Theoretical study of the dechlorination reaction pathways of octachlorodibenzo-p-dioxin.
The dechlorination reaction pathways of 1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin (OCDD) by the hydrogen atom are investigated by the density-functional theory B3PW91 method. The dechlorination reactions have large exothermicity and small activation energies. The activation energies (approximately 5 kcal/mol) of the sigma-complex formation due to the hydrogen addition are lower than those (approximately 9 kcal/mol) of the direct chlorine abstraction. It is suggested that the sigma-complex plays an important role in the reactions, although it has scarcely been shown in previous studies of the dechlorination of dioxins. The sigma-complex formation is favored at low temperatures and the chlorine abstraction is favored at high temperatures. Furthermore, it is found that the lateral positions have a marginal preference over the longitudinal positions. The dechlorination of OCDD by the hydrogen atom is thus not likely to result in a dominant formation of the laterally substituted toxic congeners.
Fueno
Hiroyuki
H
h54367@sakura.kudpc.kyoto-u.ac.jp
Tanaka
Kazuyoshi
K
Sugawa
Seiichi
S
D002713:Chlorine / Q000737:chemistry*; D004785:Environmental Pollutants; D017745:Incineration; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives* / Q000737:chemistry*; D012037:Refuse Disposal; D013696:Temperature
D004785:Environmental Pollutants; D000072317:Polychlorinated Dibenzodioxins; D002713:Chlorine; C018117:octachlorodibenzo-4-dioxin