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1.
在密度泛函理论B3LYP/6-31G *水平上,研究了ClONO 2+Cl( 2P 3/2)Cl 2+NO 3和ClONO 2+Cl( 2P 3/2)ClO+ClONO(cis)及ClONO 2+Cl( 2P 3/2)ClOCl+NO 2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ClONO 2+Cl( 2P 3/2)Cl 2+NO 3反应活化能垒最低,为4.5kJ/mol,是反应主通道. 相似文献
2.
The reaction between SiCl 4 and O 2 at 1 atm between 25 and 1200°C has been followed by mass spectrometry. Below 600°C no reaction with O 2 is noted. Above 600°C the reaction proceeds in two steps. Between 800 and 1000°C the 28Si/ 32O 2 peak height ratio is constant with no evolution of Cl 2. It is suggested that silicon oxychlorides are being formed in this temperature regime. Above 1000°C the reaction between SiCl 4 and O 2 intensifies with concomitant production of Cl 2. It is suggested that above 1000°C the reaction SiCl 4 + O 2 → SiO 2 + Cl 2 becomes important. At low temperatures (<800°C) adsorbed H2O and OH groups from the surface of the fused silica tube react with SiCl4 to form HCl. The importance of this reaction decreases with increasing temperature. The increased production of HCl above 1000°C is ascribed to H2O and H2 diffusing from the tube. 相似文献
3.
采用量子化学密度泛函理论(DFT)对NO与NH i自由基的反应机理进行了研究,并结合经典过渡态理论对各反应速率常数进行了计算。结果表明,NO与NH 2自由基的反应体系可通过六个反应通道形成N 2+H 2O、N 2O+H 2和N 2H+OH。从能量变化和反应速率两方面考虑,产物N 2+H 2O最容易生成,其最佳反应通道为NO+NH 2→→N 2+H 2O;NO与NH自由基的反应体系可通过七个反应通道形成N 2+OH、N 2O+H和N 2H+O;其中,N 2+OH最容易生成,最佳反应通道为NO+NH→→N 2+OH。比较发现, NH比NH 2自由基更易与NO发生反应生成N 2。因此,在实际运行中改变操作条件,实现NH 2等向NH方向转化,有利于NO x的还原。 相似文献
4.
The reaction of singlet oxygen with a variety of allyltin compounds CH 2=CHCH 2SnR 3 (R 3 = Me 3, Bu 3, allyl 3, (cyclo-C 6H 113, Ph 3, allylBu 2, Bu 2Cl, Bu 2OAc, allylCl 2, allylCl 2bipy) has been investigated, and the allylperoxytin compounds, 3-stannylallyl hydroperoxides, and 4-stannyl-1,2-dioxolanes which result from M-ene, H-ene and cycloaddition processes, respectively, have been identified by NMR spectroscopy. As the tin centre becomes more electropositive, as indicated by the 13C NMR shift of the allylic CH 2 group, the proportion of the M-ene reaction increases, and when δCH 2 is above about 23.7, the allylperoxytin compound is the only product. An exception to this rule is tetraallyltin, δCH 2 16.13, which similarly shows only the M-ene reaction. This is tentatively ascribed to the special effect of hyperconjugation between the C---Sn σ-bond and the remaining π-systems. A polar solvent favours the M-ene reaction. The cycloaddition reaction is favoured by low temperature, and at − 70°C in a non-polar solvent it may become the major route. Diallylmercury and allylmercury chloride react with singlet oxygen to show only the M-ene reaction, but also undergo extensive photosensitized decomposition. With 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD), allylmercury chloride shows only the M-ene reaction. 相似文献
5.
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CH 3CF 2O 2与HO 2自由基反应机理. 结果表明, CH3CF 2O 2与HO 2自由基反应存在两条可行的通道. 通道CH3CF 2O 2+HO 2→IM1→TS1→CH 3CF 2OOH+O 2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O 2和CH 3CF 2OOH. 这与实验结果是一致的;而通道CH 3CF 2O 2+HO 2→IM2→TS2→IM3→TS3→IM4+IM5→IM4+TS4→IM4+OH+O 2→TS5+OH+O 2→CH 3+CF 2O+OH+O 2→CH 3OH+CF 2O+O 2的控制步骤活化能为93.42 kJ•mol -1,其产物是CH 3OH、CF 2O和O 2. 结果表明这条通道也能发生,这与前人的实验结果一致. 相似文献
6.
