Enthalpic characteristics of solvation of 1-AZA-18-Crown-6 in aqueous-ethanol and aqueous dimethylsulfoxide solvents

The heat effects of dissolution of 1-aza-18-crown-6 in mixed water-ethanol and water-dimethylsulfoxide solvents at 298.15 K are determined by the calorimetric method. Dissolution of 1-aza-18-crown-6 is found to be exothermic in water and in water-organic solvents with initial co-solvent additions. For co-solvent contents greater than 0.2 mole fraction, dissolution of 1-aza-18-crown-6 is accompanied by an endo effect, which increases with the increasing content of both ethanol and dimethyl sulfoxide. The enthalpies of transfer of 1-aza-18-crown-6 from water to aqueous solutions of ethanol and dimethyl sulfoxide are calculated. The enthalpic characteristics of solvation of crown ethers in aqueous-organic solvents are compared.