锗烯与异硫氰酸反应机理的量子化学研究

采用密度泛函理论B3LYP方法研究了GeH2自由基与HNCS的反应机理,并在B3LYP/6-311++G**水平上对反应物,中间体,过渡态进行了全几何参数优化,通过频率分析和IRC确定中间体和过渡态。为了得到更精确的能量值,用QCISD(T)/6-311++G**方法计算了各个驻点的单点能,计算结果表明单重态的锗烯与异硫氰酸的反应有抽提硫、插入N-H键、抽提亚氨基的路径,而经由三元环中间体的抽提硫反应GeH2+HNCS→IM3→TS2→IM4→TS3→IM5→GeH2S+HNC(P1),反应能垒最低,为主反应通道,甲锗硫醛和异氰氢酸为主产物。锗烯经由四元环中间体抽提硫的反应为竞争反应通道。     

SiH2自由基与HNCO反应机理的理论研究

采用密度泛函理论B3LYP方法研究了SiH₂自由基与HNCO的反应机理, 并在B3LYP/6-311＋＋G**水平上对反应物、中间体、过渡态进行了全几何参数优化, 通过频率分析和内禀反应坐标(IRC)确定了中间体和过渡态. 为了得到更精确的能量值, 又用QCISD(T)/6-311＋＋G**方法计算了在B3LYP/6-311＋＋G**水平优化后的各个驻点的相对能量. 计算结果表明SiH₂自由基与HNCO的反应有五条反应通道, 其中顺式反应通道SiH₂＋HNCO→IM3→ TS4→IM5→TS5→IM6→SiH₂NH＋CO反应能垒最低, 为主反应通道.     

OClO与OH反应机理的理论研究

用密度泛函B3LYP/-311+G~(* *)和级电子相关倒映 合簇CCSD(T)/6-311+G~(* *)方法研究了OClO与OH反应的微观机理，研究结果表明：该反应经过缔合、H转移 和离解等复杂过程，最终得到四种产物，分别为HOCl+O_2，HCl+O_3,ClO+HO_2和 HOClO_2,从能量上看，形成HOCl+O_2和HCl+O_3的通道更容易进行，而形成 ClO+HO_2的通首在动力学上是最不利的。     

OXO (X=Cl,Br)与X (2P3/2)反应机理的理论研究

用密度泛函B3LYP/6-311+G**和高级电子相关的组态相互作用QCISD(T)/6-311+G**方法研究了OXO与X (2P3/2)双自由基反应的微观机理.研究结果表明该反应存在两个反应通道,产物分别为XO和X2+O2.由于形成产物XO的活化势垒较低,因而是主要反应通道,这与实验观察到的结果是一致的.而形成X2+O2的通道从动力学上看是不利的.     

4-乙酰基-1,3-二氟苯硝化反应机理研究

以4-氨基-1,3-二氟苯、乙酸酐和浓硝酸等为原料,合成了4-乙酰基-5-硝基-1,3-二氟苯,并且采用FTIR和1H NMR对产物进行了表征.采用量子化学方法,探讨了在酸催化条件下4-乙酰基-1,3-二氟苯硝化反应过程中的微观机理,在密度泛函理论的B3LYP/6-311G**水平下搜索得到反应路径,并对各中间体、过渡态和产物进行几何优化、振动频率分析和标准热力学函数计算;反应路径经过IRC验证.在MP2/6-311G**水平上对所有中间体、过渡态和产物进行更精确的能量计算.     

硅炔氢加成生成甲硅烷基硅烯的量子化学研究

利用量子化学从头算和密度泛函理论(DFT), 研究了硅炔和氢气分子加成生成甲硅烷基硅烯的反应机理. 在B3LYP/6-311G**水平上, 全参数优化了反应通道上各驻点(反应物、过渡态和产物)的几何构型, 计算出了它们的振动频率和零点振动能(ZPVE), 并对它们进行了振动分析, 以确定过渡态的真实性. 各物质总能量由QCISD(T)/6-311G**// B3LYP/6-311G**给出, 并对能量进行了零点能校正. 计算表明, 硅炔与氢分子加成反应可生成稳定的甲硅烷基硅烯. 热力学与动力学计算表明, 反应过程是一个放热、熵减少而自发趋势和反应程度较大的反应.     

D-苯丙氨酸与Cu＋(1S0, 3d10)气相反应理论研究

用量子化学密度泛函(DFT)方法研究D-苯丙氨酸与一价基态金属阳离子Cu^＋在气相中反应的机理. 在B3LYP/6-31G*水平上, 优化了反应包含的4个反应通道的反应物、中间体、过渡态和产物的几何构型, 并采用B3LYP/DZVP, B3LYP/[6-311＋G**(C,H,O)＋Lanl2dz(Cu)], B3LYP/6-311＋G**, MP2/6-311＋G** 等方法对各驻点进行了单点能计算. 通过对计算结果的分析, 获得了其单重态反应势能面的一般轮廓、各驻点几何构型优化参数, 明确了其反应机理.     

