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丙烯的臭氧化反应动力学研究 总被引:3,自引:0,他引:3
使用自行研制的烟雾箱实验装置, 研究了模拟实际大气环境臭氧浓度下(最小浓度6.6×10−8)臭氧与丙烯的反应动力学. 结合Model 49C-O3 Analyzer与GC-FID对臭氧与丙烯在282~314 K温度范围内的速率常数进行了测定, 得到臭氧初始浓度为6.61×10−8、温度为282 K时臭氧与丙烯的反应速率常数为6.73×10−18 cm3•molecule−1•s−1. 并根据不同温度下测得的反应速率常数, 求得该反应的阿仑尼乌斯方程为k2=(5.8±1.2)×10−15e(−1907±53)/T. 对比前人结果, 我们测得的速率常数偏小, 活化能偏高, 但速率常数的最大误差仅为11%, 活化能的最大误差为5%. 说明我们的研究设备在实际大气条件下是可靠的, 可用于进一步深入研究臭氧有关的反应. 相似文献
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Kinetic spectrophotometric method for rapid determination of trace formaldehyde in foods 总被引:1,自引:0,他引:1
A simple and sensitive kinetic-spectrophotometric method was developed for the determination of ultra trace amount of formaldehyde in food samples. The method was based on the oxidation of rhodamine B (RhB) by potassium bromate in sulfuric acid medium (formaldehyde as catalyst). The reaction was monitored by measuring the decrease in absorbance of the dye at 515 nm after 6 min. The developed method allowed the determination of formaldehyde in the range of 10–100 μg L−1 with good precision, accuracy and the detection limit was down to 2.90 μg L−1. The relative standard deviations for the determination of 10 and 60 μg L−1 of formaldehyde were 3.0% and 1.9% (n = 10), respectively. The method was found to be sensitive, selective and was applied to the determination of formaldehyde in foods with satisfactory results. 相似文献
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《Journal of Saudi Chemical Society》2020,24(4):364-373
High-performance gas sensors can offer great potentials for monitoring and detection of volatile organic compounds (VOCs) in both domestic and industrial environment. In the present work, a new HCHO gas sensor was constructed with reduced graphene oxide (RGO) induced by the oximation reaction. The gas-sensing performance test results suggested that the RGO hydroxylamine hydrochloride (RGO/HA-HCl) sensor presented a high response of 75% at 16 ppm HCHO at room temperature, and a high selectivity for HCHO suffering little interference with high concentrations of volatile organic compounds, including methanol, ethanol, and methylbenzene, dichloromethane and water. Additionally, the RGO/HA-HCl sensor also showed a good long-term stability with RSD of 5.83% for a 15-day continuous sensing test, and the detection limit (DL) could reach 0.023 ppm under ambient conditions. Moreover, the mechanism for the high sensitivity and selectivity of formaldehyde was further established by in-situ gas chromatography mass spectrometry (GC–MS). This work would provide a reliable new HCHO gas sensor which could be used for monitoring and forewarning the emission of HCHO for a better protection and improvement of our environment. 相似文献
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动力学光度法测定痕量甲醛 总被引:11,自引:0,他引:11
在稀硫酸溶液中,痕量甲醛对氯酸钾氧化玫瑰桃红R褪色反应有催化作用,研究了其动力学条件,测定了动力学反应参数,建立了测定痕量甲醛的动力学光度分析新方法,线性范围为0.02—0.5mg/L,检出限为8.0μg/L;灵敏度较高,选择性较好;该法用于新建住宅室内空气及建筑粘合剂中痕量甲醛的测定,结果满意。 相似文献
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S. L. Khursan S. A. Grabovskii N. N. Kabal'nova E. G. Galkin V. V. Shereshovets 《Russian Chemical Bulletin》2000,49(8):1338-1348
The products and kinetics of the thermal decomposition of dimethyldioxirane (DMDO) were studied. The reaction proceedsvia three parallel pathways: isomerization to methyl acetate, oxygen atom insertion into the C−H bond of a solvent molecule (acetone),
and the solvent-induced homolysis of the O−O bond in the DMDO molecule. The contribution of the latter reaction channel isca. 23% at 56°C. The overall kinetic parameters of DMDO thermolysis in oxygen atmosphere were determined. The free radical-induced
DMDO decomposition occurs in an inert atmosphere. The formal kinetics of this reaction was investigated. The mechanism of
the DMDO thermolysis is discussed.
Dedicated to Professor E. T. Denisov on the occasion of his 70th Birthday.
Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1344–1354, August, 2000. 相似文献
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动力学分光光度法及荧光光度法测定痕量甲醛 总被引:10,自引:0,他引:10
在稀硫酸溶液中,研究了甲醛对催化KClO3氧化丁基罗丹明B褪色及荧光猝灭的动力学条件,建立了测定痕量甲醛的动力学光度及荧光光度分析方法,方法线性范围分别为0.02~0.27μg/mL和0.01~2.45μg/mL,检出限分别为1.2×10-8g/mL和3.8×10-9g/mL。该法灵敏度较高,选择性较好,用于湖水、饮料和漆料中痕量甲醛的测定,结果令人满意。 相似文献
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X. L. Zeng W. H. Chen J. C. Liu J. L. Kan 《Journal of Thermal Analysis and Calorimetry》2008,91(2):359-363
This paper presents calorimeter measurement for the thermal decomposition of n-propyl nitrate (NPN), isopropyl nitrate (IPN) and 2-ethylhexyl nitrate (EHN). Similar experimental results of triethylene
glycol dinitrate (tri-EGDN) and tetraethylene glycol dinitrate (tetra-EGDN) are included for comparison. The potential energy
surfaces (PESs) along O-NO2 bond stretch are investigated using the DFT (B3P86, B3PW91 and B3LYP), ab initio Hartree-Fock and PM3 methods. The good coincidence
of experimental with theoretical results indicates that initial stage in the thermal decomposition of five nitrates is only
unimolecular homolytical dissociation of the O-NO2 bonds and the activation energies of thermolysis by DSC correspond to the energies of O-NO2 bond scission of nitrates. 相似文献
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Lingling Peng 《Tetrahedron letters》2006,47(46):8175-8178
An unusual dehydroxymethylation has been observed in an acyclic primary alcoholic system. The relief of steric congestion is considered as the primary driving force in this reaction. 相似文献
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The reaction between urea and formaldehyde in water solution was theoretically investigated by using B3LYP and MP2 methods.It was found that the addition of the nitrogen atom in urea to the carbonyl group in formaldehyde precedes the proton transfer and the proton migration from water to the carbonyl group occurs before the proton abstraction from the nitrogen.With one or two water molecules involved in the TS.the activation energy barrier is lowered compared to the TS of the mechanism with no water participation.The energy change along the reaction coordinate clearly shows that a zwitterionic-like intermediate does not exist on the PES.The reaction between urea and formaldehyde occurs in a concerted mechanism but with asynchronous characters.This is different from the stepwise mechanism recently found for the amination reactions of formaldehyde. 相似文献
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Summary The optimization of in situ derivatization and preconcentration of formaldehyde in air using solid phase microextraction with
gas chromatographic determination was investigated. A dimethylpolysiloxane coating (7 μm) solid-phase microextraction needle
was used in the final procedure as a support for derivatizing reagents such as 2,4-dinitrophenylhydrazine and acetylacetone.
Standard concentrations of formaldehyde in air were obtained using a headspace technique and equilibrium concentrations of
formaldehyde in air were calculated using Henry's law. After derivatization on the fiber, the derivative was thermally desorbed
in the injector of a gas chromatograph and analyzed using an electron capture detector. A detection limit of 0.17 mg m−3 was obtained. Calibration was done at 296 K. Reproducibility of the method was 9.6%. Some real air samples were also analyzed.
The method is very convenient and ideal for the rapid determination of formaldehyde in air.
Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997 相似文献
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Kinetic compensation effect and thermolysis mechanisms of organic polynitroso and polynitro compounds 总被引:1,自引:0,他引:1
Svatopluk Zeman 《Thermochimica Acta》1997,290(2):199-217
The present study starts from the published values of the Arrhenius parameters Ea and log A of thermolysis in the condensed state of seven nitrosamines and one hundred organic polynitro compounds. On the basis of the linear relationship between Eaand log A, the set studied has been divided into several reaction series, each of which is characterized by a mechanism of primary thermolysis. For compounds with intense intermolecular interactions in a crystal, the classification mentioned is codetermined by the stabilizing effect of the crystal lattice. In the context of this effect, the absence of an effect of solid-liquid transition on thermal reactivity of octogen (HMX) has been confirmed. The idea also presented is that, in the primary homolysis in thermolyses of polynitro compounds, there takes place a mutual interaction of molecules of the given compound, which is analogous to termination interactions of nitroarenes in radical polymerizations. 相似文献
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Jennifer Paola Hernández Mancera Francisco Núñez-Zarur Soledad Gutiérrez-Oliva Alejandro Toro-Labbé Ricardo Vivas-Reyes 《Journal of computational chemistry》2020,41(23):2022-2032
Quantum chemical calculations were used to study the mechanism of Diels-Alder reactions involving chiral anthracenes as dienes and a series of dienophiles. The reaction force analysis was employed to obtain a detailed scrutiny of the reaction mechanisms, it has been found that thermodynamics and kinetics of the reactions are quite consistent: the lower the activation energy, the lower the reaction energy, thus following the Bell-Evans-Polanyi principle. It has been found that activation energies are mostly due to structural rearrangements that in most cases represented more than 70% of the activation energy. Electronic activity mostly due to changes in σ and π bonding were revealed by the reaction electronic flux (REF), this property helps identify whether changes on σ or π bonding drive the reaction. Additionally, new global indexes describing the behavior of the electronic activity were introduced and then used to classify the reactions in terms of the spontaneity of their electronic activity. Local natural bond order electronic population analysis was used to check consistency with global REF through the characterization of specific changes in the electronic density that might be responsible for the activity already detected by the REF. Results show that reactions involving acetoxy lactones are driven by spontaneous electronic activity coming from bond forming/strengthening processes; in the case of maleic anhydrides and maleimides it appears that both spontaneous and non-spontaneous electronic activity are quite active in driving the reactions. 相似文献
