This study investigates the decomposition of 2,2′,4,4′,5-pentabrominated diphenyl ether (BDE99), a commonly detected pollutant in the environment. Debromination channels yielding tetrabrominated diphenyl ethers and hydrogen abstracting aromatic bromine atom formations play significant roles in the reaction of BDE99 + H, in which the former absolutely predominates bimolecular reactions. Polybrominated dibenzo-p-dioxins (PBDDs) and polybrominated dibenzofurans (PBDFs) can be produced during BDE99 pyrolysis, especially for PBDFs under inert conditions. The expected dominant pathways in a closed system are debromination products and PBDF formations. The bimolecular reaction with hydroxyl radical mainly leads to hydroxylated BDE99s rather than hydroxylated tetrabrominated diphenyl ethers. PBDDs are then generated from ortho-hydroxylated PBDEs. HO₂ radical reactions rarely proceed. The total rate constants for the BDE99 reaction with hydrogen atoms and hydroxyl radicals exhibit positive dependence on temperature with values of 1.86 × 10^–14 and 5.24 × 10^–14 cm³ molecule^–1 s^–1 at 298.15 K, respectively.

中文翻译：

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2,2'，4,4'，5-五溴二苯醚的机理和动力学转变的理论研究

这项研究调查了2,2'，4,4'，5-五溴代二苯醚（BDE99）的分解，BDE99是环境中常见的污染物。脱溴通道产生四溴代二苯醚和氢提取芳族溴原子的形成在BDE99 + H的反应中起重要作用，其中前者绝对占主导地位的双分子反应。多溴二苯并pBDE99热解过程中可能会生成二恶英（PBDDs）和多溴二苯并呋喃（PBDFs），尤其是在惰性条件下的PBDFs。封闭系统中预期的主要途径是脱溴产物和PBDF形成。与羟基自由基的双分子反应主要导致羟基化的BDE99而不是羟基化的四溴代二苯醚。然后从邻羟基化的多溴二苯醚中生成多溴二苯并二恶英。HO ₂自由基反应很少进行。BDE99与氢原子和羟基自由基反应的总速率常数与温度呈正相关，其值为1.86×10 ^–14和5.24×10 ^–14 cm ³分子^–1 s ^–1 分别为298.15K。