Solubilities in binary solvent systems II. The importance of non-specific interactions

Abstract

Solubilities have been determined at 25°C for p-benzoquinone in binary mixtures of cyclohexane with n-heptane, cyclooctane and isooctane, in mixtures of n-heptane with n-dodecane, and in binary mixtures of carbon tetrachloride with n-heptane and n-octane. The Nearly Ideal Binary Solvent (NIBS) model predicts these solubilities with a maximum deviation of 5% and an overall standard deviation of 1.6%. The NIBS model correctly predicts maxima for the mole fraction solubility of p-benzoquinone in both cyclohexane + n-heptane and cyclohexane + isooctane mixtures. The success of this simple model, based entirely on non-specific interactions, is significant considering the solubility of p-benzoquinone changes by a factor of 6 in the two binary solvent mixtures containing carbon tetrachloride. Solution models that attribute all solubility enhancement to the formation of stoichiometric complexes require several equilibrium constants to mathematically describe the 6-fold range of p-benzoquinone solubilities in these two solvent mixtures.