自由基HO2与C2H2反应势能面的理论研究

应用量子化学从头计算和密度泛函理论(DFT)对HO2+C2H2反应体系的反应机理进行了研究.在B3LYP/6-311G**和CCSD(T)/6-311G**水平上计算了HO2+ C2H2反应的二重态反应势能面.计算结果表明,主要反应方式为自由基HO2的H原子和C2H2分子中的C原子结合,经过一系列异构化,最后分解得到主要产物P1 (CH2O+ HCO).此反应是放热反应,化学反应热为-321.99 kJ·mol-1.次要产物为P2 (CO2 +CH3),也是放热反应.     

Studies on the Reaction Mechanism of Br2 ＋ I2 = 2IBr

1 INTRODUCTION Interhalogen compounds have played an impor- tant role in environment and chemical engineering production. During the course of ozone exhaustion induced by sunlight in polar region, Br2, BrCl and HOBr are all precursors of Br atom[1]. Lately, scien- tists have detected that the content of BrCl in polar region sunlight was 35 ppt, larger than that of Br2 (25 ppt). Previous studies suggested that the con- centration of BrCl and O3 exhibits obvious negative correlation: w…     

Theoretical and Experimental Studies on the Reaction Mechanism of Cl2 ＋ I2- 2ICl

1 INTRODUCTION The reactions between halogen and halogen are basic reactions in chemistry. Especially, in the syn- thesis of iodo-substituted aromatic hydrocarbon, the reaction Cl2 I2 = 2ICl could heighten the usage of iodine atom to 100%. So far, to the best of our know- ledge, the studies about halogen-halogen reaction mechanisms are very few. In detail, only the struc- ture and stability studies of X2Y- (X, Y = Cl, Br and I) ions by calculating reaction potential energy sur- face…     

One-pot synthesis of 2-(quinoxalin-2-yl)benzoate through NBS-mediated sequential reaction of 2-alkynylbenozate and aryl-1,2-diamine

A metal-free route involving a sequential reaction of 2-alknylbenzoate and aryl-1,2-diamine is described for the generation of 2-(quinoxalin-2-yl)benzoate. The sequential reaction combines NBS-mediated diketonization of 2-alknylbenzoate and condensation reaction with aryl-1,2-diamine, and proceeds smoothly under mild reaction conditions and an array of 2-(quinoxalin-2-yl)benzoate is achieved with high efficiency and excellent functional group tolerance. Mechanism studies indicate oxygen transfer reaction is observed and water is incorporated into neighboring ester group.     

Br2+Cl2=2BrCl反应机理的理论和实验研究

用(U)MP2方法, 取6-311G*基组, 研究了反应Br2+Cl2=2BrCl的机理, 求得四中心和三中心的过渡态, 通过比较反应通道的活化能的大小, 得到如下结论: 双分子基元反应的最小活化能小于Cl2和Br2的离解能, 在没有光引发的条件下, 标题反应将以分子与分子作用形式完成; 若有光引发, Br2或Cl2先解离成原子, 再经过Br原子与Cl2反应或Cl原子与Br2反应, 能较快完成标题反应. 分别测定了光照和避光两种条件下的反应体系在412 nm处吸光度的变化, 证实了理论研究的结果.     

CIONO2与O(3P)的反应机理

采用密度泛函方法Ｂ３ＬＹＰ／６－３１Ｇ＾＊研究了反应Ｏ（＾３Ｐ）＋ＣｌＯＮＯ２→ＣｌＯ＋ＮＯ３反应Ｏ（＾３Ｐ）＋ＣｌＯＮＯ２→Ｏ２＋ＣｌＯＮＯ的反应机。该结果与大部分实验者的推论是一致的,对于后一反应,其两种反应途径的活化势垒较为相近,表明两种反应途径均是可能的。     

