Atmospheric oxidation of hexachlorobenzene: New global source of pentachlorophenol

Kovačević, Goran; Sabljić, Aleksandar

doi:10.1016/j.chemosphere.2016.06.026

Cited by 14 publications

(14 citation statements)

References 39 publications

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“…In monohalogenated benzenes, uorobenzene and chlorobenzene, the hydrogen atom is pointing approximately to the center of the aromatic ring 79,81 while for perhalogenated benzenes, hexauorobenzene and hexachlorobenzene, an oxygen atom is pointing approximately to the center of the aromatic ring. 83,84 The separations between hydroxyl radical hydrogen and the center of the aromatic ring are 2.35 and 2.44Å, respectively, for uorobenzene and chlorobenzene while the separations (1) between hydroxyl radical oxygen and the aromatic ring are somewhat larger for hexauorobenzene and hexachlorobenzene, i.e. 2.76 and 2.89Å, respectively.…”

Section: Formation and Properties Of Prereaction Complexesmentioning

confidence: 99%

“…Furthermore, the relative translation of the hydroxyl radical with respect to halogenated benzenes in the prereaction complexes was treated as a two-dimensional particle-in-the-box potential. 79,81,83,84 Reaction between the hydroxyl radical and individual halogenated benzene is divided into two steps (eqn (1)). The rst step is the association of reactants and formation of a prereaction complex and the corresponding rate constants were calculated by combining the statistical thermodynamics calculations using the Thermo program from the MULTIWELL program package [92][93][94] and RRKM method 95,96 in the high pressure limiting regime.…”

Section: Computational Frameworkmentioning

confidence: 99%

“…A more detailed description of computational methods and procedures can be found in the original studies. 79,81,83,84…”

Section: Computational Frameworkmentioning

confidence: 99%

“…3). 97 The formation of prereaction complexes proceeds across loose transition states 79,81,83,84,95,96 which are favorable for the formation of prereaction complexes since those transition states reduce the dissociation rate of prereaction complexes (eqn (1)). The loose transition states seem to be analogous to the outer transition state suggested for the addition of the hydroxyl radical to ethylene.…”

Section: Formation and Properties Of Prereaction Complexesmentioning

confidence: 99%

“…Those results coupled with the RRKM (Rice-Ramsperger-Kassel-Marcus) kinetic theory have successfully reproduced the measured reaction rates and unusual temperature dependence for the oxidation of uorobenzene 79 and chlorobenzene. 81 Recently, the same approach was also successfully applied to obtain valuable information on the reaction mechanism and reaction-path dynamics for atmospheric oxidation of perhalogenated benzenes, 83,84 one of them being hexachlorobenzene, a model persistent organic pollutant (POP) from the original list of the twelve major POPs listed under the Stockholm Convention. 85,86 In this study, a comparative analysis will be made on the reaction mechanisms, thermodynamic data, calculated reaction rates and their temperature dependence as well as on the potential stable products of the atmospheric oxidation of halogenated benzenes by OH radicals.…”

Section: Introductionmentioning

confidence: 99%

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Atmospheric oxidation of halogenated aromatics: comparative analysis of reaction mechanisms and reaction kinetics

Kovačević

Sabljić

2017

Environ. Sci.: Processes Impacts

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Atmospheric transport is the major route for global distribution of semi-volatile compounds such as halogenated aromatics as well as their major exposure route for humans. Their major atmospheric removal process is oxidation by hydroxyl radicals. There is very little information on the reaction mechanism or reaction-path dynamics of atmospheric degradation of halogenated benzenes. Furthermore, the measured reaction rate constants are missing for the range of environmentally relevant temperatures, i.e. 230-330 K. A series of recent theoretical studies have provided those valuable missing information for fluorobenzene, chlorobenzene, hexafluorobenzene and hexachlorobenzene. Their comparative analysis has provided additional and more general insight into the mechanism of those important tropospheric degradation processes as well as into the mobility, transport and atmospheric fate of halogenated aromatic systems. It was demonstrated for the first time that the addition of hydroxyl radicals to monohalogenated as well as to perhalogenated benzenes proceeds indirectly, via a prereaction complex and its formation and dynamics have been characterized including the respective transition-state. However, in fluorobenzene and chlorobenzene reactions hydroxyl radical hydrogen is pointing approximately to the center of the aromatic ring while in the case of hexafluorobenzene and hexachlorobenzene, unexpectedly, the oxygen is directed towards the center of the aromatic ring. The reliable rate constants are now available for all environmentally relevant temperatures for the tropospheric oxidation of fluorobenzene, chlorobenzene, hexafluorobenzene and hexachlorobenzene while pentachlorophenol, a well-known organic micropollutant, seems to be a major stable product of tropospheric oxidation of hexachlorobenzene. Their calculated tropospheric lifetimes show that fluorobenzene and chlorobenzene are easily removed from the atmosphere and do not have long-range transport potential while hexafluorobenzene seems to be a potential POP chemical and hexachlorobenzene is clearly a typical persistent organic pollutant.

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