Extraction of Alkali Metal (Na—Cs) Picrates with Dibenzo-18-crown-6 into Various Organic Solvents. Elucidation of Fundamental Equilibria which Govern the Extraction-Ability and -Selectivity

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• 作者：Yajima ; Setsuko ; Yahata ; Tsuyoshi ; Takeda ; Yasuyuki
• 关键词：solvent extraction ; extractability ; selectivity ; fundamental equilibria ; ion ; pair formation constants in water ; distribution constants ; solvent effects ; regular solution theory ; molar volume ; solubility parameter ; dibenzo ; 18 ; crown ; 6 ; alkali met
• 刊名：Journal of Inclusion Phenomena and Molecular Recognition inChemistry
• 出版时间：2000
• 出版年：2000
• 期刊代码：19_09230750
• 类别：soc
• 卷：38
• 期：1/4
• 页码：305-322
• 数据来源：sp

摘要

In order to quantitatively investigate effects of the size, the structuralrigidity, and the lipophilicity of dibenzo-18-crown-6 (DB18C6) on itsextraction-ability and -selectivity for alkali metal ions, constants of theoverall extraction (Kex), the distribution for various diluents of lowdielectric constants (K$\_D,MLA$), and the aqueous ion-pairformation (K$\_\; MLA$) of DB18C6-alkali metal (Na-—Cs) picrate 1:1:1 complexes were determined at 25°C; the partition constants of DB18C6 itself were also measured at 25°C. The log K$\_MLA$ of Na, K, Rb, and Cs are -0.14 ± 0.11, 1.30 ± 0.10, 1.00 ± 0.09, and 0.24 ± 0.11, respectively. The partition behavior of DB18C6 and its1:1:1 complexes with the alkali metal picrates can be clearly explained byregular solution theory, except for chloroform. The molar volumes andsolubility parameters of DB18C6 and the 1:1:1 complexes were determined.A relation between molar volumes of the complexes and K$\_MLA$is discussed. The magnitude of Kex is largely determined by that ofK$\_D,MLA$. For every diluent, the extraction selectivity of DB18C6increases in the order Na > Cs > Rb > K. The K extraction-selectivity of DB18C6 over Na is the highest among all the combinations of the two neighboring alkali metals in the periodic table. The extraction-ability and -selectivity for the alkalimetal picrates and their change with the diluent of DB18C6 were completely elucidated by the four fundamental equilibria and regular solution theory.