硅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方法确认了中间体和过渡态. 又用QCISD(T)/6-311＋＋G**//B3LYP/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硅烯与异硫氰酸的反应有抽提硫、插入、抽提亚氨基的路径. 而经由三元环中间体的抽提硫反应SiH2＋HNCS→IM1→TS2→IM3→TS3→IM4→SiH2S＋HNC(P1), 反应能垒最低, 为主反应通道, 硫代硅甲醛和异氰氢酸为主产物. 硅烯直接抽提硫、插入N—H键和经由三元环中间体的亚氨基抽提反应为竞争反应通道, 在室温下可以发生, 应为次反应通道.     

CH2与HNCO反应机理的量子化学研究

异氰酸(HNCO)分解引发的一系列自由基反应是氮氧化物快速消除机理所研究的领域,由于该反应在燃烧化学中讨论氮氧化物NOx的消除过程十分重要,所以获得这些反应准确的位垒就成为实验化学和理论化学所要解决的问题,本文采用量子化学方法,研究了CH2与HNCO体系的反应机理,力求从理论角度给出合理的解释。     

二氯乙烯锗烯与甲硫醛环加成的反应机理

利用MP2/6-311+G*方法计算了单线态二氯乙烯锗烯与甲硫醛的各种反应机理. 计算结果表明两者之间的环加成反应具有很好的选择性, 优势反应路径分为三步: 首先两种反应物经过无能垒的放热反应形成中间体INT, 然后INT经历过渡态TS3异构化为P31, 最后P31继续与甲硫醛反应形成二环杂环化合物P33. 其中第一步反应放热103.4 kJ·mol-1, 后两步反应能垒分别为0.7 和32.3 kJ·mol-1.     

亚烷基锗烯与环氧乙烷及环硫乙烷抽提氧和硫反应的量子化学研究

用量子化学密度泛函理论(DFT)的B3LYP和从头算MP2方法在6-311G(d, p)水平上对亚烷基锗烯与环氧乙烷的氧转移及环硫乙烷的硫转移的反应机理进行了系统的研究, 计算了势能面上各驻点的构型参数、振动频率和能量; 并用CCSD(T)/6-311G(d)方法进行了单点能校正. 结果表明, 亚烷基锗烯与环氧乙烷和环硫乙烷抽提氧和硫的反应存在顺反两种反应方式, 分别生成锗杂烯酮(P1)、硫代锗杂烯酮(P4)以及锗杂环氧乙酮(P2)、锗杂环硫乙酮(P5), 环状产物P2和P5能继续与环氧乙烷或环硫乙烷反应, 进一步生成更稳定的产物甲醛(P3-1)、一氧化锗(P3-2)及锗烯的二硫化物(P6), 且反式反应是主要的反应通道. 同时还研究了该反应中环氧乙烷C—O键和环硫乙烷C—S键的解离过程, 并与亚烷基卡宾和环氧乙烷及环硫乙烷的抽提反应进行了比较.     

CH2X(X=H,F,Cl)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CH2X(X=H,F,Cl)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.从CH2X(X=H,F,Cl)与O3的反应机理的研究结果看,它们与O3反应的活性都比较强,相对而言,活性大小顺序为CH2F＞CH3＞CH2Cl,也就是说,CH2F自由基与臭氧间的反应活性最强,对大气臭氧的损耗将是最大的.同时研究还发现CH2X(X=H,F,Cl)系列自由基与O3的反应都是强放热反应.     

锗硅烯与CH3OH加成反应机理及区域选择性

采用密度泛函理论方法,在B3LYP/6-311++G(d, p)水平,研究了几种锗硅烯与CH₃OH的加成反应的微观机理和势能剖面,分析了锗硅烯中Si=Ge双键的极性对加成反应区域选择性的影响.研究结果表明,锗硅烯可分别与CH₃OH的单聚体或二聚体发生加成反应.所有加成反应均从初始亲核或亲电复合物的形成开始.母体锗硅烯H₂Si=GeH₂与CH₃OH二聚体的加成反应比其与CH₃OH单聚体的相应反应在动力学上更容易些,但在其它锗硅烯与CH₃OH的反应中情况则相反.用Ph或SiMe₃基团取代H₂Si=GeH₂中的H原子在动力学上使反应变得不利且SiMe₃基团的影响更显著.加成反应的区域选择性与锗硅烯中Si=Ge双键的极性以及Si-O(Ge-H)和Ge-O (Si-H)键的相对强弱都有关.     

