密度泛函理论研究SiN与ClO反应的产物通道

利用量子化学从头算和密度泛函理论研究了SiN和ClO的反应机理。在B3LYP/6-311++G(d,p)水平上优化得到了反应势能面上各驻点的几何构型;通过频率分析和内禀反应坐标计算对过渡态与反应物和产物的连接关系进行确认。在CCSD(T)/cc-pVTZ水平上对各物种的能量进行校正,得到了反应势能面。计算结果表明,该反应体系存在单态和三态势能面,其中单态势能面上反应通道(1)和(2)是主反应通道,1P4为主产物。     

氧与次溴酸反应理论研究

用密度函数理论(DFT)对氧原子与次溴酸HOBr在势能面上的反应进行了研究,用B3LYP方法计算了势能面上各驻点物种的参数、能量等.结果表明:O与HOBr在势能面上有两个通道,简单可概括为摘H和摘Br反应,两通道的产物相同,均为HO、BrO.计算出反应热为42.3kJ/mol,根据等链反应特点,得到HOBr的生成热为-41.4kJ/mol.     

OH-与CH2CIF反应的阴离子产物通道

理论研究了羟基负离子(OH-)与氟氯代甲烷(CH2CIF)反应的阴离子产物通道.分别在B3LYP/6-31+G(d,p)和B3LYP/6-311++G(2d,p)水平上得到反应势能面上各关键物种的优化构型,进而计算得到谐振频率和零点能.基于CCSD(T)/6-311+G(3df,3dp)水平的相对能量,描述了由质子转移和双分子亲核取代(SN2)过程生成各阴离子产物的途径.各阴离子产物途径势垒的计算结果表明质子转移过程是实验中的主要产物通道,与以往实验测量的结论相符.此外,计算还显示双分子亲核取代过程得到了非典型的阴离子产物,其中动力学效应可能会导致F-的生成.     

FOX-12制备过程的反应机理及动力学

采用量子化学计算方法, 在B3LYP/6-311G(d,p)水平上研究了N-脒基脲二硝基酰胺盐(FOX-12)制备过程的反应机理. 优化得到了反应势能面上各稳定点的几何构型, 通过内禀反应坐标(IRC)确认了反应物、 中间体、 过渡态及产物之间的相关性. 为了得到更可靠的反应能量和势能面信息, 进一步在MP2/6-311++G(3df,3pd)水平上对得到的构型进行能量校正, 结果表明, 先取代磺酸基通道(A1)和先取代氢通道(B)都能生成二硝基酰胺酸(HDN), 其中通道A为主反应通道; HDN可以通过HDN→FOX-12与HDN→ADN→FOX-12 两种途径转化为目标产物FOX-12, 而第2种途径为较优途径. 应用经典过渡态理论(TST)与变分过渡态理论(CVT)以及小曲率隧道效应模型校正的变分过渡态理论(CVT/SCT)计算了在200~400 K范围内各反应通道相关基元反应的速率常数, 提供了在上述温度区间内的三参数Arrhenius关系式.     

单重态二溴卡宾和甲醛环加成反应的量化研究

采用量子化学密度泛函理论,研究了单重态二溴卡宾和甲醛环加成反应的机理.在B3LYP/6-31G*基组水平上,优化得到了反应途径上反应物、过渡态、中间体和产物的几何构型;计算并考察了四种可能反应途径势能面上各驻点的构型参数、振动频率和能量;通过振动分析对过渡态和中间体构型进行了确认.计算结果表明,二溴卡宾和甲醛反应有四条反应通道,其中c反应通道(即0°-0°型)控制步骤的活化能仅为13.7 kJ·mol－1,反应容易进行.     

HBr与HONO反应机理的量子化学研究

采用密度泛函理论和耦合簇理论等方法,研究了HBr与HONO的反应机理.在6-311G(d,p)基组水平上,对反应势能面上的反应物、中间体、过渡态和产物的构型进行了几何结构优化.通过内禀反应坐标(IRC)确认了反应物、过渡态、中间体和产物之间的相关性.利用CCSD(T)和QCISD(T)方法计算了各分子单点能量,计算结果表明,HBr与HONO的主要反应通道为HBr+tran-HONO→tran-IM1→tran-TS1→IM2→P1,其主要产物为H_2O和BrNO.     

HOSO+NO反应的机理及动力学

在B3LYP/6-311++G(d,p)水平上研究了HOSO+NO的反应机理. 优化得到了反应势能面上各驻点的几何构型, 通过内禀反应坐标(IRC)确认了反应物、中间体、过渡态和产物的相关性. 在CCSD(T)/6-311++G(d,p)水平上对计算得到的构型进行了能量校正. 应用经典过渡态理论(TST)与变分过渡态理论(CVT), 并结合小曲率隧道(SCT)效应模型校正的方法计算了标题反应在200-3000 K温度范围内的速率常数k^TST、k^CVT和k^CVT/SCT. 计算结果表明: HOSO+NO反应在单重态和三重态条件下均可发生, 其中单重态反应为主反应通道, HNO+SO₂为主产物. 并利用电子密度拓扑分析方法研究主反应通道反应过程中的化学键变化.     

