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.     

CF3O2自由基和NO反应机理的理论研究

用密度泛函理论(DFT)的B3LYP方法, 分别在6-31G、6-311G、6-311+G(d)基组水平上研究了CF3O2自由基和NO反应机理. 研究结果表明, CF3O2自由基和NO反应存在三条可行的反应通道, 优化得到了相应的中间体和过渡态. 从活化能看, 通道CH3O2+NO→IM1→TS1→IM2→TS2→CF3O+ONO的活化能最低, 仅为70.86 kJ•mol-1, 是主要反应通道, 主要产物是CF3O和NO2. 而通道CH3O2+NO→IM1→TS3→CF3ONO2和CH3O2+NO→TS4→IM3→TS5→IM4→TS6→CF3O+NOO的活化能较高, 故该反应难以进行.     

Theoretical Investigation of CH3CF2O2+HOO Reaction

The reactions of CH3CF2O2 with HOO are important chemical cyclic processes of photochemical contamination. In this paper, the reaction pathways and reaction mechanism of CH3CF2O2+HOO are investigated extensively with the Gaussian 98 package at the B3LYP/6-311++G** basis sets. The use of vibrational mode analysis and electron population analysis to reveal the reaction mechanism is firstly reported. The study shows that CH3CF2CO2+HOO→IM1→TS1→CH3CF2O2H+O2 channel is the energetically most favorable, CH3CF2CO2H and O2 are the principal products, and the formation of CH3OH and CF2O is also possible.     

烯丙基自由基(·C3H5)与一氧化氮(NO)反应势能面的理论研究

在CCSD(T)/6-311G(d,p)//B3LYP/6-311G(d,p)+ZPE水平上对反应·CHCHCH3+NO进行了计算, 并建立了其单重态的反应势能面. 在该反应中, 分别找到生成P1(CH3CHO+HCN), P2(CH3CHO+HNC), P3(CH3CN+HCHO), P4(CH3CCH+HNO)的4条产物通道, 其中·CHCHCH3和NO中的氮原子直接连接形成m1(trans-CH3CHCHNO), m1经过顺反异构形成m2(cis-CH3CHCHNO), m2再经过CCNO四元环合, 然后发生环解离, 最后生成产物P1(CH3CHO+HCN)是最可行的产物通道, 其余三条通道为次要产物通道. 该体系中生成P1的反应路径与同类体系·C2H3+NO的主要反应路径相类似, 两者的差别是前者为动力学可行的反应, 而后者为动力学不可行反应, 这使得·CHCHCH3+NO反应比·C2H3+NO反应更具有实际意义.     

CH_2CH(~2A')自由基与臭氧反应机理的理论研究

用量子化学MP2（full）方法,在6－311+ +G~(**)基组水平上研究了CH_2CH (~2A~＇)自由基与臭氧反应的机理,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QCISD（T,full）/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,研究结果表明 ：CH_2CH(~2A~＇)自由基与臭氧反应有两条可行的反应通道,分别为：CH_2CH (~2A~＇)+O_3→TS1→M1→TS2→O_2+OCH_2CH→TS4+O_2→O_2(~3∑_g)+CH_2CHO (~2A~＂)和CH_2CH(~2A~＇)+O_3→M2→TS3→O_2(~3∑_g)+CHO(~2A~＂),后一个反 应通道较容易发生,而且反应活化能小（2.97kJ/mol）,说明CH_2CH(~2A~＇)自由 基与臭氧之间的反应活性很强。     

CH2+O2反应的反应机理

The mechanisms of the CH2＋ O2→ H2O＋ CO and CH2＋ O2→ H2＋ CO2 reactions have been studied by performing ab initio CAS(8,8)/6-31G(d,p) calculations, and five intermediates(IMn) and eight transitions(TSn) have been located along the reaction paths. The predicted path for the CH2＋ O2→ H2O＋ CO is: CH2＋ O2→ TS1→ IM1→ TS2→ IM2→ TS3→ IM3→ TS4→ IM4a→ TS5→ H2O＋ CO. For the CH2＋ O2→ H2＋ CO2 reaction, there are two paths: (i) CH2＋ O2→ TS1→ IM1→ TS2→ IM2→ TS3→ IM3→ TS6→ H2＋ CO2 and (ii) CH2＋ O2→ TS1→ IM1→ TS2→ IM2→ TS3→ IM3→ TS4→ IM4a→ TS7→ IM4b→ TS8→ H2＋ CO2, with the latter path more favorable energetically.     

