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Infinite dilution activity coefficients from ab initio solvation calculations

Authors

  • Shiang-Tai Lin,

    1. Center for Molecular and Engineering Thermodynamics, Dept. of Chemical Engineering, University of Delaware, Newark, DE 19716
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  • Stanley I. Sandler

    Corresponding author
    1. Center for Molecular and Engineering Thermodynamics, Dept. of Chemical Engineering, University of Delaware, Newark, DE 19716
    • Center for Molecular and Engineering Thermodynamics, Dept. of Chemical Engineering, University of Delaware, Newark, DE 19716
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Abstract

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.

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