Thermodynamic properties of aqueous non-electrolyte mixtures. Excess enthalpies of water + cyclic ether mixtures at 298.15 K

Abstract

Molar excess enthalpies, H E, for water with oxolane, 1,3-dioxolane, oxane, 1,3-dioxane and 1,4-dioxane mixtures were measured as a function of composition at 298.15 K in a CRMT precision calorimeter. For all the mixtures studied, H E vs. x curves show exothermal mixing in the water-rich region which becomes endothermic at high cyclic ether concentrations. These curves have been interpreted in terms of intercomponent molecular interactions and hydrophobic stabilization of the water structure by cyclic ether molecules. The results obtained indicate that the geometry, the number of oxygen atoms in the ring and their relative position have an important action on these two effects.