The products of the thermal decomposition of CH3CHO

We have used a heated 2 cm × 1 mm SiC microtubular (μtubular) reactor to decompose acetaldehyde: CH(3)CHO + Δ → products. Thermal decomposition is followed at pressures of 75-150 Torr and at temperatures up to 1675 K, conditions that correspond to residence times of roughly 50-100 μs in the μtubular reactor. The acetaldehyde decomposition products are identified by two independent techniques: vacuum ultraviolet photoionization mass spectroscopy (PIMS) and infrared (IR) absorption spectroscopy after isolation in a cryogenic matrix. Besides CH(3)CHO, we have studied three isotopologues, CH(3)CDO, CD(3)CHO, and CD(3)CDO. We have identified the thermal decomposition products CH(3) (PIMS), CO (IR, PIMS), H (PIMS), H(2) (PIMS), CH(2)CO (IR, PIMS), CH(2)=CHOH (IR, PIMS), H(2)O (IR, PIMS), and HC≡CH (IR, PIMS). Plausible evidence has been found to support the idea that there are at least three different thermal decomposition pathways for CH(3)CHO; namely, radical decomposition: CH(3)CHO + Δ → CH(3) + [HCO] → CH(3) + H + CO; elimination: CH(3)CHO + Δ → H(2) + CH(2)=C=O; isomerization∕elimination: CH(3)CHO + Δ → [CH(2)=CH-OH] → HC≡CH + H(2)O. An interesting result is that both PIMS and IR spectroscopy show compelling evidence for the participation of vinylidene, CH(2)=C:, as an intermediate in the decomposition of vinyl alcohol: CH(2)=CH-OH + Δ → [CH(2)=C:] + H(2)O → HC≡CH + H(2)O.     

溶液中甲醇和二氯亚砜的化学反应

用B3LYP方法和SCIPCM模型(模拟溶剂效应)研究了甲醇和二氯亚砜在两种非极性(ε<15)和两种极性(ε>15)溶剂中的反应(最终产物为氯代甲烷和二氧化硫). 反应过程由反应(1)和反应(2)组成, CH3OS(O)Cl是反应(1)的主要产物和反应(2)的反应物. 反应(2)有“前面取代”(经过渡态TS3f)和“背后取代”(先经CH3OS(O)Cl的电离, 再经过渡态TS3b)两种机理. 计算表明, 在气相和四种溶剂中反应(1)和(2)都是放热反应, 反应(1)具有相同的反应途径(经过渡态→中间体→过渡态), 溶剂的极性对反应(2)有很大的影响. 在气相和非极性溶剂中, TS3f的能量比(CH3OSO++Cl-)离子对(中间体IM2)的能量低, 反应(2)应为前面取代机理; 在极性溶剂中, IM2和TS3b的能量都比TS3f低, 反应(2)应为背后取代机理.     

SiH3+O(3P)反应机理的理论研究

The reaction for SiH3+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 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 pathway is the SiH3+O(3P)→IM1→TS3→IM2→TS8→HOSi+H2. The other minor products include the HSiOH+H, H2SiO+H and HSiO+H2. Furthermore, the products HOSi, HSiO and HSiOH(cis) can undergo dissociation into the product SiO. In addition, the calculations provide a possible interpretation for disagreement about the mechanism of the reaction SiH4+O(3P). It suggests that the products HSiOH, H2SiO and SiO observed by Withnall and Andrews are produced from the secondary reaction SiH3+O(3P) and not from the reaction SiH4+O(3P).     

