The characteristic pathway for degradation of halogenated aliphatic compounds in groundwater or other environments with relatively anoxic and/or reducing conditions is reductive dechlorination. For 1,2-dihalocarbons, reductive dechlorination can include hydrogenolysis and dehydrohalogenation, the relative significance of which depends on various structural and energetic factors. To better understand how these factors influence the degradation rates and products of the lesser halogenated hydrocarbons (in contrast to the widely studied per-halogenated hydrocarbons, like trichloroethylene and carbon tetrachloride), density functional theory calculations were performed to compare all of the possible pathways for reduction and elimination of 1,2,3-trichloropropane (TCP). The results showed that free energies of each species and reaction step are similar for all levels of theory, although B3LYP differed from the others. In all cases, the reaction coordinate diagrams suggest that β-elimination of TCP to allyl chloride followed by hydrogenolysis to propene is the thermodynamically favored pathway. This result is consistent with experimental results obtained using TCP, 1,2-dichloropropane, and 1,3-dichloropropane in batch experiments with zerovalent zinc (Zn0, ZVI) as a reductant.

中文翻译：

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减少1,2,3-三氯丙烷（TCP）：化学计算计算的途径和机理。

在具有相对缺氧和/或还原条件的地下水或其他环境中，卤代脂肪族化合物降解的特征途径是还原性脱氯。对于1,2-二卤代烃，还原性脱氯可包括氢解和脱卤化氢，其相对重要性取决于各种结构和能量因素。为了更好地理解这些因素如何影响较少卤代烃的降解速率和产物（与广泛研究的全卤代烃，如三氯乙烯和四氯化碳相反），进行了密度泛函理论计算，比较了所有可能的途径。减少和消除1,2,3-三氯丙烷（TCP）。结果表明，尽管B3LYP彼此不同，但所有物种的自由能和反应步骤在所有理论水平上都是相似的。在所有情况下，反应坐标图表明TCP的β-消除为烯丙基氯，然后氢解为丙烯是热力学上有利的途径。该结果与使用TCP，1,2-二氯丙烷和1,3-二氯丙烷在零价锌（Zn0，ZVI）作为还原剂的分批实验中获得的实验结果一致。