Studies on Synthetic Ionophores. VI. Synthesis of Polyether Carboxylic Acids and Their Use as Carriers for Alkali Metal Ion Transport through Liquid Membrane

Abstract

ω-Hydroxy carboxylic acids (3, 5, 6, 7, 10, 12, 14, 17, 18, 20, and 22) bearing 2–6 ether oxygens and aromatic rings with or without a tetrahydrofuran ring and the ω-methoxy and ω-benzyloxy derivatives of 5 (8 and 9) were synthesized. These were employed as carriers for active and competitive transport of alkali metal ions through liquid membrane as well as for extraction of alkali metal ions to organic layers. Effect of hydrophobic group of aromatic and tetrahydrofuran rings, number of ether oxygens, and terminal hydroxyl group of the ionophores on the ion transport ability and selectivity were investigated. The hydrophobic groups increased total amount of transported ions as well as partition coefficients. The ionophore, 5, which contains five ether oxygens, two aromatic rings, and o-toluic acid moiety transported K+ selectively over Na+ and Li+ through 1,2-dichloroethane being consistent with the extraction experiments. The m- and p-substituted isomers, 6 and 7, exhibited no transport ability through 1,2-dichloroethane. The ω-alkoxy derivatives of 5 (8 and 9) exhibited less selectivity for K+ through 1,2-dichloroethane than 5 did. Through 1-hexanol, the ionophores, 5–9, including linoleic acid with no ether linkage transported alkali metal ions. The ionophores (3, 12, 20, and 22) containing 2–4 ether oxygens did not exhibit high transport ability.

The rubidium salt of an ω-hydroxycarboxylic acid with six ethereal O atoms

“…Model compound (2) was synthesized using successive Williamson's methods (Kuboniwa et al, 1985). An ion-transport experiment using (2) through a ClCH 2 CH 2 Cl liquid membrane was carried out in a Utube apparatus as described previously (Yamaguchi et al, 1988), however, transported ions were analyzed by atomic absorption spectrometry instead of¯ame analysis. The analysis showed that 22% of Na + and 73% of K + were transported by (2) with errors of about 5% in 5 d. A solution of RbOH in MeOH (0.54 ml, 3.74 mM) was added to the solution of (2) (11.3 mg) in 20 ml MeOH and the mixture was stirred overnight.…”

“…Naturally occurring acid ionophores are known to mediate active ion transport through lipophilic membranes by formation of hydrophobic complexes with ions (Taylor et al, 1982, and references therein) and their structures were studied to provide information on their function (Duesler & Paul, 1983, and references therein). We have synthesized a series of relatively simple 3-hydroxycarboxylic acids as model compounds for the naturally occurring ionophores to investigate the relationship between the primary molecular structures and ion-transport properties (Kuboniwa et al, 1982(Kuboniwa et al, , 1985Yamazaki et al, 1978Yamazaki et al, , 1979Yamaguchi et al, 1988Yamaguchi et al, , 1989.…”

“…The model compounds, (1)-(3), transport K + over Na + through the ClCH 2 CH 2 Cl membrane using the pH gradient of outer aqueous phases. The competitive ion-transport experiments show that the amount of transported ions, as well as K + selectivity over Na + , increases in the order of (1) → (2) → (3) (Kuboniwa et al, 1985;Yamaguchi et al, 1988). The model compound, (1), having five ethereal O atoms, forms a 2:2 dimer with K + .…”

Separation of the Intramembrane Diffusion Potential and the Donnan Potential on the Basis of the Potential Transient Measurement: Application to the Analysis of Reverse Ion Permeation Driven by pH Difference

“…4 were calculated by using Eqs. [3]- [6], respectively. The values of K a and u Na /u H obtained from the best fit of the theoretical curves with the experimental results in the range of low hydrogen ion concentration were 0.21 (mol dm Ϫ3 ) and 0.080, respectively.…”

“…For the liquid membrane-aqueous electrolyte systems including an ionic carrier with weakly ionized groups, the ion permeation against the own concentration difference driven by pH difference has been investigated by many workers (1)(2)(3)(4)(5)(6). Moreover, it has been suggested that the incorporation of metal ions into the reversed micellar structure in the liquid membrane facilitate the ion permeation process (7,8).…”