Evaluation of total molecular surface area for predicting air-water partitioning properties of hydrophobic aromatic chemicals

Abstract

Aqueous solubilities of various substituted naphthalenes and terphenyls have been measured and quantitative structure property relationships (QSPRs) using total molecular surface area (TSA) have been evaluated for predicting aqueous solubility and saturation vapor pressure of hydrophobic organic contaminants. Methods for calculating TSA and assumptions for estimating the molar free energy of fusion were examined. Substantial improvements in model predictive capability compared to previously published relationships was observed when TSA is calculated using energy minimized (sterically viable) molecular coordinates and a consistent set of van der Waals radii. The model equation developed between TSA and mole fraction solubility permits aqueous solubility predictions of aromatic chemicals from 5°C to 40°C with an average absolute factor of error (AFE) of 2.2. However, a similar relation between TSA and saturation vapor pressure (p sat) was not in agreement with experimental data.