Molecular Properties and Fate of Organic Chemicals.
Abstract
Quantitative structure property relationships (QSPRs) utilizing total molecular surface area (TSA) are evaluated for predicting physical-chemical properties (aqueous solubility and saturation vapor pressure) used to determine environmental partitioning and transport of hydrophobic organic contaminants. The theoretical relationship between the physical-chemical properties and TSA is reexamined and, methods and parameters for calculating TSA were compared including: standard (planar) geometries and bond lengths versus energy minimized molecular coordinates, van der Waals versus contact/reentrant surface area, and van der Waals radii. Two assumptions for estimating the molar free energy of fusion are also evaluated. A strong, thermodynamically sound relationship between TSA and aqueous solubility allows for solubility predictions of aromatic chemicals from 5 deg C to 40 deg C with an average absolute error of 92 degrees. A weaker, empirical relationship between saturation vapor pressure and TSA yields vapor pressure estimates for organic contaminants with an average absolute error of 232% between 5 deg C and 40 deg C. The results indicate that the work of cavity formation in water and/or the work of adhesion between the solute and water is the dominant term in the dissolution process, and is adequately described via a TSA-QSPR. Conversely, the work required to remove a molecule from bulk liquid to vapor is loosely related to TSA. The predicted physical-chemical properties can be used to determine the air/water partition coefficients of organic contaminants at environmental temperatures.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1992
- Accession Number
- ADA260090
Entities
People
- Anders W. Andren
Organizations
- University of Wisconsin–Madison