A kinetic and product study of the gas-phase reaction of ozone with vinylcyclohexane and methylene cyclohexane

The gas-phase reaction of ozone with vinylcyclohexane and methylene cyclohexane has been investigated at ambient T and p=1 atm of air in the presence of sufficient cyclo-hexane or 2-propanol added to scavenge OH. The reaction rate constants, in units of 10⁻¹⁸ cm³ molecule⁻¹ s⁻¹, are 7.52±0.97 for vinylcyclohexane (T=292±2 K) and 10.6±1.9 for methylene cyclohexane (T=293±2 K). Carbonyl reaction products were cyclohexyl meth-anal (0.62±0.03) and formaldehyde (0.47±0.04) from vinylcyclohexane and cyclohexanone (0.55±0.10) and formaldehyde (0.60±0.05) from methylene cyclohexane, where the yields given in parentheses are expressed as carbonyl formed, ppb/reacted ozone, ppb. The sum of the yields of the primary carbonyls is close to the value of 1.0 that is consistent with the simple mechanisms: O₃+cyclo(C₆H₁₁)−CH(DOUBLEBOND)CH₂→α(HCHO+cyclo(C₆H₁₁)CHOO)+(1−α)(HCHOO+cyclo(C₆H₁₁)CHO) for vinylcyclohexane and O₃+(CH₂)₅C(DOUBLEBOND)CH₂→α(HCHO +(CH₂)₅COO)+(1−α)(HCHOO+(CH₂)₅C(DOUBLEBOND)O) for methylene cyclohexane. The coefficients α are 0.43±0.10 for vinylcyclohexane and 0.52±0.05 for methylene cyclohexane, i.e., (formaldehyde+the substituted biradical) and (HCHOO+cyclohexyl methanal or cyclo-hexanone) are formed in ca. equal yields. Reaction rate constants, carbonyl yields, and reaction mechanisms are compared to those for alkene structural homologues. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 855–860, 1997     

Products and kinetics of the heterogeneous reaction of suspended vinclozolin particles with ozone

Vinclozolin is a widely used fungicide that can be released into the atmosphere via application and volatilization. This paper reports an experimental investigation on the heterogeneous ozonation of vinclozolin particles. The ozonation of vinclozolin adsorbed on azelaic acid particles under pseudo-first-order conditions is investigated online with a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS). The ozonation products are analyzed with a combination of VUV-ATOFMS and GC/MS. Two main ozonation products are observed. The formation of the ozonation products results from addition of O(3) on the C-C double bond of the vinyl group. The heterogeneous reactive rate constant of vinclozolin particles under room temperature is (2.4 ± 0.4) × 10(-17) cm(3) molecules(-1) s(-1), with a corresponding lifetime at 100 ppbv O(3) of 4.3 ± 0.7 h, which is almost comparable with the estimated lifetime due to the reaction with atmospheric OH radicals (～1.7 h). The reactive uptake coefficient for O(3) on vinclozolin particles is (6.1 ± 1.0) × 10(-4).     

Kinetic and product study of the gas‐phase reaction of sabinaketone with OH radical

Sabinaketone is one major photooxidation product of sabinene, an important biogenic volatile organic compound. This article provides the first product study and the second rate constant determination of its reaction with OH radicals. Experiments were investigated under controlled conditions for pressure and temperature in the LISA indoor simulation chamber using FTIR spectrometry. Kinetic study was carried out at 295 ± 2 K and atmospheric pressure using the relative rate technique with isoprene as the reference compound. The rate constant was found to be k_{sabinaketone + OH} = (7.1 ± 1.0) × 10^?12 molecule^?1 cm³ s^?1. Acetone and formaldehyde were detected as products of the reaction with the respective yields of R_acetone = 0.9 ± 0.2 and R_HCHO = 1.2 ± 0.3. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 415–421, 2007     

Kinetic study of the hydroxyl radical-propene reaction

Absolute rate coefficients for the reactions of OH with C₃H₆ and C₃D₆ were measured at temperatures from 293 to 896 K and at pressures from 25 to 600 Torr helium. Mechanistic information of importance to atmospheric and combustion modeling was obtained.     

Kinetic relationships and mechanism of ozone reaction with polystyrene in CCl4 solution

In this work a study is made of the degradation on ozonation of unfractionated polystyrene (PS) in CCl₄ solution. It was found that the ozone attack of PS molecules is accompanied by hydrogen abstraction from tertiary CH bonds and by the formation of ozonides due to the reaction of ozone with the aromatic rings. A scheme of PS degradation in solution is suggested; several kinetic parameters are evaluated.     

Kinetic study of the reaction between iodide and N-chloramines

We carried out a kinetic study of the reaction between iodide ion and various primary N-chloramines and found it to be first-order in the latter. Experiments also showed the rate constant for the reaction to be directly proportional to the iodide and hydrogen ion concentrations. The influence of the buffer concentration reveals the presence of general acid catalysis processes. © 1996 John Wiley & Sons, Inc.     