A temperature-dependent relative-rate study of the OH initiated oxidation of n-butane: the kinetics of the reactions of the 1- and 2-butoxy radicals

The kinetics of the reactions of 1-and 2-butoxy radicals have been studied using a slow-flow photochemical reactor with GC-FID detection of reactants and products. Branching ratios between decomposition, CH3CH(O*)CH2CH3 --> CH3CHO + C2H5, reaction (7), and reaction with oxygen, CH3CH(O*)CH2CH3+ O2 --> CH3C(O)C2H5+ HO2, reaction (6), for the 2-butoxy radical and between isomerization, CH3CH2CH2CH2O* --> CH2CH2CH2CH2OH, reaction (9), and reaction with oxygen, CH3CH2CH2CH2O* + O2 --> C3H7CHO + HO2, reaction (8), for the 1-butoxy radical were measured as a function of oxygen concentration at atmospheric pressure over the temperature range 250-318 K. Evidence for the formation of a small fraction of chemically activated alkoxy radicals generated from the photolysis of alkyl nitrite precursors and from the exothermic reaction of 2-butyl peroxy radicals with NO was observed. The temperature dependence of the rate constant ratios for a thermalized system is given by k7/k6= 5.4 x 10(26) exp[(-47.4 +/- 2.8 kJ mol(-1))/RT] molecule cm(-3) and k9/k8= 1.98 x 10(23) exp[(-22.6 +/- 3.9 kJ mol(-1))/RT] molecule cm(-3). The results agree well with the available experimental literature data at ambient temperature but the temperature dependence of the rate constant ratios is weaker than in current recommendations.     

Theoretical Study on Mechanism of Reaction of OH with HO2NO2

The reaction of HO2NO2 (peroxynitric acid, PNA) with OH was studied by the hybrid density functional B3LYP and CBS-QB3 methods. Based on the calculated potential energy surface, five reaction channels, H2O+NO2+O2, HOOH+NO3, NO2+HO3H, HO2+HONO2 and HO2+HOONO, were examined in detail. The major reaction channel is PNA+OH→M1→TS1→H2O+NO2+O2. Taking a pre-equilibrium approximation and using the CBS-QB3 energies, the theoretical rate constant of this channel was calculated as 1.13×10-12 cm3/(molecule s) at 300 K, in agreement with the experimental result. Comparison between reactions of HOONO2+OH and HONO2+OH was carried out. For HOR+OH reactions, the total rate constants increase from R=NO2 to R=ONO2, which is consistent with experimental measurements.     

二氧化三氮(N3O2)中性分子和离子的一些重要反应过程的理论研究

二重态的N3O2中性分子作为中间体, 在N3O2阴离子的光解离反应和NO+N2O←→N2+NO2反应中均起重要作用. 在CCSD(T)/6-311G(d,p)//B3LYP/6-311G(d,p)+ZPE的水平上, 对这两个反应进行了理论计算. 结果表明, 在N3O2阴离子的光解离反应中, 该阴离子先在光照下解离为与其具有相同的W构型的中性分子和一个电子, 这个中性分子是一个过渡态, 它将打破C2v构型变成具有Cs对称性的W型中间异构体, 然后再经过一个过渡态, 裂解成N2O+NO两个小分子. 这个裂解过程的能垒非常低(5.96 kJ/mol), 因此在实验中很难检测到W型的中间异构体. 在另一个重要的[N3O2]体系的反应(NO+N2O←→N2+NO2)中, 找到了两条反应通道, 其中不经过中间异构体的一步转化通道更为可行.     

