Ab Initio Study of the Mechanism of Forming a Spiro-Si-heterocyclic Ring Compound Involving Ge from Cl_2Ge=Si:and Formaldehyde

The X2Ge=Si:(X = H, Me, F, Cl, Br, Ph, Ar···) is a new species. Its cycloaddition reaction is a new area for the study of silylene chemistry. The mechanism of cycloaddition reaction between singlet Cl2Ge=Si: and formaldehyde has been investigated with 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 reaction rule presented is that the two reactants firstly form a four-membered Ge-heterocyclic ring silylene through the [2+2] cycloaddition reaction. Owing to the 3p unoccupied orbital of Si: atom in the four-membered Ge-heterocyclic ring silylene and the π orbital of formaldehyde forming a π→p donor-acceptor bond, the four-membered Ge-heterocyclic ring silylene further combines with formaldehyde to form an intermediate. Because the Si: atom in intermediate shows sp3 hybridization after transition state, the intermediate isomerizes to a spiro-Si-heterocyclic ring compound involving Ge via a transition state. Simultaneously, the ring strain of the four-membered Ge-heterocyclic ring silylene makes it isomerize to a twisted four-membered ring product. The research result indicates the laws of cycloaddition reaction between X2Ge=Si:(X = H, Me, F, Cl, Br, Ph, Ar···) and the asymmetric π-bonded compounds, which are significant for the synthesis of small-ring and spiro-Si-heterocyclic ring compound involving Ge. The study extends the research area and enriches the research content of silylene chemistry.     

Ab Initio Study of the Mechanism of Forming a Spiro-Ge-heterocyclic Ring Compound Involving Si from Me2Si=Ge: and Formaldehyde

X2Si=Ge:(X = H, Me, F, Cl, Br, Ph, Ar···) is a new species. Its cycloaddition reaction is a new area for the study of germylene chemistry. The mechanism of cycloaddition reaction between singlet state Me2Si=Ge: and formaldehyde has been investigated with the CCSD(T)//MP2/cc-pvtz method. From the potential energy profile, it could be predicted that the reaction has one dominant reaction pathway. The reaction rule presented is that the two reactants first form a four-membered Si-heterocyclic ring germylene through the [2+2] cycloaddition reaction. Because of the 4p unoccupied orbital of Ge: atom in the four-membered Si-heterocyclic ring germylene and the π orbital of formaldehyde form a π→p donor-acceptor bond, the four-membered Si-heterocyclic ring germylene further combines with formaldehyde to form an intermediate. Because the Ge atom in the intermediate undergoes sp3 hybridization after transition state, then the intermediate isomerizes to a spiro-Ge-heterocyclic ring compound involving Si via a transition state. The research result indicates the laws of cycloaddition reaction between H2Si=Ge: and formaldehyde. It has important reference value for the cycloaddition reaction between X2Si=Ge:(X= H, Me, F, Cl, Br, Ph, Ar···) and asymmetric π-bonded compounds, which is significant for the synthesis of small-ring and spiro-Ge-heterocyclic compounds involving Si. The study extends research area and enriches the research content of germylene chemistry.     

Ab Initio Study on the Mechanism of Cycloaddition Reaction between Silylene Carbene （H_2Si=C：） and Acetone

The mechanism of cycloaddition reaction between singlet silylene carbene and acetone has been investigated with CCSD(T)//MP2/6-31G method. From the potential energy profile, it can be predicted that the reaction has two competitive dominant reaction pathways. One consists of two steps: (1) the two reactants (R1, R2) firstly form a four-membered ring intermediate (INT4) through a barrier-free exothermic reaction of 585.9 kJ/mol; (2) Then intermediate (INT4) isomerizes to CH3-transfer product (P4.1) via a transition state (TS4.1) with energy barrier of 5.3 kJ/mol. The other is as follows: on the basis of intermediate (INT4) created between R1 and R2, intermediate (INT4) further reacts with acetone (R2) to form the intermediate (INT5) through a barrier-free exothermic reaction of 166.3 kJ/mol; Then, intermediate (INT5) isomerizes to a silicic bis-heterocyclic product (P5) via a transition state (TS5), for which the barrier is 54.9 kJ/mol. The presented rule of this reaction: the [2+2] cycloaddition effect between the π orbital of silylene carbene and the π orbital of π-bonded compounds leads to the formation of a four-membered ring intermediate (INT4); The unsaturated property of C atom from carbene in the four-membered ring intermediate (INT4) results in the generation of CH3-transfer product (P4.1) and silicic bis-heterocyclic compound (P5).     

