Quantitative relationships between molecular structures, environmental temperatures and solid vapor pressures of...

Area of Science:

• Environmental Chemistry
• Physical Chemistry
• Computational Chemistry

Background:

• Polychlorinated dibenzodioxins and dibenzofurans (PCDD/Fs) are persistent organic pollutants with environmental and health concerns.
• Accurate prediction of their solid vapor pressure (PS) is crucial for environmental fate modeling and risk assessment.
• Existing models may not fully capture the complex factors influencing PCDD/F vapor pressure.

Purpose of the Study:

• To develop robust, temperature-dependent predictive models for the solid vapor pressure (PS) of PCDD/Fs.
• To investigate the role of quantum chemical and topological descriptors in influencing PS values.
• To identify the key factors governing PS of PCDD/Fs.

Main Methods:

• Development of predictive models using quantum chemical and topological descriptors.
• Inclusion of Kier symmetry index (S0K) and Kier flexibility index (PHI) as predictor variables.
• Partial Least Squares (PLS) regression and cross-validation (Qcum2) for model validation.

Main Results:

• The developed models demonstrated good predictive ability and robustness, with a cumulative variance (Qcum2) of 0.972.
• Topological descriptors (S0K and PHI) significantly improved model statistical significance, highlighting the role of entropic factors.
• Identified key factors influencing log PS values: temperature, intermolecular dispersive interactions, entropic factors, and dipole-related interactions.

Conclusions:

• The developed models can reliably estimate PS values for PCDD/Fs at various temperatures.
• Topological descriptors provide valuable insights into the entropic contributions affecting vapor pressure.
• Understanding these factors is essential for predicting the environmental behavior of PCDD/Fs.