氯固相合成Ti-ZSM-5催化苯乙烯环氧化对映选择性 的研究

用TiCl~4气固相同晶取代法制得的Ti-ZSM-5作催化剂。研究了以H~2O~2为氧化剂氧化苯乙烯生成环氧苯乙烷的对映选择性,发现生成的环氧苯乙烷主要以R构型为主。考察了反应时间,反应温度,催化剂Ti-ZSM-5以及氧化剂[w(H~2O~2)=30%]的用量等反应条件对苯乙烯环氧化反应对映性的影响。结果表明,反应温度是影响环氧化反应对映选择性的重要因素,降低反应温度有利于提高对映选择性(ee),当反应温度≤40℃时,ee值可达100%;而反应时间,催化剂及氧化剂[w(H~2O~2)=30%]用量对环氧化反应的对映选择性几乎没有影响。     

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…     

Pd(PPh3)2Cl2-CuCl体系催化有机高价碘杂环化合物与末端炔烃的化学选择性交叉偶联反应

以有机高价碘杂环化合物1,2为底物,在Pd(PPh3)2Cl2-CuCl催化剂存在下与末端炔烃进行交叉偶联反应,实验发现该反应为--化学选择性反应,控制反应体系的物料比、温度及反应时间可以分别得到单偶联或双偶联产物,从而证实了有机高价碘杂环化合物的碘盐在进行交叉偶联反应时的反应活性比sp2的碘化物高.     

ClONO2与Cl(2P3/2)的反应机理

在密度泛函理论B3LYP/6-31G^*水平上,研究了ClONO₂+Cl(²P_3/2)Cl₂+NO₃和ClONO₂+Cl(²P_3/2)ClO+ClONO(cis)及ClONO₂+Cl(²P_3/2)ClOCl+NO₂的反应机理.计算得到各可能反应途径的过渡态,并经过内禀反应坐标(IRC)分析加以证实.反应ClONO₂+Cl(²P_3/2)Cl₂+NO₃反应活化能垒最低,为4.5kJ/mol,是反应主通道.     

The electrochemical reaction mechanism of selenocystine on selenium-gold film modified glassy carbon electrode

A simple and selective voltammetric method based on selenium-gold film modified glassy carbon electrode has been developed for investigating electrochemical reaction mechanism of selenocystine. With N₂ saturated, redox reactions between selenocystine (SeC) and selenocysteine (SeCys) were judged to be two simple electron-transfer processes. With air saturated, the reduction reaction was diagnosed to be EC catalytic reaction (the chemical oxidation reaction of the SeCys by O₂ (C) following the electron-transfer reaction (E)) and oxidation reaction is a simple electron-transfer process. With pure O₂ saturated, only reduction peak was observed and the reaction was judged to be EC catalytic reaction. The electron-transfer numbers of redox reaction were calculated to be 2 by chronocoulometry and rotating disk electrode.     

2-取代吲哚的染料敏化光氧化反应

2-苯基吲哚 (1a) 在甲醇中的染料敏化光氧化反应给出2-苯基-2-(2'-苯基-3'-吲哚基)二氢吲哚-3-酮 (2a) 和2-甲氧基-2-苯基二氢吲哚-3-酮 (4a), 相应N-甲基取代产物由1-甲基-2-苯基吲哚 (1b) 的类似反应获得。发现反应产物分布随吲哚 (1) 的浓度和介质酸度的变化而变化。对反应机理进行了推测, 其中当1a的反应在乙腈中进行时, 分离到了相应的反应中间体: 2-苯基-3H-吲哚-3-酮 (3a)。     

A full dimensional, nine-degree-of-freedom, time-dependent quantum dynamics study for the H2+C2H reaction

A full dimensional, nine-degree-of-freedom (9DOF), time-dependent quantum dynamics wave packet approach is presented for the study of the H2+C2H-->H+C2H2 reaction system. This is the first full dimensional quantum dynamics study for a diatom-triatom reaction system. The effects of the initial vibrational and rotational excitations of the reactants on the reactivity of this reaction are investigated. This study shows that vibrational excitations of H2 enhance the reactivity; whereas, the vibrational excitations of C2H only have a small effect on the reaction probability. In addition, the bending excitations of C2H, compared to the ground state reaction probability, hinder the reactivity. Comparison of the ground state reaction probabilities of the 9DOF and 8DOF shows the reaction probability from the full dimensional calculation is larger, with more prominent resonance features.     