锗烯与乙烯环加成反应的理论研究

用RHF/6-31G^*解析梯度方法研究了单重态锗烯与乙烯环加成反应的机理,用二级微扰方法对各构型的能量进行了相关能校正,并用统计热力学方法和过渡态理论计算了该反应在不同温度下的热力学函数的变化和动力学性质。结果表明,此反应历程由两步组成:1)锗烯与乙烯生成了一中间配合物,是一无势垒的放热反应,2)中间配合物异构化为产物锗杂环丙烷,此步势垒经零点能校正后为26.9kJ.mol^-^1(MP2/6-31G^*//6-31G^*);从热力学和动力学的综合角度考虑,该反应在200-300K温度下进行为宜,如此,反应既有较大的自发趋势和平衡常数,又具有较快的反应速率。     

单态卡宾与臭氧反应机理的量子化学研究

为了研究单态卡宾与臭氧反应机理,本文采用密度泛函理论Gaussian-3方法(G3B3)优化了反应物、中间体、过渡态和产物的几何构型。探讨了单态卡宾与臭氧反应可能途径,并通过频率分析对过渡态和中间体进行了验证,研究结果表明：单态卡宾与臭氧反应有两条反应通道,分别具有亲核反应和亲电反应特征,相对而言亲核反应通道较易发生,且为强放热反应。     

甲醛光催化降解反应机理的量子化学研究

分别采用B3LYP,MP2方法在6-311++G(2df,pd)水平研究了甲醛光催化降解反应的微观机理,找到了可能的反应通道,预测反应产物为HCOOH与H2O.并得到了各反应通道的反应物、中间体、过渡态和产物的优化构型、谐振频率.成功地解释了实验结论.从键长和能量的变化角度,讨论了化学反应过程中化学键的变化规律,整个反应通道中各势能面均较低,从理论角度分析该反应室温下能够进行,为空气中的甲醛降解反应的实验研究提供理论依据.     

CH3O与ClO双自由基反应机理的量子化学研究

在QCISD(T)／6—311 G(d,p)／／B3LYP／6．311 G(3df,3pd)水平上,对CH3O与CIO自由基反应进行了理论研究．结果表明,该反应共有三个反应通道,产物分别为HOCI CH2O,CH2O HCl和CH3CI O2(1△)．不论从动力学角度,还是从热力学角度看,形成产物HOCl CH2O的通道均是最有利的,因此为主要反应通道,这与实验观察到的结果是一致的．     

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.     

Theoretical studies on the reaction mechanism of CH2CH radical with HNCO

The reaction mechanism of CH₂CH radical with HNCO has been investigated systematically by density functional theory (DFT). The geometries and harmonic frequencies of reactants, intermediates, transition states, and products have been optimized with the B3LYP at different levels. At the same time, AIM is performed to calculate the charge density of some bonding critical points and the charges of some atoms. Nine feasible reaction pathways have been investigated. The results indicated that the main pathway is CH₂CH + HNCO → IMA1 → TSA1 → CH₂CH₂ + NCO, which is characterized by hydrogen atom transferring. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

C2H3和NO2反应势能面的理论研究

在CCSD(T)／6—311G(d，p)／／B3LYP／6—3llG(d，p)水平上给出了反应C2H3 NO2的详细势能面信息，并列出了中间体和过渡态的几何构型．通过深入分析反应路径及反应机理，得到5个能量可行的产物和6条反应通道，其中产物C2H3O NO的形成又有利，而产物CH2CO HNO则是次要产物，其他产物在通常条件下可以忽略．     

