Fugacity ratio estimations for high-melting rigid aromatic compounds

Area of Science:

• Environmental Chemistry
• Physical Chemistry
• Chemical Engineering

Background:

• Environmental fate prediction relies on partitioning behavior, quantified by vapor pressure and aqueous solubility.
• Accurate values for the solid or liquid state are crucial for modeling chemical distribution.
• Fugacity ratios link solid and liquid state properties, essential for these calculations.

Purpose of the Study:

• To evaluate the accuracy of fugacity ratio calculations for organic compounds.
• To investigate discrepancies between experimental and thermodynamic approaches for fugacity ratios.
• To develop an improved method for estimating fugacity ratios and enhance environmental fate predictions.

Main Methods:

• Calculated fugacity ratios using experimental entropies of fusion and melting points.
• Compared results with a thermodynamically rigorous approach using heat capacity data.
• Derived a correction factor based on melting point to improve fugacity ratio estimations.

Main Results:

• Experimental fugacity ratios systematically deviated from rigorous thermodynamic calculations for specific organic compound classes.
• A universal entropy of fusion value led to significant over/underestimations (over 1 order of magnitude).
• A simple, melting-point-based correction factor improved fugacity ratio accuracy to within 0.1-0.2 log units.

Conclusions:

• Standard methods for calculating fugacity ratios can introduce substantial errors in environmental fate predictions.
• The derived correction factor offers a more accurate and practical approach for estimating fugacity ratios.
• Improved fugacity ratio estimation enhances the reliability of models predicting the environmental behavior of organic compounds.