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1.
Structural Chemistry - The reaction mechanism of disulfur (S2) and O3 on the triplet and singlet potential energy surfaces has been investigated theoretically at the... 相似文献
2.
Dan Bing Yongfang Zhao Fengyou Hao Xinying Li Fengli Liu Guohua Zhang Pingxia Zhang 《International journal of quantum chemistry》2007,107(5):1085-1091
Ab initio calculations of the potential energy surface (PES) for the Br+O3 reaction have been performed using the MP2, CCSD(T), and QCISD(T) methods with 6‐31G(d), 6‐311G(d), and 6‐311+G(3df). The reaction begins with a transition state (TS) when the Br atom attacks a terminal oxygen of ozone, producing an intermediate, the bromine trioxide (M), which immediately dissociates to BrO+O2. The geometry optimizations of the reactants, products, and intermediate and transition states are carried out at the MP2/6‐31G(d) level. The reaction potential barrier is 3.09 kcal/mol at the CCSD(T)/6‐311+G(3df)//MP2 level, which shows that the bromine atom trends intensively to react with the ozone. The comparison of the Br+O3 reaction with the F+O3 and Cl+O3 reactions indicates that the reactions of ozone with the halogen atoms have the similar reaction mechanism. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
3.
The reaction of C2H5OH and O3 on the singlet potential energy surface is carried out using the MP2 and CCSD(T)//MP2 theoretical approaches in connection with the 6-311++G(d,p) basis set. Three pre-reactive complexes C1, C2, and C3 are formed between ethanol and ozone at atmospheric pressure and 298.15 K temperature. With variety of the complexes, seven types of product are obtained which four types of them have enough thermodynamic stability. In thermodynamic approach, the most favor product begins with the formation of pre-reactive C2 complex and produces the CH3CH(OH)2 + O2 as final adduct in a process that is computed to be exothermic by ?53.759 kcal/mol and spontaneous reaction by ?51.833 kcal/mol in Gibbs free energy. In kinetic viewpoint, the formation of CH3COH + cis-H2O3 as a final adducts is the most favor path. 相似文献
4.
I. Garcia V. Uc M. E.Ruiz Y. G. Smeyers A. Vivier Bunge 《Journal of Molecular Structure》1995,340(1-3):149-158
Unrestricted Hartree-Fock calculations have been carried out to study the benzylperoxyl radical, an intermediate atmospheric contaminant. For this purpose, quantum mechanical MP2//UHF ab initio calculations were performed by using 6-31G** and 6-31 + G** basis sets. Because no previous experimental nor theoretical data were available for benzylperoxyl, the results were compared with those of the smaller unsaturated peroxyl radicals, such as allylperoxyl. It is found that the calculated absolute minimal energy corresponds to a trans conformation in which the O---O bond is sticking away from the benzene ring. Benzylperoxyl is found also to exhibit an unusually O---O small bond order, which reflects the weakness of the bond, i.e. its ability to react with NO forming NO2 and subsequently ozone. A peculiar MO diagram is obtained, with the unpaired MO deeply located in the “doubly” occupied MO space. This effect is also observed in allylperoxyl. Structural parameters, charges, spin densities and dipole moments are also reported. 相似文献
5.
We applied the semiclassical initial value representation method to calculate energies, lifetimes, and wave functions of scattering resonances in a two-dimensional potential for O+O2 collision. Such scattering states represent the metastable O3* species and play a central role in the process of ozone formation. Autocorrelation functions for scattering states were computed and then analyzed using the Prony method, which permits one to extract accurate energies and widths of the resonances. We found that the results of the semiclassical wave packet propagation agree well with fully quantum results. The focus was on the 16O16O18O isotopomer and the anomalous isotope effect associated with formation of this molecule, either through the 16O16O+18O or the 16O+16O18O channels. An interesting correlation between the local vibration mode character of the metastable states and their lifetimes was observed and explained. New insight is obtained into the mechanism by which the long-lived resonances in the delta zero-point energy part of spectrum produce the anomalously large isotope effect. 相似文献
6.
