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应用密度泛函理论的MPW1K,BHandHLYP和MPWB1K方法,结合6-31+G(d,p)基组优化了烯丙醇与臭氧反应势能面上各驻点的几何构型,通过同一水平的振动频率分析确认了中间体和过渡态.反应路径上的驻点都在HL理论水平下进行单点能量校正,并进行了MPW1K/6-31+G(d,p)水平下的零点振动能校正(ZPE).对反应机理的详尽分析表明臭氧抽取烯丙醇羟基基团中H的通道的反应势垒比臭氧加合烯丙醇双键基团通道的反应势垒高,臭氧与烯丙醇双键加合生成臭氧化物为最可几反应路径.在加合反应历程中,氢迁移通道需经过氢迁移和离解等复杂过程,最终要产生少量的OH自由基,与烃烯类臭氧化反应产生大量OH自由基的结果相反. 相似文献
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The theoretic study of reaction between BrONO2 and O(3P) is reported by using the molecular orbital ab initio and density function theory (DFT). Equilibrium structural parameters, harmonic vibrational frequencies, total energy and zero energy of reactants, transition states, inter mediates and products during reactions are computed by B3LYP theory level with the basis set 6-311+G(d,p). The transition states and inter mediates of the reaction are verified by frequency analysis, and the relation ship of reactants, transition states, intermediates and products is affirmed by Intrinsic Reaction Coordinate(IRC) calculation. The activation energy of the reaction has also been calculated. Based on the optimized structure, the single point energy of all species is obtained by CCSD(T) with the basis set 6-311+G(d,p). The results show that there are three exothermic channels and their corresponding products are: cis-Br ONO + 3O2, trans-BrONO + 3O2 and BrOO+NO2. The activation energy of three channels is 91.58, 101.25, 51.17kJ/mol under B3LYP and 141.19, 148.39, 103.21 kJ/molunder CCSD(T) theory level. The third channel is the dominant channel. 相似文献
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本文应用密度泛函理论(DFT)研究钛系催化剂催化聚酯热降解的反应机理。分别以Ti(OEt)4化合物以及Ti(OEt)3 阳离子化合物为催化剂,探讨了二苯甲酸乙二酯(EDB)解聚反应的Lewis酸催化热降解反应机理(M1机理)和烷氧基配位催化热降解反应机理(M2机理)。结果表明,Lewis酸催化热降解反应机理在两种催化剂下的解聚反应能垒与无催化剂反应非常相似,未表现出明显促进作用;Ti(OEt)3 催化剂在M2机理中明显降低了解聚反应能垒,是聚酯热降解反应的催化活性中心。经轨道相互作用分析发现,阳离子催化剂和反应物EDB之间存在较为明显的轨道相互作用。 相似文献
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用DFT-B3LYP方法和IEF-PCM溶剂化模型研究了反铂抗癌药物trans-[PtCl2(piperidine)(Am)](Am=2-picoline(1),3-picoline(2),4-picoline(3)),trans-[PtCl2(piperidine)(piperazine)](4),trans-[PtCl2(pipera-zine)2](5)and trans-[PtCl2(iminoether)2](6)的水解过程.水解反应是药物与DNA靶分子作用的关键活化步骤.全优化和表征了一水解和二水解反应经由一般的SN2路径过程所有物种的势能面稳定点.结果发现反应过程遵循已经建立的平面正方形配合物的配体取代反应理论,即取代反应通常通过一个三角双锥过渡态结构的铂配体交换反应发生.得到的过渡态结构与以前的相关工作一致,所有反应都是吸热反应;所有体系的二水解能垒都高于一水解.与顺铂相比,这些配合物都有更快的水解反应速率;并与以前类似的反铂配合物的研究做了比较.研究结果提供了这些配合物水解反应过程的详细能量变化,对理解药物与DNA靶分子的作用机理和新型反铂抗癌药物的设计有帮助. 相似文献
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Aun团簇催化水煤气变换反应机理的密度泛函理论研究 《燃料化学学报》2017,45(12):1473-1480
利用密度泛函理论(DFT)研究了Au10、Au13和Au20三类团簇的稳定性和对水煤气变换(WGSR)反应的催化活性,考察了各物质在Aun团簇上的吸附行为和微观反应机理。结果表明,三类Aun团簇的稳定性顺序为Au10Au13Au20,而Aun团簇中电子离域性及吸附能力大小趋势为Au13Au10Au20。在三类Aun团簇上,水煤气变换反应的控速步骤均为H2O的解离,但其反应机理路径有所不同。Au10团簇上为羧基机理,COOH*中间体直接解离;Au13团簇上为氧化还原机理,两个OH*发生歧化反应;Au20团簇上为羧基机理,COOH*和OH*发生歧化反应。通过对三类团簇上的最佳反应路径进行比较发现,Au13团簇在低温下具有较好的催化活性。 相似文献
