NH2(2B1)与C2H4反应机理的从头算研究

用从头算MP2方法,在6-311G**基组下,对NH2 2B1)与C2H4的加成和氢迁移反应机理进行了研究,优化得到反应的过渡态,并通过振动分析和内禀反应坐标(IRC)加以证实.计算了两个反应的能垒和1500K～2000K温度范围内的速率常数.结果表明:在1500K～2000K温度范围内加成反应是NH2(X 2B1)与C2H4的反应的主要通道,同时报道了两个反应沿反应路径变化信息.     

C4H（2Σ+）+H2反应机理的直接动力学研究

贫氢分子CnH是燃烧火焰、行星大气中的重要的中间体.这些分子与其它一些分子或自由基的反应在星际化学中起着非常重要的作用.虽然这些分子的电子结构和光谱性质已经进行了广泛的研究,但是研究这些反应的机理和动力学性质也是亟需的.因此,我们采用直接动力学方法对线性分子丁二炔自由基C4H(CCCCH)夺氢气(H2)分子中HAT的反应的微观机理和动力学性质进行了理论研究.本研究分别在BB1K/6-311+G(2d,2p),B3LYP/6-311+G(2d,2p)和M06-2x/6-311+G(2d,2p)水平上优化得到了各稳定点的结构及振动频率.为了得到更为可靠的反应能量和势能面信息,在BB1K/6-311+G(2d,2p)优化结构的基础上用CCSD(T)/aug-cc-pVTZ水平进行了单点能量校正.对于此反应研究了两条不同的氢吸附通道,C4H(C1C2C3C4H)中的C1和C4分别吸氢,即通道1(R1)和通道2(R2).计算得出:通道1和通道2的能垒分别为3.58 kcal/mol和26.56 kcal/mol,结果表明C4H中C1端吸氢是主要通道.反应过程中的电子转移可以为理解氢原子转移(HAT)提供重要的线索,因此,我们利用NBO对反应过程中的电子转移行为进行了详细的分析.本工作运用经典过渡态理论(VTST)与变分过渡态理论(CVT)和变分过渡态理论结合小曲率隧道效应校正(CVT/SCT)的方法计算了该反应在40～1000 K温度区间的速率常数.除对于最低频率的配分函数采用了阻尼内转动近似外,其它频率都采用谐振子模型处理.计算得到的总的CVT/SCT反应速率常数与已有的实验值符合得很好.我们还提供了40～1000K温度范围内的三参数Arrhenius表达式.这些公式有利于今后在较宽的温度范围内迄今没有实验数据的反应的研究.     

H原子与CH3NH2抽氢反应的动力学计算

用QC ISD(T)/6-311 G(3DF,3PD)/MP2/6-311G(D,P)方法研究了H原子与CH3NH2的抽氢反应过程。该反应包含两个反应通道:H分别从CH3基团(R1)和NH2(R2)基团上抽氢。R1势垒比R2势垒低3.42kJ/mol,表明R1是主反应通道。在从头算的基础上,用变分过渡态理论(CVT)加小曲率隧道效应(SCT)研究了各反应温度范围为200~4000K内的速率常数,所得结果与实验值符合的很好。动力计算表明,在所研究的温度范围内,变分效应对速率常数的计算影响不大,而在低温范围内,隧道效应起了很重要的作用。     

C_2H_3与C_2H_5OH和CH_3HCO间的脱氢反应对乙醇-碳氢混合燃料燃烧过程的影响

在QCISD(T)/6-311++G(d,p)//B3LYP/6-311G(d,p)的水平下计算了乙醇及乙醇燃烧裂解产物与C2H3之间的脱氢反应机理,利用正则变分过渡态理论(CVT)结合小曲率隧道效应模型(SCT)计算400~2000 K范围内的速率,对比OH,H及CH3等自由基相似脱氢反应速率,选择2条具有较快反应速率的通道(C2H3+C2H5OH→TS1→C2H4+C2H5O和C2H3+CH3HCO→TS4→C2H4+CH3CO).将这2个反应耦合到正庚烷/乙醇混合燃料及异辛烷/乙醇混合燃料的机理中,利用CHEMKIN程序中预混火焰模型模拟混合燃料的燃烧过程并进行路径分析.对比相应的实验数据发现,改进的动力学模型对燃烧过程中C2H3路径上相近组分的预测精度有较大改善,而对C2H3路径上较远的组分丙炔(C3H4)和乙烯基乙炔(C4H4)等影响不大.     