诱导自催化法制备Ni-P超细非晶合金的动力学研究

加入诱导剂(如KBH~4)可使Ni^2+与H~2PO~2^-反应在常温下进行, 便于测量反应中放出的H~2体积, 有利于研究反应的动力学过程及其与反应条件下关系。反应为二级自催化反应, 反应活化能约60kj.mol^-1, pH值不影响反应速率常数, 但pH值越大, 反应诱导期越长, 一般可在40min内完成。由于加入诱导剂能一次成核,生成的Ni-P非晶合金为均匀的球形颗粒。     

PRODUCTION OF LIGHT ALKENES FROM CO AND/OR CO_2 HYDROGENATION OVER K-Fe-MnO/SILICALITE-2 CATALYST

High selectivity to light alkenes can be achieved from CO and CO_2hydrogenation over K-Fe-MnO/Si-2 catalyst.The alkene selectivity isinsensitive to reaction temperature for CO hydrogenation,while apparentlyincreases for CO_2 hydrogenation with raising reaction temperature.An increasein alkene selectivity is observed for both CO and CO_2 hydrogenation with GHSVrising,While a decrease with the elevation of reaction pressure for both CO/H_2and CO_2/H_2 reaction.A two-step mechanism is suggested forCO_2 hydrogenation to form hydrocarbons,by which the variations incontributions of CO and HC as products of CO_2/H_2 reaction with change ofreaction temperature,GHSV and pressure are explained.Moreover,thecatalyst is favorable for selective production of light olefins,which can alsoconcern the slightly secondary reactions of light olefins to some extent.     

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.     

Nitrite impurities are responsible for the reaction observed between vitamin B12 and nitric oxide in acidic aqueous solution

The reaction between aquacobalamin, Cbl(H2O), and NO was studied at low pH. As previously reported, the final product of the reaction is the same as that obtained in the reaction of NO and reduced Cbl(H2O), viz. Cbl(NO-). Nevertheless, this reductive nitrosylation is preceded by a faster reaction (accompanied by small absorbance changes) that depends on the HNO2 concentration but not on the NO concentration. Kinetic and UV-vis spectroscopic data show that Cbl(NO2-) is generated during this reaction. Spectroscopic data show that the dimethylbenzimidazole group trans to the NO2- ligand is protonated and partially dechelated at pH 1, by which a reaction with NO is induced. DFT calculations were performed to compare the ability of NO and NO2- to bind to cobalamin and their influence on the stability of the dimethylbenzimidazole group. The reductive nitrosylation reaction shows a quadratic dependence on the HNO2 concentration and an inverse dependence on the NO concentration. It also strongly depends on pH and is no longer observed at pH > 4. On the basis of earlier work performed on a series of Co(III) porphyrins, a mechanism is proposed that can quantitatively account for the HNO2 and NO dependencies. The reductive nitrosylation reaction is practically dominated by a back reaction, i.e., the reaction between Cbl(NO-) and HNO2, which accounts for the strange NO and HNO2 concentration dependencies observed.     