HO_2+NO气相反应机理及主通道速率常数的理论研究

采用CCSD(T)/aug-cc-p VTZ//MP2/aug-cc-p VTZ方法构建了HO_2+NO反应的单、三重态反应势能剖面.研究结果表明,标题反应在单、三重态均存在3条反应通道,分别经抽氧、加成和抽氢反应生成产物NO_2+OH、HNO_3和HNO+O_2.其中抽氧、加成反应的优势通道发生在单重态势能面上(通道R1和R2),而抽氢的优势通道则发生在三重态势能面上(通道R6).利用经典过渡态理论(TST)并结合Wigner矫正模型在200K~1500K温度范围内计算了优势通道R1,R2和R6的速率常数kTST/W.结果显示,在计算温度范围内抽氧、加成反应的通道R1和R2始终存在竞争,且抽氢反应通道R6在高温区500K~1500K竞争作用也逐渐显现,但抽氧通道R1分支比始终大于81%,具有绝对优势.     

CH3SH与NO2的反应机理及动力学

在G3B3,CCSD(T)/6-311++G(d,p)//B3LYP/6-311++G(d,p)水平上详细研究了CH3SH与基态NO2的微观反应机理.在B3LYP/6-311++G(d,p)水平得到了反应势能面上所有反应物、过渡态和产物的优化构型,通过振动频率分析和内禀反应坐标(IRC)跟踪验证了过渡态与反应物和产物的连接关系.在CCSD(T)/6-311++G(d,p)和G3B3水平计算了各物种的能量,得到了反应势能面.利用经典过渡态理论(TST)与变分过渡态理论(CVT)并结合小曲率隧道效应模型(SCT),分别计算了在200～3000K温度范围内的速率常数kTST,kCVT和kCVT/SCT.研究结果表明,该反应体系共存在5个反应通道,其中N进攻巯基上H原子生成CH3S+HNO2的通道活化势垒较低,为主要反应通道.动力学数据也表明,该通道在200～3000K计算温度范围内占绝对优势,拟合得到的速率常数表达式为k1CVT/SCT=1.93×10-16T0.21exp(-558.2/T)cm3·molecule-1·s-1.     

OH-与CH2ClF反应的阴离子产物通道

理论研究了羟基负离子(OH^-)与氟氯代甲烷(CH₂ClF)反应的阴离子产物通道. 分别在B3LYP/6-31+G(d,p)和B3LYP/6-311++G(2d,p)水平上得到反应势能面上各关键物种的优化构型, 进而计算得到谐振频率和零点能. 基于CCSD(T)/6-311+G(3df,3dp)水平的相对能量, 描述了由质子转移和双分子亲核取代(S_N2)过程生成各阴离子产物的途径. 各阴离子产物途径势垒的计算结果表明质子转移过程是实验中的主要产物通道, 与以往实验测量的结论相符. 此外, 计算还显示双分子亲核取代过程得到了非典型的阴离子产物, 其中动力学效应可能会导致F^-的生成.     

Ru(II)催化有机叠氮与炔反应机理的理论研究

采用密度泛函理论, 对在Ru(II)催化剂存在下, 有机叠氮化合物和末端炔的反应机理作了深入理论研究. 在B3LYP/LANL2DZ水平上, 对该反应体系中势能面各驻点的几何构型进行了全优化计算, 并经振动频率分析确定了过渡态和中间体, 通过内禀反应坐标(IRC)的计算, 确认了反应物、中间体、过渡态和产物的相关性. 对多个反应通道的协同反应以及分步反应进行了研究. 结果表明: 协同反应通道Ic和分步反应通道IIc是反应能垒较低的反应通道, 活化自由能较其它反应通道低, 有利于1,5-二取代1,2,3-三唑的生成, 具有特定的区域选择性, 与实验结果吻合.     

CH3CH2+O(3P)反应机理的理论研究

The reaction for CH3CH2+O(3P) was studied by ab initio method. The geometries of the reactants, intermediates, transition states and products were optimized at MP2/6-311+G(d,p) level. The corresponding vibration frequencies were calculated at the same level. The single-point calculations for all the stationary points were carried out at the QCISD(T)/6-311+G(d,p) level using the MP2/6-311+G(d,p) optimized geometries. The results of the theoretical study indicate that the major products are the CH2O＋CH3, CH3CHO+H and CH2CH2+OH in the reaction. For the products CH2O＋CH3 and CH3CHO+H, the major production channels are A1: (R)→IM1→TS3→(A) and B1: (R)→IM1→TS4→(B), respectively. The majority of the products CH2CH2+OH are formed via the direct abstraction channels C1 and C2: (R)→TS1(TS2)→(C). In addition, the results suggest that the barrier heights to form the CO reaction channels are very high, so the CO is not a major product in the reaction.     

