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Showing papers on "Elementary reaction published in 1997"


Journal ArticleDOI
TL;DR: In this paper, the kinetics of elementary surface reactions involved in the reforming of methane to synthesis gas over supported nickel were studied using transient isotopic methods, and an overall model that describes the reactions of methane with steam and CO2 in microkinetic terms was constructed based on these rate constants and on previously published steam reforming and CO 2methanation data.

231 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present a review of the evolution of the NO-CO reaction on rh and present the data for the elementary reaction steps, obtained primarily on Rh(1 1 1) at UHV conditions.

206 citations


Journal ArticleDOI
TL;DR: In this paper, the oxidation of CO by O2 was investigated in an isothermal fixed-bed microreactor under intrinsic conditions, i.e., in the absence of mass and heat transfer limitations, in the temperature range from 436 to 503 K, with CO and O2inlet partial pressures between 0.12 and 8.5.

145 citations


Journal ArticleDOI
TL;DR: In this paper, an isotopic scrambling reaction was studied in a high-pressure flow reactor and the measured rate constants were (2.3 ± 1.0) × 10-13 exp[−(2100 ± 250)/T] cm3 molecule-1.
Abstract: Gas-phase hydrogen (H) abstractions from molecules by free radicals have been studied extensively. They form the simplest class of elementary reactions and also play a key role in atmospheric chemistry and so are the centerpiece of models of reactivity. Despite intense scrutiny, two fundamental mechanistic issues remain unresolved: (1) Do H abstractions proceed directly or indirectly? (2) Do thermodynamic or electronic interactions determine their reaction barrier? The thermoneutral identity reaction, OH + H2O → H2O + OH, provides an excellent opportunity to answer these questions. Several theoretically predicted H2O−HO complexes raise the possibility of an indirect mechanism, while no thermodynamic forcing influences the reaction barrier. To examine the various reactivity models, the isotopic scrambling reactions 18OH + H216O → H218O + 16OH and 16OD + H216O → H16OD + 16OH are studied in a high-pressure flow reactor. The measured rate constants are (2.3 ± 1.0) × 10-13 exp[−(2100 ± 250)/T] cm3 molecule-1 ...

143 citations


Journal ArticleDOI
TL;DR: In this article, a generalized expression was developed to predict the apparent first-order rate constants for the decomposition of C8−C16 n-alkanes at 425 °C.
Abstract: Kinetics of thermal decomposition of C10−C14 n-alkanes and their mixtures was studied under near-critical and supercritical conditions. Supercritical-phase thermal decomposition of n-alkanes can be represented well by an apparent first-order kinetics, even though the decomposition was not a true first-order process. A generalized expression was developed to predict the apparent first-order rate constants for the decomposition of C8−C16 n-alkanes at 425 °C. Pressure had a significant effect on the apparent first-order rate constant in the near-critical region. This large pressure effect can be attributed to the significant changes in density and possibly to the changes in the rate constants of elementary reactions with pressure in this region. Individual compounds interacted with each other in the thermal reaction of n-alkane mixtures. The overall first-order rate constants for n-alkane mixtures can be predicted satisfactorily from the rate constants for pure compounds.

98 citations


Journal ArticleDOI
TL;DR: In this paper, the authors studied the kinetics of the oxidation of carbon monoxide by oxygen in the temperature range 0 < ϑ < 80°C on alumina-supported Pt/SnO2 catalysts, the respective areas of the two active compounds being varied independently of each other.

75 citations


Journal ArticleDOI
TL;DR: In this paper, steady-state isotopic transient kinetic analysis (SSITKA) was used to estimate the concentrations of adsorbed reaction intermediates as well as the time constants involved in the rate determining elementary reaction steps.

70 citations


Journal ArticleDOI
TL;DR: In this article, the atmospheric oxidation mechanism of n-butane is investigated by means of density functional theory and ab initio calculations, which predicts the detailed pathways leading to experimentally observed products of nbutane oxidation.
Abstract: The atmospheric oxidation mechanism of n-butane is investigated by means of density functional theory and ab initio calculations. Calculation of energies of reactants, transition states, and stable intermediates predicts the detailed pathways leading to experimentally observed products of n-butane oxidation. Also serving as a model system for the oxidation of larger alkanes, quantitative information is obtained for elementary reaction steps that heretofore have been subject to speculation. Complete basis set model chemistries CBS-4 and CBS-q were used with B3LYP/6-31G(d,p) optimized geometries to calculate energies of over 70 stable species and transition states. Energies based on density functional theory were obtained at the B3LYP/6-311+G(3df,2p)//B3LYP/6-31G(d,p) level of theory. The principal pathway following formation of the 1-butyl radical from hydroxyl (OH) attack on n-butane is found to be 1,5-H shift of the 1-butoxy radical. After conversion to the δ-hydroxy-1-butoxy radical, another 1,5-H shift...

