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

Based on quantum chemical and topological descriptors, temperature-dependent predictive models for solid vapor pressure (PS) of PCDD/Fs were developed. The inclusion of the two topological descriptors, Kier symmetry index (S0K) and Kier flexibility index (PHI), as predictor variables, improved the statistical significance of models. Thus the entropic factors described by the two topological descriptors play a role in influencing the PS values. The cumulative variance of the dependent variable explained by the PLS components and determined by cross-validation (Qcum2), for the final model, is 0.972, indicating that the model has good predictive ability and robustness, and could be used to estimate PS values of PCDD/Fs at different temperatures. The main factors governing log PS values of PCDD/Fs, from important to less important, are temperature, intermolecular dispersive interactions, entropic factor, and intermolecular dipole-dipole and dipole-induced dipole interactions.