类锗烯H2C=GeLiCl与RH(R=F,OH, NH2)的插入反应

采用DFT B3LYP和QCISD方法研究了不饱和类锗烯H2C=GeLiCl与RH(R=F, OH, NH2)的插入反应. 在B3LYP/6-311+G(d,p)水平上优化了反应势能面上的驻点构型. 结果表明, H2C=GeLiCl与HF、H2O 或NH3发生插入反应的机理相同. QCISD/6-311++G(d,p)//B3LYP/6-311+G(d,p)计算的三个反应的势垒分别为173.53、194.48和209.05 kJ·mol-1, 反应热分别为60.18、72.93和75.34 kJ·mol-1. 相同条件下发生插入反应时, 反应活性顺序都是H—F>H—OH>H—NH2.     

类硅烯H2C＝SiLiBr与RH (R＝F, OH, NH2)的插入反应

采用DFT B3LYP和QCISD方法研究了类硅烯H2C＝SiLiBr与RH (R＝F, OH, NH2)的插入反应. 在B3LYP/6- 311＋G(d,p)水平上优化了反应势能面上的驻点构型. 结果表明, H2C＝SiLiBr与HF, H2O或NH3发生插入反应的机理相同. QCISD/6-311＋＋G(d,p)//B3LYP/6-311＋G(d,p)计算的三个反应的势垒分别为148.62, 164.42和165.07 kJ•mol－1, 反应热分别为－69.63, －43.02和－28.27 kJ•mol－1. 相同条件下发生插入反应时, 反应活性都是H—F＞H—OH＞H—NH2.     

CH3F与C2H3反应机理的理论研究

采用密度泛函B3LYP/6-311G(d,p)方法对CH3F与C2H3的反应体系进行了理论研究,获得了反应的势能面信息及可能的微观机理.在QCISD(T)/6-311++G(d,p)水平上精确计算了各反应物种的单点能.结果表明,除抽提氢反应外,标题反应还存在抽提氟(R1)、消氟化氢(R2)、消氢(R3)和自由基形成(R4)四类反应.在QCISD(T)/6-311++G(d,p)//B3LYP/6-311G(d,p)水平上,R1,R2,R3和R4反应的能垒分别是163.9,152.2,209.8和224.2kJ·mol-1,相应反应能为-56.6,-164.3,-2.7和-156.0kJ·mol-1,所有反应均放热,为热力学允许的反应.     

CHF_3与O(~3P)反应机理的理论研究

采用从头算MP2/6-311G(d,p)方法研究了CHF3与O(3 P)的反应机理,优化了所有反应物、产物和过渡态的几何构型,并通过振动频率分析和内禀反应坐标(IRC)方法确证了过渡态的真实性.在QCISD(T)/6-311++G(d,p)水平上精确计算了各反应物种的单点能.结果表明,标题反应共存在4类反应,分别为抽提氢反应(R1)、抽提氟反应(R2),消氟化氢反应(R3)和消氢反应(R4),在QCISD(T)/6-311++G(d,p)//MP2/6-311G(d,p)水平上,R1,R2,R3和R4反应的能垒分别为70.7,378.7,294.7和307.2kJ·mol-1,抽提氢反应为主反应通道.     

不饱和类硅烯H2C=SiNaCl的密度泛函理论研究

采用密度泛函理论方法,在B3LYP/6-311G(d,p)水平上研究了不饱和类硅烯H2C=SiNaCl的结构.结果表明,不饱和类硅烯H2C=SiNaCl共有4种平衡构型,其中非平面的p-配合物型构型能量最低,是不饱和类硅烯H2C=SiNaCl存在的主要构型.对平衡构型间异构化反应的过渡态进行了计算,求得了转化势垒.计算预言了最稳定构型的振动频率和红外强度.     

杂环型稳定硅烯插入HF、H_2O和NH_3反应

硅烯为卡宾的硅类似物,在有机光和热化学中作为一类重要的反应活性中间体引起了化学界的广泛兴趣.杂环型硅烯是实验合成的稳定硅烯,因其在有机硅化学中的重要作用,十几年来在实验和理论上均有研究报道.本文基于单重态杂环型硅烯的特殊电子性质和丰富的化学反应性,系统探讨了几种杂环型硅烯的插入反应.使用密度泛函理论(DFT),在B3LYP/6-311++G(d,p)水平上研究了三种氮杂环型不饱和硅烯(1,3,4)和两种氮杂环型饱和硅烯(2,5)分别与H—X(X=F,OH,NH2)键的插入反应,阐明了插入反应的机理并对各反应的结果进行了比较.杂环型硅烯与H—X的插入反应机理类似于简单硅烯,体现了硅烯的亲电亲核的双重反应性.由反应势垒和反应热看,五种硅烯与H—X键的插入反应均为HF最容易,H2O次之,NH3最难.饱和硅烯的反应性比不饱和硅烯的反应活性高,这也间接验证了杂环型饱和硅烯在实验中较难合成.     

