Complex formation of crown ethers with cations in water-organic solvent mixtures.: Part II.: Thermodynamics of interactions of Na+ ion with benzo-15-crown-5 ether in the mixtures of water with dimethylsulfoxide at 298.15 K

The equilibrium constants of complex formation of crown ether (benzo-15-crown-5 ether) with sodium cation have been determined by molar conductance at various molar ratios of benzo-15-crown-5 ether and sodium iodide in the mixtures of water with dimethylsulfoxide at 298.15 K. The solution enthalpy of benzo-15-crown-5 ether in the dimethylsulfoxide-water-sodium iodide system has been measured at 298.15 K. The thermodynamic functions of complex formation of benzo-15-crown-5 ether with sodium iodide were calculated. The linear enthalpy-entropy relationship for complex formation was discussed. The transfer enthalpy of the benzo-15-crown-5 ether/Na+ complex from pure dimethylsulfoxide to the examined mixtures was calculated and discussed. The contribution of the benzene ring in the thermodynamic functions of complex formation and in the standard enthalpy of complex solvation was analysed. (C) 2003 Elsevier B.V. All rights reserved.