二氟亚烷基卡宾与甲醛环加成反应机理的理论研究

用二阶微扰理论研究单重态二氟亚烷基卡宾与甲醛发生的环加成反应机理,采用MP2/6-31G^*方法计算了势能面上各驻点的构型参数、振动频率和能量.结果表明,单重态二氟亚烷基卡宾与甲醛的环加成反应主要有两种反应通道,通道1中,两个反应物经a,b和c三条反应途径生成三元环构型的产物P1,其中途径c是主反应途径,该途径有两步组成:(Ⅰ)二氟亚烷基卡宾与甲醛生成了1个富能中间体(INT1c),是无势垒放热反应,放出能量为219.18kJ/mol;(Ⅱ)中间体(INT1c)异构化为产物二氟亚烷基环氧乙烷,其势垒为134.71kJ/mol.通道2的反应途径由三步组成:(Ⅰ)反应物首先生成了1个富能中间体(INT1b),为无势垒的放热反应,放出的能量142.77kJ/mol;(Ⅱ)中间体(INT1b)异构化成另一中间体(INT2),其势垒为22.31kJ/mol;(Ⅲ)中间体(INT2)异构化成四元环构型产物P2,其势垒为11.98kJ/mol.     

单态卡宾与臭氧反应机理的量子化学研究

为了研究单态卡宾与臭氧反应机理,本文采用密度泛函理论Gaussian-3方法(G3B3)优化了反应物、中间体、过渡态和产物的几何构型。探讨了单态卡宾与臭氧反应可能途径,并通过频率分析对过渡态和中间体进行了验证,研究结果表明：单态卡宾与臭氧反应有两条反应通道,分别具有亲核反应和亲电反应特征,相对而言亲核反应通道较易发生,且为强放热反应。     

亚烷基卡宾与甲醛环加成反应机理的理论研究

用二阶微扰理论研究了单重态亚烷基卡宾与甲醛发生的三种环加成反应的机理 ，采用MP2/6－31G~*方法计算了势能面上各驻点的构型参数、振动频率和能量。根 据能量数据可以预言环加成反应（1）的a途径将是单重态亚烷基卡宾与甲醛环加成 反应的主要反应通道，该反应由两步组成：（I）亚烷基卡宾与甲醛生成了一富能 中间体（INT1a），是一无势垒的放热反应，（II）中间体异构化为产物亚烷基环 乙烷，其势垒为24.1 kJ·mol~(-1)(MP2/6-31G~*)。     

卤代羰基叶立德:“推-拉”稳定作用对四苯基环戊二烯酮与卡宾的脱氧反应的影响(英文)

研究了四苯基环戊二烯酮与三溴甲基苯基汞（二溴卡宾的前体化合物）的卡宾反应，发现该反应可给出比通常有立体障碍的酮要高得多的脱氧（以脱CO的形式）产率．本文从羰基叶立德中间体的“推-拉”稳定作用以及该中间体的构象和电子分布的角度出发，并结合产物分析对这一反常现象进行了讨论，发现在潜芳香结构的羰基化合物与二卤卡宾的反应中，有可能由于“推-拉”作用形成具有芳香结构的羰基是中间体，该中间体由于正负电荷及以较好的分散以及其接近0°／90°型的构象，有效地阻碍了分子间环加成和分子内电环化这两个竞争反应的进行，从而使脱氧途径成为该反应的主渠道．本项研究进一步揭示了一些尚未被人了解的反应规律，合理地解释了反应机理．     

CH_3自由基和O（~3P）反应机理的量子化学研究

用分子轨道从头计算MP2（full）方法和密度泛函理论（DFT）中的B3LYP方法 研究了CH_3自由基和三线态O原子反应的微观机理，优化得到了反应途径上的反应 物、过渡态、中间体和产物的几何构型，通过振动分析对过渡态和中间体构型进行 了确认，在G3不平上计算了能量，同时用经典过渡态理论对该反应的绝对速率常数 进行了理论计算。研究结果表明：CH_3自由基与O（~3P）反应有四条不同的放热反 应通道，主反应通道为IM1→TS1→CH_2O + H，同时反应可彻底裂解生成CO, H_2 及H。     