Theoretical Studies of PCl3/H2 Gas Chromatography Mechanism

Density functional theory B3LYP method was firstly applied to fully optimize the geometrical configuration of each stable point on PCl3/H2 gas chromatography reaction potential energy surface on the 6-311G** basis set, and single point energy was computed at the QCISD(T)/ 6-311G** level, then the transition state was validated by analyzing the unique imaginary vibration modes of each transition state and calculating intrinsic reaction coordinate (IRC), and the major reaction and competing reaction paths of PCl3/H2 gas chromatography reaction were presented through comparing active energy barrier, and phosphor was finally gained from the reaction of PH and PCl.     

CH3(2A′)自由基与臭氧反应机理的量子化学研究

用量子化学UMP2方法，在6-311++G**基组水平上研究了CH3(2A′)自由基与臭氧反应机理，全参数优化了反应过程中反应物、中间体、过渡态和产物的几何构型，在UQCISD(T)/6-311++G**水平上计算了它们的能量；并对它们进行了振动分析，以确定中间体和过渡态的真实性；同时应用经典过渡态理论计算了反应的速率常数，并与实验值进行了比较, CH3自由基与臭氧反应速率常数的理论计算结果为: 4.73×10－14 cm3•molecule－1•s－1，与实验报导的结果(k=2.52×10－14 cm3•molecule－1•s－1)很接近，同时发现CH3(2A′)自由基与O3的反应是强放热反应.     

DFT法研究离子液中EMIM＋催化丁烯双键异构反应机理

利用密度泛函方法(DFT)分别在B3LYP/6-31G**和B3LYP/6-311＋＋G**的计算水平上优化了离子液体中1-乙基-3-甲基咪唑阳离子(EMIM＋)催化丁烯双键异构反应过程中的反应物、产物以及过渡态的几何构型,分析了反应过程中键参数的变化.通过振动分析对平衡态和过渡态进行了验证,并得到了零点能.通过计算内禀反应坐标(IRC),确认了对应于过渡态的反应物和产物. 计算结果表明,EMIM＋催化丁烯双键异构可以基元反应的方式一步完成,1-丁烯异构化为2-丁烯的活化能约为192 kJ•mol－1, 逆反应活化能约为208 kJ•mol－1, 可在室温或高于室温条件下进行.     

Theoretical Study on the Reaction Mechanism of F2 ＋ 2HBr = 2HF ＋ Br2

1 INTRODUCTION The replacement reactions between halide and hy- drogen halide, or halide and halide are basic reac- tions in chemistry. Goldfinger et al. have speculated by experiment that the gas reaction between chlorine and hydrogen bromide might be a two-step intermo- lecular reaction[1, 2]. But gas reactions between other halides and hydrogen halides haven’t been reported experimentally so far. About theoretical investiga- tion, colinearity quantum mechanics, vibrational tran- sitio…     

HNCS与CH2(X2Π)反应微观动力学的理论研究

用量子化学密度泛函理论的UB3LYP/6-311+G**方法和高级电子相关的UQCISD(T)/6-311+G**方法研究了异硫氰酸(HNCS)与乙炔基自由基(C2H(X2Π))反应的微观机理. 采用双水平直接动力学方法IVTST-M, 获取反应的势能面信息, 应用正则变分过渡态理论并考虑小曲率隧道效应, 计算了在250～2500 K温度范围内反应的速率常数. 研究结果表明, HNCS与C2H(X2Π)反应为多通道、多步骤的复杂反应, 共存在三个可能的反应通道, 主反应通道为通过分子间H原子迁移, 生成主要产物NCS+C2H2. 反应速率常数随温度升高而增大, 表现为正温度效应. 速率常数计算中变分效果很小. 在低温区隧道效应对反应速率的贡献较大, 反应为放热反应.     

DFT法研究3-羟基丙烯醛的双键旋转异构反应机理

利用密度泛函理论(DFT)分别在B3LYP/6-31G**和B3LYP/6-311＋＋G**的计算水平上优化了基态3-羟基丙烯醛分子在双键旋转异构反应过程中的平衡态以及过渡态的几何构型，分析了反应过程中键参数的变化，计算了该反应的内禀反应坐标(IRC)，发现在重排反应途径上存在一个四元环骨架的中间体.通过振动分析对平衡态和过渡态进行了确认，并得到了零点能.计算结果表明，基态3-羟基丙烯醛分子的双键旋转异构反应经过两步完成，第一步反应位垒稍高，第二步反应位垒较低，存在着发生重排反应的可能性.     

