1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH), as an emerging brominated flame retardant (EBFR) pollutant, has been often observed in the air, and to comprehend its fate in the environment is still challenging due to the diversity of its stereoisomers. In this work, the environmental transformation behavior and potential toxicological implications of TBECH stereoisomers under the oxidation of OH· in the gas phase were investigated by computational chemistry. Our results indicate the complexity of the TBECH transformation reactions and the diversity of its transformation products in the atmosphere. Although the reactions of TBECH enantiomers with OH· exhibit highly consistency, it is obvious that the reactions of the four diastereoisomers of TBECH with OH· and their subsequent reactions have both specificity and similarity. The dehydrogenation intermediates produced by H-abstraction of OH· in the initial reactions may undergo oxidative debromination, hydroxylation and decomposition reactions, leading to the transformation into low bromine and monohydroxy substituted compounds, as well as debrominated or unbrominated unsaturated fatty ketones. The toxicity assessments show that all transformation products are less toxic to aquatic organisms than TBECH, but some of them are still classified at toxic or harmful levels. More importantly, some transformation products still exhibit carcinogenic and teratogenic activity. To our knowledge, this study provides, for the first time, a deep insight into the transformation mechanism, kinetics, and environmental impacts of atmospheric TBECH by theoretical calculations.

1,2-二溴-4-（1,2-二溴乙基）环己烷（TBECH）作为一种新兴的溴化阻燃剂（EBFR）污染物，经常在空气中被观察到，要了解其在环境中的命运仍然具有挑战性由于其立体异构体的多样性。在这项工作中，通过计算化学研究了TBECH立体异构体在气相OH·氧化下的环境转化行为和潜在的毒理学意义。我们的结果表明了TBECH转化反应的复杂性及其在大气中转化产物的多样性。尽管TBECH对映异构体与OH·的反应表现出高度的一致性，但是很明显，TBECH的四种非对映异构体与OH·的反应及其随后的反应具有特异性和相似性。在初始反应中通过H-吸收OH·所产生的脱氢中间体可能会发生氧化脱溴，羟基化和分解反应，从而导致向低溴和单羟基取代的化合物以及脱溴或未溴化的不饱和脂肪酮的转化。毒性评估表明，所有转化产物对水生生物的毒性均低于TBECH，但其中一些仍被分类为有毒或有害水平。更重要的是，某些转化产物仍表现出致癌和致畸活性​​。据我们所知，本研究首次通过理论计算深入了解了大气中TBECH的转化机理，动力学和环境影响。