Theoretical Study on the Mechanism of CF2 Reaction with CH2O

The insertion reaction mechanism of CF2 with CH2O was investigated at the B3LYP/6-311G（d）//MP2/6-311G（d） level. The geometric conformations at each stationary point in reaction potential surface were fully optimized and the transition states were verified by intrinsic reaction coordinate （IRC） and frequency analysis. The energies of all reactants were calculated with CCSD（T）/6-311G（d）//G2MP2 methods. Results indicated that the P1 reaction route with difuoroaldehyde as product is the dominant reaction pathway, which exhibits nucleophilic character. According to NBO analysis, the starting point of insertion reaction is the interaction between carbene LP（C3） and formaldehyde π（Cl-O2）. Besides, the thermodynamic and dynamic properties of dominated reaction （1） at different temperature were studied with statistic thermodynamic method and Eyring transition state theory adjusted by Wigner means, from which the proper temperature （500- 1200 K） of reaction （1） could be estimated. Finally, the thermo- dynamic and dynamic properties of insertion reaction mechanisms （CF2, CX2 （X = Cl, Br） with CH2O） were compared and discussed.     

碳质表面异相还原NO2的反应机理

基于量子化学密度泛函理论（DFT），研究了碳质表面异相还原NO₂的反应机理，针对Zigzag与Armchair两种碳质表面，采用M06-2X方法与6-311G （d）基组联用，优化得到了不同反应路径下所有驻点的几何构型与能量，并对各路径进行了热力学与动力学分析，重点探究了CO在NO₂异相还原反应中的作用规律，同时考察了碳质表面与反应温度对异相反应的影响。计算结果表明，NO₂在碳质表面的异相还原过程主要分为两个阶段，即NO₂还原阶段与碳氧化物释放阶段。通过对比无CO分子参与的反应可知，参与反应的CO分子可以降低各阶段的反应能垒并且加快各阶段的反应速率；CO分子存在时，NO₂还原阶段的反应能垒被降低，促进了NO₂还原成NO的异相反应过程，同时参与反应的CO分子与碳质表面剩余氧原子结合，形成CO₂分子并释放，使碳氧化物释放阶段的反应能垒降低，从而促进了整体还原反应的进行。此外，与Armchair型相比，基于Zigzag型碳质表面的NO₂异相还原反应能垒更低且反应速率更快，说明NO₂异相还原反应更容易在Zigzag型碳质表面进行。最后，由反应动力学分析可知，随着温度上升，各阶段的反应速率均增大，说明提高温度对碳质表面的NO₂异相还原能够起到促进作用。     

Bond and mode selectivity in the reaction of atomic chlorine with vibrationally excited CH2D2

The title reaction is investigated by co-expanding a mixture of Cl2 and CH2D2 into a vacuum chamber and initiating the reaction by photolyzing Cl2 with linearly polarized 355 nm light. Excitation of the first C-H overtone of CH2D2 leads to a preference for hydrogen abstraction over deuterium abstraction by at least a factor of 20, whereas excitation of the first C-D overtone of CH2D2 reverses this preference by at least a factor of 10. Reactions with CH2D2 prepared in a local mode containing two quanta in one C-H oscillator /2000>- or in a local mode containing one quantum each in two C-H oscillators /1100> lead to products with significantly different rotational, vibrational, and angular distributions, although the vibrational energy for each mode is nearly identical. The Cl+CH2D2/2000>- reaction yields methyl radical products primarily in their ground state, whereas the Cl+CH2D2/1100> reaction yields methyl radical products that are C-H stretch excited. The HCl(v=1) rotational distribution from the Cl+CH2D2/2000>- reaction is significantly hotter than the HCl(v=1) rotational distribution from the Cl+CH2D2/1100> reaction, and the HCl(v=1) differential cross-section (DCS) of the Cl+CH2D2/2000>- reaction is more broadly side scattered than the HCl(v=1) DCS of the Cl+CH2D2/1100> reaction. The results can be explained by a simple spectator model and by noting that the /2000>- mode leads to a wider cone of acceptance for the reaction than the /1100> mode. These measurements represent the first example of mode selectivity observed in a differential cross section, and they demonstrate that vibrational excitation can be used to direct the reaction pathway of the Cl+CH2D2 reaction.