Quantitative Structure-Activity Relationships Study on the Rate Constants of Polychlorinated Dibenzo-p-Dioxins with OH Radical

The OH-initiated reaction rate constants (k(OH)) are of great importance to measure atmospheric behaviors of polychlorinated dibenzo-p-dioxins (PCDDs) in the environment. The rate constants of 75 PCDDs with the OH radical at 298.15 K have been calculated using high level molecular orbital theory, and the rate constants (k(α), k(β), k(γ) and k(OH)) were further analyzed by the quantitative structure-activity relationships (QSAR) study. According to the QSAR models, the relations between rate constants and the numbers and positions of Cl atoms, the energy of the highest occupied molecular orbital (E(HOMO)), the energy of the lowest unoccupied molecular orbital (E(LUMO)), the difference ΔE(HOMO-LUMO) between E(HOMO) and E(LUMO), and the dipole of oxidizing agents (D) were discussed. It was found that E(HOMO) is the main factor in the k(OH). The number of Cl atoms is more effective than the number of relative position of these Cl atoms in the k(OH). The k(OH) decreases with the increase of the substitute number of Cl atoms.