Accession Number : ADA260090

Title :   Molecular Properties and Fate of Organic Chemicals.

Descriptive Note : Final rept. 15 Aug 88-14 Aug 92,

Corporate Author : WISCONSIN UNIV-MADISON

Personal Author(s) : Andren, Anders W.

Report Date : SEP 1992

Pagination or Media Count : 231

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.

Descriptors :   *CONTAMINANTS, *ORGANIC COMPOUNDS, *CHEMICAL COMPOUNDS, ADHESION, AIR, CAVITIES, CHEMICAL PROPERTIES, CHEMICALS, COEFFICIENTS, COORDINATES, ENERGY, ERRORS, ESTIMATES, FREE ENERGY, LIQUIDS, MOLECULES, PARAMETERS, PREDICTIONS, PRESSURE, SATURATION, SOLUBILITY, SOLUTES, SOUND, STANDARDS, STRUCTURES, SURFACES, TEMPERATURE, TRANSPORT, VAPOR PRESSURE, VAPORS, WATER, WORK, YIELD, MOLECULAR PROPERTIES, HYDROPHOBIC PROPERTIES, CHEMICAL BONDS, THERMODYNAMICS, AROMATIC COMPOUNDS, COLLOIDS, CHLORINATED HYDROCARBONS, DEGRADATION, ABIOTIC PROCESSES, THESES, POLYCHLORINATED BIPHENYLS.

Subject Categories : Organic Chemistry
      Environmental Health and Safety
      Physical Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE