Stability of complexes of alkali metal cations with dicyclohexyl-18-crown-6 in water saturated nitrobenzene

From extraction experiments and gamma-activity measurements, the exchange e xtraction constants corresponding to the general equilibrium M+(aq)+NaL+(nb ) reversible arrow ML+(nb)+Na+(aq) taking place in the two-phase water-nitr obenzene system (M+ = Li+, K+, Rb+, Cs+: L = dicyclohexyl-18-crown-6; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Further, the stabil ity constants of the ML+ complexes in nitrobenzene saturated with water wer e calculated; they were found to increase in the cation order Cs+<Rb+<Na+<L i+<K+. Finally, the stability constants of alkali metal cations with dicycl ohexyl-18-crown-6 in various solvents were summarized and discussed.