Rate constants for the tunneling reaction (HD + D → h + D 2) in solid HD increase steeply with increasing temperature above 5 K, while they are almost constant below 4.2 K. The apparent activation energy for the tunneling reaction above 5 K is 95 K, which is consistent with the energy (91–112 K) for vacancy formation in solid hydrogen. The results above 5 K were explained by the model that the tunneling reaction was accelerated by a local motion of hydrogen molecules and hydrogen atoms. The model of the tunneling reaction assisted by the local motion of the reactans and products was applied to the temperature dependence of the proton-transfer tunneling reaction (C 6H 6− + C 2H 5OH → C 6H 7 + C 2H 5O −) in solid ethanol, the tunneling elimination of H 2 molecule of H 2 molecule ((CH 3) 2 CHCH(CH 3) 2+ → (CH 3) 2 C = C(CH 3) 2+ + H 2) in solid 2,3-dimethylbutane, and the selective tunneling reaction of H atoms in solid neo-C 5H 12-alkane mixtures. 相似文献
7.
在φ80×3 000mm耐高温不锈钢管气流床反应器中,以150-180μm胜利褐煤为气化原料,考察了800和900℃时添加氧气前后褐煤转化率的变化,研究了氧化反应对水蒸气气化反应影响的宏观特征。结果表明,添加氧气后褐煤转化率明显大于O_2和H_2O气氛下褐煤转化率之和,即向水蒸气气氛添加氧气后褐煤转化率的增幅大于氧气氧化作用导致的褐煤转化率的增幅,随着H_2O含量增大以及温度的升高此现象愈加明显。该协同作用主要是氧化反应对水蒸气气化反应的促进作用造成的。利用φ40×200 mm石英圆筒流化床反应器进行了类似的实验,也发现了该协同作用。同时,借鉴收缩核模型并结合气流床气化实验条件推导了水蒸气气化宏观动力学方程,得到的速率方程(Z-(1-x))~(1/3)=(tβk_(H_2O)/Rρ_C)φ_(H_2O)=K_(H_2Oφ_(H_2O))与实验值吻合较好,添加氧气后水蒸气气化反应速率和水蒸气气化反应表观速率常数K_(H_2O)明显增大,这是氧气对水蒸气气化反应促进作用的动力学特征。 相似文献
8.
The reaction of HOCl + HCl → Cl 2 + H 2O in the presence of chlorine anion Cl − has been studied using ab initio methods. The overall exothermicity is 15.5 kcal mol −1 and this reaction has been shown to have a high activation barrier of 46.5 kcal mol −1. Cl − is found to catalyze the reaction via the formation of HOCl·Cl −, ClH·HOCl·Cl − and Cl −·H 2) intermediate ion-molecule complexes or by interacting with a concerted four-center transition state of the reaction of HOCl + HCl. 相似文献
9.
Partial oxidation of methane (POM) to make syngas has been largely studied in recent years because of its potential to reduce the cost of syngas. Two reaction schemes have been proposed for the reaction:one is the sequence of combustion of CH 4 followed by reforming of unconverted CH 4 with CO 2 and H 2O,and the other is the direct partial oxidation of CH 4 to CO and H 2 without the experience of CO 2 and H 2O as reaction intermediates. In the industrial process, if the combustion-reforming mechanism predominantly contributes to the conversion of methane to syngas, severe heat management problems have to be taken into account. Therefore, the elucidation of the reaction pathway is of vital importance. In this paper, in situ time-resolved FTIR (in situ TR-FTIR) spectroscopy was used to study the POM reaction over lwt%Pd/SiO 2. The results of catalytic performance evaluation on the POM reaction over lwt%Pd/SiO 2 under different space velocity are also presented. It is expected that the additional proof can be presented to interpret POM mechanism. 相似文献
10.
Only trace of quinhydrone, a urease-inhibitor, can inhibit enzymatically promoting hydrolytic reaction of urea [1]. A new enzymatic inhibition kinetic spectrophotometry method [2] for determination of trace quinhydrone was obtained by urea and P-dimethylamino-benzadehyde (color reagent) developing action. In this reaction, maximal absorptive wavelength is 420 nm. The enzymatic promoting reaction rate, log (A 0/A 1),enzymatic inhibition reaction rate, log (A 0/A 2,and their difference, log (A 2/A 1), are measured by detecting the remains of urea. All factors (urease, urea and color reagent dosage; reaction temperature; heating time), effecting log (A 2/A 1) were investigated. 相似文献
11.
