CH_2CO+CH_2的多通道反应的理论研究  

Theoretical Study on the Multi-channel Reaction Mechanism of CH_2CO+CH_2

作　　者：李会学[1] 李志锋[1] 王晓峰[1] 董小宁[1] 朱元成[1] 

机构地区：[1]天水师范学院生命科学与化学学院,天水741001

出　　处：《化学学报》2010年第2期115-124,共10页Acta Chimica Sinica

基　　金：天水师范学院重点学科建设资助项目

摘　　要：利用密度泛函(DFT)和自然键轨道理论(NBO)及高级电子耦合簇[CCSD(T)]和电子密度拓扑(AIM)方法,对单重态和三重态CH2与CH2CO反应的微观机理进行了研究.在B3LYP/6-311+G(d,p)水平上优化了反应通道各驻点的几何构型.在CCSD(T)/6-311+G(d,p)水平上计算了各物种的单点能量,并对总能量进行了校正.计算表明,单重态CH2与CH2CO的C-H键可发生插入反应,与C=C、C=O可发生加成反应,存在三条反应通道,产物为CO和C2H4,从能量变化和反应速控步骤能垒两方面考虑,反应II更容易发生.对反应通道中的关键点进行了自然键轨道及电子密度拓扑分析.三重态CH2与CH2CO的反应存在三条反应通道,一条是与C-H键的插入反应,另一条是三重态CH2与C=C发生加成反应,产物为CO和三重态C2H4,通道II势垒较低,更容易发生.最后一条涉及双自由基的反应活化能最大,最难发生.The reaction mechanisms of singlet and triplet CH2 with CH2CO have been studied by using the density functional theory（DFT）,natural bond orbital（NBO）,coupled cluster single and double excitation [CCSD（T）] and atoms in molecules（AIM） methods.The geometries of reactants,transition states and products were completely optimized by B3LYP/6-311＋G（d,p）.All the energy values of the species were obtained at the CCSD（T）/6-311G＋（d,p） level.The calculated results indicated that the singlet CH2 could not only insert the C—H（reaction I） but also could react with C=C,C=O（reactions Ⅱ and ⅡI）.There are three main pathways existing when the products CO and C2H4 are generated.Reaction Ⅱ happens more easily according to the energy changes and the barrier in its rate-controlling step.In addition,the important geometries in the main pathways have been studied by AIM theory and NBO analysis.There are three reactive pathways as triplet CH2 reacts with CH2CO,the first one is the triplet CH2 insertion into a C—H;the second one is addition reaction by the triplet CH2 to the C=C of CH2CO,which is easier for its lower potential barrier;however,the last pathway involving a diradical is the most difficult to occur for its biggest activation energy.

关 键 词：乙烯酮 CH2自由基 密度泛函理论 自然键轨道理论 电子密度拓扑分析 

分 类 号：O643.12[理学—物理化学]