Ru(II)催化有机叠氮与炔反应机理的理论研究

采用密度泛函理论, 对在Ru(II)催化剂存在下, 有机叠氮化合物和末端炔的反应机理作了深入理论研究. 在B3LYP/LANL2DZ水平上, 对该反应体系中势能面各驻点的几何构型进行了全优化计算, 并经振动频率分析确定了过渡态和中间体, 通过内禀反应坐标(IRC)的计算, 确认了反应物、中间体、过渡态和产物的相关性. 对多个反应通道的协同反应以及分步反应进行了研究. 结果表明: 协同反应通道Ic和分步反应通道IIc是反应能垒较低的反应通道, 活化自由能较其它反应通道低, 有利于1,5-二取代1,2,3-三唑的生成, 具有特定的区域选择性, 与实验结果吻合.     

亚烷基卡宾与丙烯环加成反应机理的理论研究

用二阶微扰理论研究了单重态亚烷基卡宾与丙烯环加成反应的机理，采用 MP2/6-31G~*方法计算了势能面上各驻点的构型参数、振动频率和能量。根据所得 势能面上的能量数据可以预言，反应（1）的a途径和反应（2）的b途径将是单重态 亚烷基卡宾与丙烯环加成反应的两条相互竞争的主反应通道，两反应途径均由两步 组成，(I)两反应物分别生成了富能中间体INT1a和INT2b，它们均是无势垒的放热 反应，放出的能量分别为60.28和26.33kJ·mol~(-1).(II)中间体INT1a和INT2b分 别通过过渡态TS1a和TS2b异构化为三元环产物P1和四元环产物P2，其势垒分别为 16.43和12.73kJ·mol~(-1)。     

密度泛函理论研究SiC与C2H4反应的产物通道

在B3LYP/6-311++G(d,p)水平上研究了SiC与乙烯的单重态和三重态反应机理,优化得到了反应物、过渡态、中间体和产物的几何构型;通过振动分析对过渡态和中间体构型进行了确认。在CCSD(T)/cc-pVTZ水平上对计算得到的构型进行了能量校正。计算结果表明,SiC+C2H4反应在单重态和三重态条件下均可发生,其中单重态反应为主反应通道,1P5为主产物。     

Ru(II)催化有机叠氮与炔反应机理的理论研究

采用密度泛函理论, 对在Ru(II)催化剂存在下, 有机叠氮化合物和末端炔的反应机理作了深入理论研究. 在B3LYP/LANL2DZ水平上, 对该反应体系中势能面各驻点的几何构型进行了全优化计算, 并经振动频率分析确定了过渡态和中间体, 通过内禀反应坐标(IRC)的计算, 确认了反应物、中间体、过渡态和产物的相关性. 对多个反应通道的协同反应以及分步反应进行了研究. 结果表明: 协同反应通道Ic和分步反应通道IIc是反应能垒较低的反应通道, 活化自由能较其它反应通道低, 有利于1,5-二取代1,2,3-三唑的生成, 具有特定的区域选择性, 与实验结果吻合.     

氧原子与羟亚甲基自由基反应机理的理论研究

用量子化学从头计算法对氧原子与羟亚甲基自由基在最低双重态势能面上的反应进行了研究,计算了势能面上各驻点的构型参数、振动频率和能量。计算采用G2(MP2)理论方法。计算结果表明,反应首先形成中间体OCH_2OH,而后经不同过渡态解离为H_2CO+OH或H+HCOOH。由中间体形成甲醛和甲酸的过渡态的能量分别比反应物低202.5和355.3kJ/mol,计算得到2个反应通道的反应热分别为-314.1和-402.9kJ/mol,与实验结果(-307和-398kJ/mol)符合很好。根据能量数据可以预言形成甲酸的通道将是主要的反应通道。     

