Extraction of alkali metal picrates with poly- and bis(crown ether)s.

Extraction of alkali metal picrates by new poly- and bis(crown ether)s containing benzo-15-crown-5 and benzo-18-crown-6 moieties was carried out with chloroform as water-immiscible solvent. The poly- and bis(crown ether)s were found to extract the picrates more effectively than the corresponding monocyclic crown ethers. In particular, poly- and bis(benzo-15-crown-5), and bis(benzo-18-crown-6) are remarkably effective extracting reagents for potassium and rubidium, and for caesium, respectively. Extraction equilibrium constants and the complexation constants in the chloroform phase were also evaluated and the contribution of the complexation constants to the extractability is discussed.