硝酸溴与三重态氧原子反应机理的密度泛函研究

The theoretic study of reaction between BrONO2 and O(3P) is reported by using the molecular orbital ab initio and density function theory (DFT). Equilibrium structural parameters, harmonic vibrational frequencies, total energy and zero energy of reactants, transition states, inter mediates and products during reactions are computed by B3LYP theory level with the basis set 6-311+G(d,p). The transition states and inter mediates of the reaction are verified by frequency analysis, and the relation ship of reactants, transition states, intermediates and products is affirmed by Intrinsic Reaction Coordinate(IRC) calculation. The activation energy of the reaction has also been calculated. Based on the optimized structure, the single point energy of all species is obtained by CCSD(T) with the basis set 6-311+G(d,p). The results show that there are three exothermic channels and their corresponding products are: cis-Br ONO + 3O2, trans-BrONO + 3O2 and BrOO+NO2. The activation energy of three channels is 91.58, 101.25, 51.17kJ/mol under B3LYP and 141.19, 148.39, 103.21 kJ/molunder CCSD(T) theory level. The third channel is the dominant channel.     

多通道反应O(3P)＋CH2F的理论研究

用密度泛函理论研究了氧原子与氟代甲基自由基的反应.反应中出现的所有物种的平衡构型用B3LYP方法在6-311＋＋G（2d, 2p）基组水平上进行了优化，同时对各物种进行了频率分析；在同一理论水平上计算了各反应通道的势能面变化，分析了反应物、中间体、过渡态、产物的振动模式随反应途径的变化关系，阐明了该多通道反应的反应机理.     

N(4S)+CH3X(X=Cl、Br)反应机理的理论研究

The reaction of N(4S)+CH3X(X=Cl、Br) was studied by the ab initio method. The geometries of the reactants, transition states and products were optimized at the MP2/6-311+G(d,p) level. The corresponding vibration frequencies were calculated at the same level. The single-point calculations for all the stationary points were carried out at the MP2/6-311++G(3df,2p) and the QCISD(T)/6-311+G(d,p) levels using the MP2/6-311+G(d,p) optimized geometries. The energies of all the stationary points were calculated by the G2MP2 method. The results of this theoretical study indicate that the reaction has three reaction channels: H abstraction reaction channel a, Cl or Br abstraction reaction channel b and substitution reaction channel c. For the N(4S)+CH3Cl reaction, reaction channel a is the main reaction channel. Reaction channels b and c may have a slight contribution in the reaction. For the N(4S)+CH3Br reaction, reaction channel a is the main reaction channel. Reaction channels b and c may have some contribution in the reaction.     

SiH3与NO2反应机理的理论研究

The reaction between silyl radicals and nitric oxide was studied by using the B3LYP/6 311G and the high-level electron-correlation CCSD(T)/6-311G methods. The geometries for reactants, the transition states and the products were completely optimized. All the transition states are verified by the vibrational analysis and the intrinsic reaction coordinate (IRC) calculations. The results show that the reaction is via multi-channel and multi-step. Five products may be formed via the complex reaction channels, i.e. association, H-shift and dissociation.     

CH3CHF自由基与HNCO反应机理的理论

采用密度泛函理论的B3LYP方法, 在6- 311++G(d, p)基组水平上研究了CH3CHF自由基与HNCO的微观反应机理, 优化了反应过程中的反应物、中间体、过渡态和产物, 在QCISD(T)/6- 311++G(d, p)水平上计算体系在反应通道各驻点的能量. 振动分析结果和IRC分析结果证实了中间体和过渡态的真实性, 计算所得的成键临界点电荷密度变化也确认了该反应过程, 并找到了七条反应通道. 其中生成氟代烷基酰亚胺稳定分子的通道活化能垒最低, 在该反应体系中是与氢迁移平行竞争较易发生的一条反应通道.     

Thermochemical and kinetic analyses on oxidation of isobutenyl radical and 2-hydroperoxymethyl-2-propenyl radical

In recognition of the importance of the isobutene oxidation reaction in the preignition chemistry associated with engine knock, the thermochemistry, chemical reaction pathways, and reaction kinetics of the isobutenyl radical oxidation at low to intermediate temperature range were computationally studied, focusing on both the first and the second O2 addition to the isobutenyl radical. The geometries of reactants, important intermediates, transition states, and products in the isobutenyl radical oxidation system were optimized at the B3LYP/6-311G(d,p) and MP2(full)/6-31G(d) levels, and the thermochemical properties were determined on the basis of ab initio, density functional theory, and statistical mechanics. Enthalpies of formation for several important intermediates were calculated using isodesmic reactions at the DFT and the CBS-QB3 levels. The kinetic analysis of the first O2 addition to the isobutenyl radical was performed using enthalpies at the CBS-QB3 and G3(MP2) levels. The reaction forms a chemically activated isobutenyl peroxy adduct which can be stabilized, dissociate back to reactants, cyclize to cyclic peroxide-alkyl radicals, and isomerize to the 2-hydroperoxymethyl-2-propenyl radical that further undergoes another O2 addition. The reaction channels for isomerization and cyclization and further dissociation on this second O2 addition were analyzed using enthalpies at the DFT level with energy corrections based on similar reaction channels for the first O2 addition. The high-pressure limit rate constants for each reaction channel were determined as functions of temperature by the canonical transition state theory for further kinetic model development.