Ab Initio Study of the Mechanism of Cycloaddition Reaction between H2Ge=Ge: and Acetaldehyde

The mechanism of cycloaddition reaction between singlet state H2Ge=Ge: and acetaldehyde has been investigated with the MP2/6-311++G** method. From the potential energy profile, it could be predicted that the reaction has two competitive dominant reaction pathways. The reaction rule presented is that the two reactants firstly form a four-membered Ge-heterocyclic ring germylene through the [2+2] cycloaddition reaction. As the 4p unoccupied orbital of Ge: atom in the four-membered Ge-heterocyclic ring germylene and the π orbital of acetaldehyde form a π→p donor-acceptor bond, the four-membered Ge-heterocyclic ring germylene further combines with acetaldehyde to give an intermediate. Because the Ge atom in intermediate exhibits sp3 hybridization after transition state, the intermediate isomerizes to a spiro-Ge-heterocyclic ring compound via a transition state. Simultaneously, the ring strain of the four-membered Ge-heterocyclic ring germylene makes it isomerize to a twisted four-membered ring product.     

Features of Mechanism of Cycloaddition Reaction between Me_2Ge=Sn: and Ethylene

X_2Ge=Sn:(X = H, Me, F, Cl, Br, Ph, Ar···) are new species of chemistry. The cycloaddition reaction of X_2Ge=Sn: is a new study field of stannylene chemistry. To explore the rules of cycloaddition reaction between X_2Ge=Sn: and the symmetric p-bonded compounds, the cycloaddition reactions of Me_2Ge=Sn: and ethylene were selected as model reactions in this paper, and the mechanism was investigated for the first time here using the MP2 theory together with the 6-311++G** basis set for C, H and Ge atoms and the LanL2dzbasis set for Sn atoms. From the potential energy profile, it could be predicted that the reaction has one dominant reaction channel. The reaction rule present is that the 5p unoccupied orbital of Sn in Me_2Ge=Sn: and the π orbital of ethylene form a p → p donor–acceptor bond, resulting in an intermediate which, due to its instability, makes itself isomerize into a four-membered Ge-heterocyclic ring stannylene. Because the 5p unoccupied orbital of Sn atom in the four-membered Ge-heterocyclic ring stannylene and the π orbital of ethylene form a p → p donor-acceptor bond, the four-membered Ge-heterocyclic ring stannylene further combines with ethylene to get another intermediate. Because the Sn atom in this intermediate exhibits sp3 hybridization after transition state, the intermediate isomerizes to a Ge-heterocyclic spiro-Sn-heterocyclic ring compound. The research result indicates the laws of cycloaddition reaction between X_2Ge=Sn: and the symmetric π-bonded compounds. This study opens up a new research field for stannylene chemistry.     

双桥反应机理的从头计算研究

有大量文献[1-3]对有机化学反应中的反式加成、邻基参与下的反式消去反应所涉及的三元环过程（我们称之为单桥反应机理）进行了研究·负离子以相等的几率进攻成桥的二个碳原子中的任意一个，因而对大量反应的立体选择性给出了很好的解释．但是有些反应却不能用这一机理解释．FinarN］指出其原因还不清楚，并推测这是由于桥键可以断裂而形成开环经典离子，使原来的桥原子所跨碳碳单键旋转．这儿相当于给出了两种并存的机理．HoPkhson等人＊以乙烯和氟或氯加成为模型，对单桥机理进行了量子化学从头算研究·得到这两个反应的活化能分别大于5…     

NH2自由基与O3反应机理的从头计算

采用量子化学从头计算的UMP2(full)方法研究了NH2自由基与臭氧的反应机理，优化了反应物、中间体、过渡态和产物的几何构型，并做了频率分析.结果表明, NH2自由基与臭氧反应有两条反应通道，其中一条反应活化能很小，反应极易发生.化学反应热的计算结果与实验结果吻合较好.     