57 citations


Journal ArticleDOI
TL;DR: In this paper, the basis set dependence of the reaction energy defects, barrier heights, and saddle point geometries have been determined for each theoretical method, including multireference configuration interaction, perturbation theory, and coupled cluster methods.
Abstract: An explicit treatment of electron correlation is required to predict accurate energetics, barrier heights, and saddle point geometries for chemical reactions. Several theoretical methods for treating electron correlation (multireference configuration interaction, perturbation theory, and coupled cluster methods) have been thoroughly evaluated for the F(2P) + H2(X1Σg+) and O(3P) + H2(X1Σg+) abstraction reactions as well as for the H‘(2S) + HCl(X1Σ+) exchange reaction using correlation consistent basis sets. The basis set dependence of the reaction energy defects, barrier heights, and saddle point geometries have been determined for each theoretical method. Addition of diffuse functions to the basis set (aug-cc-pVnZ) was found to substantially increase the convergence rate. Calculations with the largest basis set (aug-cc-pV5Z) allowed an unambiguous comparison of the relative performance of each correlation method. For each reaction, the R-UCCSD(T) results closely parallel the most accurate MRCI results and...

55 citations


Journal ArticleDOI
TL;DR: In this paper, Hartree−Fock and density functional theory calculations have been carried out to investigate the detailed kinetics and mechanisms of hydrocarbon thermal cracking, and the results of the elementary reactions involved in the overall cracking of paraffin molecules agree well with the generally accepted free radical mechanism.
Abstract: Unrestricted Hartree−Fock and density functional theory calculations have been carried out to investigate the detailed kinetics and mechanisms of hydrocarbon thermal cracking. The calculations of the elementary reactions involved in the overall cracking of paraffin molecules agree well with the generally accepted free radical mechanism. The results can be summarized as follows: (1) Initiation cracking, the calculated bond dissociation energy (BDE) for C−C homolytic scission is ∼95 kcal/mol at the MP2/6-31G* level and ∼89 kcal/mol at the B3LYP/6-31G* level. No transition states are found in the reactions. (2) H-transfer reaction, the calculated energy barriers (activation energy) are 15−17 kcal/mol at the MP2/6-31G* level and 10−12 kcal/mol at the B3LYP level. The reverse reaction has about the same energy barrier. The calculated transition state structures for both reactions lie in the middle between the reactant and product. (3) Radical decomposition−“β scission”, the activation energy for the radical d...

53 citations


Journal ArticleDOI
TL;DR: In this article, a detailed chemical-kinetic mechanism is proposed, which is comprised of 350 elementary reactions and 65 reactive species, and a reaction path analysis was conducted using the integral averaged reaction rates, and the major reaction pathways were identified.

Journal ArticleDOI
TL;DR: In this paper, the chemical structure of a premixed n-decane/O2/N2 flame (equivalence ratio 1.7) stabilized at atmospheric pressure on a flat-flame burner has been computed with two reaction mechanisms.
Abstract: The chemical structure of a premixed n-decane/O2/N2 flame (equivalence ratio 1.7) stabilized at atmospheric pressure on a flat-flame burner has been computed with two reaction mechanisms. In the first one, the consumption of the fuel molecule is described in detail, The five different n-decyl radicals formed by H atom abstraction from the decane molecule were distinguished and their consumption reactions were considered in a systematic way. This mechanism comprises 78 species involved in 638 elementary reactions. Modeling with this detailed mechanism led to species mole fraction profiles in good agreement with the experimental results. The main. reaction paths for the formation of final and intermediate species have been identified with special emphasis on benzene formation. The second mechanism was derived from the first one by successively removing an increasing number of n-decyl radicals. For most species, it is possible to maintain the reliability of the model with only one n-decyl radical in...

