高等学校化学学报 ›› 2022, Vol. 43 ›› Issue (10): 20220271.doi: 10.7503/cjcu20220271

• 物理化学 • 上一篇    下一篇

·OH自由基引发CH3SSCH3+自由基裂解反应机理的理论研究

程媛媛1(), 郗碧莹2   

  1. 1.东华理工大学江西省质谱科学与仪器重点实验室
    2.化学生物与材料科学学院, 南昌 330013
  • 收稿日期:2022-04-24 出版日期:2022-10-10 发布日期:2022-06-13
  • 通讯作者: 程媛媛 E-mail:cyy@ecut.edu.cn
  • 基金资助:
    国家自然科学基金(22103011);东华理工大学博士启动基金(DHBK2018065)

Theoretical Study on the Fragmentation Mechanism of CH3SSCH3 Radical Cation Initiated by OH Radical

CHENG Yuanyuan1(), XI Biying2   

  1. 1.Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation
    2.School of Chemistry,Biology and Material Science,East China University of Technology,Nanchang 330013,China
  • Received:2022-04-24 Online:2022-10-10 Published:2022-06-13
  • Contact: CHENG Yuanyuan E-mail:cyy@ecut.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(22103011);the Research Fund of East China University of Technology, China(DHBK2018065)

摘要:

采用UωB97X-D/6-311+G**方法, 研究了气相、 甲苯和水中OH自由基(·OH)引发CH3SSCH3自由基阳离子(CH3SSCH3?+, DMDS?+)裂解的反应机理, 并讨论了溶剂效应对反应的影响. 结果表明, ·OH和DMDS·+首先形成自由基耦合产物CH3S(OH)SCH3+(R1)和氢提取产物复合物[CH2=SSCH3+H2O]+(R2); 随后R1裂解直接发生 S—S键断裂协同质子转移, 而R2裂解依次发生构象变化、 C=S键亲碳加成和S—S键断裂协同质子转移. 去质子化的裂解产物为CH3SOH, CH2=S和HSCH2OH. 甲苯略微降低了裂解反应速控步骤的自由能垒. 水溶剂有利于R1裂解, 但不利于R2裂解, 尤其是单个水分子参与反应. 在气相、 甲苯和水中, 以·OH和DMDS·+为初始反应物, 虽然速控步骤的自由能垒为167.6~202.8 kJ/mol, 但裂解反应均是放热反应(?154.3~?31.4 kJ/mol).

关键词: 羟基自由基, CH3SSCH3自由基阳离子, 裂解, 反应机理, 密度泛函理论

Abstract:

The fragmentation mechanism of CH3SSCH3 radical cation(CH3SSCH3?+, DMDS?+) initiated by OH radical(·OH) in the gas phase, toluene, and water was studied at the UωB97X-D/6-311+G** level. The influence of solvent effect on the reaction was discussed. The results show that DMDS·+ firstly reacts with ·OH to form the radical coupling product CH3S(OH)SCH3+(R1) or the hydrogen abstraction product complex[CH2=SSCH3+H2O]+(R2). Then, cleavage of S—S bond concerted proton transfer directly occurs for the fragmentation of R1. While, conformational change, carbophilic addition to C=S double bond and cleavage of S—S bond concerted proton transfer occur in turn for the fragmentation of R2. Deprotonated products are CH3SOH, CH2=S, and HSCH2OH. Toluene slightly reduces the free energy barrier of the rate determining step in the fragmentation reaction. Water solvent is favorable for the fragmentation of R1, but unfavorable for the fragmentation of R2, especially an explicit water molecule participates in the reaction. In the gas phase, toluene, and water, with ·OH and DMDS·+ as initial reactant, although the free energy barriers of the rate determining steps are 167.6—202.8 kJ/mol, the fragmentation reactions are all exothermice reactions(?154.3— ?31.4 kJ/mol).

Key words: OH Radical, CH3SSCH3 Radical cation, Fragmentation, Reaction mechanism, Density functional theory

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