Infinite dilution activity coefficients from ab initio solvation calculations

A Group Contribution Solvation (GCS) model was developed to calculate infinite dilution activity coefficients (γ ∞ ) based on modern computational chemistry. The GCS model results in an average error of 7% in γ ∞ for the limited number of data points among water, n‐hexane, acetonitrile and n‐octanol, whereas the errors are 47% and 52% with the UNIFAC model and the modified UNIFAC model, respectively. GCS was also used to calculate infinite dilution partition coefficients, which can be used to determine how a dilute solute partitions between two solvents. Solutes were examined in three different liquid‐liquid systems: water/n‐hexane, water/acetonitrile, and water/n‐octanol. With GCS, the average errors are 22% (for 18 solutes), 18% (for 14 solutes) and 14% (for 15 solutes) for these solvent systems, while comparable errors are 237%, 286% and 226% with UNIFAC; and 342%, 414% and 306% with modified UNIFAC. The GCS model is a powerful new tool to predict the octanol‐water partition coefficients.