The Reaction of CH_3+NO in Gaseous Phase

NOx is a major pollutant product from combustion processes. In hydrocarbon combustion there are a number of radicals as CH2, C2H, CH3 and C2H3 can react with NO1-3. A large amount of CH3 exists in natural gas combustion flame. Therefore the reaction of CH3 with NO is very important. A rate constant (k =1.510-11exp(-60k/T) cm3molecule-1s-1) of the overall CH3+NO reaction was measured with laser flash photolysis/absorption spectroscopy over the temperature range 296-509 K and at pre…     

烯丙基自由基(·C3H5)与氧气(O2)反应机理的理论计算

用量子化学计算方法对CH3CH=·CH与O2气的反应机理进行了理论研究, 在B3LYP/6-311G(d,p) 水平下优化稳定分子结构和寻找过渡态, 并在此构型的基础上, 采用CCSD(T)/6-311G(d,p)方法得到各驻点的高级单点能量. 找到主要路径R(CH3CH=·CH+O2)→m1(trans-CH3CH=CHOO)→m2(形成COO三元环)→m3(C—C键断裂,同时生成CH3CH—O—CHO)→P2(C—O键断裂生成CH3CHO+CHO); 并与C2H3等共轭体系进行了对比.     

丁二酸脱水制备丁二酸酐的微观反应机理研究

丁二酸脱水法是工业生产丁二酸酐的方法之一. 用量子化学密度泛函理论(DFT)对该反应的微观机理进行了详细研究, 得到了该反应的微观过程. 根据计算和分析可知: 丁二酸脱水制备丁二酸酐的微观反应途径为IM1→TS1→IM2→TS2→IM3→TS3→P＋H₂O, 在反应过程中IM3为氢键复合物, 整个反应的速控步为IM3→TS3→P＋H₂O, 其所需活化能为167.17 kJ/mol.     

Partial oxidation of propylene catalyzed by VO3 clusters: a density functional theory study

Density functional theory (DFT) calculations are carried out to investigate partial oxidation of propylene over neutral VO 3 clusters. C=C bond cleavage products CH 3CHO + VO 2CH 2 and HCHO + VO 2CHCH 3 can be formed overall barrierlessly from the reaction of propylene with VO 3 at room temperature. Formation of hydrogen transfer products H 2O + VO 2C 3H 4, CH 2=CHCHO + VO 2H 2, CH 3CH 2CHO + VO 2, and (CH 3) 2CO + VO 2 is subject to tiny (0.01 eV) or small (0.06 eV, 0.19 eV) overall free energy barriers, although their formation is thermodynamically more favorable than the formation of C=C bond cleavage products. These DFT results are in agreement with recent experimental observations. VO 3 regeneration processes at room temperature are also investigated through reaction of O 2 with the CC bond cleavage products VO 2CH 2 and VO 2CHCH 3. The following barrierless reaction channels are identified: VO 2CH 2 + O 2 --> VO 3 + CH 2O; VO 2CH 2 + O 2 --> VO 3C + H 2O, VO 3C + O 2 --> VO 3 + CO 2; VO 2CHCH 3 + O 2 --> VO 3 + CH 3CHO; and VO 2CHCH 3 + O 2 --> VO 3C + CH 3OH, VO 3C + O 2 --> VO 3 + CO 2. The kinetically most favorable reaction products are CH 3CHO, H 2O, and CO 2 in the gas phase model catalytic cycles. The results parallel similar behavior in the selective oxidation of propylene over condensed phase V 2O 5/SiO 2 catalysts.     

CH3CF2O2与HO2自由基反应机理的理论研究

用密度泛函理论(DFT)的B3LYP方法，在6-311G、6-311+G(d)、6-311++G(d, p) 基组水平上研究了CH₃CF₂O₂与HO₂自由基反应机理. 结果表明, CH3CF₂O₂与HO₂自由基反应存在两条可行的通道. 通道CH3CF₂O₂＋HO₂→IM1→TS1→CH₃CF₂OOH＋O₂的活化能为77.21 kJ•mol^－1，活化能较低，为主要反应通道，其产物是O₂和CH₃CF₂OOH. 这与实验结果是一致的；而通道CH₃CF₂O₂＋HO₂→IM2→TS2→IM3→TS3→IM4＋IM5→IM4＋TS4→IM4＋OH＋O₂→TS5＋OH＋O₂→CH₃＋CF₂O＋OH＋O₂→CH₃OH＋CF₂O＋O₂的控制步骤活化能为93.42 kJ•mol^－1，其产物是CH₃OH、CF₂O和O₂. 结果表明这条通道也能发生，这与前人的实验结果一致.     