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H2CO和NO2反应机理的密度泛函理论计算研究 总被引:2,自引:2,他引:2
用密度泛函理论方法在UB3LYP/ 6-311++G(d,p)并包含零点能水平上计算得到了H2CO和NO2反应的势能面.在势能面上找到了由H2CO和NO2反应生成HCO和trans-HONO的两条反应通道.直接H迁移反应通道的势垒只有90.54 kJ*mol-1,是主要的反应通道,其TST速率是7.9 cm3*mol-1*s-1,与文献值相符;另一条通道是H2CO异构化为trans-HCOH,然后C位H迁移,最后生成的HOC分子异构化为HCO,这条通道反应势垒高达348.03 kJ*mol-1,是一条次要反应通道. 相似文献
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《Journal of computational chemistry》2017,38(14):1093-1102
A comprehensive picture on the mechanism of the epoxy‐carboxylic acid curing reactions is presented using the density functional theory B3LYP/6‐31G(d,p) and simplified physical molecular models to examine all possible reaction pathways. Carboxylic acid can act as its own promoter by using the OH group of an additional acid molecule to stabilize the transition states, and thus lower the rate‐limiting barriers by 45 kJ/mol. For comparison, in the uncatalyzed reaction, an epoxy ring is opened by a phenol with an apparent barrier of about 107 kJ/mol. In catalyzed reaction, catalysts facilitate the epoxy ring opening prior to curing that lowers the apparent barriers by 35 kJ/mol. However, this can be competed in highly basic catalysts such as amine‐based catalysts, where catalysts can enhance the nucleophilicity of the acid by forming hydrogen‐bonded complex with it. Our theoretical results predict the activation energy in the range of 71 to 94 kJ/mol, which agrees well with the reported experimental range for catalyzed reactions. © 2017 Wiley Periodicals, Inc. 相似文献
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Transition structures associated with the C-C bond-formation step of the proline-catalyzed intermolecular aldol reaction
between acetone and isobutyraldehyde have been studies using density functional theory methods at the B3LYP/6-31G** computational
level. A continuum model has been selected to represent solvent effects. For this step, which is the stereocontrolling and
rate-determining step, four reactive channels corresponding to the syn and anti arrangement of the active methylene of the
enamine relative to the carboxylic acid group of l-proline and the re and si attack modes to both faces of the aldehyde carbonyl group have been analyzed. The B3LYP/6-31G**
energies are in good agreement with experiment, allowing us to explain the origin of the catalysis and stereoselectivity for
these proline-catalyzed aldol reactions.
Received: 2 April 2002 / Accepted: 18 July 2002 / Published online: 11 October 2002
Acknowledgements. This work was supported by research funds provided by the Ministerio de Educación y Cultura of the Spanish Government by
DGICYT (project PB98–1429). All the calculations were performed on a Cray–Silicon Graphics Origin 2000 of the Servicio de
Informática de la Universidad de Valencia. We are most indebted to this center for providing us with computer capabilities.
