共查询到20条相似文献,搜索用时 0 毫秒
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Yu Zhen Fang Chuan Lu Jian Hua Zhou Wan Yong Ma School of Chemical Engineering Shandong Institute of Light Industry Jinan China 《中国化学快报》2008,19(4):493-496
The synthesis reaction of trichlorogermyl crylic acid has been studied systematically by using quantum chemistry methods for the first time.Geometries of reactants,transition states,and products have been optimized,respectively at the B3LYP/6-311G(d,p) level.Vibrational frequencies,IR intensities and relative energies for various stationary points have been determined.The reaction pathways are identified by intrinsic reaction coordinate(IRC)calculations.Theoretical analysis provided conclusive evidence that the process is completed through five pathways of addition reaction of double bond,and the transition states are found to be four- membered ring compounds.Solvent effects are taken into account with the PCM model at the same level.This preliminary study shows that the complex formation is favored by the use of polar solvent. 相似文献
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Maria del Carmen Michelini Nino Russo Stefano Alcaro Lucyna A. Wozniak 《Tetrahedron》2012,68(27-28):5554-5563
The mechanism of the Stec reaction between phosphoroselenanilidate or phosphonoanilidate and CS2, activated by strong bases, has been studied computationally, using DFT methods, and experimentally, by low temperature 31P NMR spectroscopy. From molecular calculations, the reaction pathway of the reaction has been revealed with several transition states and intermediates, including a low energy spirocyclic pentacoordinate transition state and acyclic tetracoordinate intermediates, which eventually were correlated with short living molecules detected by NMR spectroscopy. 相似文献
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After defining reaction mechanism, reaction path, reaction coordinate, reaction profile, and classical trajectories, dynamic and static approaches suitable (or promising) for analysis of reaction mechanism are critically discussed. 相似文献
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Lai‐Cai Li Yan Zheng Dong Zha An‐Min Tian Ming‐Hou Xu 《International journal of quantum chemistry》2006,106(7):1672-1682
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 相似文献
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Pang JL Xie HB Zhang SW Ding YH Tang AQ 《The journal of physical chemistry. A》2008,112(23):5251-5257
The HCNO + CN reaction is one potentially important process during the NO-reburning process for the reduction of NOx pollutants from fossil fuel combustion emissions. To compare with the recent experimental study, we performed the first theoretical potential energy surface investigation on the mechanism of HCNO + CN at the G3B3 and CCSD(T)/aug-cc-pVTZ levels based on the B3LYP/6-311++G(d,p) structures, covering various entrance, isomerization, and decomposition channels. The results indicate that the most favorable channel is to barrierlessly form the entrance isomer L1c NCCHNO followed by successive ring closure and concerted CC and NO bond rupture to generate the product P1 HCN + NCO. However, the formation of P4 (3)HCCN + NO, predicted as the only major product in the recent experiment, is kinetically much less competitive. This conclusion is further supported by the master equation rate constant calculation. Future experimental reinvestigations are strongly desired to test the newly predicted mechanism for the CN + HCNO reaction. Implications of the present results are discussed. 相似文献
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Xiu Hui Lu Yue Hua Xu Ping Ping Xiang Xin Che 《International journal of quantum chemistry》2008,108(1):75-83
Mechanism of the cycloadditional reaction between singlet germylidene (R1) and formaldehyde (R2) has been investigated with MP2/6‐31G* method, including geometry optimization, and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by CCSD(T)//MP2/6‐31G* method. From the potential energy profile, it can be predicted that the dominant reaction pathway of the cycloadditional reaction between singlet germylidene and formaldehyde is reaction (4) , which consists of three steps: the two reactants (R1, R2) first form an intermediate INT1b through a barrier‐free exothermic reaction of 28.1 kJ/mol; this intermediate reacts further with formaldehyde (R2) to give an intermediate INT4, which is also a barrier‐free exothermic reaction of 37.2 kJ/mol; subsequently, the intermediate INT4 isomerizes to a heteropolycyclic germanic compound P4 via a transition state TS4, for which the barrier is 18.6 kJ/mol. The dominant reaction has an excellent selectivity and differs considerably from its competitive reactions in thermodynamic property and reaction rate. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 相似文献
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The potential energy surfaces (PESs) of the electrocyclic reactions of o-xylylene at the ground and the lowest excited states are calculated by CASSCF molecular orbital and MRMP2 methods. The lowest excited state geometry of o-xylylene has C(2v) symmetry and is about 65 kcal mol(-1) in energy above the ground state. The PESs in the vicinity of the conical intersection are different from those of the electrocyclic reaction of cis-butadiene. In the vicinity of the conical intersection, the transition state at the ground state relating to methylene-cycloheptadienyl carbene is located. The transition state is only 4.3 kcal mol(-1) lower in energy than the conical intersection at the CASSCF(10,10)/6-31G(d) level and 0.5 kcal mol(-1) lower at the MRMP2/6-311+G(d,p) level. The transition state corresponding to benzocyclobutene does not locate in the vicinity of the conical intersection because of the resonance energy between benzene ring and methylene group. 相似文献
