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Product Channels (product + channel)
Selected AbstractsKinetics of the CH3O2 + HO2 reaction: A temperature and pressure dependence study using chemical ionization mass spectrometryINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 10 2007M. Teresa Raventós-Duran A temperature and pressure kinetic study for the CH3O2 + HO2 reaction has been performed using the turbulent flow technique with a chemical ionization mass spectrometry detection system. An Arrhenius expression was obtained for the overall rate coefficient of CH3O2 + HO2 reaction: k(T) = (3.82+2.79,1.61) × 10,13 exp[(,781 ± 127)/T] cm,3 molecule,1 s,1. A direct quantification of the branching ratios for the O3 and OH product channels, at pressures between 75 and 200 Torr and temperatures between 298 and 205 K, was also investigated. The atmospheric implications of considering the upper limit rate coefficients for the O3 and OH branching channels are observed with a significant reduction of the concentration of CH3OOH, which leads to a lower amount of methyl peroxy radical. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 571,579, 2007 [source] Kinetics and mechanism for the CH2O + NO2 reaction: A computational studyINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 5 2003Z. F. Xu The reactants, products, and transition states of the CH2O + NO2 reaction on the ground electronic potential energy surface have been searched at both B3LYP/6,311+G(d,p) and MPW1PW91/6,311+G(3df,2p) levels of theory. The forward and reverse barriers are further improved by a modified Gaussian-2 method. The theoretical rate constants for the two most favorable reaction channels 1 and 2 producing CHO + cis -HONO and CHO + HNO2, respectively, have been calculated over the temperature range from 200 to 3000 K using the conventional and variational transition-state theory with quantum-mechanical tunneling corrections. The former product channel was found to be dominant below 1500 K, above which the latter becomes competitive. The predicted total rate constants for these two product channels can be presented by kt (T) = 8.35 × 10,11T6.68 exp(,4182/T) cm3/(mol s). The predicted values, which include the significant effect of small curvature tunneling corrections, are in quantitative agreement with the available experimental data throughout the temperature range studied (390,1650 K). © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 184,190, 2003 [source] Capturing pressure-dependence in automated mechanism generation: Reactions through cycloalkyl intermediatesINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 3 2003David M. Matheu Chemical kinetic mechanisms for gas-phase processes (including combustion, pyrolysis, partial oxidation, or the atmospheric oxidation of organics) will often contain hundreds of species and thousands of reactions. The size and complexity of such models, and the need to ensure that important pathways are not left out, have inspired the use of computer tools to generate such large chemical mechanisms automatically. But the models produced by existing computerized mechanism generation codes, as well as a great many large mechanisms generated by hand, do not include pressure-dependence in a general way. This is due to the difficulty of computing the large number of k(T, P) estimates required. Here we present a fast, automated method for computing k(T, P) on-the-fly during automated mechanism generation. It uses as its principal inputs the same high-pressure-limit rate estimation rules and group-additivity thermochemistry estimates employed by existing computerized mechanism-generation codes, and automatically identifies the important chemically activated intermediates and pathways. We demonstrate the usefulness of this approach on a series of pressure-dependent reactions through cycloalkyl radical intermediates, including systems with over 90 isomers and 200 accessible product channels. We test the accuracy of these computer-generated k(T, P) estimates against experimental data on the systems H + cyclobutene, H + cyclopentene, H + cyclohexene, C2H3 + C2H4, and C3H5 + C2H4, and make predictions for temperatures and pressures where no experimental data are available. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 95,119, 2003 [source] Crossed-Beam and Quantum Dynamics Studies of the Reaction Cl + CHD3ISRAEL JOURNAL OF CHEMISTRY, Issue 1 2007Gunnar Nyman The ground-state reaction of Cl + CHD3 was studied with joint experimental and theoretical efforts. Experiments were performed under crossed-beam conditions using a time-sliced velocity imaging detection method. By taking the images over the energy range of chemical significance,from threshold to about 9 kcal/mol,the reactive excitation functions as well as the dependence of product angular distributions and of the energy disposal on initial collision energies were obtained for both isotopic product channels. Theoretically, reduced dimensionality quantum dynamics calculations were performed for the HCl + CD3 channel, and the results are in excellent agreement with experimental findings. Comparisons with previously reported results on Cl + CH4/CD4, both experimental and theoretical, were also made to gain deeper insights into the dynamics of this benchmark atom + polyatomic reaction. [source] | ||||||||||