CH自由基和NO2反应研究Ⅱ.反应的动力学计算

采用MP2(FULL)/6-31G(d)方法从动力学计算上探讨了CH自由基与NO2反应的可能途径,找到了反应物,中间体及产物之间的能量通道和过渡态,报道了它们的构型、电子态及能量.并通过频率分析和IRC方法对所有的过渡态进行了验证.在此基础上求出了各步反应的活化能.在以前热力学研究的基础上,对于可能的反应通道进一步作了动力学分析,找到了反应主产物通道的分支比,与实验得到的分支比基本吻合.     

Cl_2 2HI=2HCl I_2反应机理的理论研究

分别在MP2/3-21G!!、CCSD(T)/3-21G!!//MP2/3-21G!!和B3LYP/3-21G!!3种水平上,计算研究了气相反应Cl2 2HI=2HCl I2的机理,求得一系列四中心和三中心的过渡态.通过比较六种反应通道的活化能大小,得到了相同的结论:双分子基元反应Cl2 HI"HCl ICl和ICl HI"I2 HCl的最小活化能小于Cl2、HI和ICl的解离能,从理论上证明了反应Cl2 2HI=2HCl I2将优先以分子与分子作用形式分两步完成.用内禀反应坐标(IRC)验证了MP2/3-21G!!方法计算得到的过渡态.     

Ab initio Study of Mechanism of Forming a Germanic Hetero-Polycyclic Compound between Germylidene (H2C=Ge:) and Acetone

The mechanism of the cycloaddition reaction of forming a germanic hetero‐polycyclic compound between singlet germylidene (R1) and acetone (R2) has been investigated with CCSD(T)//MP2/6‐31G* method. From the surface energy profile, it can be predicted that the dominant reaction pathway for this reaction consists of three steps: (1) the two reactants (R1, R2) firstly form a twisted four‐membered ring intermediate (INT2); (2) the intermediate (INT2) reacts further with acetone (R2) to give another intermediate (INT4); (3) intermediate (INT4) isomerizes to a hetero‐polycyclic germanic compound (P4) via a transition state TS4. The presented rule of this reaction: the [2+2] cycloaddition effect between the π orbital of germylidene and the π orbital of π‐bonded compounds leads to the formation of four‐membered ring intermediate (INT2). The 4p unoccupied orbital and the lone‐pair sp electrons of Ge in the four‐membered ring intermediate (INT2) react with the π orbital and the antibonding π* orbital of π‐bonded compounds, respectively, forming the π→p and sp→ π* cyclic donor‐acceptor bonds, resulting in the generation of a stable germanic hetero‐polycyclic compound (P4).     

Ab initio Study of Mechanism of Cycloaddition Reaction between Germylene Silylene (H2GeSi:) and Acetone

The mechanism of the cycloaddition reaction between singlet germylene silylene (H₂GeSi:) and acetone has been investigated with CCSD(T)/6‐31G*//MP2/6‐31G* method. From the potential energy profile, we could predict that the reaction has two competitive dominant reaction channels. The present rule of this reaction is that the [2+2] cycloaddition reaction of the two (‐bonds in germylene silylene and acetone generates a four‐membered ring silylene with Ge. Because of the unsaturated property of Si atom in the four‐membered ring silylene with Ge, it could further react with acetone, resulting in the generation of a bis‐heterocyclic compound with Si and Ge. Simultaneously, the ring strain of the four‐membered ring silylene with Ge makes it isomerize to a twisted four‐membered ring product.     

