The temperature dependence of the rate constant for the reaction HO2 + HO2 → H2O2 + O2 (2k1) has been determined using flash photolysis techniques, over the temperature range 298–510 K, in a nitrogen diluent at a total pressure of 700 Torr. The overall second order state constant is given by k1 = (4.14 ± 1.15) × 10?13 exp[(630 ± 115)/T] cm3 molecule?1 s?1, where the quoted errors refer to one standard deviation. This result is compared with previous findings and the negative activation energy is shown to be consistent with the observation that the rate constant is pressure dependent at 700 Torr. 相似文献
A combined EPR/LMR spectrometer and fast-flow system has been used to investigate the reactions HO2 + NO(k1), HO2 + OH(k2), HO2 + HO2(k3) at room temperature. The rate constants have been measured: k1 = (7.0 ± 0.6) × 10?12 cm3 s?1 (P = 7–10 Torr);k2 = (5.2 ± 1.2) × 10?11 cm3 s?1 (P = 8–10 Torr);k3 = (1.65 ± 0.3) × 10?12 cm3 s?1 (P = 2.1–24.9 Torr). The conclusion is drawn from analysis of the literature and the present work that k2 and k3 do not depend on pressure up to 1 atm. 相似文献
Peroxynitric acid has been identified by Fourier transform, infrared, long-path spectroscopy as a product of the UV-irradiated dilute mixtures of HONO, CO, Nox in synthetic air at 24 ± 2°C. The characteristic peaks of this compound are identical to those observed by Niki, in irradiated Cl2, H2, NO2, air mixtures and Hanst, in irradiated Cl2, CH2O, NO2, air mixtures. The concentration of the reactants and products of the HONO, CO, NOx, air system have been determined as a function of irradiation time. The changes observed were computer simulated using a combination of thirty elementary reactions. The data suggests that both reactions (1) and (2) occur as a result of HO2-NO2 interactions in the gas phase: HO2 + NO2 å HONO + O2 (1); HO2 + NO2(+M) å HO2NO2(+M)(2). The data give the preliminary estimates: k1/k2 ≈0.7 ±0.4; k1/k3 ≈ 0.043 ± 0.02; k2/k3 ≈ 0.058 ± 0.02, where reaction (3) is: HO2 + NO å HO + NO2. These data and computer simulations of sunlight-irradiated, NOx, hydrocarbon, aldehyde-polluted atmospheres suggest that peroxynitric acid may be formed in urban atmospheres at rates which are comparable to those observed for peroxyacetyl nitrate (PAN), and it is concluded that HO2NO2 may contribute to the “oxidant” found in these atmopheres. 相似文献
The rate coefficient for the reaction OH + HO2 =H2O + O2 has been determined from measurements of the steady-state absorption of HO2 at 210 nm, in low-frequency square-wave modulated photolysis of O3 + H2O mixtures. The value obtained was (9.9 ± 2.5) × 10?11 cm3 molecule?1 s?1 at 308 K and 1 atm pressure. 相似文献
The title reaction has been investigated by the FD/LMR technique at room temperature. The rate constant of the overall reaction was estimated to be 2.6×1012 cm3 mol–1 s–1. The yield of HO2 formation was found to be unity, 1.00±0.05. 相似文献
Upper limits for the rate constant for the reaction Br + H2O2 → HBr + HO2 have been measured over the temperature range 298 to 417 K in a discharge flow, system using a mass spectrometer as a detector. Results are K1< 1.5 × 10?15 cm3 s?1 at 298 K and K1< 3.0 × 10?15 cm3 s?1 at 417 K, respectively. The implication to Stratospheric chemistry is discus 相似文献
Ab initio calculations including electron correlation effects (mainly on CEPA-PNO level) have been performed for the potential energy surface of the reaction of 3P oxygen atoms with molecular hydrogen. The collinear abstraction reaction (C∞v symmetry) and the vertical insertion reaction (C2v) have been investigated with particular emphasis.The influence of the orbital basis size and of electron correlation both on the reaction energy and on the barrier height and location for the abstraction reaction has been studied in some detail. Our extrapolated value for the barrier for this reaction is 13.4 ± 1.0 kcal/mol, in fair agreement with the experimental activation energy, while the insertion reaction has to pass over a barrier of =48 kcal/mol. The analysis of electron correlation effects reveals that it is compulsory to include all singly and doubly substituted configurations, to correct for unlinked cluster contributions and to use fairly large basis sets if one wants to get accurate ab initio potential surfaces for the reactions of triplet oxygen atoms. 相似文献
The rate constant of the reaction OH (v = 0) + O3 HO2 + O2 was measured over the temperature range from 220 to 450°K at total pressures between 2 and 5 torr using ultraviolet fluorescent scattering for the detection of OH radicals. An Arrhenius expression, k1 = 1.3 × 10?12 exp(?1900/RT) cm3/sec was obtained and the rate constant for the reaction HO2 + O3OH + 2O2 was inferred to be less than 0.1 k1 over the entire temperature interval. 相似文献
Four new low-dimensional phenylarsonates, A(HO3AsC6H5)(H2O3AsC6H5) (A = Tl(1), Na(2), K(3) and Rb(4)), have been synthesized and characterized by X-ray diffraction, spectroscopic and thermal studies. They crystallize in triclinic
unit cells and have approximately planar arrangement of A+ ions, coordinated to oxygen atoms of phenylarsonates, on both sides. Structure of thallium phenylarsonate as determined by
single crystal X-ray diffraction, is one-dimensional, whereas those of alkalimetal analogues are two-dimensional. Successful
intercalation reactions of compounds1 and2 with primaryn-alkyl amines have been demonstrated.
