吡唑衍生物与碘甲烷反应的密度泛函理论研究  

Density Functional Theory Study on the Reactions of Pyrazole Derivatives with CH_(3)I

作　　者：沈福刚[1] 段文勇[1] 孙宏伟[1] 陈兰[1] 陈沛全[1] 赖城明[1] 李正名[1] 

机构地区：[1]南开大学化学学院,天津300071

出　　处：《高等学校化学学报》2006年第11期2175-2178,共4页Chemical Journal of Chinese Universities

基　　金：天津市科委高性能计算基金(批准号:043185111-5);南开大学'南开之星'高性能计算项目资助

摘　　要：采用密度泛函方法对3-甲硫基-4氰-基-5-氨基吡唑与碘甲烷反应的机理进行了研究.提出了两种可能的反应途径:反应途径Ⅰ为反应物先脱去吡唑上的质子,生成阴离子中间物,然后碘甲烷分别进攻中间物吡唑环上的2个氮原子,生成两种异构产物;反应途径Ⅱ为反应物通过分子间氢转移存在两种异构体,碘甲烷直接进攻每个异构反应物吡唑上的氮原子,形成中间物,然后脱去碘化氢,生成产物.计算结果表明,途径Ⅱ应为主要反应途径.还找出了两种异构产物间甲基迁移反应的过渡态,得出该反应的活化能为278.5 kJ/mol,在常温下甲基迁移反应不容易进行.Density functional（B3LYP） calculations, using the 6-31 G^＊ and LANL2DZdp ECP Polarization basis sets, were employed to study the reaction pathway involving 3-methylthio-4-cyano-pyrazole and iodomethane. According to the structure of pyrazole derivatives, two possible reaction pathways were examined. Pathway Ⅰ proceeded associated with the dehydrogenation of the reactants and the attack of CH3I on both nitrogen atoms of pyrazole. Pathway Ⅱ was as follows ： first, due to the hydrogen transfer of the reactants, two isomers are formed; then CH3I attacks on nitrogen atom of the isomers to form intermediates; finally the intermediates dehydroiodinate to form two products. The results from the calculation suggest that pathway Ⅱ is the dominant reaction channel.

关 键 词：密度泛函理论 过渡态 吡唑衍生物 反应途径 

分 类 号：O641[理学—物理化学]