Synthesis and cation-extraction study of chromogenic 14-crown-4 derivatives for spectrophotometric determination of lithium Original Research Article

Three kinds of proton-dissociable chromogenic 14-crown-4 ethers have been synthesized, all of which possess a dinitrophenol chromophore. Proton-dissociation behavior of the chromogenic crown ethers in aqueous 1,4-dioxane (1/1), and extraction equilibria between the 1,2-dichloroethane solution containing the chromogenic crown ether and aqueous solutions of alkali-metal ions have been investigated spectrophotometrically. An excellent lithium-ion-selective chromogenic 14-crown-4 derivative was obtained by introducing a bulky decalino subunit and dinitrophenol chromophore, which has small pKa value, into the ethano-bridge section of the 14-crown-4 ring.