类硅烯H_2SiLiF二聚反应的理论研究

从理论上研究了类硅烯H2SiLiF的三元环构型为反应物的二聚反应2H2SiLiF→H2SiSiH2+2LiF。在MP2/6-31G(d)和QCISD(T)/6-31G(d)水平下的计算结果表明,H2SiLiF的二聚反应经过两个阶段:阶段I,先形成过渡态TS1,经过中间体Int,形成一个四元环的中间产物Pro1,同时消去一个LiF;阶段Ⅱ,Pro1继续反应形成过渡态TS2,进而解离生成产物H2SiSiH2和一个LiF。从能量上看,反应易停留在中间产物阶段。本文对反应物、过渡态以及产物的结构、稳定性等方面进行了讨论,很好解释了实验结果。     

H2ClCS单分子分解反应机理的理论研究

用量子化学B3LYP/6 - 311+G(d,p)方法优化了H2ClCS单分子分解反应驻点物种的几何构型,并在相同水平上通过频率计算和内禀反应坐标(IRC)分析对过渡态结构及连接性进行了验证.用QCISD(T)/6-311++G(d,p)方法计算各物种的单点能,并对总能量进行了零点能校正.利用经典过渡态理论(TST)与...     

不饱和类锗烯H2C=GeLiCl的DFT研究

采用密度泛函理论方法, 在B3LYP/6-311G(d, p)水平上研究了不饱和类锗烯H2C=GeLiCl的结构及异构化反应. 结果表明, 不饱和类锗烯H2C=GeLiCl有三种平衡构型, 其中非平面的p-配合物型构型能量最低, 是其存在的主要构型. 对平衡构型间异构化反应的过渡态进行了计算,求得了转化势垒. 计算预言了最稳定构型的振动频率和红外吸收强度.     

不饱和类硅烯H_2CSiNaCl的密度泛函理论研究

采用密度泛函理论方法,在B3LYP/6-311G(d,p)水平上研究了不饱和类硅烯H2CSiNaCl的结构.结果表明,不饱和类硅烯H2CSiNaCl共有4种平衡构型,其中非平面的p-配合物型构型能量最低,是不饱和类硅烯H2CSiNaCl存在的主要构型.对平衡构型间异构化反应的过渡态进行了计算,求得了转化势垒.计算预言了最稳定构型的振动频率和红外强度.     

Theoretical study on the insertion reactions of the germylenoid H2GeClMgCl with RH (R = F, OH, NH2)

The insertion reactions of the germylenoid H₂GeClMgCl with RH (R = F, OH, NH₂) have been studied by using the DFT B3LYP and QCISD methods. The geometries of the stationary points on the potential energy surfaces of the reactions were optimized at the B3LYP/6-311+G(d, p) level of theory. The calculated results indicate that all the mechanisms of the three insertion reactions are identical to each other. The QCISD/6-311++G(d, p)//B3LYP/6-311+G(d, p) calculated potential energy barriers for the three insertion reactions of R = F, OH, and NH₂ are 164.62, 193.30, and 200.73 kJ mol^?1, and the reaction energies for the three reactions are ?57.46, ?35.65, and ?22.22 kJ mol^?1, respectively. Under the same situation, the insertion reactions should occur easily in the following order H-F > H-OH > H-NH₂. In THF solvent the insertion reactions get more difficult than in gas phase.     

Theoretical Prediction on the Germylenoid HB=GeLiF and Its Insertion Reaction with R-H（R = F,OH,NH_2）

In the present work we investigated a novel triplet ground-state germylenoid HB=GeLiF as well as its insertion reactions with RH(R = F,OH and NH2) using the DFT B3LYP and QCISD methods for the first time.Geometry optimization calculations show that the triplet HB=GeLiF has three equilibrium structures,in which the four-membered ring structure is the most stable with the lowest energy.All mechanisms of the three insertion reactions of germylenoid HB=GeLiF with RH(R = F,OH,and NH2) are identical to each other.Based on the calculated results,it is concluded that under the same conditions the insertion reactions should occur easily in the order of H-F > H-OH > H-NH2.In THF solvent the insertion reactions get more difficult than in the gas phase.     

Theoretical studies of the geometries of H2GeLiCl and its insertion reaction with R-H (R = F,OH, NH2)

The geometries and insertion reactions of germylene derivative H₂GeLiCl with R-H (R = F, OH, NH₂) have been investigated at the B3LYP/6-311+G^* level of theory. The potential barriers of the three reactions are 93.5, 151.3, and 194.1 kJ/mol, including the zero-point vibration energy corrections, respectively. The mechanisms of all the three reactions are identical, i.e., an intermediate has been located during the insertion reaction. The intermediate could dissociate to substituted germylene and LiCl as a barrier process. Correspondingly, the reaction free energies for the three reactions are −7.4, 49.9, and 64.4 kJ/mol, respectively.

