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Estimation of Physical Properties and Chemical Reactivity Parameters of Organic Compounds for Environmental Modeling by SPARC
Citation:
HILAL, S. H. AND L. A. Carreira. Estimation of Physical Properties and Chemical Reactivity Parameters of Organic Compounds for Environmental Modeling by SPARC. Presented at SETAC Europe 19th Annual Meeting, Goteborg, SWEDEN, May 31 - June 04, 2009.
Impact/Purpose:
The research goal of this subtask is driven by the need for chemical property information at a wide range of environmental conditions (e.g., temperature, pressure, media, pH) where reliable literature data do not exist and for new chemicals with few existing literature values.
Description:
Mathematical models for predicting the transport and fate of pollutants in the environment require reactivity parameter values that is value of the physical and chemical constants that govern reactivity. Although empirical structure activity relationships have been developed that allow estimation of some constants, such relationships are generally valid only within limited families of chemicals. The computer program, SPARC, uses computational algorithms based on fundamental chemical structure theory to estimate a large number of chemical and physical properties for a wide range of organic molecules from molecular structure. A "toolbox" of mechanistic perturbation models has been developed that can be implemented where needed for a specific reactivity query. Resonance models were developed and calibrated using measured light absorption spectra, whereas electrostatic interaction models were developed using measured pKas in water. Solvation models (i.e., dispersion, induction, H-bonding, etc.) have been developed using various measured physical properties data. At the present time, SPARC’s physical property models predict vapor pressure and heat of vaporization (as a function of temperature), boiling point (as a function of pressure), diffusion coefficient (as a function of pressure and temperature), activity coefficient, solubility, partition coefficient and GC retention time as a function of solvent and temperature. For chemical reactivity, SPARC estimates pKas in any solvent and in the gas phase, zwitterionic/hydration constants, tautomeric equilibrium, carboxylic acid ester/organophosphorus hydrolysis rate constants, E1/2 reduction potential and electron affinity. SPARC is online and can be used at http://ibmlc2.chem.uga.edu/sparc.