Mechanisms of transformation of polychlorinated diphenyl ethers into polychlorinated dibenzo-p-dioxins and dibenzofurans

Mohammednoor Altarawneh, Bogdan Z. Dlugogorski

Research output: Contribution to journalArticleResearchpeer-review

Abstract

This study presents a detailed mechanistic account of the formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) from polychlorinated diphenyl ethers (PCDEs). It applies the recently developed meta hybrid M06-2X functional and deploys the 2,2'-dichlorodiphenylether (2,2'-DCDE) molecule as a representative model compound for all PCDEs congeners. We find that, exceedingly high activation enthalpies prevent the direct formation of PCDFs from PCDEs via unimolecular elimination of HCl or Cl2. Rather, loss of an ortho H/Cl atom initiates the transformation of PCDEs into PCDD/Fs. Subsequent formation of PCDFs takes place through ring-closure reactions with modest activation enthalpies, whereas the addition of a ground state oxygen molecule at an apparent ortho radical site of a PCDE congener commences a complex, yet very exothermic, mechanism leading to the formation of PCDDs. Splitting the ether linkage through H/Cl addition at the pivot carbon constitutes a major source for the formation of chlorophenoxy radicals and chlorobenzene molecules. Our kinetic and mechanistic analyses demonstrate that, the degree and pattern of chlorination of PCDEs display a negligible effect on the formation pathways of PCDD/Fs from PCDEs.

Original languageEnglish
Pages (from-to)129-135
Number of pages7
JournalChemosphere
Volume114
Issue numberNovember
Early online date13 May 2014
DOIs
Publication statusPublished - Nov 2014
Externally publishedYes

Fingerprint

dibenzofuran
ether
dioxin
Ethers
PCDF
PCDD
Molecules
enthalpy
Enthalpy
Chemical activation
Chlorination
Halogenation
chlorobenzene
polychlorinated diphenyl ethers
dibenzo(1,4)dioxin
Polychlorinated Dibenzodioxins
Dibenzofurans
Ether
Ground state
chlorination

Cite this

Altarawneh, Mohammednoor ; Dlugogorski, Bogdan Z. / Mechanisms of transformation of polychlorinated diphenyl ethers into polychlorinated dibenzo-p-dioxins and dibenzofurans. In: Chemosphere. 2014 ; Vol. 114, No. November. pp. 129-135.
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Mechanisms of transformation of polychlorinated diphenyl ethers into polychlorinated dibenzo-p-dioxins and dibenzofurans. / Altarawneh, Mohammednoor; Dlugogorski, Bogdan Z.

In: Chemosphere, Vol. 114, No. November, 11.2014, p. 129-135.

Research output: Contribution to journalArticleResearchpeer-review

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