A theoretical study of the reaction pathway in the photodimerization of anthracene

The approximation proposed by Salem to calculate the interaction energy between conjugated systems has been used to obtain different potential surfaces for anthracene photodimerization in order to establish the reaction pathway.     

Direct experimental evidence for a heterogeneous reaction of ozone with bromide at the air-aqueous interface

Recent experimental and theoretical evidence has indicated an enhancement of the heavier halide ions at the air-aqueous interface, relative to their bulk concentrations. This, along with an order of magnitude discrepancy between measured and predicted Br2 production in the reaction of ozone with deliquesced NaBr aerosol, has led to the suggestion that an interface reaction occurs between ozone and bromide. We have used harmine, a beta-carboline alkaloid, as an interface-sensitive fluorescent pH probe in order to measure pH changes associated with the interfacial reaction of ozone and bromide. The rate of pH change depends upon the bulk bromide concentration in a way which is well described by a Langmuir-Hinshelwood kinetic model. In the presence of octanol at the interface, the rate of pH change tracks the octanol adsorption isotherm, as expected if octanol enhances the concentration of ozone at the surface.     

Computational study on the multi-channel mechanism of disulfur and ozone reaction

Structural Chemistry - The reaction mechanism of disulfur (S2) and O3 on the triplet and singlet potential energy surfaces has been investigated theoretically at the...     

多孔物质气固反应动力学研究

利用自主研制的微型流化床反应分析仪（MFBRA）在等温条件下测试了高比表面活性炭氧化反应,并根据基于固体转化的热分析动力学方法及考虑气体在微孔内扩散与反应的应用化工动力学方法求算了动力学参数．在内外扩散抑制最小化的实验条件下,粒径小于5μm的活性炭在700-1000℃的燃烧反应动力学研究表明,根据微型流化床中实验数据,采用等温热分析动力学方法求算得内扩散控制区活化能约为95kJ／mol;弓l入化工动力学方法中的随机孔模型对低温区等温燃烧数据拟合,可得孔结构参数在0．17m^-3左右,反应活化能为178kJ／mol,约为内扩散反应活化能的两倍,最为接近本征的碳燃烧反应活化能．     

Semiclassical wave packet study of ozone forming reaction

We have applied the semiclassical wave packet method (SWP) to calculate energies and lifetimes of the metastable states (scattering resonances) in a simplified model of the ozone forming reaction. All values of the total angular momentum up to J=50 were analyzed. The results are compared with numerically exact quantum mechanical wave packet propagation and with results of the time-independent WKB method. The wave functions for the metastable states in the region over the well are reproduced very accurately by the SWP; in the classically forbidden region and outside of the centrifugal barrier, the SWP wave functions are qualitatively correct. Prony's method was used to extract energies and lifetimes from the autocorrelation functions. Energies of the metastable states obtained using the SWP method are accurate to within 0.1 and 2 cm(-1) for under-the-barrier and over-the-barrier states, respectively. The SWP lifetimes in the range of 0.5相似文献   

Direct dynamics study on the reaction of acetaldehyde with ozone

The hydrogen abstraction reaction of ozone with acetaldehyde has been studied theoretically over the temperature range 250-2500 K. Two different reactive sites of acetaldehyde molecule, CH(3) and CHO groups have been investigated, and results confirm that the CHO group is a highly reactive site. In this study, the geometries and harmonic vibrational frequencies of all stationary points are calculated at the MPW1K, BHandHLYP, and MPWB1K levels of theory. The minimum energy paths (MEPs) were obtained at the MPW1K/6-31+G(d,p) level of theory. To refine the energies along the MEPs of each channel, single-point energy calculations were performed by a higher-level energy calculation method (denoted as HL). The rate constants were evaluated based on the MEPs from the HL method in the temperature range 250-2500 K by using the conventional transition state theory (TST), the canonical variational transition state theory (CVT), the microcanonical variational transition state theory (muVT), the CVT coupled with small-curvature tunneling (SCT) correction (CVT/SCT), and the muVT coupled with Eckart tunneling correction (muVT/Eckart). The fitted three-parameter Arrhenius expressions of the calculated CVT/SCT and muVT/Eckart rate constants of the H abstraction from CHO group are k CVT/SCT(T) = 4.92 x 10(-27).T 3.77.e(-7867.0/T) and k muVT/Eckart(T) = 2.10 x 10(-27).T(3.90).e(-7706.2/T), respectively. The fitted three-parameter Arrhenius expressions of the calculated CVT/SCT and muVT/Eckart rate constants of the H abstraction from CH3 group are k(CVT/SCT)(T) = 1.27 x 10(-27).T(3.94).e(-14554.1/T) and k muVT/Eckart(T) = 1.62 x 10(-26).T(3.66).e(-15459.8/T), respectively.     

