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- Title
Atmospheric degradation of 2,3,7,8-tetrachlorinated dibenzo- p-dioxins in the presence of NO<sub>3</sub> at night.
- Authors
Zhao, Yuyang; Sun, Xiaomin; Bai, Jing; Zhang, Chenxi; Zhang, Jianghua
- Abstract
The density functional theory (DFT) has been applied to studies on the homogeneous gas-phase degradation of 2,3,7,8-tetrachlorinated dibenzo- p-dioxins (2,3,7,8-TeCDD) initiated by the NO3 radical, which is an important atmospheric species at night. The geometrical parameters and vibrational frequencies of all the stationary points were calculated at the MPWB1K/6-31+G (d,p) level. Potential energies were calculated at the MPWB1K/6-311+G (3df,2p) level. Three sites on 2,3,7,8-TeCDD react with the NO3 radical with different barriers and reaction heats. The addition of NO3 to the carbon atom on the central C-O ring is the most appropriate pathway and with the lower barriers, and the central ring of polychlorinated dibenzo- p-dioxin is opened in the subsequent reactions. Some other pathways are stressed for the dechlorination mechanism. Canonical variational transition-state theory with small curvature tunneling contribution was used to calculate the rate constants of each elementary reaction over the temperature range of 200-400 K. The Arrhenius equations were fitted to show the relationship between rate constants and temperature.
- Subjects
ARRHENIUS equation; CHEMICAL kinetics; NUMERICAL calculations; CHEMICAL reactions; POLYCHLORINATED dibenzodioxins; DECHLORINATION (Chemistry)
- Publication
Canadian Journal of Chemistry, 2013, Vol 91, Issue 6, p398
- ISSN
0008-4042
- Publication type
Article
- DOI
10.1139/cjc-2012-0443