Quantitative relationships between molecular structures, environmental temperatures and octanolair partition coefficients of polychlorinated biphenyls
A quantitative model that incorporates information on both environmental temperatures (T) and molecular structures, for logarithm of octanolair partition coefficient to base 10 (logKOA) of polychlorinated biphenyls (PCBs) was developed. Partial least squares (PLS) analysis together with 16 theoretical molecular structural descriptors was used to develop the Quantitative relationships between structures, environmental temperatures and properties (QRSETP) model. The cross-validated Qcum2 value for the optimal QRSETP model is 0.976, indicating a good predictive ability for logKOA of PCBs at different environmental temperatures. T, ELUMO (the energy of the lowest unoccupied molecular orbital), molecular size or average molecular polarizability (?), and the net atomic charges on chlorine, hydrogen and carbon atoms of PCB molecules, are major factors governing logKOA. The lower the ELUMO, the greater the intermolecular interactions between octanol and PCB molecules, and thus the greater the logKOA values. Because of intermolecular dispersive forces, the more chlorine atoms in PCB molecules, the greater the molecular size or ?, the greater the logKOA. The largest negative net atomic charge on a carbon atom (qC?) and molecular size or average molecular polarizability (?) are major factors governing temperature dependence of logKOA. PCB molecules with low qC? values and more chlorines (big size or ?) tend to have strong temperature dependence, due to intermolecular electrostatic interactions and dispersive forces, respectively.
temperature octanolair partition coefficient pcb pls theoretical molecular structural descriptors