title: Mechanism and direct kinetic study of the polychlorinated dibenzo-p-dioxin and dibenzofuran formations from the radical/radical cross-condensation of 2,4-dichlorophenoxy with 2-chlorophenoxy and 2,4,6-trichlorophenoxy.
abstract: A direct density functional theory (DFT) kinetic calculation is carried out for the homogeneous gas-phase formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from the cross-condensation of 2,4-dichlorophenoxy radical (2,4-DCPR) with 2-chlorophenoxy radical (2-CPR) and 2,4,6-trichlorophenoxy radical (2,4,6-TCPR). The possible formation mechanism is investigated and compared with the PCDD/F formation mechanism from the self-condensation of 2,4-DCPR, 2-CPR, and 2,4,6-TCPR. The rate constants and their temperature dependence of the crucial elementary reactions are computed by the canonical variational transition-state theory with the small curvature tunneling contribution over the temperature range of 600-1200 K. This study shows that the multichlorine substitutions suppress the PCDD/F formations. Because of a lack of experimental kinetic data, the present theoretical results are expected to be useful and reasonable to estimate the kinetic properties, such as the pre-exponential factors, the activation energies, and the rate constants, of the elementary reactions involved in the formation of PCDD/Fs.
authors.affiliation: Environment Research Institute, Shandong University, Jinan, People's Republic of China.
authors.forename: Fei
authors.initials: F
authors.lastname: Xu
authors.forename: Wanni
authors.initials: W
authors.lastname: Yu
authors.forename: Qin
authors.initials: Q
authors.lastname: Zhou
authors.forename: Rui
authors.initials: R
authors.lastname: Gao
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Sun
authors.forename: Qingzhu
authors.initials: Q
authors.lastname: Zhang
authors.forename: Wenxing
authors.initials: W
authors.lastname: Wang
mesh_terms: D000393:Air Pollutants / Q000138:chemical synthesis*; D001572:Benzofurans / Q000138:chemical synthesis*; D000072338:Dibenzofurans, Polychlorinated; D005609:Free Radicals / Q000737:chemistry; D006843:Hydrocarbons, Chlorinated / Q000737:chemistry*; D017745:Incineration; D007700:Kinetics; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives* / Q000138:chemical synthesis
chemical_list: D000393:Air Pollutants; D001572:Benzofurans; D000072338:Dibenzofurans, Polychlorinated; D005609:Free Radicals; D006843:Hydrocarbons, Chlorinated; D000072317:Polychlorinated Dibenzodioxins