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采用密度泛函理论B3LYP方法研究了GeH2自由基与HNCS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IRC确定中间体和过渡态。为了得到更精确的能量值,用QCISD(T)/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锗烯与异硫氰酸的反应有抽提硫、插入N-H键、抽提亚氨基的路径,而经由三元环中间体的抽提硫反应GeH2+HNCS→IM3→TS2→IM4→TS3→IM5→GeH2S+HNC(P1),反应能垒最低,为主反应通道,甲锗硫醛和异氰氢酸为主产物。锗烯经由四元环中间体抽提硫的反应为竞争反应通道。 相似文献
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Vahid Saheb 《Kinetics and Catalysis》2013,54(6):671-676
The potential energy surface for the reaction of hydrogen atom with carbon dioxide is explored by using various quantum chemical methods including W1BD, CBS-QB3, G4, G3B3, CCSD(T), QCISD(T), CCSD, M06-2X, and BB1K.Transition state theory and a modified strong collision/RRKM model are employed to calculate the thermal rate coefficients for the reaction. The results of calculation show that the overall rate constant for the reaction H + CO2 are pressure-independent over the temperature range of 300 to 3500 K. By using the energies at the W1BD level, the non-Arrhenius expression k = 9.8T 2.9exp(?74.8 kJ/mol/RT) L mol?1 s?1 was found for the reaction. 相似文献
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The reaction of a F atom with an NCO radical was studied at 6‐311+g* level, using DFT methods. All geometries, vibrational frequencies, and energies of different stationary points were calculated by HF, UMP2, and DFT methods, and the results agreed with the experimental values. The vibrational frequencies and vibrational modes of the reactant, intermediates, transition states, and products were calculated and the changes of these frequencies and modes were analyzed. Simultaneously, the vibrational modes of various species were assigned. The relationship and the change among these confirmed the mechanism of the reaction and the process of electron transfer. The major channel for the reaction was found to be the cis‐channel. At the same time the rate constant was estimated. A new method of analyzing reaction mechanism is also presented. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 52–60, 2003 相似文献
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Bon-Su Lee Ikchoon Lee Chang Hyun Song Jae Young Choi 《Journal of computational chemistry》1985,6(5):486-491
The hydrogen atom transfer reaction between substituted methanes (substituents; H, F, CH3, OH, and CN) and methyl radicals was studied by 4-31G (UHF) calculations using the MINDO/3 geometries. The transition state structures and energy barriers were determined, and variations of the transition state and of the reactivity due to the change of substituent were analyzed based on the potential energy surface characteristics. It was concluded that the reaction is of the SH2 type with a backside attack, and transition state variations are controlled by the vector sum of the component parallel to (Hammond rule) and one perpendicular to the reaction coordinate (anti-Hammond rule). It was also concluded that the most important factor influencing the reactivity is bond dissociation energy effect directly related to the spin transfer of the radical species, and the polar effect need not be overemphasized. 相似文献
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Phosphotriesterase (PTE) is a binuclear zinc enzyme that catalyzes the hydrolysis of extremely toxic organophosphate triesters. In the present work, we have investigated the reaction mechanism of PTE using the hybrid density functional theory method B3LYP. We present a potential energy surface for the reaction and provide characterization of the transition states and intermediates. We used the high resolution crystal structure to construct a model of the active site of PTE, containing the two zinc ions and their first shell ligands. The calculations provide strong support to an associative mechanism for the hydrolysis of phosphotriesters by PTE. No protonation of the leaving group was found to be necessary. In particular, the calculations demonstrate that the nucleophilicity of the bridging hydroxide is sufficient to be utilized in the hydrolysis reaction, a feature that is of importance for a number of other di-zinc enzymes. 相似文献
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为了从微观上理解半纤维素热解过程及其主要产物的形成演变机理,采用密度泛函理论方法B3LYP/6-31G++(d,p),对O-乙酰基-吡喃木糖的热解反应机理进行了量子化学理论研究。在热解过程中,O-乙酰基-吡喃木糖中的O-乙酰基首先脱出,形成乙酸和中间体IM1,该步反应能垒为269.4 kJ/mol。IM1进一步发生开环反应形成IM2,开环反应能垒较低,为181.8 kJ/mol。对中间体IM2设计了四种可能的热解反应途径,对各种反应的反应物、产物、中间体和过渡态的结构进行了能量梯度全优化,计算了各热解反应途径的热力学和动力学参数。计算结果表明,反应路径(4)和反应路径(2)是O-乙酰基-吡喃木糖热解的主要反应通道,乙酸、乙醛、乙醇醛、丙酮、CO、CO2、CH4等小分子产物是热解的主要产物。这与相关实验结果分析是一致的。 相似文献
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The mechanism of the A2 hydrolysis of acetamide has been investigated theoretically using MNDO Method. Fully optimized geometries of all species at the stationary points corresponding to energy minima and energy maxima along the reaction coordinate are determined for the two reaction paths: the rate-determining nucleophilic attack of water on the carbonyl carbon (i) of the O-protonated tautomer and (ii) of the N-protonated form. Results show that the latter provides a lower energy path by 7.5 Kcal/Mol compared to the former.Tetrahedral species' found were not at the energy minima but at or near the saddle points. Optimizied structures and formal charges on heavy atoms showed that the bond interchange with the concurrent proton interchange takes place at the rate-determining step. The negative charge on N atom was found to increase in the rate-determining step relative to that of the ground state, the O-protonated acetamide, and hence substitution of electron withdrowing group on N is predicted to depress the activation energy in agreement with the experimental results. 相似文献