Solvent classification based on gas-liquid partition constants and the solvation parameter model.

Gas-solvent partition constants for varied compounds were assembled from multiple sources for 53 organic solvents and water. The solvation parameter model was used to determine five solvent parameters (system constants) obtained from calibration models for the gas-solvent partition constants and subsequently used as variables for solvent classification. The system constants describe the solvents capability to enter into interactions with polarizable lone pair electrons, e system constant, interactions of a dipole-type (induction and orientation), s system constant, the solvent's hydrogen-bond basicity and acidity, a and b system constants, and the opposing contribution of solvent cohesion (cavity formation) and solute-solvent dispersion interactions, l system constant. The organic solvents are assigned to eight groups with similar solvation properties using hierarchical cluster analysis with the five system constants as variables. Water is identified as a singular solvent and excluded from the classification. Diisopropyl ether is also identified as a singular solvent but has properties not far removed from those of other oxygen-containing solvents (esters, cyclic ethers, aliphatic ketones, etc.) Within group variation of solvent properties indicates a general lack of solvents with duplicate properties with each group comprised of solvents with a narrow range of system constants. In preliminary work, compound descriptors were assigned for 19 further compounds and updated for a further 61 with all compounds compliant with the WSU-2025 descriptor database. These compounds facilitated the construction of calibration models for an additional 20 organic solvents that could then be merged with a database of system constants for 33 organic solvents and water.