The recombination of ozone via the chaperon mechanism, i.e., ArO+O2 --> Ar+O3 and ArO2+O --> Ar+O3, is studied by means of classical trajectories and a pairwise additive Ar-O3 potential energy surface. The recombination rate coefficient has a strong temperature dependence, which approximately can be described by T(-n) with n approximately 3. It is negligible for temperatures above 700 K or so, but it becomes important for low temperatures. The calculations unambiguously affirm the conclusions of Hippler et al. [J. Chem. Phys. 93, 6560 (1990)] and Luther et al. [Phys. Chem. Chem. Phys. 7, 2764 (2005)] that the chaperon mechanism makes a sizable contribution to the recombination of O3 at room temperature and below. The dependence of the chaperon recombination rate coefficient on the isotopomer, studied for two different isotope combinations, is only in rough qualitative agreement with the experimental data. The oxygen atom isotope exchange reaction involving ArO and ArO2 van der Waals complexes is also investigated; the weak binding of O or O2 to Ar has only a small effect. 相似文献
7.
Oxidation of hydrogen cyanide with ozone on the singlet potential energy surface is carried out using the MP2 and CCSD(T)//MP2 theoretical approaches in connection with the 6-311++G(d,p) basis set. In this reaction, energy barrier of transition states are low, so the reaction of HCN with ozone can occur easily at atmospheric condition. With variety of pre-reactive complex, five types of products are obtained at the MP2 method which four types of them have enough thermodynamic stability at the standard condition. CO2 + HNO are final adducts in a process that is computed to be exothermic by ?132.605 kcal/mol in standard enthalpy and spontaneous by ?144.166 kcal/mol in Gibbs free energy of reaction. In kinetic viewpoint, the production of OCN + HO2 adducts path with one low level transition state is the most favored path. 相似文献
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9.
The photochemical mechanisms behind the ozone dynamics in the stratosphere have been studied for a long time. Though the differential
equations describing the kinetics associated with them are well known, their mathematical properties have not been fully explored.
In this work some of these mathematical properties as well as their physical implications are investigated in the simplest
photochemical mechanism, namely, Chapman’s one. 相似文献
10.
《Journal of Photochemistry》1980,12(1):67-74
The rate of formation of ozone by O(3P) + O2(3Σg−) recombination following an energy pulse such as flash photolysis or pulse radiolysis is typically only about half the rate of disappearance of O(3P). Measurements of the growth of the Hartley band of ozone under several experimental conditions are shown to be consistent with reaction of 0.62 of the available O(3P) to form a metastable state of ozone. Deactivation of the metastable state by ground state O2 is slow (approximately 10−16 cm3 molecule−1 s−1), but it is significant because of its large excess. Deactivation and decomposition of the metastable state by singlet molecular oxygen is rapid. 相似文献
11.
O. S. Subbotin T. P. Adamova R. V. Belosludov H. Mizuseki Y. Kawazoe V. R. Belosludov 《Journal of Structural Chemistry》2012,53(4):627-633
Structural, dynamic, and thermodynamic properties of ozone, oxygen, and mixed ozone-oxygen hydrates are investigated. The thermodynamic stability regions of these hydrates are found. Ozone can form hydrates at ambient pressure and temperatures below 230 K. Strong dependence of the binary hydrate formation pressure on the ozone concentration in the gas phase is shown. In the formation of the hydrate, ozone concentrates in the hydrate phase. At an ozone concentration of 5 mol.% in the gas phase, the ozone content in the hydrate reaches 40%. 相似文献
12.
Acosta-Silva C Bertran J Branchadell V Oliva A 《Journal of the American Chemical Society》2012,134(13):5817-5831
Ribosomes transform the genetic information encoded within genes into proteins. In recent years, there has been much progress in the study of this complex molecular machine, but the mechanism of peptide bond formation and the origin of the catalytic power of this ancient enzymatic system are still an unsolved puzzle. A quantum-mechanical study of different possible mechanisms of peptide synthesis in the ribosome has been carried out using the M06-2X density functional. The uncatalyzed processes in solution have been treated with the SMD solvation model. Concerted and two-step mechanisms have been explored. Three main points suggested in this work deserve to be deeply analyzed. First, no zwitterionic intermediates are found when the process takes place in the ribosome. Second, the proton shuttle mechanism is suggested to be efficient only through the participation of the A2451 2'-OH and two crystallographic water molecules. Finally, the mechanisms in solution and in the ribosome are very different, and this difference may help us to understand the origin of the efficient catalytic role played by the ribosome. 相似文献
13.