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Extensive kinetic studies were performed to investigate the mechanism of the chlorpromazine (CP)-hydrogen peroxide reaction utilized in the catalytic determination of iodide. This reaction proceeds by two independent, parallel reactions, one through the formation of a red free radical, another directly to form the colorless product. The red color formation is catalyzed by traces of iodide. The color formation reaction was followed by measuring the increase in absorbance at 525 nm and its kinetic investigations were carried out by the initial rate method. The reaction rate curves for colorless sulfoxide formation were obtained by following the increase in absorbance at 335 nm, and the analysis was carried out by the integration method. The disappearance rate of CP is given by -d[CP]dt = k3[I−[H2O2][H+] + k6[CP][H2O2][H+] + k9[CP][H2O2][H+] + k10[CP][H2O2], where the first and second terms correspond to the chromogenic reaction and the third and fourth to colorless sulfoxide formation. Mechanisms consistent with each term were proposed and analytical implications of the kinetic studies are discussed. 相似文献
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Eduardo Chamorro Jairo Quijano Rafael Notario Claudia Snchez Luis A. Len Gabriel Chuchani 《International journal of quantum chemistry》2003,91(5):618-625
The gas‐phase thermal decomposition of 3‐hydroxypropionitrile, 3‐hydroxybutyronitrile, and 3‐hydroxy‐3‐methylbutyronitrile has been studied at the MP2/6‐31G(d) level of theory at 683.15 K and 0.06 atm. Results based both in energy and structure data seem to indicate a favorable route of decomposition via a six‐membered cyclic transition state (similar to those suggested for thermal decomposition of other related compounds, such as β‐hydroxyketones, β‐hydroxyalkenes, and β‐hydroxyalkynes) rather than a four‐membered cyclic transition state or even a quasiheterolytic pathway. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003 相似文献
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C60S+ was synthesized through the gas-phase ion-molecule reaction of C60 with the plasmas of carbon disulfide under self-chemical-ionization (self-CI) conditions in the ion source of a mass spectrometer. Semi-empirical PM3-UHF and density functional B3LYP levels of theory with 6-31G(d) basis set calculations were performed on all the possible structures and electronic properties of the product. The results showed that the most stable structure among the possible isomers was the 6/6 closed derivative. The reaction energies of C60+S+→C60S+ and C60+S→C60S were also calculated to suggest the possibility of C60S synthesis in condensed phase. 相似文献
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We present a high-level theoretical study on the gas-phase reaction between formaldehyde and hydroperoxyl radical carried out using the DFT-B3LYP, QCISD, and CCSD(T) theoretical approaches in connection with the 6-311+G(d,p), 6-311+G(2df,2p), and aug-cc-pVTZ basis sets. The most favorable reaction path begins with the formation of a pre-reactive complex and produces the peroxy radical CH(2)(OO)OH in a process that is computed to be exothermic by 16.8 kcal/mol. This reaction involves a process in which the oxygen terminal of the HO(2) moiety adds to the carbon of formaldehyde, and, simultaneously, the hydrogen of the hydroperoxyl group is transferred to the oxygen of the carbonyl in a proton-coupled electron-transfer mechanism. Our calculations show that this transition state lies below the sum of the energy of the reactants, and we computed a rate constant at 300 K of 9.29 x 10(-14) cm(3) molecule(-1) s(-1), which is in good agreement with the experimental results. Also of interest in combustion chemistry, we studied the hydrogen abstraction process by HO(2), the result of which is the formation of HCO + H(2)O(2). We found two reaction paths with activation enthalpies close to 12 kcal/mol. For this process, we computed a rate constant of 1.48 x 10(-16) cm(3) molecule(-1) s(-1) at 700 K, which also agrees quite well with experimental results. 相似文献
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A theoretical study of the reaction of lithium aluminum hydride with formaldehyde and cyclohexanone.
Geometries and energies of the reactants, complexes, and transition states for the reactions of lithium aluminum hydride with formaldehyde and cyclohexanone were obtained using ab initio and density functional (Becke3LYP/6-31G**) molecular orbital calculations. Two pathways for reaction with formaldehyde and four transition states corresponding to axial and equatorial attack at cyclohexanone were located. The transition state structures had reactant-like geometries. Predicted stereoselectivity of the reduction of cyclohexanone strongly favors axial approach of hydrogen, in agreement with experimental data. Analysis of the transition state structures suggests that electronic effects are more important than torsional effects in controlling stereoselectivity. 相似文献