Dedicated to Prof J Gopalakrishnan on his 62nd birthday. 相似文献
New global three dimensional potential energy surfaces for the Cl+H2 reactive system have been constructed using accurate multireference configuration interaction calculations with a large basis set. The three lowest adiabatic potential energy surfaces correlating asymptotically with Cl(^2p)+H2 have been transformed to adiabatic representation, which leads to a fourth coupling potential for non-linear geometries. In addition, the spin-orbit coupling surfaces have also been computed using the Breit-Pauli Hamiltonian. Properties of the new potential are described. Reaction dynamics based on the new potential agrees with the recent experimental results quite well. 相似文献
The reaction of O2(1Δg) with HO2(X?) was studied in an isothermal flow reactor in the pressure range 7?p? 10.7 mbar at temperatures between 299?T? 423 K. H-atom production was observed in the reaction O2(1Δg) + HO2(Ã2A′) - H(2S)+ 2O2 (3Σg?). The rate of this reaction (k1) is estimated to be k1 = (1 ± 0.5) × 1014 CM3 Mol?1 s?1. The implications of this reaction to recent determinations of the rate of the reaction H + O2(1Δg) are discussed. 相似文献
The rate constants for the reactions OH(X2Π, ν = O) + NH3 → k1 H2O + NH2 and OH(X2Π, ν = O) + O3k2 → HO2 + O2 were measured at 298°K by the flash photolysis resonance fluorescence technique. The values of the rate constants thus obtained are K1 = (4.1 ± 0.6) × 10?14 and k2 = (6.5 ± 1.0) × 10?14 in units of cm3 molecule ?1 sec1. The results are discussed in terms of understanding the dynamics of the perturbed stratosphere. 相似文献
Theoretical studies of the dynamics of the reactions O(3p)+H2/HD(ν=0, j=0)→OH+H have been performed with quasi-classical trajectory method (QCT) on an ab initio potential surface for the lowest triplet electronic state of H2O(aA"). The QCT-calculated integral cross sections are in good agreement with the earlier time-dependent quantum mechanics results. The state-resolved rotational distributions reveal that the product OH rotational distributions for O+HD have a preference for populating highly internally excited states compared with the O+H2 reaction. Distributions of differential cross sections show that directions of scattering are strongly dependent on the choice of quantum state. The polarization dependent generalized differential cross-sections and the distributions were calculated and a pronounced isotopic effect is revealed. The calculated results indicate that the product polarization is very sensitive to the mass factor. 相似文献
Efficient and convenient synthesis of β-acetamido ketones has been achieved by one-pot reaction of acetophenone, aryl aldehydes,
acetyl chloride, and acetonitrile in the presence of 3-methyl-1-(4-sulfonylbutyl)imidazolium hydrogensulfate [HO3S(CH2)4MIM][HSO4], a Br?nsted-acidic ionic liquid, as a green and reusable catalyst in solvent-free media at room temperature. The catalyst
could be recycled and reused without noticeable decrease in catalytic activity. 相似文献
Quantum chemical calculations at the B3LYP/TZVP level of theory have been carried out for the initial steps of the addition reaction of ethylene to OsO3(CH2). The calculations predict that there are two reaction channels with low activation barriers. The kinetically and thermodynamically most favored reaction is the [3+2]O, C addition which has a barrier of only 2.3 kcal mol−1. The [3+2]O, O addition has a slightly higher barrier of 6.5 kcal mol−1. Four other reactions of OsO3(CH2) with C2H4 have significantly larger activation barriers. The addition of ethylene to one oxo group with concomitant migration of one hydrogen atom from ethylene to the methylene ligand yields thermodynamically stable products but the activation energies for the reactions are 16.7 and 20.9 kcal mol−1. Even higher barriers are calculated for the [2+2] addition to the OsO bond (32.6 kcal mol−1) and for the addition to the oxygen atom yielding an oxiran complex (41.2 kcal mol−1). The activation barriers for the rearrangement to the bisoxoosmaoxirane isomer (36.3 kcal mol−1) and for the addition reactions of the latter with C2H4 are also quite high. The most favorable reactions of the cyclic isomer are the slightly exothermic [2+2] addition across the OsO bond which has an activation barrier of 46.6 kcal mol−1 and the [3+2]O, O addition which is an endothermic process with an activation barrier of 44.3 kcal mol−1. 相似文献