Reaction Mechanism and Kinetics for HCCO Radical with NO

The mechanism and dynamical properties for the reaction of HCCO radicals with NO were investigated theoretically. The minimum energy paths(MEP) of the reaction were calculated by using the density functional theory(DFT) at the B3LYP/6-311 G^** level, and the energies along the MEP were further refined at the QCISD(T)/6-311 G^** level. It is found that the reaction mechanism of the title reaction involves three channels, producing HCNO CO, HONC CO and HCN CO2 products, respectively. Channel 1 is the most favorable path. The rate constant for channel 1 were calculated over a temperature range of 800-2500 K by using the canonical variational transition-state theory(CVT). The rate constant for the main path is negatively dependent on temperature, which is a characteristic of radical reactions with negative activation energy, and the variational effect for the rate constant calculation is small in the whole temperature range.     

Comparison of levels of electronic structure theory in direct dynamics simulations of C2H5F --> HF + C2H4 product energy partitioning

Direct dynamics simulations at the MP2/6-311++G** level of theory were performed to study C(2)H(5)F --> HF + C(2)H(4) product energy partitioning. The simulation results are compared with experiment and a previous MP2/6-31G* simulation. The current simulation with the larger basis set releases more energy to HF vibration and less to HF + C(2)H(4) relative translation as compared to the previous simulation with the 6-31G* basis set. The HF rotation and vibration energy distributions determined from the current simulation are in overall very good agreement with previous experimental studies of C(2)H(5)F dissociation by chemical activation and IRMPA. A comparison of the simulations with experiments suggests there may be important mass effects for energy partitioning in HX elimination from haloalkanes. The transition state (TS) structures and energies calculated with MP2 and the 6-31G* and 6-311++G** basis sets are compared with those calculated using CCD, CCSD, CCSD(T), and the 6-311++G** basis set.     

CH3SS与XO (X＝F,Cl, Br)反应过程的电子密度拓扑研究

利用MP2/6-311＋＋G(d,p)//B3LYP/6-311＋＋G(d,p)对CH3SS与XO (X＝F, Cl, Br)的反应机理进行了研究. 着重从电子密度拓扑分析角度讨论了化学键的生成和断裂. 计算结果表明单线态反应为主要反应通道, 且由于该通道的反应能垒低、放热明显, 说明CH3SS与XO在大气中比较容易进行. 电子密度拓扑分析表明, 在单线态抽氢反应通道中存在着四元环状过渡结构, 随着反应进行, 此四元环状过渡结构通过一个T-型结构变为三元环状过渡结构, 最后环状结构消失得到产物.     

OXO(X=Cl,Br)与H(2S)反应机理的量子化学研究

卤素二氧化物自由基(OXO)是重要的同温层物种，在极地的夜间含量尤其丰富，由于其光解产生的卤素原子会造成臭氧的严重损耗，因此愈来愈受到人们的广泛关注嘲．OXO自由基可以通过自由基之间的反应或微波放电等方式获得，有关它与其它大气物种的反应已经进行了许多研究，Bemand等在实验上研究了Cl，H，O与OClO的反应动力学，对于OBrO与H之间的反应目前尚未见实验研究的报道，只有Guhua等在理论上对部分XBrO2(X=H，Cl，Br)同分异构体进行了研究．     

Theoretical study of initiated reaction mechanism of polymerization of maleic anhydride catalyzed by OH−1 anion

A theoretical study of the polymerization reaction mechanism of maleic anhydride (MA) initiated by hydrate is presented. The reaction pathway has been studied with the density functional theory (DFT) method at the B3LYP/6‐311G** level. The geometrical parameters of transition states (TS) are optimized; intrinsic reaction coordinate (IRC) calculations have also been performed to obtain further credible features. Frequency analyses of all the stationary points are calculated at the same basis sets. The total energies of all geometries are corrected at second‐order Møller–Plesset (MP2)/6‐311G**. Calculation results reveal that the reaction mechanism is attributable to anion polymerization. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Theoretical Studies on the Abstraction Reaction of Atomic O（^3p） with Si2H6

The hydrogen abstraction reaction of O(^3P) with Si2H6 has been studied theoretially. Two transition states of ^3A″ and ^3A′ symmetries have been located for this abstraction reaction. Geometries have been optimized at the UMP2 leve with 6-311G (d) basis set. G3MP2 has been used for the final single-point energy calculation. The rate constants have been calculated over a wide temperature range of 200-3000K using canonical variational transition-state sheory (CVT) with small curvature tunneling effect(SCT). The calculated CVT/SCT rate constants match well with the experimental value.     

Theoretical Study on the Structure and Isomerization of CH_3SB

1 INTRODUCTION Solid boron and materials containing boron are po-tential excellent rocket fuel. Many studies arefocused in experiment and theory on the boroncompounds, among which simple boroncompound-HOB with simple structure can be readilyprepared. There are many reports on the experimentaland theoretical re- search results of the molecule aswell as unsaturated CH3NH=B and H2N=B exceptHOB. Very recently, some theoretical studies ofunsaturated CH3OB…