Diels-Alder reaction mechanisms of substituted chiral anthracene: A theoretical study based on the reaction force and reaction electronic flux

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.     

Kinetic study of heterogeneous reaction of deliquesced NaCl particles with gaseous HNO3 using particle-on-substrate stagnation flow reactor approach

Heterogeneous reaction kinetics of gaseous nitric acid with deliquesced sodium chloride particles NaCl(aq) + HNO3(g) --> NaNO3(aq) + HCl(g) were investigated with a novel particle-on-substrate stagnation flow reactor (PS-SFR) approach under conditions, including particle size, relative humidity, and reaction time, directly relevant to the atmospheric chemistry of sea salt particles. Particles deposited onto an electron microscopy grid substrate were exposed to the reacting gas at atmospheric pressure and room temperature by impingement via a stagnation flow inside the reactor. The reactor design and choice of flow parameters were guided by computational fluid dynamics to ensure uniformity of the diffusion flux to all particles undergoing reaction. The reaction kinetics was followed by observing chloride depletion in the particles by computer-controlled scanning electron microscopy with energy-dispersive X-ray analysis (CCSEM/EDX). The validity of the current approach was examined first by conducting experiments with median dry particle diameter D(p) = 0.82 microm, 80% relative humidity, particle loading densities 4 x 10(4) 相似文献   

Kinetics study of the aromatic bicyclic peroxy radical + NO reaction: overall rate constant and nitrate product yield measurements

The measurements of the overall bicyclic peroxy radical + NO rate constant for the 1,3,5-trimethylbenzene (1,3,5-TMB) system and of the nitrate product yields for the benzene, toluene, p-xylene, and 1,3,5-TMB systems were performed via the turbulent flow chemical ionization mass spectrometry technique. While the overall rate constant was found to be consistent with the value used in the most detailed aromatic oxidation kinetic model (Master Chemical Mechanism, MCM), the nitrate product yields were found to be generally lower than predicted by the MCM and to have a different aromatic species-specific dependence than the MCM predicts.     

Kinetic and mechanistic study on the reaction of alkylcobaloximes with azoles

The kinetics of axial water substitution by azoles (pyrazole and 1,2,4-triazole) in three different cobaloximes, viz.trans-[Co(Hdmg)(2)(R)H(2)O] where Hdmg = dimethylglyoximate, R = PhCH(2), Et and CF(3)CH(2), were studied as a function of azole concentration, temperature and pressure in aqueous solution. The second order rate constants for the substitution of water in trans-[Co(Hdmg)(2)(R)H(2)O] for R = Et at pH 6.0, 25 degrees C and I= 0.1 M (NaClO(4)), were found to be 1309 and 1200 M(-1) s(-1) for pyrazole (Pz) and 1,2,4-triazole (Tz), respectively, and those obtained for R = PhCH(2) were found to be 755 and 691 M(-1) s(-1), respectively. The second order rate constants in the case of R = CF(3)CH(2) were found to be 0.358 and 0.348 M(-1) s(-1) for Pz and Tz, respectively. The relative order of reactivity for the different alkyls being Et > PhCH(2) > CF(3)CH(2). The activation parameters (DeltaH([not equal]), DeltaS([not equal]) and DeltaV([not equal])) obtained for these reactions were found to be in the range of 65-87 kJ mol(-1), 24-47 J mol(-1) K(-1) and 2.5-7.7 cm(3) mol(-1), respectively. These data suggest that an I(d) substitution mechanism operates where the azoles participate in the transition state.     

Kinetic study of reaction of difluorocarbene with cyclopentadiene

Russian Chemical Bulletin -     

Kinetic and mechanistic study of the reaction of 2,6-dichlorophenol-indophenol and cysteine

In this work the reaction of cysteine (H(2)Q) with 2,6-dichlorophenolindophenol (D) is studied kinetically in the pH range 2.5-9.0. Taking into consideration the distribution diagrams for the species H(3)Q(+), H(2)Q, HQ(-), Q(2-) for cysteine and DH(+)(2), DH, D(-) for 2,6-dichlorophenolindophenol the reaction rate constants k(i) for all possible combinations of the reacting species were determined. The maximum reactivity appears at pH 6.88 with an overall reaction constant k = 306 1.mole(-1).sec(-1) at 22 degrees . The effect of the concentrations of the reagents and the ionic strength on the reaction rate is also given. From Arrhenius plots an activation energy E(a) = 8.1 kcal/mole was calculated. Working curves for the determination of cysteine in aqueous solutions are also presented applying the reaction rate method. Finally the paper includes important analytical information for the calculation of the errors due to interference of cysteine by the kinetic determination of ascorbic acid, using its reaction with 2,6-dichlorophenolindophenol.