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Bond dissociation enthalpies (BDEs) are computed using the Density Functional Theory (DFT) for a selected set of C–Br, C–O, and C–Br bonds susceptible to homolysis in the thermal degradation of four brominated flame retardants (BFRs): decabromo-diphenyl, decabromo-diphenylethane, 1,2-bis(2,4,6-tribromophenoxy)-ethane, and 3,4,5,6-tetrabromo-1,2-die...
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Removal of brominated flame retardants (BFRs) from polymers before disposal or recycling will alleviate negative environmental effects and ensure safe usage of recycled products. Extraction of BFRs in supercritical CO2 is appealing but also presents challenges to industries due to limited solubility and lack of kinetic studies. For a more comprehen...
This contribution reports a thermodynamic assessment for the bromination of electric arc furnace dust (EAFD) by-products sourced from thermal degradation of tetrabromobisphenol A (TBBA); i.e., the most widely deployed brominated flame retardant. Upon TBBA’s pyrolysis, HBr is released in conjunction with several volatile organic compounds leaving a...
The ubiquitous presence of brominated flame retardants (BFRs) in indoor air, dust, and even in human tissue could be attributed to their emissions from BFR-containing products. Nevertheless, the emission behavior of BFRs, especially novel BFRs from consumer materials, to the indoor environment has still not been well understood. To evaluate the eff...
Citations
... In a theoretical study of the energetics of bond scission in the brominated flame retardants (BFRs) decabromodiphenyl, decabromo-diphenylethane, 1,2-bis(2,4,6-tribromophenoxy)ethane, and diethyl tetrabromophthalate, Maftei et al. [107] reported that debromination was the dominant decomposition pathway of brominated diphenyls and brominated phthalates, whereas scission to form brominated phenoxyls and benzyl radicals was the preferred pathway in aromatic BFRs containing ether and alkyl bridges, respectively. There are relatively few brominated organic compounds with measured enthalpies of formation. ...
The contents of issues 3 and 4 of Structural Chemistry from the calendar year 2018 are summarized in the present review. A brief thermochemical commentary and recommendations for future research have been added to the summary of each paper.
The thermal processes of materials containing decabromodiphenyl ether (BDE-209) normally result in the exposure of BDE-209 to high-temperature environments, generating a series of hazardous compounds. However, the evolution mechanisms of BDE-209 during oxidative thermal processes remain unclear. Thus, this paper presents a detailed investigation on the oxidative thermal decomposition mechanism of BDE-209 by utilizing density functional theory methods at the M06/cc-pVDZ theoretical level. The results show that the barrierless fission of the ether linkage dominates the initial degradation of BDE-209 at all temperatures, with branching ratio over 80%. The decomposition of BDE-209 in oxidative thermal processes is mainly along BDE-209 → pentabromophenyl and pentabromophenoxy radicals → pentabromocyclopentadienyl radicals → brominated aliphatic products. Additionally, the study results on the formation mechanisms of several hazardous pollutants indicate that the ortho-phenyl-type radicals created by ortho-C-Br bond fission (branching ratio reached 15.1% at 1600 K) can easily be converted into octabrominated dibenzo-p-dioxin and furan, which require overcoming the energy barriers of 99.0 and 48.2 kJ/mol, respectively. The O/ortho-C coupling of two pentabromophenoxy radicals also acts as a non-negligible pathway for the formation of octabrominated dibenzo-p-dioxin. The synthesis of octabromonaphthalene involves the self-condensation of pentabromocyclopentadienyl radicals, followed by an intricately intramolecular evolution. Results presented in this study can enhance our understanding of the transformation mechanism of BDE-209 in thermal processes, and offer an insight into controlling the emissions of hazardous pollutants.
Benchmark calculations using state-of-the-art DFT functionals and composite methods for bond dissociation energy and enthalpy of formation of halogenated polycyclic aromatic hydrocarbons are performed.
