SYNTHESIS AND CATION-EXTRACTION STUDY OF CHROMOGENIC 14-CROWN-4 DERIVATIVES FOR SPECTROPHOTOMETRIC DETERMINATION OF LITHIUM

Three kinds of proton-dissociable chromogenic 14-crown-4 ethers have b een synthesized, all of which possess a dinitrophenol chromophore. Pro ton-dissociation behavior of the chromogenic crown ethers in aqueous 1 ,4-dioxane (1/1), and extraction equilibria between the 1,2-dichloroet hane solution containing the chromogenic crown ether and aqueous solut ions of alkali-metal ions have been investigated spectrophotometricall y. An excellent lithium-ion-selective chromogenic 14-crown-4, derivati ve was obtained by introducing a bulky decalino subunit and dinitrophe nol chromophore, which has small pK(a) value, into the ethano-bridge s ection of the 14-crown-4 ring. (C) 1998 Elsevier Science B.V. All righ ts reserved.