F+HC≡CH→HC≡C+HF反应的理论研究

在大气化学和燃烧历程的研究中，只含两个碳原子的碳氢化合物自由基的研究占有很重要的地位．乙炔与氟原子的反应是实验室制取HCZC·自由基的重要方法．因此乙炔与氟原子的反应在动力学研究中一直很受重视．乙炔与氟原子的反应存在有以下三种反应方式问：门抽取反应：F＋C。H。     

Photochemical Rearrangements of 6-Methoxymethylbicyclo[4.4.0]Dec-1-En-3-One and 6-Methoxymethylbicyclo[4.3.0]Non-1-En-3-One

The irradiation of the title compounds 6 and 12 in isooctane and benzene was investigated. The photochemical reactions took place sluggishly upon n→π^* excitation (λ > 300 nm) in deoxygenated solutions but more rapidly in the presence of air; deconjugation to yield β,γ-unsaturated ketones and lumiketone rearrangement were the main primary photochemical reactions. In contrast, intramolecular hydrogen abstraction by the C_α-carbon was the main reaction upon π→^* excitation (λ = 254 nm).     

Ab initio group contribution method for activation energies of hydrogen abstraction reactions.

The group contribution method for activation energies is applied to hydrogen abstraction reactions. To this end an ab initio database was constructed, which consisted of activation energies calculated with the ab initio CBS-QB3 method for a limited set of well-chosen homologous reactions. CBS-QB3 is shown to predict reaction rate coefficients within a factor of 2-4 and Arrhenius activation energies within 3-5 kJ mol(-1) of experimental data. Activation energies in the set of homologous reactions vary over 156 kJ mol(-1) with the structure of the abstracting radical and over 94 kJ mol(-1) with the structure of the abstracted hydrocarbon. The parameters required for the group contribution method, the so-called standard activation group additivity values, were determined from this database. To test the accuracy of the group contribution method, a large set of 88 additional activation energies were calculated from first principles and compared with the predictions from the group contribution method. It was found that the group contribution method yields accurate activation energies for hydrogen-transfer reactions between hydrogen molecules, alkylic hydrocarbons, and vinylic hydrocarbons, with the largest deviations being less than 6 kJ mol(-1). For reactions between allylic and propargylic hydrocarbons, the transition state is believed to be stabilized by resonance effects, thus requiring the introduction of an appropriate correction term to obtain a reliable prediction of the activation energy for this subclass of hydrogen abstraction reactions.     

F+CH_3OH碰撞反应机机理和反应势能面

以MP2（full）/6-311 + +g(d,p)水平上详细研究了氟原子与甲醇抽氢反应的 多通道反应机理，得到了各条通道中涉及的驻点的构型和振动频率及其能量，给出 了两张完整的反应势能面，结果表明，氟原子从C原子上抽氢时有一条明显的最低 能量通道，而从氧原子上抽氢时要涉及多条分支通道和多个驻点构型，给出了各分 支通道势能面示意图，结果表明以形成五元环状过渡态通道为优势通道，计算得到 经途径1生成CH_2OH时反应放热170.62kJ/mol，经分支途径6生成CH_3O自由基时反 应放热119.4 kJ/mol，此结果与实验值一致。     

Hydride abstraction of methylamine with Cu(S) in the gas phase: A density functional theory study

The gas-phase hydride abstraction of methylamine with Cu⁺(¹S) is theoretically investigated by using density functional theory. Geometries for all the stationary points involved are fully optimized at both the B3LYP/6-311++G(d,p) and B3LYP/6-311++G(3df,2p) levels and the reaction is analyzed in terms of the topology of potential energy surface. Approach of Cu⁺ towards methylamine could form either “classical” N or “nonclassical” η¹-methyl-H attached complex with the former being the global minimum. Both complexes are found to be key intermediates for the hydride abstraction, which could transfer into each other via two parallel routes, i.e., concerted metal movement and stepwise C-H activation-rearrangement. A charge-transfer process is detected for the “nonclassical” complex converting to a precursor species (CuH-NH₂CH₂⁺), which accounts for the final products by a nonreactive dissociation.     