Correspondence to: L. R. Domingo e-mail: domingo@utopia.uv.es 相似文献
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The B3LYP hybrid density functional method has been carried out to study theoretically the mechanism of Pd(0)-catalyzed alkyne cyanoboration reaction. Both the intermolecular and intramolecular alkyne cyanoboration reactions were studied. For each reaction, three paths were proposed. In path A of each reaction, the first step is B-CN bond oxidative addition to bisphosphine complex Pd(PH(3))(2), in path B of each reaction, the first step is alkyne coordination to bisphosphine complex Pd(PH(3))(2), and in path C of each reaction, the first step is the PH(3) dissociation from Pd(PH(3))(2) to form monophosphine complex Pd(PH(3)). For both reactions, path B is favored. The dissociation and recoordination of phosphine ligand are found to be very important for the entire reaction, in agreement with the experiment. In both intermolecular and intramolecular cyanoboration reactions, cyano migration is preferred to take place compared with alkenylboryl migration for the formation of the final cis products. The rate-determining step for both intermolecular and intramolecular cyanoboration reactions is found to be the insertion of carbon-carbon triple bond into Pd-B bond with the activation energy of 38.4 and 34.3 kcal/mol relative to the initial reactants, respectively. These values suggest that intramolecular reaction is relatively easy to occur. 相似文献
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Zhengcheng Wen Zhihua Wang Jiangrong Xu Junhu Zhou Kefa Cen 《International journal of quantum chemistry》2011,111(5):1081-1091
Despite of its fundamental importance, the mechanism of the reaction between ozone and dioxins are still lack detailed investigation so far. It is well-known that quantum chemical calculation is a well-established method for investigating chemical reactions. In this article, quantum chemical calculation was employed to investigate the mechanism of the reaction between ozone and dioxins, as exemplified by 2,3,7,8-TCDD. The theoretical study showed that, 2,3,7,8-TCDD was gradually destructed by ozone via six cleavages of the CC bonds. All the six cleavages of the CC bonds were calculated and discussed in detail based on the theoretical calculations by the UB3LYP/6-31G(d) method. At the same time, the energies of stationary points along the reaction process were calculated by the UMP2/6-311g(d,p)//UB3LYP/6-31G(d) method and the activation energy was obtained. The obtained activation energy was 12.25 kcal/mol, which was lower than that of the reaction between benzene and O3(16.64 kcal/mol). This indicated that, by comparison with benzene, 2,3,7,8-TCDD could be more efficiently destructed by O3. The reason for this result was also discussed. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
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He Bian Honghong Zhang Ling Pei Qian Wang Fang Wang Yun Zhang Jinshe Chen 《International journal of quantum chemistry》2020,120(8):e26146
Density functional theory was adopted in this work to reveal the reaction mechanism of CH2SH with HO2. Reaction rate constants were computed from 200 to 2000 K using the transition state theory combined with Wigner and Eckart tunneling correction. Moreover, localized orbital locator, atoms in molecules and Mayer bond order analyses were used to study the essence of chemical bonding evolution. Eleven singlet paths and three triplet ones are located on the potential surface (PES). The results show that the main products on the singlet PES are 1CH2S and H2O2, whereas on the triplet PES they are CH3SH + 3O2, which are coincident with the similar reaction of CH3S and HO2. This conclusion is also supported by rate constant calculation results. Interestingly, all the possible paths are involved in the hydrogen transfer. The results have provided underlying insights to the analogous reactions and further experimental studies. 相似文献
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My‐Phuong Pham Buu Q. Pham Lam K. Huynh Ha Q. Pham Maurice J. Marks Thanh N. Truong 《Journal of computational chemistry》2014,35(22):1630-1640
A comprehensive picture on the mechanism of the epoxy‐phenol curing reactions is presented using the density functional theory B3LYP/ 6‐31G(d,p) and simplified physical molecular models to examine all possible reaction pathways. Phenol can act as its own promoter by using an addition phenol molecule to stabilize the transition states, and thus lower the rate‐limiting barriers by 27.0–48.9 kJ/mol. In the uncatalyzed reaction, an epoxy ring is opened by a phenol with an apparent barrier of about 129.6 kJ/mol. In catalyzed reaction, catalysts facilitate the epoxy ring opening prior to curing that lowers the apparent barriers by 48.9–50.6 kJ/mol. However, this can be competed in highly basic catalysts such as amine‐based catalysts, where catalysts are trapped in forms of hydrogen‐bonded complex with phenol. Our theoretical results predict the activation energy in the range of 79.0–80.7 kJ/mol in phosphine‐based catalyzed reactions, which agrees well with the reported experimental range of 54–86 kJ/mol. © 2014 Wiley Periodicals, Inc. 相似文献
