The effects of solvent properties on solid-liquid phase equilibrium of ethylene thiourea

Abstract

The effect of solvent properties on solid-liquid phase equilibrium of ethylene thiourea (ETU) was investigated for the first time in terms of solvent polarity, hydrogen bonding donor and acceptor propensity, as well as cohesive energy density. To this end, equilibrium solubility of ETU in twelve solvents including alcohols, ketones, nitriles and water was experimentally determined by the gravimetric method at temperatures ranging from 283.15 K to 323.15 K. The solubility increases expectedly with increasing temperature in all solvents. Moreover, the statistical correlations were well performed by the modified Apelblat equation, λh equation, van't Hoff equation, and NRTL model in which the modified Apelblat equation receives the best regression performance. Further, the investigations over the effect of solvent properties reveal that the solvent polarity and cohesive energy density determine the solubility of ETU in alcohols, whereas in non-alcohol solvents the hydrogen bonding acceptor propensity plays the key role. Finally, thermodynamic functions of mixing were derived, and the results also suggest the important role of solute-solvent hydrogen bonding interactions in non-alcohol solvents.