Ab initio and density function theory computational studies of the CH4 + H → CH3 + H2 reaction

The activation barrier for the CH₄ + H → CH₃ + H₂ reaction was evaluated with traditional ab initio and Density Functional Theory (DFT) methods. None of the applied ab initio and DFT methods was able to reproduce the experimental activation barrier of 11.0-12.0 kcal/mol. All ab initio methods (HF, MP2, MP3, MP4, QCISD, QCISD(T), G1, G2, and G2MP2) overestimated the activation energy. The best results were obtained with the G2 and G2MP2 ab initio computational approaches. The zero-point corrected energy was 14.4 kcal mol⁻¹. Some of the exchange DFT methods (HFB) computed energies which were similar to the highly accurate ab initio methods, while the B3LYP hybrid DFT methods underestimated the activation barrier by 3 kcal mol⁻¹. Gradient-corrected DFT methods underestimated the barrier even more. The gradient-corrected DFT method that incorporated the PW91 correlational functional even generated a negative reaction barrier. The suitability of some computational methods for accurately predicting the potential energy surface for this hydrogen radical abstraction reaction was discussed.     

Halide abstraction as a route to cationic molybdenum(IV) compounds: Crystal and molecular structure of [CpMoCI(MeCN)4][SbCl6]2 · MeCN

Treatment of CpMoC1₃(MeCN)₂ with SbCl₅ in acetonitrile solution provides the solvated cationic series [CpMoCl₂(MeCN)₃]⁺, [CpMoCl(MeCN)₄]²⁺ and [CpMo(MeCN)₆]³⁺ as hexachloroantimon(V)ate salts following sequential halide abstraction. Characterization follows from microanalytical and spectroscopic (IR, and ¹H NMR) data and, in the case of [CpMoCl(MeCN)₄][SbCl₆]₂ · MeCN, by X-ray crystallographic studies. The structure is disordered but individual cations contain a six coordinated pseudo-octahedral metal geometry in which the cyclopentadienyl ligand (regarded as unidentate) and the chlorine atom occupy axial positions with an equatorial array of four acetonitrile ligands.     

Thermodecarbonylation of α-substituted cycloalkanones: a convenient one-carbon ring contraction method

A new and very convenient one-carbon ring contraction method is reported. Pyrolysis of α-substituted cycloalkanones at 600-650 °C under flow conditions produces the ring contracted compounds under loss of carbon monoxide. Substrates varying in ring size and nature of the α-substituent have been investigated.     

A Possible Reaction Channel from BrONO to BrNO2

A possible isomeriztion channel from BrONO( bromine nitrite) to BrNO2 (nitryl bromide) is predicted by means of MP2 and QCISD(T) (single-point) methods.The channel is a direct bromine abstraction reaction from BrONO molecule by NO2 in which the forward reaction barrier is 89.30 kJ/mol at final UQCISD(T)/6-311 G(2df)//UMP2/6-311G(d) level of theory with zero-point energies included,The result can explian the available experiments very well.     

多环芳烃与不饱和自由基氢提取反应类的动力学研究

对2~6个环的多环芳烃的氢提取反应类进行了系统研究, 提取氢原子的不饱和自由基包括丙炔基自由基（C₃H₃）、 烯丙基自由基（C₃H₅）、 丁二烯基自由基（nC₄H₅, iC₄H₅）、 环戊二烯基自由基（C₅H₅）以及苯基自由基（C₆H₅）. 采用M06-2X/cc-pVTZ方法得到了多环芳烃的电子结构信息, 利用过渡态理论并结合Eckart隧道校正, 计算了所有反应在500~2500 K范围内的反应速率常数.考察了多环芳烃的大小、 结构对反应速率常数的影响, 对比了不同氢提取自由基及不同氢提取反应类型的速率常数. 结果表明, 多环芳烃的大小对反应速率常数影响不大, 但是多环芳烃的环结构对反应速率常数影响较大. 将不同的氢提取反应类简化为发生在五元环上的C₅类和发生在六元环上的C₆类两类, 结果表明, C₆类的反应活性高于C₅类. 研究了nC₄H₅, iC₄H₅以及C₆H₅自由基与多环芳烃的氢提取反应, 它们的氢提取反应活性大小顺序为C₆H₅>nC₄H₅>iC₄H₅. 通过对每类典型反应的速率常数取平均值, 总结出相应类型的速率规则, 可用于构建多环芳烃和碳烟机理.