Theoretical study on the mechanism of the cycloaddition reaction between stannylene and ethylene or formaldehyde

The mechanism of the cycloaddition reaction of singlet stannylene and ethylene or formaldehyde has been studied by using density functional theory. The geometrical parameters, harmonic vibrational frequencies and energies of stationary points for potential energy surface are calculated by RB3LYP/3–21G* method. The results show that the two reaction processes are both two steps: (1) stannylene and ethylene or formaldehyde form an energy‐rich intermediate complex respectively, which is an exothermal reaction with no barrier; (2) two intermediate complexes isomerize to the product, respectively, with the barriers of these two reactions being 52.97 and 45.15 kJ/mol at RB3LYP/3–21G* level.     

Theoretical Study on Mechanism of Cycloadditional Reaction Between Dichloro-Germylidene and Formaldehyde

Mechanism of the cycloadditional reaction between singlet dichloro-germylidene and formaldehyde has been investigated with MP2/6-31G^* method, including geometry opti-mization, vibrational analysis and energies for the involved stationary points on the poten-tial energy surface. From the potential energy profile, we predict that the cycloaddition reaction between singlet dichloro-germylidene and formaldehyde has two competitive dom-inant reaction pathways, going with the formation of two side products (INT3 and INT4), simultaneously. Both of the two competitive reactions consist of two steps, two reactants firstly form a three-membered ring intermediate INT1 and a twisted four-membered ring intermediate INT2, respectively, both of which are barrier-free exothermic reactions of 41.5 and 72.3 kJ/mol; then INT1 isomerizes to a four-membered ring product P1 via transition state TS1, and INT2 isomerizes to a chlorine-transfer product P2 via transition state TS2,with the barriers of 2.9 and 0.3 kJ/mol, respectively. Simultaneously, P1 and INT2 further react with formaldehyde to form INT3 and INT4, respectively, which are also barrier-free exothermic reaction of 74.9 and 88.1 kJ/mol.     

Theoretical study of mechanism of cycloaddition reaction between dimethylmethylene carbene and formaldehyde

The cycloaddition mechanism of forming a polycyclic compound between singlet dimethylmethylene carbene(R1) and formaldehyde(R2) has been investigated with MP2/6‐31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated with CCSD(T)//MP2/6‐31G* method. From the potential energy profile, it can be predicted that the dominant reaction pathway of the cycloadditional reaction between singlet dimethylmethylene carbene and formaldehyde consists of two steps: (1) the two reactants(R1, R2) firstly form an energy‐enricheded intermediate (INT1a) through a barrier‐free exothermic reaction of ΔE = 11.3 kJ/mol. (2) Intermediate (INT1a) then isomerizes to a three‐membered product (P1) via a transition state (TS1a) with an energy barrier of 20.0 kJ/mol. The dominant reaction has an excellent selectivity and differs considerably from its competitive reactions in reaction rate. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Theoretical study of mechanism of cycloaddition reaction between dimethylmethylenesilylene and formaldehyde

The mechanism of cycloaddition reaction between singlet dimethylmethylenesilylene and formaldehyde has been investigated with MP2/6‐31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of different conformations are calculated by CCSD(T)//MP2/6‐31G* method. From the potential energy surface, it can be considered in thermodynamics and dynamics that reaction (1) and reaction (4) are the two dominant competitive reaction channels of cycloaddition reaction between dimethylmethylenesilylene and formaldehyde. The reaction process of reaction (1) is that: the two reactants (R1, R2) first form intermediates INT1a and INT1b through two reaction paths, a and b, which are barrier‐free exothermic reactions of 31.8 and 43.9 kJ/mol; then, INT1a and INT1b isomerize to a four‐membered ring product P1 via transition states TS1a and TS1b, with energy barriers of 26.3 and 24.4 kJ/mol. Reaction (4) also has two reaction paths, a and b, each of which consists of three steps are as follows: (i) the two reactants (R1, R2) first form intermediates INT3a and INT3b, which are barrier‐free exothermic reactions of 64.5 and 44.2 kJ/mol. (ii) INT3a and INT3b further react with formaldehyde (R2) to form intermediates INT4a and INT4b, through barrier‐free exothermic reactions of 22.9 and 22.2 kJ/mol. (iii) INT4a and INT4b then isomerize to form silapolycyclic product P4 via transition states TS4a and TS4b, with energy barriers of 39.7 and 29.3 kJ/mol. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Theoretical study of mechanism of cycloaddition reaction between dimethyl‐silylene carbene [(CH3)2SiC:] and formaldehyde