Is the CH2OH + O2 → CH2 = O + HO2 Reaction Barrierless? An Ab Initio Study on the Reaction Mechanism

The reaction mechanism of the CH₂OH + O₂ gas-phase reaction was investigated by means of ab initio calculations. MP2 and QCISD methodologies were used to obtain the stationary points on the potential energy surface. Single-point high-level QCISD(T) calculations were performed over the QCISD results in order to refine the energy of the transition states and the minima found. A new transition state concerning the initial O₂ addition to the CH₂OH radical was found, not reported so far for this reaction. Extra CCSD optimisation and single-point high-level CCSD(T) calculations upon the QCISD results confirm this TS. Additional RASSCF calculations show that its wave function has no significant multireferential character.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

亚甲基硅烯与乙烯环加成反应机理的理论研究

The mechanism of a cycloaddition reaction between singlet methylidenesilene and ethylene has been investigated with MP2/6-31G^＊ and B3LYP/6-31G^＊ methods, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. Energies of the involved conformers were calculated by CCSD（T）//MP2/6-31G＊ and CCSD（T）//B3LYP/6-31 G＊ methods, respectively. The results show that the dominant reaction pathway of the cycloaddition reaction is that a complex intermediate is firstly formed between the two reactants through a barrier-free exothermic reaction of 13.3 kJ/mol, and the complex is then isomefized to a four-membered ring product P2,1 via a transition state TS2.1 with a barrier of 32.0 kJ/mol.     

Ab initio Study of Mechanism of Forming Germanic Hetero-Polycyclic Compound between Germylene Carbene (H2Ge=C: ) and Formaldehyde

The mechanism of the cycloaddition reaction of forming germanic hetero‐polycyclic compound between singlet germylene 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 CCSD (T)//MP2/6‐31G* method. From the potential energy profile, we predict that the cycloaddition reaction of forming germanic hetero‐polycyclic compound between singlet germylene carbene and formaldehyde has two competitive dominant reaction pathways. First dominant reaction pathway consists of four steps: (1) the two reactants (R1, R2) first form an intermediate (INT1) through a barrier‐free exothermic reaction of 117.5 kJ/mol; (2) intermediate (INT1) then isomerizes to a four‐membered ring compound (P2) via a transition state (TS2) with an energy barrier of 25.4 kJ/mol; (3) four‐membered ring compound (P2) further reacts with formaldehyde (R2) to form an intermediate (INT3), which is also a barrier‐free exothermic reaction of 19.6 kJ/mol; (4) intermediate (INT3) isomerizes to a germanic bis‐heterocyclic product (P3) via a transition state (TS3) with an energy barrier of 5.8 kJ/mol. Second dominant reaction pathway is as follows: (1) the two reactants (R1, R2) first form an intermediate (INT4) through a barrier‐free exothermic reaction of 197.3 kJ/mol; (2) intermediate (INT4) further reacts with formaldehyde (R2) to form an intermediate (INT5), which is also a barrier‐free exothermic reaction of 141.3 kJ/mol; (3) intermediate (INT5) then isomerizes to a germanic bis‐heterocyclic product (P5) via a transition state (TS5) with an energy barrier of 36.7 kJ/mol.     

Density Functional Theory Study on Mechanism of Forming Spiro-Ge-heterocyclic Ring Compound from Me2Ge=Ge: and Acetaldehyde

The H₂Ge=Ge:, as well as and its derivatives (X₂Ge=Ge:, X=H, Me, F, Cl, Br, Ph, Ar, : : :) is a kind of new species. Its cycloaddition reactions is a new area for the study of germy-lene chemistry. The mechanism of the cycloaddition reaction between singlet Me₂Ge=Ge: and acetaldehyde was investigated with the B3LYP/6-31G* method in this work. From the potential energy profile, it could be predicted that the reaction has one dominant re-action pathway. The reaction rule is that the two reactants firstly form a four-membered Ge-heterocyclic ring germylene through the [2+2] cycloaddition reaction. Because of the 4p unoccupied orbital of Ge: atom in the four-membered Ge-heterocyclic ring germylene and the π orbital of acetaldehyde forming a π→p donor-acceptor bond, the four-membered Ge-heterocyclic ring germylene further combines with acetaldehyde to form an intermedi-ate. Because the Ge atom in intermediate happens sp3 hybridization after transition state, then, intermediate isomerizes to a spiro-Ge-heterocyclic ring compound via a transition state. The research result indicates the laws of cycloaddition reaction between Me₂Ge=Ge: and ac-etaldehyde, and lays the theory foundation of the cycloaddition reaction between H₂Ge=Ge: and its derivatives (X₂Ge=Ge:, X=H, Me, F, Cl, Br, Ph, Ar, : : :) and asymmetric π-bonded compounds, which are significant for the synthesis of small-ring and spiro-Ge-heterocyclic ring compounds.     

