Thermodynamic properties of aqueous non-electrolyte mixtures. Enthalpy of mixing and liquid-liquid equilibrium of water + aliphatic aldehyde mixtures

Abstract

The liquid-liquid equilibrium, L-L, and the enthalpy of mixing, H M, for water with ethanal, propanal and butanal mixtures were determined at 298.15 K. For all the mixtures studied, H M vs. x curves show exothermic mixing in the water-rich region which becomes endothermic at high aldehyde concentrations. These curves have been interpreted in terms of intercomponent molecular interactions and hydrophobic stabilization of the water structure by molecules of aldehyde. The results obtained indicate that the number of alkyl groups in the aldehyde plays an important role in determining the magnitude of these effects and also influences the miscibility.