：19_09230750
• 类别：soc
• 卷：42
• 期：3/4
• 页码：323-331
• 数据来源：sp

摘要

To quantitatively elucidate the effects of the benzo group on the extraction-selectively and -ability of benzo-15-crown-5 (B15C5)for alkali metal ions, the constants of the overall extraction (K$\_ex$), thedistribution for various diluents having low dielectric constants (K$\_D,MLA$), and the aqueousion-pair formation (K$\_MLA$) of B15C5-alkali metal (Li, Na, K) picrate 1:1:1 complexes (MLA) weredetermined at 25 °C. The partition constants of B15C5were also measured at 25 °C. The log K$\_\; MLA$ values for Li$^+$, Na$^+$, and K$^+$ are -0.32 ± 0.22, 2.66 ± 0.19, and 0.71 ± 0.47, respectively. In going from 15-crown-5 (15C5) to B15C5, the benzo group considerably decreasesthe K$\_MLA$ value for the same alkali metal ion. The distributionbehavior of B15C5 and its 1:1:1 complexes with the alkali metal picrates closely obeys regularsolution theory, omitting chloroform. Molar volumes and solubility parameters of B15C5and the 1:1:1 complexes were determined. For every diluent, the K$\_ex$ valuefor B15C5 increases in the order Li$^+$ < K$^+$ < Na$^+$. K$\_D,MLA$ makes anunfavorable contribution to the Na$^+$ extraction-selectivity of B15C5 because of the smallest molar volume of the Na(B15C5)A complex. The Na$^+$ extraction-selectivity of B15C5 is determined completely by much the highest K$\_Na(B15C5)A$ value.The extraction-ability and -selectivity of B15C5 for the alkali metal picrates are compared with those of 15C5on the basis of the underlying equilibrium constants.