Passive Transport of Alkali and Alkaline Earth Metal Cations by Cooperative Carrier Composed of n-Alkyl Oligo (oxyethylene) Ether and Alkanoic acid

Abstract

Homogeneous oligo(oxyethylene)n-dodecyl ethers(C₁₂E_m, m=28)and higher alkanoic acids(C₈C₁₈)were examined as carriers for the competitive passive transport of alkali(Li⁺, Na⁺, and K⁺)and alkaline earth metal(Mg²⁺, Ca²⁺, and Ba²⁺)cations through a chloroform membrane.
1) The linear polyethers, combined with an alkanoic acid, effectively mediated cation-transport similarly to cooperative carriers composed of crown ether and alkanoic acid as reported previously^l4)16).
2) 2-Bromoalkanoic acids (BAA) were superior to those unsubstituted as co-carriers in both transport efficiency and cation-selectivity for two competitive systems (Table-1 and -2).
3) For a monovalent cations system, the polyethers combined with BAA (C₁₂E_m-BAA) had essentially the same selectivity (K⁺>Na⁺>>Li⁺). Their transport efficiency increased with m (Fig.-3).
4) The selectivity of divalent cations except Mg²⁺ was found to depended on m of C₁₂E_m-BAA, and plots of efficiency vs. m for Ca²⁺ and Ba²⁺ gave maxima at m=5 and m=6, respectively (Fig.-5).
5) The effect of the acyl chain length of BAA on the transport ability of these cooperative carriers was also examined (Fig.-4 and -6).