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采用密度泛函理论(DFT)方法,从静态与动态两大方面分析了白藜芦醇分子酚羟基在不同溶剂中清除自由基活性的能力大小.通过白藜芦醇的结构参数、前线轨道理论、3种抽氢反应机制等方面分析了分子活性位与其性质的关系.探讨了白藜芦醇分子不同位置酚羟基清除·OH和·OOH的抗氧化机理,得到了该分子与·OOH发生抽氢反应时的过渡态结构.计算结果表明,在任何溶剂中白藜芦醇分子C(4')位上酚羟基活性最高,发生抽氢反应时反应热最小,是高活性位点. 相似文献
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Qinmi Wang Hualiang Jiang Jianzhong Chen Kaixian Chen Ruyun Ji 《International journal of quantum chemistry》1998,70(3):515-525
The acylation process in the acetylcholinesterase (AChE)-catalyzed hydrolysis of the neurotransmitter, acetylcholine (ACh), has been determined with the semiempirical quantum chemical calculation method AM1 using the model molecules extracted from the X-ray crystal structure of Torpedo Californica AChE. For the sake of identifying the microfeatures of the mechanism of this reaction, two types of possible mechanisms, stepwise mechanism and cooperative mechanisms, were proposed and studied with AM1 methods. All the model molecules for the possible reactants, intermediates, transition states, and products in the reaction pathways of the two mechanisms were obtained. Energy profiles, the structural properties of the transition states, indicate that the acylation of AChE-catalyzed hydrolysis of ACh adopts the cooperative mechanism, i.e., the proton transfer from Ser220 of AChE to His440 occurs simultaneously with the nucleophilic attack of Ser200 to the carbonyl carbon atom of ACh. This result is in agreement with the kinetic data and the secondary isotope effects of AChE-catalyzed reactions. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 515–525, 1998 相似文献
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Valentin Gogonea 《International journal of quantum chemistry》2005,104(3):342-353
This article presents a theoretical investigation of the reaction mechanism of imidazole nitration by peroxynitrite using density functional theory calculations. Understanding this reaction mechanism will help in elucidating the mechanism of guanine nitration by peroxynitrite, which is one of the assumed chemical pathways for damaging DNA in cells. This work focuses on the analysis of the potential energy surface (PES) for this reaction in the gas phase. Calculations were carried out using Hartree–Fock (HF) and density functional theory (DFT) Hamiltonians with double‐zeta basis sets ranging from 6‐31G(d) to 6‐31++G(d,p), and the triple‐zeta basis set 6‐311G(d). The computational results reveal that the reaction of imidazole with peroxynitrite in gas phase produces the following species: (i) hydroxide ion and 2‐nitroimidazole, (ii) hydrogen superoxide ion and 2‐nitrosoimidazole, and (iii) water and 2‐nitroimidazolide. The rate‐determining step is the formation of a short‐lived intermediate in which the imidazole C2 carbon is covalently bonded to peroxynitrite nitrogen. Three short‐lived intermediates were found in the reaction path. These intermediates are involved in a proton‐hopping transport from C2 carbon to the terminal oxygen of the ? O? O moiety of peroxynitrite via the nitroso (ON? ) oxygen. Both HF and DFT calculations (using the Becke3–Lee–Yang–Parr functional) lead to similar reaction paths for proton transport, but the landscape details of the PES for HF and DFT calculations differ. This investigation shows that the reaction of imidazole with peroxynitrite produces essentially the same types of products (nitro‐ and nitroso‐) as observed experimentally in the reaction of guanine with peroxynitrite, which makes the former reaction a good model to study by computation the essential characteristics of the latter reaction. Nevertheless, the computationally determined activation energy for imidazole nitration by peroxynitrite in the gas phase is 84.1 kcal/mol (calculated at the B3LYP/6‐31++G(d,p) level), too large for an enzymatic reaction. Exploratory calculations on imidazole nitration in solution, and on the reaction of 9‐methylguanine with peroxynitrite in the gas phase and solution, show that solvation increases the activation energy for both imidazole and guanine, and that the modest decrease (15 kcal mol?1) in the activation energy, due to the adjacent six member ring of guanine, is counterbalanced by solvation. These results lead to the speculation that proton tunneling may be at the origin of experimentally observed high reaction rate of guanine nitration by peroxynitrite in solution. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
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Yuan Yongning Yuan Nini Guo Tuo Bai Hongcun Xia Hongqiang Ren Yanjiao Guo Qingjie 《Structural chemistry》2022,33(3):721-731
Structural Chemistry - A detailed theoretical analysis of the mechanism of chemical bond activation in cyclohexane catalysed by the atomic transition-metal cation Ni+ was performed by density... 相似文献