Journal ArticleDOI
TL;DR: In this paper, the information obtained on the elementary reaction steps from cluster calculations can be used to predict the overall rate of a catalytic reaction in transition metal and zeolite catalysis.
Abstract: Density functional theory enables quantitative computational analysis of reaction intermediates. The cluster approach makes application to heterogeneous catalysis possible. Two cases, one from transition metal catalysis, the other from zeolite catalysis will be analyzed. It will be shown that the information obtained on the elementary reaction steps from cluster calculations can be used to predict the overall rate of a catalytic reaction. In transition metal catalysis CH activation and CO oxidation will be discussed. In zeolite catalysis methanol activation and the hydroisomerization of hexane are treated.

Journal ArticleDOI
TL;DR: In this paper, the thermochemistry and thermal unimolecular decomposition reactions of the chlorinated disilanes have been characterized using ab initio molecular orbital techniques, and energy barriers and conventional transition state theory rate constants for all of the reactions are presented.
Abstract: The thermochemistry and thermal unimolecular decomposition reactions of the chlorinated disilanes have been characterized using ab initio molecular orbital techniques. Silylene, chlorosilylene, dichlorosilylene, and hydrogen elimination reactions and their reverse insertions were considered. Reactant, product, and transition-state geometries and vibrational frequencies were calculated at the MP2/6-31G(d,p) level. Energetics were obtained at the MP2/6-31+G(2df,p), MP4/6-31+G(2df,p), G2(MP2), and/or G2 levels of theory, depending on the number of chlorine atoms in the molecule. In addition to the expected insertion reactions, direct reaction paths for SiHCl + SiHnCl4-n h SiH2 + SiHn-1Cl5-n and SiHCl + SiHnCl4-n h SiCl2 + SiHn+1Cl3-n were observed, with energetic barriers lying a few kcal/mol above the insertion reactions. To our knowledge, these concerted, two-atom exchange reactions have not previously been observed or predicted. They appear to represent a new type of elementary reaction for these compounds. Heats of formation for the chlorinated disilane reactants and chlorinated silylsilylene products of hydrogen elimination were calculated using isodesmic reactions. Energy barriers and conventional transition state theory rate constants for all of the reactions are presented. These can provide a basis for the construction of a detailed mechanism for the multistep thermal decomposition of the chlorinated silanes, which plays an important role in the chemical vapor deposition of epitaxial silicon from the chlorinated silanes.

Journal ArticleDOI
TL;DR: In this article, a Langmuir-Hinshelwood formalism is developed for the catalytic reaction step and is demonstrated to fit best with the kinetics of HS.
Abstract: The oxidation of sulfide in oxygen-saturated aqueous solutions is accelerated by dissolved or silica-bonded cobalt phthalocyanines. On the basis of thermodynamical considerations it is postulated that the catalyst enhances the formation of disulfide as the initial elementary reaction step. The following reaction steps are largely unaffected by the catalyst, as indicated by a product ratio sulfate/thiosulfate=0.86, comparable to that of the uncatalyzed autoxidation. A Langmuir-Hinshelwood formalism is developed for the catalytic reaction step and is demonstrated to fit best with the kinetics. In addition, from the kinetic data free enthalpies for the adsorption of HS - (1) at the dissolved phthalocyanine (ΔG=-17.6 kJ/mole) and (2) at the immobilized complex (ΔG=-20.0 kJ/mole) are calculated.