Theoretical study on the reaction mechanism of the methyl radical with nitrogen oxides

The radical-molecule reaction mechanism of CH3 with NOx (x = 1, 2) has been explored theoretically at the B3LYP/6-311Gd,p and MC-QCISD (single-point) levels of theory. For the singlet potential energy surface (PES) of the CH3 + NO2 reaction, it is found that the carbon to middle nitrogen attack between CH3 and NO2 can form energy-rich adduct a (H3CNO2) with no barrier followed by isomerization to b1 (CH3ONO-trans), which can easily convert to b2 (CH3ONO-cis). Subsequently, starting from b (b1, b2), the most feasible pathway is the direct N-O bond cleavage of b (b1, b2) leading to P1 (CH3O + NO) or the 1,3-H-shift and N-O bond rupture of b1 to form P2 (CH2O + HNO), both of which may have comparable contribution to the reaction CH3 + NO2. Much less competitively, b2 can take a concerted H-shift and N-O bond cleavage to form product P3 (CH2O + HON). Because the intermediates and transition states involved in the above three channels are all lower than the reactants in energy, the CH3 + NO2 reaction is expected to be rapid, as is consistent with the experimental measurement in quality. For the singlet PES of the CH3 + NO reaction, the major product is found to be P1 (HCN + H2O), whereas the minor products are P2 (HNCO + H2) and P3 (HNC +H2O). The CH3 + NO reaction is predicted to be only of significance at high temperatures because the transition states involved in the most feasible pathways lie almost above the reactants. Compared with the singlet pathways, the triplet pathways may have less contributions to both reactions. The present study may be helpful for further experimental investigation of the title reactions.     

Branching ratios in the hydroxyl reaction with propene

The branching ratios for the reactions of attachment of hydroxyl radical to propene and hydrogen-atom abstraction were measured at 298 K over the buffer gas pressure range 60-400 Torr (N(2)) using a subatmospheric pressure turbulent flow reactor coupled with a chemical ionization quadrupole mass spectrometer. Isotopically enriched water H(2)(18)O was used to produce (18)O-labeled hydroxyl radicals in reaction with fluorine atoms. The β-hydroxypropyl radicals formed in the attachment reactions 1a and 1b , OH + C(3)H(6) → CH(2)(OH)C(?)HCH(3) (eq 1a ) and OH + C(3)H(6) → C(?)H(2)CH(OH)CH(3) (eq 1b ), were converted to formaldehyde and acetaldehyde in a sequence of secondary reactions in O(2)- and NO-containing environment. The (18)O-labeling propagates to the final products, allowing determination of the branching ratio for the attachment channels of reaction 1. The measured branching ratio for attachment is β(1b) = k(1b)/(k(1a) + k(1b)) = 0.51 ± 0.03, independent of pressure over the 60-400 Torr pressure range. An upper limit on the hydrogen-abstraction channel, OH + C(3)H(6) → H(2)O + C(3)H(5) (eq 1c ), was determined by measuring the water yield in reactions of OH and OD radicals (produced via H(D) + NO(2) → OH(OD) + NO reactions) with C(3)H(6) as k(1c)/(k(1a) + k(1b) + k(1c)) < 0.05 (at 298 K, 200 Torr N(2)).     

La+活化NH3的自旋禁阻反应机理

采用密度泛函理论的UB3LYP方法,计算研究了气相中La+活化NH3的两态反应机理。为了理解由La+活化NH3过程中自旋翻转行为,对自旋态分别为单重态和三重态两个反应势能面进行了计算研究,其结果表明,La+活化NH3的过程是通过自旋态势能面交叉产生的自旋禁阻反应,单、三重态势能面最低能量交叉点(MECP)附近的系间窜越导致H向La+转移和脱H2反应能垒的降低。此外,运用自然键轨道(NBO)布居分析,研究了反应中各个物种的成键特性。所确定的最低能量反应路径为:3La++NH3→3IM1→MECP→1TS12→1IM2→1TS23→1IM3→1LaNH++H2。