C_2(a~3Π_u)自由基与若干不饱和碳氢化合物反应的温度效应

运用脉冲激光光解-激光诱导荧光(PLP-LIF)的方法研究了C2(a3Πu)自由基与若干不饱和碳氢化合物(C2H4(k1),C2H2(k2),C3H6(k3)和2-C4H8(k4))气相反应的温度效应.在298-673 K的温度范围内,获得了这些反应的双分子反应速率常数.获得的速率常数可以用Arrhenius公式表达如下:k1(T)=(4.53±0.05)×10-11exp[(196.41±5.20)/T],k2(T)=(3.94±0.04)×10-11exp[(143.04±4.28)/T],k3(T)=(7.96±0.17)×10-11exp[(185.10±8.86)/T],k4(T)=(1.04±0.02)×10-10exp[(180.34±7.67)/T],误差为±2σ.由获得的双分子反应速率常数及其所呈现的负温度效应,在298-673 K温度范围内,C2(a3Πu)自由基和这些不饱和碳氢化合物的反应遵循加成机理.     

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.     

Ind2ZrCln(OC6H3-3,5-Me2)2-n/一氯二乙基铝催化乙烯齐聚的研究

合成了 Ind2 Zr(OC6 H3- 3,5 - Me2 ) 2 (A)、 Ind2 Zr Cl(OC6 H3- 3,5 - Me2 ) (B)和 Ind2 Zr Cl2 (C) 3个化合物 ,并在不同反应温度、陈化温度、反应时间等条件下 ,分别考察了每个化合物与 Et2 Al Cl所组成的催化体系对乙烯齐聚活性和选择性的影响 .在相同条件下 ,催化剂活性顺序为 A>B>C;在最佳反应条件下 ,Ind2 Zr(OC6 H3- 3,5 - Me2 ) 2的催化活性为 195 1g齐聚物 / (g Zr· h) ,C4～ 1 0 烯烃选择性为 95 .0 % ,1- C4～ 1 0 =(直链 α-烯烃 )选择性为 85 .5 % .     

CH3CH2S自由基H迁移异构化及裂解反应的理论研究

采用密度泛函方法(B3LYP)在6-311+G(d,p)基组水平上研究了CH3CH2S自由基H迁移异构化以及裂解反应的微观动力学机理. 在QCISD(T)/6-311++G(d,p)//B3LYP/6-311+G(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)分别计算了在200~2000 K温度区间内的速率常数kTST和kCVT, 同时获得了经小曲率隧道效应模型(SCT)校正后的速率常数kCVT/SCT. 研究结果表明, CH3CH2S自由基1,2-H迁移、1,3-H迁移、C—C键断裂和β-C—H键断裂反应的势垒ΔE≠分别为149.74, 144.34, 168.79和198.29 kJ/mol. 当温度低于800 K时, 主要发生1,2-H迁移反应, 高于1800 K时, 主要表现为C—C键断裂反应, 在1300—1800 K范围内, 1,3-H迁移反应是优势通道, 在计算的整个温度段内, β-C—H键断裂反应可以忽略.     

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.     

新型磷-钒-氧层状化合物[H2en]2[H3O]6[Co(H2O)2(VO)8(OH)4(PO4)8]的水热合成与晶体结构

金属磷酸盐材料在吸附、离子交换、离子传导和催化剂方面有潜在的应用前景[1～5]. 近年来, 通过水热反应合成了一些A-V-P-O化合物. 在这些化合物中, A一般为碱金属或有机阳离子, 如层状结构的[H2N(C4H8)2NH2][(VO)4(OH)4(PO4)2][6] 和[H2N(C2H4)3NH2][(VO)8(HPO4)3(PO4)4*(OH)2]*2H2O[6], 一维链状结构的 [H2NCH2CH2NH3(VO)(PO4)][7], 手性双螺旋结构的 [(CH3)2NH2]K4[(VO)10(H2O)2(OH)4(PO4)7]*H2O[8]以及具有三维骨架结构的化合物 [H3N(CH2)3NH3K(VO)3(PO4)3][9], [H3N(CH2)3NH3]2[V(H2O)2(VO)6(OH)2(HPO4)3(PO4)5]*3H2O[10]和[H3N(CH2)2NH3][(VO)3(H2O)2(PO4)2(HPO4)4][11].     

A product branching ratio controlled by vibrational adiabaticity and variational effects: kinetics of the H + trans-N2H2 reactions

The abstraction and addition reactions of H with trans-N(2)H(2) are studied by high-level ab initio methods and density functional theory. Rate constants were calculated for these two reactions by multistructural variational transition state theory with multidimensional tunneling and including torsional anharmonicity by the multistructural torsion method. Rate constants of the abstraction reaction show large variational effects, that is, the variational transition state yields a smaller rate constant than the conventional transition state; this results from the fact that the variational transition state has a higher zero-point vibrational energy than the conventional transition state. The addition reaction has a classical barrier height that is about 1 kcal∕mol lower than that of the abstraction reaction, but the addition rates are lower than the abstraction rates due to vibrational adiabaticity. The calculated branching ratio of abstraction to addition is 3.5 at 200 K and decreases to 1.2 at 1000 K and 1.06 at 1500 K.     

