Ionic recognition by proton-ionizable lariat ethers and their polymers

To probe the influence of structural variation within dibenzo-16crown-5-oxyacetic acids upon the selectivity of alkali metal cation separations by solvent extraction and liquid membrane transport processes, studies have now been conducted in homogeneous solution by NMR spectroscopy and titration calorimetry and in the solid state. Condensation polymerization of such proton-ionizable lariat ethers with formaldehyde produces a new class of ion-exchange resins which contain cyclic polyether binding sites as well as ion-exchange site for metal ion complexation. Proton-ionizable lariat (ref. 1) ethers are crown ethers which possess a pendent acidic group (eg. carboxylic acid, sulfonic acid, phosphonic acid). Compared with neutral crown ethers and lariat ethers, proton-ionizable lariat ethers have an important advantage that the transfer of a metal ion into an organic medium in a separation process does not require concomitant transport of an aqueous phase anion (refs. 2 and 3). practical applications in which hard, hydrophilic aqueous phase anions, such as chloride, nitrate or sulfate, would be involved. The reaction of bisphenols with epichlorohydrin and metal hydroxides in aqueous solvents provides a convenient synthesis of dibenzocrown ethers containing a three-carbon bridge with a hydroxyl group on the center carbon (ref. 4). dibenzocrown ether alcohols may be transformed into lariat ether carboxylic acids, such as 1-2 (refs. 5-7). proton-ionizable lariat ethers to prevent loss of the crown ether carboxylate from the organic layer into a contacting highly alkaline aqueous phase during solvent extract ion (ref. 8). This factor is of immense importance for potential Such Lipophilic groups are incorporated into these