이온성 크라운에테르 포스포닉산에 의한 알칼리 금속 양이온과 알칼리 토금속 양이온의 용매추출

Solvent Extractions of Alkali Metal Cations and Alkaline Earth Cations by Ionizable Crown Ether Phosphonic Acids

A comparison of alkali metal cation and alkaline earth cation solvent extraction was made for three additional monoionizable crown ethers and one diionizable crown ether. sym-(n-Octyldibenzo)-16-crown-5-oxyacetic acid underline{1} exhibited high efficiency and selecvity in solvent extraction of alkali metal cations with respect to that observed with alkaline earth cations. Sizes of Na^+ and Ca^{2+} appropriately match with the cavity size of monoethyl sym-bis[4(5)-tert-butylbenzo]-16-crown-5-oxymethylphosphonic acid underline{3}. As the result, Na^+ and Ca^{2+} are the best extracted. sym-(n-Octyldibenzo)-16-crown-5-oxymethyldiphosphonic acid underline{4}was found to be somewhat selective for Na^+ over Li^+ and other alkaline earth metal cations. In the complexation of alklaine earth cations by crown ether diphosphonic acid underline{4}, Ca^{2+} and Sr^{2+} are the appropriate sizes, but lager Ba^{2+} may be due to favorable formation of a sandwich type complex between the crown ether cavity and the dianion of the deprotonated crown ether phoaphonic acid moiety.