Two possible reaction mechanisms of VS^+(^3∑^-, 1^Г) with CO in the gas phase have been studied by using B3LYP/TZVP and CCSD(T)/6-311+G (3df, 3pd) methods: the O/S exchange reaction (VS^++CO→VO^++CS) and the S-transfer reaction (VS^+ + CO → V^+ + COS). The two reactions proceed via two-step and one-step mechanism, respectively. The barriers of the triplet and singlet PESs are 30.6 and 50.9 kcal/mol, respectively, for O/S exchange reaction and 7.3 and 50.2 kcal/mol, respectively, for the S-transfer reaction. The results indicate that the triplet ground state reaction is more favorable, and the S-transfer reaction is more favorable than the O/S exchange reaction, which is in good agreement with the experimental observation. 相似文献
12.
The substitution reactions of XC 6H 4COCl [X=2-, 3-, or 4-CH 3; 2-, 3-, or 4-CH 3O; 2-, or 4-I; or 2-, 3-, or 4-NO 2] and YC 6H 4COONa [Y=2-, 3-, or 4-CH 3; 2-, 3-, or 4-CH 3O; 2-I; 4-NO 2; or H] in a two-phase H 2O/CH 2Cl 2 medium using pyridine-1-oxide (PNO) as an inverse phase transfer catalyst were investigated. In general, the kinetics of the reaction follows a pseudo-first-order rate law, with the observed rate constant being a linear function of the concentration of PNO in the water phase. In contrast to other analogous reactions, the hydrolysis reaction of 2-, 3-, or 4-NO 2C 6H 4COCl in H 2O/CH 2Cl 2 medium is catalyzed considerably by PNO and reaches an equilibrium. In the PNO-catalyzed reaction of XC 6H 4COCl and XC 6H 4COONa in H 2O/CH 2Cl 2 medium, the order of reactivities of XC 6H 4COCl toward reaction with PNO in CH 2Cl 2 is 2-IC 6H 4COCl>4-IC 6H 4COCl>(C 6H 5COCl,3-CH 3OC 6H 4COCl)>3-CH 3C 6H 4COCl>(2-CH 3C 6H 4COCl,4-CH 3C 6H 4COCl)>4-CH 3OC 6H 4COCl>2-CH 3OC 6H 4COCl. Combined with the results of other analogous reactions, good Hammett correlations with positive reaction constant were obtained for the meta- and para-substituents, which supports that the XC 6H 4COCl–PNO reaction in CH 2Cl 2 is a nucleophilic substitution reaction. 相似文献
13.
The pyrolysis mechanism of important intermediate 1-hexene of carbon matrix precursor cyclohexane was studied theoretically. Possible reaction paths were designed based on the potential surface scan and electron structure of the initial C–C bond breaking reactions. Thermodynamic and kinetic parameters of the possible reaction paths were computed by UB3LYP/6-31+G* at different temperature ranges. The results show that 1-hexene pyrolyzes at 873 K. When below 1273 K, the major reaction paths are those that produce C 3H 4, and above 1273 K, the major reaction paths are those that produce C 3H 3 from the viewpoint of thermodynamics. From the viewpoint of kinetics, the major product is C 3H 3, it results from the pyrolysis reaction of 1-hexene cracking bond C 3–C 4 and generating C 3H 5 and C 3H 7 with the activation energy Δ E0≠θ=296.32 kJ/mol. Kinetic results also show that product C 3H 4 accompany simultaneously, which is the side reaction starting from the pyrolysis of 1-hexene forming C 4H 7 and C 2H 5 with the activation energy of 356.73 kJ/mol. When reaching 1473 K, the rate constant of the rate-determining steps of these two reaction paths do not show much difference, which means both the reaction paths exist in the pyrolysis process at the high temperature. The above results are basically in accordance with mass spectrum analysis and far more specific. 相似文献
14.
以邻甲酚和二氧化碳为原料,以磷酸钾为中和剂一步羧化合成邻甲基水杨酸及相关产物。探讨了反应条件对产率的影响。实验结果表明,当磷酸钾与邻甲酚物料比为2.5∶1,反应温度150 ℃,反应压力3.0 MPa时,羧化反应产物总收率达到95.4%,同时邻甲基水杨酸收率也达到最大。与传统碳酸钾中和法相比,磷酸钾中和法产物在后处理过程中无二氧化碳放出,后处理过程中的磷酸根可制备为磷酸钾使用,新工艺是一条绿色化工路线。 相似文献
15.
The reaction between dimethyl sulfide (CH 3SCH 3) and nitrate radical (NO 3) is studied using density functional theory and ab initio methods. The transition state for this reaction is optimized at different levels of theory and basis sets, and then used for kinetics calculations of the rate constant. The CH 3SCH 3 + NO 3 reaction leading to CH 3SCH 2 and HNO 3 is shown to have a negative activation energy and thus negative temperature dependence. The study confirms that the NO 3 radical is a significant contributor to the oxidation of DMS in the troposphere. 相似文献
16.
