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Quantum Mechanical Predictions of the Henry’s Law Constants and Their Temperature Dependence for the 209 Polychlorinated Biphenyl Congeners

2008; American Chemical Society; Volume: 42; Issue: 22 Linguagem: Inglês

10.1021/es800876w

1520-5851

Kathy L. Phillips, Stanley I. Sandler, Richard W. Greene, Dominic M. Di Toro,

Analytical Chemistry and Chromatography

The Henry's law constants (HLCs) for all 209 polychlorinated biphenyl (PCB) congeners were predicted at 25 °C using the quantum mechanical (QM) continuum solvation models COSMO-SAC and SM6, and trends were examined. COSMO-SAC HLCs were also predicted for all congeners at 4, 11, 18, and 31 °C. The temperature dependences of the HLCs were used to calculate enthalpy of solvation (ΔHS) values. At 25 °C, COSMO-SAC and SM6 predicted similar values of the HLC, which are consistent with all but one of the available sets of measurements, and have smaller root-mean-square prediction errors than other models tested. This supports the validity of the QM values, and the recommendation of their use in environmental transport and fate models. Intercongener trends in the HLCs appear to be dominated by the strength of PCB-water polar interactions. The COSMO-SAC predictions between 4 and 31 °C indicate that the temperature dependence of the HLC is similar for all congeners. At low temperatures, the HLC predictions for several heavy congeners are substantially higher than recently reported measurements, supporting claims in the literature that these low-temperature data are inaccurate.