     

Singlet methylene insertion into polar O?H and N?H bonds of water and ammonia—Ab initio and DFT study

Correlated ab initio molecular orbital, DFT, QCISD, G3MP2, and QCISD(T) calculations have been used to investigate the geometries, energetics, and mechanisms governing the insertion reactions of ¹CH₂ into O H and N H bonds of water and ammonia, respectively, in gas phase adopting 6‐311++g(d, p) basis set. It is found that ¹CH₂ reacts with water and ammonia to produce the ylide‐like intermediates H₂C OH₂ and H₂C NH₃, which in turn undergo 1,2‐hydrogen shift to produce methanol and methylamine, respectively. Results obtained indicate that in the gas phase, the ylides and the transition states are located below the reactants' energy levels. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Theoretical investigation on the reaction of HS+ with CH3NH2

The singlet and triplet potential energy surfaces for the reaction of HS⁺ with the simplest primary amine, CH₃NH₂, were determined at the CCSD(T)/6-311+G(d,p) level using the B3LYP/6-311G(d,p) and QCISD/6-311G(d,p) geometries. All possible reaction channels were explored. The results show that three paths on the singlet potential energy surface and one path on the triplet potential energy surface are competitive. These four feasible paths provide products which are presented in the paper and they are consistent with previous experimental results. On the other hand, the stationary points involved in the most favourable path all lie below those of the reactant and thus the title reaction is expected to be rapid, which is also consistent with the experiment.     

CH3S自由基H迁移异构化及脱H2反应的直接动力学研究

采用密度泛函方法(MPW1PW91)在6-311G(d,p)基组水平上研究了CH₃S自由基H迁移反应CH₃S→CH₂SH (R1), 脱H₂反应CH₃S→HCS＋H₂ (R2)以及脱H₂产物HCS异构化反应HCS→CSH (R3)的微观动力学机理. 在QCISD(t)/6- 311＋＋G(d,p)//MPW1PW91/6-311G(d,p)＋ZPE水平上进行了单点能校正. 利用经典过渡态理论(TST)与变分过渡态理论(CVT)分别计算了各反应在200～2000 K温度区间内的速率常数k^TST和k^CVT, 同时获得了经小曲率隧道效应模型(SCT)校正后的速率常数k^CVT/SCT. 结果表明, 反应 R1, R2 和R3的势垒△E^≠分别为160.69, 266.61和241.63 kJ/mol, R1为反应的主通道. 低温下CH₃S比CH₂SH稳定, 高温时CH₂SH比CH₃S更稳定. 另外, 速率常数计算结果显示, 量子力学隧道效应在低温段对速率常数的计算有显著影响, 而变分效应在计算温度段内对速率常数的影响可以忽略.     

Theoretical studies on the pentacoordinate silylenoid PhCH<Subscript>2</Subscript>(NH<Subscript>2</Subscript>)CH<Subscript>3</Subscript>SiLiF

The structures of pentacoordinate silylenoid PhCH₂(NH₂)CH₃SiLiF were studied by density functional theory at the B3LYP/6-31G(d) level. Three equilibrium structures, the three-membered ring (1), the p-complex (2), and the σ-complex (3) structures, were located. Their energies are in the order of 2 > 1 > 3 both in vacuum and in THF. To exploit the stability of PhCH₂(NH₂)CH₃SiLiF, the insertion reactions of 1 and PhCH₂(NH₂)CH₃Si into C–F have been investigated, respectively. The results show that the insertion of PhCH₂(NH₂)CH₃Si is more favorable. To probe the influence of amine-coordination to the stability of PhCH₂(NH₂)CH₃SiLiF, the insertion reaction of PhCH₃CH₃SiLiF was also investigated. The calculations indicate that the insertion of PhCH₃CH₃SiLiF is more favorable than that of 1. So the N atom plays an important role on the stability of silylenoid PhCH₂(NH₂)CH₃SiLiF.     

DFT and ab initio direct dynamics studies on the hydrogen abstraction reactions of chlorine atoms with CH(4-n)F(n) (n = 1-3)

A direct dynamics study is carried out for the hydrogen abstraction reactions Cl + CH(4-n)F(n) (n = 1-3) in the temperature range of 200-1,000 K. The minimum energy paths (MEPs) of these reactions are calculated at the BH&H-LYP/6-311G(d,p) level, and the energies along the MEPs are further refined at the QCISD(T)/6-311+G(2df,2p) and QCISD(T)/6-311+G(d,p) (single-point) level. The rate constants obtained by using the improved canonical variational transition state theory incorporating small-curvature tunneling correction (ICVT/SCT) are in good agreement with the available experimental results. It is shown that the vibrational adiabatic potential energy curves for these reactions have two barriers, a situation similar to the analogous reactions CH(3)X+Cl (X=Cl, Br). The theoretical results show that for the title reactions the variational effect should not be neglected over the whole considered temperature range, while the small-curvature tunneling effect is only important in the lower temperature range. The effects of fluorine substitution on the rate of this kind of reactions are also examined.