应用量子化学密度泛函理论研究了燃煤烟气中As和AsO与O_2均相生成As_2O_3的反应机理。首先计算确定了各反应物、中间体、过渡态和产物的结构和能量,然后运用热力学和动力学方法对As_2O_3均相生成过程进行分析。结果表明,由As和AsO与O_2均相生成As_2O_3的最大反应能垒分别为32.9和157.2kJ/mol,在烟气中由As转化为As_2O_3更为容易进行。在500-1900 K下,各反应的正逆反应速率常数均随温度的提高而增大,但不同反应过程受温度影响的程度不同。As与O_2反应生成AsO和AsO_2的两个反应过程的平衡常数在所研究的温度范围内均大于10~5,能完全反应,可以认为是单向反应。AsO与O_2反应生成AsO_2的过程平衡常数在所研究的温度范围内小于10~5,反应不完全,转化率低。AsO与AsO_2生成As_2O_3(D3H)构型的平衡常数极低,反应难以进行,而生成As_2O_3(GAUCHE)构型反应能垒低,可自发进行。 相似文献
17.
After non-isothermal differential scanning calorimetry (DSC) and X-ray diffraction experiments are carried out, the reaction kinetics of Al-Fe 2O 3 system is analyzed by a model-free Starink method. In our study, activation energy was determined as 145 kJ/mol for 8Al-3Fe 2O 3 thermite reaction, the value is comparable to the activation energy for diffusion of Al in FeAl 2O 4 and is less than the activation energy for diffusion of Al in Fe 3Al, suggesting that the diffusion of Al into FeAl 2O 4 controls the product of the thermite reaction. 相似文献
18.
We have explored the relationships between the reaction force F( ξ), the reaction force constant κ( ξ) and the projected force constants of the intramolecular proton transfer HO−NS → ON−SH along the intrinsic reaction coordinate ξ. The structural changes and energetics associated with the reaction are analyzed in terms of the three regions defined by F( ξ): reactant, transition and product. The significance of the similarity between κ( ξ) and the variation of the force constant associated to the reaction coordinate mode, kξ( ξ), is discussed in detail. 相似文献
19.
采用CCSD(T)//M06-2X/6-311++G( d, p)方法, 结合传统过渡态理论, 研究了硝酸异丙酯与Cl原子、 OH及NO 3自由基的反应机理和动力学. 两个反应物单体首先形成氢键复合物, 随后X(X=Cl原子、 OH和NO 3自由基)提取硝酸异丙酯中叔碳的 α-H原子或甲基的 β-H原子, 室温下, 以X提取 α-H原子为主. 反应的主要历程为 Cl原子(OH或NO 3自由基)提取(CH 3) 2CHONO 2的 α-H原子, 生成HCl(H 2O或HNO 3)分子和(CH 3) 2CONO 2自由基, 后者分解为丙酮和NO 2. 结果表明, 在200~500 K温度范围内, 随着温度的升高, 丙酮和NO 2的产率降低; 在室温下, 硝酸异丙酯与Cl原子、 OH和NO 3自由基反应的速率常数分别为3.933×10 -11, 1.182×10 -13和7.134×10 -19 cm 3·molecule -1·s -1. 计算所得硝酸异丙酯与OH自由基反应的动力学数据与实验结论一致. 相似文献
20.
This survey begins with the photochemistry at 254 nm and 298 K in the system H 2O 2COO 2RH, the primary objective of which is to determine the rate constants for the reaction OH + RH → H 2O + R relative to the well-known rate constant for the reaction OH + CO → CO 2 + H. Inherent in the scheme is that the reaction HO 2+CO→OH+CO 2 is negligible compared with the OH reaction, and a literature consensus gives kHO2 < 10 −19 cm 3 molecule −1 s −1, or some 10 6 less than kOH at 298 K. Theoretical calculations establish that the first stage in the HO 2 reaction is the formation of a free radical intermediate HO 2 + CO → HOOCO (perhydroxooxomethyl) which decomposes to yield the products, and that the rate of formation of the intermediate is equal to the rate of formation of the products. The structure of the intermediate and a reaction profile are shown. High temperature rate data reported subsequent to the data in the consensus and theoretical calculations lead here to a recommendation that, in the range 250–800 K, kHO2 = 3.45 × 10−12T1/2 exp(1.15 × 104/T) cm3 molecule−1 s−1, the hard-sphere-collision Arrhenius modification. This yields kHO2(298) = 1.0 × 10−27 cm3 molecule−1 s−1 or some 1014 slower than kOH(298). 相似文献
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