CALCULATION OF PARTITION CONSTANTS FOR A SERIES OF ORGANIC-COMPOUNDS VIA A NOVEL SOLUBILITY-PARAMETER-BASED METHOD

A thermodynamic model with additional extrathermodynamic assumptions is presented for the calculation of equilibrium partition constants for a series of organic compounds. Key properties are heat of vaporization, molar liquid volume and Hildebrand-Scatchard solubility parameter of both the compounds and the phases they are partioning over. The heat of vaporization and molar liquid volume of the members of a compound series are thought to be built up from molecular skeleton and interactive substituent contributions. These contributions enable the physical discrimination of isomers within a series. Additional parameters are introduced, which are characteristic constants of an isolated compound series or a compound series solved into a particular phase. They correspond to extensions of existing solubility-parameter-based models. Depending on the availability of data and study objectives the different types of parameters are derived via a non-linear fit to experimental data. Accurate, isomer-specific results are obtained for the heat of vaporization, molar volume, solubility parameter, partition coefficient in octanol-water, chromatographic retention, vapour pressure, aqueous solubility and the Henry's law constant of the 92 methylchlorobenzenes.