Our serial studies from 1970s on chemical composition, structure determination and formation mechanism of gallstones were reviewed. The chemical component investigation of brown-pigment gallstone demonstrated that it consists of macromolecules such as proteins, glyco-proteins, polysaccharides, bilirubin polymers and pigment polymers, and biomolecules such as cholesterol, bile salts, calcium salts of carbonate, phosphate, fatty acids and bilirubinate as well as various metal ions. The binding of metal ions with bile salts and bilirubin plays important roles in gallstone formation, i.e., calcium bilirubinate complex is the major constitute of brown-pigment gallstones, and copper bilirubinate complex is critical in the black color appearance of black-pigment gallstone. The cross section of many gallstones exhibits a concentric ring structure composed of various small particles with a fractal character. This is nonlinear phenomenon in gallstone formation. A typical model system of metal ions-deoxycholate (or cho 相似文献
14.
Lai‐Cai Li Jing Wang Xin Wang An‐Min Tian Ning‐Bew Wong 《International journal of quantum chemistry》2002,87(5):288-292
Ab initio calculations of the potential energy surface for the F + O3 and Cl + O3 reactions have been performed using the G3 and G3MP2 methods, which optimize the geometry configuration of reactants, products, intermediates, and transition states. The results show that fluorine atoms react with ozone as violently as chlorine atoms. At the same time, we have studied the reaction mechanisms of F atoms and Cl atoms with methane. It is found that fluorine atoms prefer to react with methane and chlorine atoms with ozone when there is competition between ozone and methane. Therefore, we can reasonably explain why chlorine atoms play the main role of reactants depleting ozone, while the more active fluorine atoms deplete less ozone. © 2002 Wiley Periodicals, Inc.; DOI 10.1002/qua.10119 相似文献
15.
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
16.
Abstract The condensation of silicic acid with aluminate in alkaline environment, the essential reaction of zeolite synthesis, is studied
using the density functional theory, with the hybrid functional B3LYP in conjunction with the 6-311++G(d, p) basis set. The
Si(OH)4 monomer and Al(OH)4− anion are used as the reactant models to study the condensation pathway in basic solution. The solvent effect is included
by the COSMO-RS model. The study includes the complete geometry optimization and frequency calculation of reactants, products,
reaction intermediates, and transition states, as well as the calculation of the activation energy of the different pathways
involved. The intrinsic reaction coordinate method is used to verify the reactant and product corresponding to the transition
state. The calculation shows that the formation of Si–O–Al linkage can proceed via two possible reaction pathways. The first
is a single-step process, in which the formation of SiO···Al bond and removal of water are synchronous, with the activation
energy of 83.7 kJ/mol. The second is a stepwise route, in which the AlO···Si bond is first formed to give a 5-coordianted
Si intermediate, and then water is removed to yield a dimer aluminosilicate, with the barriers of 62.7 and 69.3 kJ/mol for
the two steps, respectively.
Index Abstract
Theoretical study of formation mechanism of aluminosilicate in the synthesis of zeolites
Guo-Feng Jiao, Min Pu, Biao-Hua Chen
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18.
硫铁矿制硫化铁机理的初步探讨 总被引:3,自引:0,他引:3
本文探讨了用硫铁矿(FeS_2)为原料,掺入适量铁屑,在还原性气氛中加热制备硫化铁的机理。用化学分析法和矿相分析法研究了硫铁矿离解的物理化学过程、矿物的物相变化以及铁屑所起的作用。从理论上阐明以硫铁矿为原料制备硫化铁的可能性。 相似文献
19.
Previously calculated resonance widths of the ground vibrational levels in the electronic states 1 (3)A" ((3)A(2)) and 1 (3)A' ((3)B(2)), which belong to the Wulf band system of ozone, are significantly smaller than observed experimentally. We demonstrate that predissociation is drastically enhanced by spin-orbit coupling between 1 (3)A"/X (1)A' and 1 (3)A'/1 (3)A". Multistate quantum mechanical calculations using ab initio spin-orbit coupling matrix elements give linewidths of optically bright components of the right order of magnitude. 相似文献