The potential energy surface for the CF3O2 + OH reaction has been theoretically investigated using the DFT (B3LYP/6-311G(d,p)) level of theory. Both singlet and triplet potential energy surfaces are investigated. The reaction mechanism on the triplet surface is simple. However, the reaction mechanism on the singlet surface is more complicated. It is revealed that the formation of CF3O + HO2 is the dominant channel on the triplet surface. The potential energy surface (PES) for this reaction has been given according to the relative energies calculated at the DFT/B3LYP/6-311G(d,p) level. Because this reaction involves both triplet and singlet states, triplet–singlet intersystem crossing (ISC) crossing also have been investigated in this paper. 相似文献
Quantum chemical calculations using DFT at the B3LYP level have been carried out for the reaction of ethylene with the group-7 compounds ReO2(CH3)(CH2) (Re1), TcO2(CH3)(CH2) (Tc1) and MnO2(CH3)(CH2) (Mn1). The calculations suggest rather complex scenarios with numerous pathways, where the initial compounds Re1-Mn1 may either engage in cycloaddition reactions or numerous addition reactions with concomitant hydrogen migration. There are also energetically low-lying rearrangements of the starting compounds to isomers which may react with ethylene yielding further products. The [2 + 2]Re,C cycloaddition reaction of the starting molecule Re1 is kinetically and thermodynamically favored over the [3 + 2]C,O and [3 + 2]O,O cycloadditions. However, the reaction which leads to the most stable product takes place with initial rearrangement to the dioxohydridometallacyclopropane isomer Re1a that adds ethylene with concomitant hydrogen migration yielding Re1a-1. The latter reaction has a slightly higher barrier than the [2 + 2]Re,C cycloaddition reaction. The direct [3 + 2]C,O cycloaddition becomes more favorable than the [2 + 2]M,C reaction for the starting compounds Tc1 and Mn1 of the lighter metals technetium and manganese but the calculations predict that other reactions are kinetically and thermodynamically more favorable than the cycloadditions. The reactions with the lowest activation barriers lead after rearrangement to the ethyl substituted dioxometallacyclopropanes Tc1a-1 and Mn1a-1. The manganese compound exhibits an even more complex reaction scenario than the technetium compounds. The thermodynamically most stable final product of ethylene addition to Mn1 is the ethoxy substituted metallacyclopropane Mn1a-2 which has, however, a high activation barrier. 相似文献
The CL spectra of the title reactions and their pressure dependences have been studied over the 5 × 10?6 ? 5 × 10?3 torr range in a beam-gas experiment. In the Sm + N2O, O3 and Yb + O3 reactions simple bimolecular formation of the short lived (radiative lifetime τR < 3 × 10?6 s) MO* emitters dominates the entire pressure range. In the other systems Sm + (F2, Cl2), Yb + (F2, Cl2) the CL spectra are strongly pressure dependent, indicating extensive energy transfer from long-lived intermediates. Reaction mechanisms are suggested. The quantum yields Φ, obtained by calibrating relative quantum yields with Dickson and Zare's absolute value for Sm + N2O [Chem. Phys. 7 (1975) 367], range from Φ = 2.3% (for Sm + F2, the most efficient reaction) down to Φ = 0.005% for Yb + Cl2. The following lower limit estimates were obtained for the product dissociation energies from the short wavelength CL cutoffs: D00(SmF) ? 121.3 ± 2.4 kcal/mole, D00(SmCl) ? ? 100 ± 3 kcal/mole, D00(YbO) ? 94.2 ± 1.5 kcal/moie, D00(YbF) ? 123.7 ± 2.3 kcal/mole. 相似文献