PARTITIONING OF CROWN-ETHER COMPLEXED UNIVALENT METAL DICHLOROPICRATES BETWEEN WATER AND 1,2-DICHLOROETHANE AT 298-K - THERMODYNAMIC REPRESENTATION

The extraction constant of silver and cesium dichloropicrate (MPiCl2) between water and 1,2-dichloroethane in the presence of 18-crown-6 or dibenzo-18-crown-6 (L) has been expressed in terms of the Gibbs free energy of transfer of M+ and PiCl2-, the association constant of LMPiCl2 (K(A)(LMPiCl2)), and the stability constant of LM+ (K(f)(LM+)) in the organic phase. This has been verified experimentally by partitioning MPiCl2 alone. Using suitable extrathermodynamic assumptions, DELTAG-degrees tr(PiCl2-) = 3.8 kJ mol-1, as compared to DELTAG-degrees tr(Pi-) = -7.0 kJ mol-1. This imparts favorable extractability to LMPiCl2. In addition, sodium, potassium, and thallium dichloropicrate extraction equilibria involving the above crown ethers are reported.