·OH自由基引发CH_(3)SSCH•_(3)^(+)自由基裂解反应机理的理论研究  

Theoretical Study on the Fragmentation Mechanism of CH_(3)SSCH_(3) Radical Cation Initiated by OH Radical

作　　者：程媛媛 郗碧莹 CHENG Yuanyuan;XI Biying(Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation,East China University of Technology,Nanchang 330013,China;School of Chemistry,Biology and Material Science,East China University of Technology,Nanchang 330013,China)

机构地区：[1]东华理工大学江西省质谱科学与仪器重点实验室 [2]东华理工大学化学生物与材料科学学院,南昌330013

出　　处：《高等学校化学学报》2022年第10期196-203,共8页Chemical Journal of Chinese Universities

基　　金：国家自然科学基金(批准号:22103011);东华理工大学博士启动基金(批准号:DHBK2018065)资助

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CH_(3)SSCH_(3)自由基阳离子(CH_(3)SSCH•^(3+),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CH_(3)S(OH)SCH_(3)^(+)(R1)和氢提取产物复合物[CH_(2)=SSCH_(3)+H_(2)O]^(+)(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CH_(3)SOH,CH_(2)=S和HSCH_(2)OH.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).The fragmentation mechanism of CH_(3)SSCH_(3) radical cation(CH_(3)SSCH•^(3+),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 CH_(3)S(OH)SCH_(3)^(+)(R1)or the hydrogen abstraction product complex[CH_(2)=SSCH_(3)+H_(2)O]^(+)(R2).Then,cleavage of S—S bond concerted proton transfer directly occurs for the fragmentation of R1.While,conforma⁃tional 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 CH_(3)SOH,CH_(2)=S,and HSCH_(2)OH.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 partici⁃pates 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).

关 键 词：羟基自由基 CH_(3)SSCH_(3)自由基阳离子 裂解 反应机理 密度泛函理论 

分 类 号：O643.1[理学—物理化学]