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.
Environ Sci Technol
; 45(2): 643-50, 2011 Jan 15.
Article
em En
| MEDLINE
| ID: mdl-21142174
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.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Benzofuranos
/
Poluentes Atmosféricos
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Dibenzodioxinas Policloradas
/
Hidrocarbonetos Clorados
Idioma:
En
Revista:
Environ Sci Technol
Ano de publicação:
2011
Tipo de documento:
Article