The Extraction of Alkali Metal Picrates with Dibenzo-18-Crown-6

Abstract

Abstract The distribution of alkali metal picrate complexes of macrocyclic polyether (dibenzo-18-crown-6) between water and benzene was investigated. The polyether-cation complexes were found to be of a 1:1 stoichiometry. The formation of 2:1 complexes was recognized for Rb and Cs in a large excess of the poiyether. The extractability of complex cation-picrate ion-pairs decreases in this sequence: K>Rb>Cs>Na>Li. The values of the extraction constants (logKex) were determined to be 4.65, 3.75, and 3.07 for K, Rb, and Cs compounds respectively. The thermodynamic quantities for the extraction process were calculated from the change in the extraction constants with the temperature. The extraction reactions are all exothermic, accompanied by an entropy decrease.