School of Engineering and Information Technology Murdoch University , Murdoch WA 6150, Australia.
Environ Sci Technol. 2014 Dec 16;48(24):14335-43. doi: 10.1021/es5038047. Epub 2014 Nov 24.
1,2-Bis(2,4,6-tribromophenoxy)ethane (BTBPE) is currently one of the most commonly applied novel brominated flame retardants. In this contribution, we analyze in detail the mechanisms pertinent to its thermal decomposition in view of analogous experimental findings. We demonstrate that a 1,3-hydrogen shift, leading to 2,4,6-tribromophenol (M9) and 1,3,5-tribromo-2-(vinyloxy)benzene (M10) molecules, dominates direct scission of O-CH2 bonds up to a temperature of ∼ 680 K. H atom abstraction from CH2 sites, followed by a fission of a C-C bond, produce a 2,4,6-tribromophenoxy radical (M2) and a M10 molecule. Bimolecular condensation reactions involving M2, M9, and M10 generate several congeners of brominated diphenyl ethers and their OH/OCHCH2 substituents, which serve as direct precursors for the formation of polybrominated dibenzo-p-dioxins. Reaction of M9 with a model compound of a hydrocarbon chain preferentially yields M2. Strong adsorption energy of the latter on a radical site of a hydrocarbon chain suggests that mechanisms such as Langmuir-Hinshelwood, Eley-Rideal, and Diels-Alder might be operating during the formation of PBDD/Fs from brominated flame retardants (BFRs). Reactions of alkyl primary/secondary radicals and diradical with the BTBPE molecule proceed via H abstraction from a -CH2- moiety.
1,2-双(2,4,6-三溴苯氧基)乙烷（BTBPE）是目前应用最广泛的新型溴系阻燃剂之一。在本研究中，我们根据类似的实验结果详细分析了其热分解的相关机制。我们证明，在温度约为 680 K 之前，导致 2,4,6-三溴苯酚（M9）和 1,3,5-三溴-2-（乙烯氧基）苯（M10）分子形成的 1,3-氢迁移主导着 O-CH2 键的直接断裂。CH2 位的 H 原子抽提，随后 C-C 键的断裂，生成 2,4,6-三溴苯氧基自由基（M2）和 M10 分子。涉及 M2、M9 和 M10 的双分子缩合反应生成了几种溴化二苯醚及其 OH/OCHCH2 取代物的同系物，它们是多溴代二苯并对二恶英形成的直接前体。M9 与碳氢化合物链的模型化合物的反应优先生成 M2。后者在碳氢化合物链的自由基位点上具有很强的吸附能，表明在溴系阻燃剂（BFRs）形成多溴代二苯并呋喃（PBDD/Fs）的过程中可能存在 Langmuir-Hinshelwood、Eley-Rideal 和 Diels-Alder 等机制。烷基伯/仲自由基和双自由基与 BTBPE 分子的反应是通过从-CH2 部分提取 H 原子进行的。
