Abstract: Six bis-crown ethers containing benzo-12-crown-4(A1,B1), benzo-15-crown-5(A2,B2) and benzo-18-crown-6(A3,B3) moieties bridged by pyrimidine ring were prepared by the reaction of 4,6-dichloro-5-nitropyrimidine, 2, 4-dichloro-5-nitro-6-methylpyrimidine with the 4'-aminoben-zocrown ethers, respectively.Extractions were carried out from aqueous solution of alkali metal pi-crates with these bis-crown ether solutions in chloroform.The extraction equilibrium constants were also evaluated.The results indicate that compound (A1,B1), (A2,B2) and (A3,B3) are effective extracting reagents for sodium, potassium and caesium, respectively.The cation-selectivity is more effective than the corresponding monocyclic crown ethers.

Key words: Bis-crown ether, Pyrimidine ring, Extraction equilibrium constant, Conductometry