Complex Formation of Crown Ethers with Cations in Water–Organic Solvent Mixtures. III. Thermodynamics of Interaction Between Na+ Ion with 15-Crown-5 Ether in Water–Acetonitrile Mixtures at 25°C

Enthalpies of solution of 15-crown-5 ether in the acetonitrile–water–sodium iodide system have been measured at 25°C. The equilibrium constants of complex formation of 15C5 with sodium iodide have been determined by molar conductance at various mole ratios 15C5 to sodium iodide in mixtures of water with acetonitrile at 25°C. The thermodynamic functions for complexation of the crown ether with Na⁺ were calculated. From the result, the standard Gibbs energies of complex formation as a function of the normalized Lewis acidity parameters E ^N _T and enthalpy of solvation of 15C5 in the mixtures of water with acetonitrile have been analyzed. The enthalpies of transfer of the 15C5 complex with sodium iodide from pure acetonitrile to the mixtures studied were calculated and discussed.