Theoretical Study on the Mechanism of the Cycloaddition Reaction between Alkylidene Carbene and Ethylene

The mechanism of cycloaddition reaction between singlet alkylidene carbene and ethylene has been investigated with second-order Moller-Plesset perturbation theory (MP2). By using 6-31 G^* basis, geometry optimization, vibrational analysis and energetics have been calculated for the involved stationary points on the potential energy surface. The results show that the title reaction has two major competition channels. An energy-rich intermediate (INT) is firstly formed between alkylidene carbene and ethylene through a barrier-free exothermic reaction of 63.62 kJ/mol, and the intermediate then isomerizes to a three-membered ring product (P 1) and a four-memberd ring product (P2) via transition state TS1 and TS2, in which energy barriers are 47.00 and 51.02 kJ/mol, respectively. P1 is the main product.     

亚烷基锡烯与乙烯环加成反应机理的理论研究

The mechanism of a cycloaddition reaction between singlet alkylidenestannylene and ethylene has been investigated with MP2/3-21 G^* and B3LYP/3-21 G* methods, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. Energies for the involved conformations were calculated by CCSD(T)//MP2/3-2 IG^* and CCSD(T)//B3LYP/3-21G^* methods, respectively. The results show that the dominant reaction pathway of the cycloaddition is that an intermediate (INT) is firstly formed between the two reactants through a barrier-free exothermic reaction of 39.7 kJ/mol, and the intermediate then isomerizes to a four-membered ring product (P2.1) via a transition state TS2.1 with a barrier of 66.8 kJ/mol.     

二氯亚甲基锗烯与乙烯环加成反应机理的理论研究

The mechanism of a cycloaddition reaction between singlet dichloromethylene germylene and ethylene has been investigated with B3LYP/6-31G＊ method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. Energies for the involved conformations were calculated by CCSD（T）//B3LYP/6-31G＊ method. On the basis of the surface energy profile obtained with CCSD（T）// B3LYP/6-31G＊ method for the cycloaddition reaction between singlet dichloromethylene germylene and ethylene, it can be predicted that the dominant reaction pathway is that an intermediate INT1 is firstly formed between the two reactants through a barrier-free exothermic reaction of 61.7 kJ/mol, and the intermediate INT1 then isomerizes to an active four-membered ring product P2.1 via a transition state TS2, an intermediate INT2 and a transition state TS2.1, in which energy barriers are 57.7 and 42.2 kJ/mol, respectively.     

CH自由基和NO2反应研究Ⅰ.反应的热力学计算

探讨了CH自由基与NO2反应的可能路径,通过计算确定了反应物,产物和稳定中间体的电子状态和平衡构型,并运用Gaussian-3方法和MRCISD方法对可能的反应路径进行了热力学计算.在多数情况下与实验值符合较好.对于个别与理论计算差别较大的实验值进行了评述.     

HPXF(X=Li,Na)的构型及反应性能的从头算研究

用RHF/6-31G^*从头算解析梯度法优化了类磷烯HPXF(X=Li,Na)的平衡构型,分析了各构型的结构特点及稳定性.通过与磷烯(¹HP)相比较,探讨了HPXF(X=Li,Na)的反应活性,还简单讨论了碱金属原子对HPXF(X=Li,Na)三元环构型稳定性和反应活性的影响.结果表明,HPLiF和HPNaF均具有3种平衡构型,其中三元环构型最稳定,也是参加反应的基本构型:类磷烯与相应的¹HP相比,可成为一种使反应容易控制、选择性好和易获得的亲电反应中间体.