Aqueous solubility and related thermodynamic functions of nonaromatic hydrocarbons as a function of molecular structure

The aqueous solubilities of several C-S nonaromatic hydrocarbons differing in their molecular structure (cyclooctane, cyclooctene, ethylcyclohexane, cis- and trans-1,2-dimethylcyclohexane, 2,2-dimethylhexane, and 2,5-dimethylhexane) were studied at temperatures between 274 and 313 K using a dynamic saturation column method. The resulting experimental values had an estimated uncertainty between 5 and 10%. Their correlation as a function of temperature allowed the determination of the enthalpy and heat capacity change characterizing the dissolution process. A combination with the data on pure solutes selected from the literature made it possible to calculate Henry's law constants and the air-water partition coefficients as well as the thermodynamic functions of hydration. These different data were combined with information from the literature and analyzed with respect to the molecular structure of aqueous hydrocarbons. A simple group contribution concept was found to be useful for rationalizing the evolution of the aqueous solubility of alkanes, alkenes, cycloalkanes, and cycloalkenes.