Journal ArticleDOI
TL;DR: In this article, the first ultrafast infrared study on silicon-hydrogen bond cleavage by CpMn(CO)3 was performed, which showed that the parent molecule can be recovered in a few picoseconds.
Abstract: Cleavage, or activation, of the silicon-hydrogen bond of a silane by a metal center has been the focus of many recent studies.1-6 Knowledge of this type of reaction is relevant to the central ideas of chemical bonding in general and is essential to the development of catalytic reactions such as hydrosilation. It is commonly accepted that the photochemical reaction for the oxidative addition of Et3SiH (Et ) C2H5) to CpMn(CO)3 (Cp ) C5H5) begins with the loss of a CO ligand as the result of UV irradiation, producing a coordinatively unsaturated dicarbonyl species7,8 which further reacts to activate the Si-H bond to form CpMn(CO)2(H)(SiEt3). Due to the fast reaction rates, however, the detailed reaction mechanism including the initial solvation of the nascent photogenerated chemical species has remained unclear. With the advent of ultrafast spectroscopy, especially in the infrared, it is now possible to identify such events which occur on a time scale shorter than diffusion to reveal the underlying elementary reaction steps.9 In this communication, we report the first ultrafast infrared study on silicon-hydrogen bond cleavage by CpMn(CO)3. As a result of photodissociating one CO ligand,10 the kinetics of the parent molecule recorded at 2028 cm-1 (A, Figure 1) shows an instrument limited bleach, 31% of which recovers in 32 ( 7.4 ps (Figure 2A).12 This rapid recovery of the parent bleach is due to vibrational relaxation in the ground electronic manifold of the parent molecule.9,13,14 The 31% recovery is in good agreement with reported CO loss quantum yields of 0.65 measured at 313-nm excitation.15 Subsequent spectral evolution suggests that photolysis of the parent molecules leads to two transient species including η-CpMn(CO)2 and a previously unreported intermediate. These reactive intermediates are solvated within a few picoseconds.16 The initial solvation of the nascent species through either the ethyl moiety or the Si-H bond of the solvent partitions the reaction into two channels of

Journal ArticleDOI
01 Mar 1997
TL;DR: In this paper, the authors analyzed the decomposition kinetics of n-pentyl radicals in the high temperature regime where steady state distributions are not achieved and reversible isomerization to decomposing 2 -pentyl radical is of importance through the solution of the time-dependent master equation.
Abstract: The decomposition kinetics of n-pentyl radicals in the high temperature regime where steady state distributions are not achieved and reversible isomerization to decomposing 2-pentyl radicals is of importance has been analyzed through the solution of the time-dependent master equation. The reactions are characterized by low activation thresholds and lead to large rate constants that vary with time. Particular attention is paid to branching ratios for direct decomposition of the n-pentyl radical and the decomposition that follows reversible isomerization to the 2-pentyl species. The behavior of the system under a variety of conditions is described and the use of branching ratios as a possible means of characterizing the reactions in a manner that is compatible with present methods for employing kinetic data for simulating complex chemical phenomenon is considered. At higher temperatures, rate constants and branching ratios collapse to limiting values. The combination of limiting and the onset of steady state behavior complicates the situation at lower temperatures. The overall behavior of such systems is highly dependent on the magnitude of the barrier to isomerization. The extent of departures from the high pressure-branching ratios are defined.

Journal ArticleDOI
TL;DR: In this paper, the probability of forming XCF 2 + is independent of which isotope of hydrogen is the collision partner, a result consistent with a direct reaction mechanism, and the relative yields of the bond-forming reaction which produces X CF 2 + and the non-dissociative electron transfer reaction, which forms CF 2+, have been determined as a function of the collision energy.

Journal ArticleDOI
TL;DR: In situ imaging technology developed for nuclear medicine is now being applied to study the kinetics of heterogeneous catalytic reactions under actual process conditions as mentioned in this paper, which can be compared with mathematical models based on the reaction kinetics in order to refine parameters such as activation energies and preexponential factors for elementary reaction steps.
Abstract: In situ imaging technology developed for nuclear medicine is now being applied to study the kinetics of heterogeneous catalytic reactions under actual process conditions. Minute quantities of molecules (ca. 10 -~ tool), radio-labeled with positron-emitting isotopes such as ltC;13 N; or t50 are injected as pulses into the feed streams of chemical reactors. Subsequent coincident detection of pairs of gamma photons produced via positron--electron annihilation allows the concentration of reactants, intermediates and products to be mapped as a function of both time and position within the reactor bed. As well as providing qualitative information regarding the mechanism of the reaction under investigation the data obtained can be compared with mathematical models based on the reaction kinetics in order to refine parameters such as activation energies and pre-exponential factors for elementary reaction steps. Since the technique is capable of imaging transient phenomena, information is provided that is not accessible to steady-state techniques.