Theoretical studies on cycloaddition reactions between 2-azoniaallene cations and olefins

The mechanisms of cycloaddition reactions between 2-azoniaallene cations and olefins have been explored at the B3LYP/6-31G level. It is found that the positive charge in 2-azoniaallene makes the reaction more complicated. For the reactions between olefins with Cl groups or CH(3) groups and 2-azoniaallene, the typical carboniums have been located along the reaction path. In addition, for the reactions between 1,1-dimethylethene and 1,3-dichrolo-2-azoniaallene, different paths and products have been rationalized and verified.     

CHF2CH3(HFC-152a)与F反应的反应途径及反应速率常数研究

本文用从头计算法(UMP2/6-31G)对氟与二氟乙烷的与1位、2位碳相连的氢的抽提氢反应进行研究。CHF2CH3+F→CF2CH3+HF(R1), CHF2CH3+F→CHF2CH2+HF(R2)。在内禀反应坐标(IRC)的势能剖面基础上用传统过渡态、变分过渡态理论计算了上述两个反应的速率常数及比值, 获得了与实验相一致的结果。     

NCO自由基与SO2、CS2反应的速率常数

利用波长为266 nm的激光光解CHBr3产生CH自由基,其与NO反应作为NCO自由基的来源.在298 K,总压2660 Pa的条件下,采用激光诱导荧光的方法,研究了NCO自由基与SO2、CS2的反应.得到了NCO自由基与SO2、CS2双分子反应速率常数分别为（1.8±0.3）×10－11和（3.1±0.4）×10－12 cm3•molecule－1•s－1.对这两个反应在B3LYP/6-31＋G(d)的水平上进行理论研究的结果表明,NCO自由基与SO2、CS2的反应是加成反应,其机理是NCO自由基中的N原子攻击反应物的中心原子,得到加成产物.     

Effects of a single water molecule on the OH + H2O2 reaction

The effect of a single water molecule on the reaction between H(2)O(2) and HO has been investigated by employing MP2 and CCSD(T) theoretical approaches in connection with the aug-cc-PVDZ, aug-cc-PVTZ, and aug-cc-PVQZ basis sets and extrapolation to an ∞ basis set. The reaction without water has two elementary reaction paths that differ from each other in the orientation of the hydrogen atom of the hydroxyl radical moiety. Our computed rate constant, at 298 K, is 1.56 × 10(-12) cm(3) molecule(-1) s(-1), in excellent agreement with the suggested value by the NASA/JPL evaluation. The influence of water vapor has been investigated by considering either that H(2)O(2) first forms a complex with water that reacts with hydroxyl radical or that H(2)O(2) reacts with a previously formed H(2)O·OH complex. With the addition of water, the reaction mechanism becomes much more complex, yielding four different reaction paths. Two pathways do not undergo the oxidation reaction but an exchange reaction where there is an interchange between H(2)O(2)·H(2)O and H(2)O·OH complexes. The other two pathways oxidize H(2)O(2), with a computed total rate constant of 4.09 × 10(-12) cm(3) molecule(-1) s(-1) at 298 K, 2.6 times the value of the rate constant of the unassisted reaction. However, the true effect of water vapor requires taking into account the concentration of the prereactive bimolecular complex, namely, H(2)O(2)·H(2)O. With this consideration, water can actually slow down the oxidation of H(2)O(2) by OH between 1840 and 20.5 times in the 240-425 K temperature range. This is an example that demonstrates how water could be a catalyst in an atmospheric reaction in the laboratory but is slow under atmospheric conditions.     

2,4-二氯苯氧乙酸代谢中的水解反应机理

2,4-二氯苯氧乙酸(2,4-D)是应用广泛的农用除草剂和植物生长素,在它的代谢过程中,涉及多种化学反应. 本文采用密度泛函理论B3LYP方法, 分别研究了它在代谢过程中的三条水解反应途径的机理. 研究结果表明: (I) 2,4-D水解反应有两种模式, C(1)―O键解离的氢转移和C―Cl键解离的氯被取代. (Ⅱ) C―Cl键的解离能垒明显低于C(1)―O键的解离能垒, 即水解速率较快, 反应动力学占优势. 在三条反应途径中, 途径(2)和(3)优先水解C―Cl键, 再水解C(1)―O键. 由于受反应速率的影响, 不同中间体在降解过程中的浓度有明显区别.(III) 对于水解反应,采用导体极化连续模型(CPCM)考虑溶剂化效应,可更合理地阐述水解反应机理.     

