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.     

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.     

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.     

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.     

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 a Si-heterocyclic Spiro-Sn-heterocyclic Ring Compound by Cycloaddition Reaction of Cl_2Si=Sn: and Ethylene

X_2Si=Sn:(X = H, Me, F, Cl, Br, Ph, Ar…) are new species of chemistry. The cycloaddition reaction of X_2Si=Sn: is a new study field of stannylene chemistry. To explore the rules of cycloaddition reaction between X_2Si=Sn: and the symmetric p-bonded compounds, the cycloaddition reactions of Cl_2Si=Sn: and ethylene were selected as model reactions in this paper.The mechanism of cycloaddition reaction between singlet Cl_2Si=Sn: and ethylene has been first investigated with the MP2/GENECP(C, H, Cl, Si in 6-311++G**; Sn in LanL2dz) method in this paper. From the potential energy profile, it could be predicted that the reaction has one dominant reaction channel. The reaction rule presented is that the 5p unoccupied orbital of Sn in Cl_2Si=Sn: and the π orbital of ethylene forming a p→p donor-acceptor bond, resulting in the formation of an intermediate. Instability of the intermediate makes it isomerize to a four-membered Si-heterocyclic ring stannylene. Because the 5p unoccupied orbital of Sn atom in the four-membered Si-heterocyclic ring stannylene and the π orbital of ethylene form a p→p donor-acceptor bond, the four-membered Si-heterocyclic ring stannylene further combines with ethene to form another intermediate. Because the Sn atom in the intermediate shows sp~3 hybridization after transition state, the intermediate isomerizes to a Si-heterocyclic spiro-Sn-heterocyclic ring compound. The research result indicates the laws of cycloaddition reaction between X_2Si=Sn: and the symmetric π-bonded compounds. The study opens up a new research field for stannylene 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.     

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.     

Theoretical Studies on the Mechanism of Photocycloaddition Reaction Between 6 Azauracil and Acetone

The mechanism of photocycloaddition reaction between 6-azauracll and acetone was studied by using semiemptrical SCFMO AMI method. It was found that this reaction is not a concerted one. The calculated results are as follows:(1) A T1 state exciplex is on the T1 state energy surface; (2) T exciplex as a reactant will proceed along the energy surface of T1 state to form a diradical intermediate. The energy barrier of this reaction step is 63. 6 kJ/mol; (3) The T1 state diradical intermediate happens to be close in energy to the ground state intermediate with a similar geometry. Such a situation turns out to be very favorable for an intersystem crossing (jump from the T, state to the ground state) ; (4) The final product will be formed from the ground S0 state intermediate via an energy barrier 88. 2 kJ/mol.     

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.     

Theoretical study of mechanism of cycloaddition reaction between singlet dichlorosilylene carbene (Cl<Subscript>2</Subscript>Si=C:) and formaldehyde

The mechanism of the cycloaddition reaction between singlet dichlorosilylene carbene (Cl₂Si=C:) 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 first dominant reaction pathway 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 387.9 kJ/mol; (2) intermediate (INT4) then isomerizes to H-transfer product (P4.2) via a transition state (TS4.2) with energy barrier of 4.7 kJ/mol. The second dominant reaction pathway as follows: on the basis of intermediate (INT4) created between R1 and R2, intermediate (INT4) further reacts with formaldehyde (R2) to form the intermediate (INT5) through a barrier-free exothermic reaction of 158.3 kJ/mol. Then, intermediate (INT5) isomerizes to a silicic bis-heterocyclic product (P5) via a transition state (TS5), for which the barrier is 40.1 kJ/mol.     

Ab initio study of mechanism of forming germanic bis-heterocyclic compound between germylene carbene (H2GeC:) and acetone

The mechanism of the cycloaddition reaction of forming germanic bis-heterocyclic compound between singlet germylene carbene and acetone 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 dominant reaction pathway of the cycloadditional reaction of forming germanic bis-heterocyclic compound consists of three steps: (1) the two reactants firstly form an intermediate INT4 through a barrier-free exothermic reaction of 181.4 kJ/mol; (2) INT4 further reacts with acetone (R2) to form an intermediate (INT5), which is also a barrier-free exothermic reaction of 148.9 kJ/mol; (3) INT5 then isomerizes to a germanic bis-heterocyclic product P5 via a transition state TS5 with an energy barrier of 53.3 kJ/mol.     

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.     

Ab initio Study on Mechanism of Forming a Silicic Bis-Heterocyclic Compound Between Dimethylmethylenesilylene and Ethene

The mechanism of the cycloaddition reaction of forming a silicic bis-heterocyclic compound between singlet dimethylmethylenesilylene (Me₂C=Si:) and ethene has been investigated with the CCSD(T)//MP2/6-31G^* method. From the potential energy profile, it can be predicted that, this reaction has one dominant channel. The presented rule of this dominant channel: the 3p unoccupied orbital of Si in dimethylmethylenesilylene and the π orbital of ethene forming the π→p donor-acceptor bond, resulting in the formation of three-membered ring intermediate (INT1); INT1 then isomerizes to a four-membered ring silylene (P2), which is driven by ring-enlargement effect; due to sp³ hybridization of Si atom in P2, P2 further combines with ethene to form a silicic bis-heterocyclic compound.     