The mechanism of the cycloaddition reaction between singlet dimethyl‐silylene carbene and formaldehyde has been investigated with MP2/6‐31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by zero‐point energy and CCSD (T)//MP2/6‐31G* method. From the potential energy profile, it can be predicted that the reaction has two competitive dominant reaction pathways. The main products of first dominant reaction pathway are a planar four‐membered ring product (P4) and its H‐transfer product (P4.2). The main product of second dominant reaction pathway is a silicic bis‐heterocyclic compound (P5). © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Theoretical study on the mechanism of cycloaddition reaction between dimethyl germylidene and formaldehyde

The cycloaddition mechanism of the reaction between singlet dimethyl germylidene and formaldehyde has been investigated with MP2/6-31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated with CCSD (T)//MP2/6-31G* method. From the potential energy profile, we predict that the cycloaddition reaction between singlet dimethyl germylidene and formaldehyde has two dominant reaction pathways. First dominant reaction pathway consists of three steps: (1) the two reactants (R1, R2) firstly form an intermediate INT1a through a barrier-free exothermic reaction of 43.0 kJ/mol; (2) INT1a then isomerizes to a four-membered ring compound P1 via a transition state TS1a with an energy barrier of 24.5 kJ/mol; (3) P1 further reacts with formaldehyde(R2) to form a germanic heterocyclic compound INT3, which is also a barrier-free exothermic reaction of 52.7 kJ/mol; Second dominant reaction pathway is as following: (1) the two reactants (R1, R2) firstly form a planar four-membered ring intermediate INT1b through a barrier-free exothermic reaction of 50.8 kJ/mol; (2) INT1b then isomerizes to a twist four-membered ring intermediate INT1.1b via a transition state TS1b with an energy barrier of 4.3 kJ/mol; (3) INT1.1b further reacts with formaldehyde(R2) to form an intermediate INT4, which is also a barrier-free exothermic reaction of 46.9 kJ/mol; (4) INT4 isomerizes to a germanic bis-heterocyclic product P4 via a transition state TS4 with an energy barrier of 54.1 kJ/mol.     

Ab initio study on the mechanism of forming a silapolycyclic compound between silylidene and formaldehyde

The mechanism of the cycloaddition reaction of forming a silapolycyclic compound between singlet silylidene and formaldehyde has been investigated with MP2/6-31G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by CCSD(T)//MP2/6-31G* method. From the potential energy profile, it can be predicted that the cycloaddition reaction process of forming the silapolycyclic compound (P₂) for this reaction consists of four steps: (I) the two reactants first form a semi-cyclic intermediate INT1a through a barrier-free exothermic reaction of 32.5 kJ mol⁻¹; (II) this intermediate then isomerizes to an active four-membered ring intermediate INT1 via a transition state TS1a with an energy barrier of 30.8 kJ mol⁻¹; (III) INT1 further reacts with formaldehyde to form an intermediate INT2, which is also a barrier-free exothermic reaction of 30.1 kJ mol⁻¹; (IV) INT2 isomerizes to a silapolycyclic compound P₂ via a transition state TS2 with a barrier of 50.6 kJ mol⁻¹. Comparing this reaction path with other competitive reaction paths, we can see that this cycloaddition reaction has an excellent selectivity.