Theoretical study of the reactions CF3CH2OCHF2 + OH/Cl and its product radicals and parent ether(CH3CH2OCH3) with OH

A dual-level direct dynamic method is employed to study the reaction mechanisms of CF3CH2OCHF2 (HFE-245fa2; HFE-245mf) with the OH radicals and Cl atoms. Two hydrogen abstraction channels and two displacement processes are found for each reaction. For further study, the reaction mechanisms of its products (CF3CH2OCF2 and CF3CHOCHF2) and parent ether CH3CH2OCH3 with OH radical are investigated theoretically. The geometries and frequencies of all the stationary points and the minimum energy paths (MEPs) are calculated at the B3LYP/6-311G(d,p) level. The energetic information along the MEPs is further refined at the G3(MP2) level of theory. For reactions CF3CH2OCHF2 + OH/Cl, the calculation indicates that the hydrogen abstraction from --CH2-- group is the dominant reaction channel, and the displacement processes may be negligible because of the high barriers. The standard enthalpies of formation for the reactant CF3CH2OCHF2, and two products CF3CH2OCHF2 and CF3CHOCHF2 are evaluated via group-balanced isodesmic reactions. The rate constants of reactions CF3CH2OCHF2 + OH/Cl and CH3CH2OCH3 + OH are estimated by using the variational transition state theory over a wide range of temperature (200-2000 K). The agreement between the theoretical and experimental rate constants is good in the measured temperature range. From the comparison between the rate constants of the reactions CF3CH2OCHF2 and CH3CH2OCH3 with OH, it is shown that the fluorine substitution decreases the reactivity of the C--H bond.     

F2＋2HI=2HF＋I2反应机理的研究

根据氯离子型层状复合氢氧化物(LDH-Cl)制备过程中溶液浓度变化的监测结果和不同反应进程时产物的EDS、IR、XRD、TEM、TG-DTA表征结果,研究了合成LDH-Cl的共沉淀反应动力学特征及机理.实验结果表明, LDH-Cl的生成符合多核层表面反应动力学模型;反应过程中LDH的晶胞参数c从2.421 nm变为2.399 nm,通道高度h由0.3321 nm减小为0.3228 nm,粒子直径Da由6.40 nm增大为15.16 nm, Dc由7.43 nm增大到10.93 nm,纵横比由0.86增大为1.39; IR和TG-DTA特征变化表明了层板对阴离子作用的强度和层板的结构稳定性随反应进程而提高.     

An ab initio study on thermal rearrangement reactions of 1-silylprop-2-en-1-ol H3SiCH(OH)CH=CH2

The thermal rearrangement reactions of 1-silylprop-2-en-1-ol H3SiCH(OH)CH=CH2 were studied by ab initio calculations at the G2(MP2) and G3 levels. The reaction mechanisms were revealed through ab initio molecular orbital theory. On the basis of the MP2(full)/6-31G(d) optimized geometries, harmonic vibrational frequencies of various stationary points were calculated. The reaction paths were investigated and confirmed by intrinsic reaction coordinate (IRC) calculations. The results show that the thermal rearrangements of H3SiCH(OH)CH=CH2 happen in two ways. One is via the Brook rearrangement reactions (reaction A), and the silyl group migrates from carbon atom to oxygen atom passing through a double three-membered ring transition state, forming allyloxysilane CH2=CHCH2OSiH3. In the other, the reactant undergoes a dyotropic rearrangement; the hydroxyl group migrates from carbon atom to silicon atom coupled with a simultaneous migration of a hydrogen atom from silicon atom to carbon atom, forming allylsilanol CH2=CHCH2SiH2OH (reaction B). The barriers for reactions A and B were computed to be 343.5 and 203.7 kJ/mol, respectively, at the G3 level. The changes of the thermodynamic functions, entropy (DeltaS), entropy (DeltaS(doubledagger)) for the transition state, enthalpy (DeltaH), and free energy (DeltaG) were calculated by using the MP2(full)/6-31G(d) optimized geometries, and harmonic vibrational frequencies of reactants, transition states, and products with statistical mechanical methods, and equilibrium constant K(T) and reaction rate constant k(T) in canonical variational transition-state theory (CVT) with centrifugal-dominant small-curvature tunneling approximation (SCT) were calculated over a temperature range 400-1300 K. The conventional transition-state theory (TST) rate constants were also calculated for the purposes of comparison. The influences of the vinyl group attached to the center carbon of the alpha-silyl alcohols on reactions were discussed.