Gas phase pyrolysis of endosulfan and formation of dioxin precursors of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F)

Dharmarathne, Nirmala K.; Mackie, John C.; Kennedy, Eric M.; Stockenhuber, Michael

doi:10.1016/j.proci.2016.05.001

Cited by 7 publications

(17 citation statements)

References 16 publications

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“…Improved energy calculations have been carried out at the M06-2X/GTLarge//M06-2 X /6-31+G(d,p) level of theory. We have chosen to use this method because of its previous success in the computation of large polychlorinated molecules such as endosulfan, dieldrin, hexachlorocyclopentadiene and their products. Rate constants at the high pressure limit for unimolecular reactions have been calculated by the ChemRate program using thermochemical parameters obtained from the quantum chemical computations.…”

Section: Computational Methodologymentioning

confidence: 99%

Mechanism of the Thermal Decomposition of Chlorpyrifos and Formation of the Dioxin Analog, 2,3,7,8-Tetrachloro-1,4-dioxino-dipyridine (TCDDpy)

Kennedy

Mackie

2018

Environ. Sci. Technol.

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Thermal decomposition of the pesticide, chlorpyrifos (CPf) and its major degradation product, 3,5,6-trichloro-2-pyridinol (TCpyol), has been studied by quantum chemical calculation using density functional methods at the M06-2X/GTLarge//M06-2 X/6-31+G(d,p) level of theory. Chlopyrifos was found to undergo a series of unimolecular stepwise elimination reactions releasing two molecules of ethylene and finally HOPOS to form TCpyol. TCpyol underwent oxidative decomposition initiated by abstraction of its phenolic H atom by O. Two phenoxy radicals so produced underwent combination leading to the formation of 2,3,7,8-tetrachloro-[1,4]dioxinodipyridine (TCDDpy). Via Smiles rearrangement both cis and trans TCDDpy are formed. Kinetic models have been constructed to model the decomposition of CPf into TCpyol and of the latter into cis and trans TCDDpy. Modeled results are compared with the experiments of Sakiyama et al. ( Organohalogen Compounds, 2012, 74, 1441-1444).

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Section: Computational Methodologymentioning

confidence: 99%

Mechanism of the Thermal Decomposition of Chlorpyrifos and Formation of the Dioxin Analog, 2,3,7,8-Tetrachloro-1,4-dioxino-dipyridine (TCDDpy)

Kennedy

Mackie

2018

Environ. Sci. Technol.

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“…To eliminate the surface effect, we coated the silica reactor with boron oxide (see details in the Supporting Information) as satisfactory boron oxide coating appears transparent. The flow reactor, product collection system, and analysis train have been described in detail in our earlier publications , and associated Supporting Information. A syringe pump was used to introduce reactants into the system and dilute with carrier gas.…”

Section: Experimental Methodologymentioning

confidence: 99%

“…Volatile organic compounds were analyzed by GCMS, as described previously. 5,9 Cl 2 was analyzed by ion chromatography (IC) by first dissolving the gas in dilute aqueous sodium hydroxide, in which it forms both Cl − (aq) and ClO − (aq). Both peaks in the IC were quantified to obtain the yield of Cl 2 .…”

Section: Experimental Methodologymentioning

confidence: 99%

“…The experiments proceeded for 1 h with a 5 s residence time, and the product species trapped in the condenser submerged in a glycol bath were maintained at 263 K. Gaseous species (except for Cl 2 ) were analyzed by FTIR spectrometry. Volatile organic compounds were analyzed by GCMS, as described previously. , Cl 2 was analyzed by ion chromatography (IC) by first dissolving the gas in dilute aqueous sodium hydroxide, in which it forms both Cl – (aq) and ClO – (aq). Both peaks in the IC were quantified to obtain the yield of Cl 2 .…”

Section: Experimental Methodologymentioning

confidence: 99%

“…In our previous studies of oxidative and nonoxidative decomposition of endosulfan, we discovered that reaction was initiated by retro-Diels–Alder decomposition into HCCP and the substrate 4,7-dihydro-1,3,2-dioxathiepine-2-oxide (2HDTO). This reaction takes place at about 600 K in a flow reactor of residence time 5 s. The Diels–Alder reaction is reversible; hence, decomposition is slow at temperatures below which HCCP does not decompose.…”

Section: Introductionmentioning

confidence: 99%

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Mechanism and Rate of Thermal Decomposition of Hexachlorocyclopentadiene and Its Importance in PCDD/F Formation from the Combustion of Cyclodiene Pesticides

et al. 2017

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Thermal decomposition of hexachlorocyclopentadiene (HCCP) has been studied in inert gas and under oxidative conditions in a silica flow reactor at a residence time of 5.0 s between 690 and 923 K and 1 atm pressure. Pyrolysis was initiated by Cl bond fission to form pentachlorocyclopentadienyl radical; two such radicals then combined to undergo a series of intramolecular rearrangements and Cl fissions, producing principally octachloronaphthalene (8ClNP) and Cl. This process has been studied by quantum chemical calculation, and a reaction potential energy surface has been developed. The rate constant of initial Cl atom fission has been calculated by canonical variational transition state theory as k = 1.45 × 10 exp(-222 ± 9 kJ mol/RT) s between 500 and 2000 K. A minimal kinetic model was developed to model the decomposition and major products. Oxidative decomposition was studied in nitrogen with O contents of 1, 6, 12, and 20 mol %. Increasing O to 6-8% increased the rate of decomposition of HCCP and decreased the yield of 8ClNP. Above 823 K, hexachlorobenzene (HCB) and CO became major products. The oxidative reaction has also been studied quantum chemically. At high O content (>∼10%), the rate of decomposition of HCCP declined as did yields of 8ClNP and HCB, but CO yields increased.

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Removal of PCDD/Fs, PCP and mercury from sediments: Thermal oxidation versus pyrolysis

2018

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Gas phase pyrolysis of endosulfan and formation of dioxin precursors of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F)

Cited by 7 publications

References 16 publications

Mechanism of the Thermal Decomposition of Chlorpyrifos and Formation of the Dioxin Analog, 2,3,7,8-Tetrachloro-1,4-dioxino-dipyridine (TCDDpy)

Mechanism of the Thermal Decomposition of Chlorpyrifos and Formation of the Dioxin Analog, 2,3,7,8-Tetrachloro-1,4-dioxino-dipyridine (TCDDpy)

Mechanism and Rate of Thermal Decomposition of Hexachlorocyclopentadiene and Its Importance in PCDD/F Formation from the Combustion of Cyclodiene Pesticides

Removal of PCDD/Fs, PCP and mercury from sediments: Thermal oxidation versus pyrolysis

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