Mechanistic and Kinetic Study on Self-/Cross- Condensation of PCTA/DT Formation Mechanisms from Three Types of Radicals of 2,4-Dichlorothiophenol
Mechanistic and Kinetic Study on Self-/Cross- Condensation of PCTA/DT Formation Mechanisms from Three Types of Radicals of 2,4-Dichlorothiophenol
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2,4-二氯苯硫酚三类自由基自缩合/交叉缩合PCTA/DT形成机理及动力学研究
DOI：
10.3390/ijms20112623
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发表时间：
2019-05
期刊：
影响因子：
--
通讯作者：
Qingzhu Zhang
中科院分区：
文献类型：
--
作者：
HetongWang;Chenpeng Zuo;Siyuan Zheng;Yanhui Sun;Fei Xu;Qingzhu Zhang
氯硫酚(CTPs)是多氯硫杂菲(PCTA/DTs)的关键和直接前体。氯硫苯氧基(CTPR)、巯基取代苯基和硫代苯氧基二自由基的自/交叉偶联反应是PCTA/DT形成的初始和重要步骤。本研究采用量子化学方法，在MPWB1K/6-311+G(3df，2p)/MPWB1K/6-31+G(d，p)水平上研究了2，4-二氯硫苯氧基(R1)、2-羟基-3，5-二氯苯基(R2)和3，5-二氯硫代苯氧基(DR)自偶联/交叉偶联生成PCTA/DTs的过程。利用具有小曲率隧穿贡献的正则变分过渡态理论，推导了600-1200K温度范围内的关键基元步骤的速率常数。对于PCTA的形成，一个基团中的硫酚硫和另一个基团中的邻位碳与单电子键合的S·/σ-C·缩合是最有效的硫-碳偶联方式，形成PCTA的势能排序为DR+DR>；R2+DR>；R1+R2>；R1+R1。对于PCDT的形成，σ-C·/σ-C·与两个基团中的两个邻位碳以单电子键合的方式是能量最有利的碳-碳偶联方式，形成PCDT的势能排序为：R2+DR>；R2+R2>；R1+R2>；R1+R1。从R1、R2和DR生成PCTA/DTs比从相应的氧取代基生成PCDD/DFS容易得多。
Chlorothiophenols (CTPs) are known to be key and direct precursors of polychlorinated thianthrene/dibenzothiophenes (PCTA/DTs). Self/cross-coupling of the chlorothiophenoxy radicals (CTPRs), sulfydryl-substituted phenyl radicals and thiophenoxyl diradicals evolving from CTPs are initial and important steps for PCTA/DT formation. In this study, quantum chemical calculations were carried out to investigate the homogenous gas-phase formation of PCTA/DTs from self/cross-coupling of 2,4-dichlorothiophenoxy radical (R1), 2-sulfydryl-3,5-dichlorophenyl radical (R2) and 3,5-dichlorothiophenoxyl diradical (DR) at the MPWB1K/6-311+G(3df,2p)//MPWB1K/6-31+G(d,p) level. The rate constants of crucial elementary steps were deduced over 600–1200 K, using canonical variational transition state theory with a small curvature tunneling contribution. For the formation of PCTAs, the S•/σ-C• condensation with both thiophenolic sulfur in one radical and ortho carbon in the other radical bonded to single electron is the most efficient sulfur-carbon coupling mode, and the ranking of the PCTA formation potential is DR + DR > R2 + DR > R1 + DR > R1 + R2 > R1 + R1. For the formation of PCDTs, the σ-C•/σ-C• coupling with both ortho carbon in the two radicals bonded to single electron is the energetically favored carbon-carbon coupling mode, and the ranking of the PCDT formation potential is: R2 + DR > R2 + R2 > R1 + DR > R1 + R2 > R1 + R1. The PCTA/DTs could be produced from R1, R2 and DR much more readily than PCDD/DFs from corresponding oxygen substituted radicals.
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