Chemical Functionality of the Solute

The difference between solid solubilities in a given SCF depends mainly on the solid vapor pressure and intermolecular interactions between the solvent and solute. The individual solubilities of solids can vary greatly although most values are well below 10 mol%. The differences between enhancement factors are less pronounced [14,15], however, which suggests that the vapor pressure of the solid exerts the primary influence on solubility. Intermolecular interactions between the solvent and solute depend on the types of functional groups present in their chemical structures. In general, the intermolecular interactions are dominated by dispersion forces, which accounts for the similar values of the enhancement factor for many solids. 

Solute Solubility (mole fraction) Enhancement factor 

The vapor pressure of a solid and the intermolecular interactions it is capable of are ultimately determined by its chemical structure. Differences between the solubilities of solids can also be explained in terms of structural features which limit or enhance solubility. Beginning with a parent compound, the addition of a functional group generally has the effect of reducing solubility. This applies especially to hydroxy (-OH) and carboxy (-COOH) functional groups as described by Stahl et al. [17]. 

Branching leads to more favorable solubilities compared with normal alkanes. The maximum limit of complete miscibility for branched alkanes also occurs at a much higher carbon number which is between 19 and 30. 

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