Thermochemical behaviour of crown ethers in the mixtures of water with organic solvents.: Part V. Enthalpy of solution of 12-crown-4 and 18-crown-6 ethers in the mixtures of water with dimethylsulfoxide or N,N-dimethylformamide at 298.15 K

Abstract

The enthalpy of solution of crown ethers (12-crown-4 and 18-crown-6 ethers) in the mixtures of water with dimethylsulfoxide or N,N-dimethylformamide has been measured within the whole mole fraction range at 298.15 K. The plots of enthalpy of solution of 12-crown-4 ether in these mixtures exhibit a maximum at x w≈0.5 for 12C4 and that for 18C6 at x w≈0.4. The results were compared with the standard enthalpies of solution of 15-crown-5 and benzo-15-crown-5 ethers in the same mixtures at 298.15 K. The molar enthalpy of hydrophobic hydration, Hb(W), per one -CH 2CH 2O-group in 12-crown-4, 15-crown-5 and 18-crown-6 ethers in water was calculated and it is equal to (−12 ± 2) kJ mol −1.