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.     

Theoretical study of the mechanism of cycloaddition reaction between dichloro-germylidene and acetaldehyde

The mechanism of the cycloadditional reaction between singlet dichloro-germylidene(R1) and (acetaldehyde(R2) has been investigated with MP2/6-31G* method, including geometry optimization, vibrational analysis and energies for the involved stationary points on the potential energy surface. From the potential energy profile, we predict that the cycloaddition reaction between singlet dichloro-germylidene and acetaldehyde has two competitive dominant reaction pathways. Going with the formation of two side products (INT3 and INT4), simultaneously. The two competitive reactions both consist of two steps: (1) 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 44.5 and 63.0 kJ/mol; (2) then INT1 and INT2 further isomerize to a four-membered ring product (P1) and a chlorine-transfer product (P2) via transitions (TS1 and TS2), respectively, with the barriers of 9.3 and 1.0 kJ/mol; simultaneously, P1 and INT2 react further with acetaldehyde(R2) to give two side products (INT3 and INT4), respectively, which are also barrier-free exothermic reaction of 65.4 and 102.7 kJ/mol.     

Theoretical study of mechanism of cycloaddition reaction between dichloro‐germylene carbene (Cl2GeC:) and aldehyde

The mechanism of the cycloaddition reaction between singlet dichloro‐germylene carbene and aldehyde 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 channel (A) consists of four steps: (1) the two reactants (R1, R2) first form an intermediate INT2 through a barrier‐free exothermic reaction of 142.4 kJ/mol; (2) INT2 then isomerizes to a four‐membered ring compound P2 via a transition state TS2 with energy barrier of 8.4 kJ/mol; (3) P2 further reacts with aldehyde (R2) to form an intermediate INT3, which is also a barrier‐free exothermic reaction of 9.2 kJ/mol; (4) INT3 isomerizes to a germanic bis‐heterocyclic product P3 via a transition state TS3 with energy barrier of 4.5 kJ/mol. The process of channel (B) is as follows: (1) the two reactants (R1, R2) first form an intermediate INT4 through a barrier‐free exothermic reaction of 251.5 kJ/mol; (2) INT4 further reacts with aldehyde (R2) to form an intermediate INT5, which is also a barrier‐free exothermic reaction of 173.5 kJ/mol; (3) INT5 then isomerizes to a germanic bis‐heterocyclic product P5 via a transition state TS5 with an energy barrier of 69.4 kJ/mol. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Density Functional Theory Study of Mechanism of Cycloaddition Reaction Between Dimethyl-Silylene Carbene and Acetone

The mechanism of the cycloaddition reaction between singlet dimethyl-silylene carbene and acetone has been investigated with density functional theory, From the potential energy profile, it can be predicted that the reaction has two competitive dominant reaction pathways. The presented rule of this reaction: the [2+2] cycloaddition effect between the πorbital of dimethyl-silylene carbene and the π orbital of π-bonded compounds leads to the formation of a twisty four-membered ring intermediate and a planar four-membered ring product; The unsaturated property of C atom from carbene in the planar four-membered ring product,resulting in the generation of CH₃-transfer product and silicic bis-heterocyclic compound.     

Theoretical study of mechanism of forming a silapolycyclic compound between methylenesilylene and acetone

The mechanism of the cycloaddition reaction of forming a silapolycyclic compound between singlet methylenesilylene and acetone 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 a silapolycyclic compound between singlet methylenesilylene and acetone has two competitive dominant reaction pathways. First dominant reaction pathway consists of four steps: (I) the two reactants (R1, R2) first form an intermediate (INT1) through a barrier‐free exothermic reaction of 46.2 kJ/mol; (II) intermediate (INT1) then isomerizes to a planar four‐membered ring product (P3) via transition state (TS3) with an energy barrier of 47.1 kJ/mol; (III) planar four‐membered ring product (P3) further reacts with acetone (R2) to form an intermediate (INT4), which is also a barrier‐free exothermic reaction of 40.0 kJ/mol; (IV) intermediate (INT4) isomerizes to a silapolycyclic compound (P4) via transition state (TS4) with an energy barrier of 57.0 kJ/mol. Second dominant reaction pathway consists of three steps: (I) the two reactants (R1, R2) first form a four‐membered ring intermediate (INT2) through a barrier‐free exothermic reaction of 0.5 kJ/mol; (II) INT2 further reacts with acetone (R2) to form an intermediate (INT5), which is also a barrier‐free exothermic reaction of 45.4 kJ/mol; (III) intermediate (INT5) isomerizes to a silapolycyclic compound (P5) via transition state (TS5) with an energy barrier of 49.3 kJ/mol. P4 and P5 are isomeric compounds. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010