Partition of alkali-metal ions and complex formation with poly(oxyethylene) derivatives in 1,2-dichloroethane

Abstract

The partition equilibria of electrolytes of alkali-metal, dimethylammonium and tetramethylammonium ions (M⁺) with dipicryl-amine ion or picrate ion (X⁻) in 1,2-dichloroethane (1,2-DCE) have been investigated at 25.0 °C. The thermodynamic distributionconstants of the electrolytes (M⁺·X⁻) were determined and the transfer free energy, ΔG_t⁰, of the individual ions into water-saturated 1,2-DCE were evaluated using the extrathermodynamic assumption. The value of ΔG_t⁰ of alkali-metal ion increases almost linearly with increasing dehydration energy of metal ion except for lithium. The relatively small value of ΔG_t⁰ for lithium is interpreted by the hydration of the lithium ion in the 1,2-DCE phase. The complex formation constants of the alkali-metal ions with poly(oxyethylene) derivatives in 1,2-DCE were evaluated by using the partition data of alkali-metal picrates. The order of the complex formation constant is Li⁺ < Na⁺ ∽ K⁺ > Rb⁺ > Cs⁺ for any POE compounds.