Journal ArticleDOI
01 Jan 1997
TL;DR: In this paper, the product channels of the reaction between CH 2 (X 3 B 1 ) and NO in the gas phase at room temperature and near ambient pressure were investigated by Fourier transform infrared (FTIR) spectroscopy.
Abstract: The product channels were investigated of the reaction between CH 2 (X 3 B 1 ) and NO in the gas phase at room temperature and near ambient pressure. Mixtures of CH 2 CO/NO/Ar were photolyzed at λ = 312 nm in a static reactor. The reaction products were analyzed by Fourier transform infrared (FTIR) spectroscopy. The main product (= 84%) was found to be fulminic acid, HCNO. A second channel (15%) was found to lead to HCN. Other products which were detected include CO, N 2 O, H 2 O, HONO, H 2 CO, and CO 2 . These are formed (except for the CO from the CH 2 CO photodissociation) in consecutive reactions of the accompanying H atoms and OH radicals from the HCNO and HCN reaction channels.

Journal ArticleDOI
TL;DR: In this article, the rate-ratio asymptotic analysis of premixed heptane flames is performed using a detailed chemical-kinetic mechanism consisting of 257 elementary reactions, a skeletal chemical-inertial mechanism comprising 34 elementary reactions and a reduced chemical-inketic mechanism made up of six overall steps.

Journal ArticleDOI
TL;DR: In this article, the authors outline methods used to quantify reaction kinetics for catalytic cracking and describe how the rates of specific catalytic cycles are controlled by catalyst treatment (e.g., steaming) and process conditions (eg, conversion and temperature).
Abstract: Catalytic cracking of hydrocarbons takes place via elementary reactions such as initiation processes to form carbenium ions, olefin adsorption/desorption steps, isomerization, β-scission, oligomerization, and hydride ion transfer steps These elementary steps involving reactive carbenium ion surface intermediates are the essential components of catalytic cracking that lead to various catalytic cycles and their corresponding stoichiometric reactions This review outlines methods used to quantify reaction kinetics for catalytic cracking and describes how the rates of specific catalytic cycles are controlled by catalyst treatment (eg, steaming) and process conditions (eg, conversion and temperature)

Journal ArticleDOI
TL;DR: Theoretical studies for the reaction of FNO2 with the radicals CH3, tert-butyl, and C13H21 are reported in this paper, which are templates for the radical site of a hydrogenated diamond (111) surface.
Abstract: Theoretical studies are reported for the reaction of FNO2 with the radicals CH3, tert-butyl, and C13H21, which are templates for the radical site of a hydrogenated diamond (111) surface. All struct...

Journal Article
TL;DR: In this paper, a general kinetic scheme of the Mn(II)-catalyzed oxidation of glucose by persulfate ions was suggested, and the effective activation energy is equal to 98 kJ/mol.
Abstract: The study of the kinetics of Mn(II)-catalyzed oxidation of glucose by persulfate ions showed that the process occurs via a chain radical mechanism. It is established that the reaction orders with respect to glucose and persulfate and manganese ions are close to unity. The effective activation energy is equal to 98 kJ/mol. A general kinetic scheme of the oxidation process is suggested. Analysis of the scheme with comparison of the contributions of competing reactions made it possible to establish the regime of the process under experimental conditions, to distinguish the key reactions, to develop a mathematical model of the process, and to calculate the ratio of rate constants of some elementary reactions.

Journal ArticleDOI
TL;DR: In this paper, high-temperature kinetics of Si-precursor molecules relevant to CVD and ceramic processing are described. But the authors focus on the high temperature of the Si precursor molecules.
Abstract: Experimental investigations of high-temperature kinetics of Si-precursor molecules relevant to CVD and ceramic processing are described. Reaction systems using SiH 4 , Si 2 H 6 , and SiCl 4 highly diluted in argon were studied in a shock tube, a high-temperature wave reactor, by monitoring in situ the concentrations of atomic or radical reactants Si, H, Cl, SiH, and SiH 2 . Because of the very high dilution, the measured properties are sensitive to a limited number of elementary reactions, allowing a relatively direct determination of the respective rate coefficients. Both thermal pyrolysis and laser flash photolysis methods were used to expand the investigated temperature range. An overview of the bimolecular Si-atom reactions is given.

