双冠醚研究(Ⅴ)——Schiff碱型和仲胺型双-(苯并-18-冠-6)对碱金属苦味酸盐的萃取性质

Studies on Bis-Crown Ether ( V )——Extractive Behaviour of Alkali Metal Picrates with Schiff Base and Secondary Amine Type Bis-Crown Ethers Containing Benzo-18-Crown-6 Moiety

用两类结构不同的Schiff碱型、仲胺型双-(苯并-18-冠-6)在氯仿-水体系中对碱金属苦味酸盐进行萃取,测量了配合物组成比和萃取平衡常数。

Extraction of alkali metal picrates with two different kinds of schiff base and secondary amine type bis-crown ethers containing benzo-18-crown-6 moiety was carried out in chloroform at 25 ±0. 2℃. The distribution ratio of alkali metal picrates, the stoichiometry and extraction equilibrium constantsK, of bis-crown ether-cation complexes were determined. The results show that the bis-crown ethers form1 : 1(crown unit : cation) cpmlexes with Na+,K+,Rb+ and probably form 2 : 1 intramolecular or intermolecuiar complexes -with Cs+, but mono Schiff base type bis-crown ethers preferably form 1 :1 complexes with Cs+. Moreover the K, values of the secondary amine type bis-crown ethers are much larger than those of the Schiff base type bis-crown ethers. N1 exhibits the greatest extractibility and selectivity for Cs+ ions. It is noteworthy that the bis-crown ethers N5 containing unsymmetrical crown rings has a larger extractibility for Rb+ ions.