Theoretical study of the mechanism of CH2CO + CN reaction

The potential energy surface information of the CH₂CO + CN reaction is obtained at the B3LYP/6‐311+G(d,p) level. To gain further mechanistic knowledge, higher‐level single‐point calculations for the stationary points are performed at the QCISD(T)/6‐311++G(d,p) level. The CH₂CO + CN reaction proceeds through four possible mechanisms: direct hydrogen abstraction, olefinic carbon addition–elimination, carbonyl carbon addition–elimination, and side oxygen addition–elimination. Our calculations demonstrate that R→IM1→TS3→P3: CH₂CN + CO is the energetically favorable channel; however, channel R→IM2→TS4→P4: CH₂NC + CO is considerably competitive, especially as the temperature increases (R, IM, TS, and P represent reactant, intermediate, transition state, and product, respectively). The present study may be helpful in probing the mechanism of the CH₂CO + CN reaction. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Theoretical study on the reaction mechanism of CN radical with ketene

The bimolecular single collision reaction potential energy surface of CN radical with ketene (CH2CO) was investigated by means of B3LYP and QCISD(T) methods. The calculated results indicate that there are three possible channels in the reaction. The first is an attack reaction by the carbon atom of CN at the carbon atom of the methylene of CH2CO to form the intermediate NCCH2CO followed by a rupture reaction of the C-C bond combined with -CO group to the products CH2CN CO. The second is a direct addition reaction between CN and CH2CO to form the intermediate CH2C(O)CN followed by its isomerization into NCCH2CO via a CN-shift reaction, and subsequently, NCCH2CO dissociates into CH2CN CO through a CO-loss reaction. The last is a direct hydrogen abstraction reaction of CH2CO by CN radical. Because of the existence of a 15.44 kJ/mol reaction barrier and higher energy of reaction products, the path can be ruled out as an important channel in the reaction kinetics. The present theoretical computation results, which give an available suggestion on the reaction mechanism, are in good agreement with previous experimental studies.     

CH自由基和NO~2反应研究: II.反应的动力学计算

采用MP2(FULL)/6-31G(d)方法从动力学计算上探讨了CH自由基与NO~2反应的可能途径,找到了反应物,中间体及产物之间的能量通道和过渡态,报道了它们的构型、电子态及能量。并通过频率分析和IRC方法对所有的过渡态进行了验证。在此基础上求出了各步反应的活化能。在以前热力学研究的基础上,对于可能的反应通道进一步作了动力学分析,找到了反应主产物通道的分支比,与实验得到的分支比基本吻合。     

Theoretical study of reaction mechanism for CH2CHX(XH,F, Cl) with ozone

In this work, we study the reaction mechanism of the CH₂CHX(X?H, F, Cl) with ozone reactions, using ab initio MP2 method at 6‐311++g** basis set level. The geometric configurations of reactants, intermediates, transition states, and products were optimized, and the energies were obtained at the QCISD(T)/6‐311++G** level. The transition states and intermediates of the reactions were verified by the vibrational analysis. The results show that the ozonolysis of ethylene and its derivatives is reasonable and believable along the Criegee mechanism. The results also show that the activation energies of the controlling steps along the fluoroethylene and chloroethylene with ozone reaction pathways were lower than that along the ethylene with ozone reaction pathway. That is to say, the derivatives of ethylene have the higher activity to react with ozone and deplete the ozone layer. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004     

Theoretical study on reaction mechanism of isocyanate radical NCO with ethene

The NCO + C₂H₄ reaction is simple and prototype for reaction of the NCO radical with unsaturated hydrocarbons, and it is considered to be important in fuel‐rich combustion. In this article, we for the first time perform detailed theoretical investigations for its reaction mechanism based on Gaussian‐3//B3LYP scheme covering various entrance and decomposition channels. The most favorable channel is firstly the NCO and C₂H₄ approach each other, forming a weakly‐bound complex L1 OCN···C₂H₄, followed by the formation of isomer L2 OCNCH₂CH₂ via a small barrier of 1.3 kcal/mol. Transition states of any decomposable or isomeric channels for L2 in energy are much higher than reactants, which indicate that adduct L2 has stabilization effect in this NCO + C₂H₄ reaction. The direct H‐abstraction channel leading to P1 HNCO + C₂H₃, might have an important contribution to the eventual products in high temperature. These results can well explain available kinetic experiment. Moreover, reaction mechanism for the title reaction is significantly different from the NCO + C₂H₂ reaction which proceeds on most favorably to generate the products HCN + HCCO and OCCHCN + H via a four‐membered ring intermediate. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009