Journal ArticleDOI
01 Mar 1997
TL;DR: In this paper, a new experimental approach is presented, which combines the high energy resolution of a zero kinetic energy (ZEKE) electron spectrometer with the high kinetic resolution of reflecting ion time of flight spectrometers in a coincidence experiment.
Abstract: A brief review of the literature concerning the H 2 loss reaction from ethane radical cations is given. The reaction most likely proceeds by tunneling of H atoms through a transfer barrier. In this contribution a new experimental approach is presented, which combines the high energy resolution of a zero kinetic energy (ZEKE) electron spectrometer with the high kinetic resolution of a reflecting ion time of flight spectrometer in a coincidence experiment. With this technique it is possible to measure the rate constant k(E) of the title reaction an ion energy resolution of 10 meV directly over three orders of magnitude. The implementation of this technique will ultimately enable the study of D 2 loss from isotopically labeled ethane-d6 cations.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the heterogeneous processes that contribute towards the for- mation of N2O in an environment that comes as closely as possible to exhaust conditions containing NO and SO2 among other constituents.
Abstract: We investigated the heterogeneous processes that contribute towards the for- mation of N2O in an environment that comes as closely as possible to exhaust conditions containing NO and SO2 among other constituents. The simultaneous presence of NO, SO2, O2, and condensed phase water in the liquid state has been confirmed to be necessary for the production of significant levels of N2O. The maximum rate of N2O formation occurred at the beginning of the reaction and scales with the surface area of the condensed phase and is independent of its volume. The replacement of NO by either NO2 or HONO significantly in- creases the rate constant for N2O formation. The measured reaction orders in the rate law change depending upon the choice of the nitrogen reactant used and were fractional in some cases. The rate constants of N2O formation for the three different nitrogen reactants reveal the following series of increasing reactivity: indicating the probable se- NO , NO , HONO, 2 quential involvement of those species in the elementary reactions. Furthermore, we observed a complex dependence of the rate constant on the acidity of the liquid phase where both the initial rate as well as the yield of N2O are largest at of a H2SO4/H2O solution. The pH 5 0 results suggest that HONO is the major reacting N(III) species over a wide range of acidities studied. The N2O formation in synthetic flue gas may be simulated using a relatively simple mechanism based on the model of Lyon and Cole. The first step of the complex overall reaction corresponds to NO oxidation by O2 to NO2 mainly in the gas phase, with the presence of both H2O and active surfaces significantly accelerating NO2 production. Subsequently, NO2 reacts with excess NO to obtain HONO which reacts with S(IV) to result in N2O and H2SO4 through a complex reaction sequence probably involving nitroxyl (HON) and its dimer, hyponitrous acid. q 1997 John Wiley & Sons, Inc. Int J Chem Kinet: 29: 869- 891, 1997.

Journal ArticleDOI
TL;DR: In this article, G-2 calculations have been carried out for a number of elementary reactions relevant to low-temperature silane oxidation, including the chain-branching process which enables the spontaneous ignition of silane at room temperature.
Abstract: Ab initio G-2 calculations have been carried out for a number of elementary reactions relevant to low-temperature silane oxidation. The calculations have been made to identify the chain-branching process which enables the spontaneous ignition of silane at room temperature. Extensive calculations have also been made for the reactions of major intermediates with hydrogen atoms and water vapor.

Journal ArticleDOI
01 Mar 1997
TL;DR: In this paper, a method is presented to calculate the distribution of the orbital angular momenta as a result of reactive collisions in a radial potential for complex-forming bimolecular reactions.
Abstract: A detailed modelling of a complex-forming bimolecular reaction requires the knowledge of the nascent energy and angular-momentum distribution of the intermediate complex. A method is presented to calculate the distribution of the orbital angular momenta as a result of reactive collisions in a radial potential. For the case of thermal collisions, analytical solutions are obtained. Reactions of photochemically generated species are also considered. The method is applied to the reaction of CH 4 with O 2 + and O( 1 D), respectively.

Journal ArticleDOI
TL;DR: In this paper, a mechanism-oriented kinetic model with a small CPU requirement was developed, which allows the model to be incorporated into a reactor simulation with fluid dynamics and heat and mass transfer.
Abstract: A mechanism-oriented kinetic model has been developed with a small CPU requirement which allows the model to be incorporated into a reactor simulation with fluid dynamics and heat and mass transfer. The model achieves a small CPU requirement by lumping rdicals with similar reactivity together. A 42-lump subset of the 10 5 or more radicals is used to describe all the elementary reactions with a high degree of accuracy. Structure/reactivity relationships are utilized to provide rate constants for these elementary steps. The model predictions are compared to the results of full mechanistic simulations and the reaction of pure and synthetic mixtures of model compounds.