bluuebunny/crossref_metadata_2025_split huggingface dataset:
High‐temperature kinetics of thermal decomposition of acetic acid and its products
Authors: Mackie J. C. , Doolan K. R. 
Published: January 2005

AbstractKinetics of the thermal decomposition of acetic acid vapor dilute in argon have been studied over the temperature range of 1300–1950 K in a single‐pulse shock tube. The acid was found to decompose homogeneously and molecularly via two competing firstorder reaction channels at nearly equal rates, to form methane and carbon dioxide on the one hand, and ketene and water on the other. Fall‐off behavior has been taken into account and limiting high‐pressure rate constants for both channels have been derived. Ketene was found to decompose both unimolecularly to methylene radicals and carbon monoxide and also by a radical reaction with CH2 to form ethylene and carbon monoxide. The rate constant derived for the unimolecular reaction was found to be in good agreement with an earlier shock tube measurement by H. G. Wagner and F. Zabel [Ber. Bunsenges Phys. Chem., 75, 114 (1971)]. The bimolecular reaction of ketene to produce allene and carbon dioxide, important in lower temperature reaction systems, has been found to be unimportant under the present conditions. A computer model for the decomposition kinetics involving 46 reactions of 21 species has been found to simulate the experimental yield data substantially. Sensitivity analyses have been used to identify reactions which make important contributions to the overall mechanism and yields of major products. Methylene radicals play important roles in determining yields of major species.
Kinetics of the competitive chlorinations of some perfluoroalkyl iodides determination of the bond dissociation energies D(CD3‐I), D,(C2F5‐I), and D,(i,‐C3F7‐I)
Authors: Ahonkhai Samuel I. , Whittle Eric 
Published: January 2005

AbstractThe reactions

(R = CF3, C2F5, and i,‐C3F7) have been studied competitively in the gas phase over the range of 27–231°C. The following Arrhenius parameters were obtained:

log A,(cm3/mol · s)
E,(kJ/mol)

R = CF3
13.99 ± 0.21
17.1 ± 2.0

R = C2F5
13.97 ± 0.20
11.5 ± 2.0

R = i,‐C3F7
14.18 ± 0.20
10.2 ± 2.0

The above data lead to bond dissociation energies D(R‐I) which are compared with previous published results. The following values are recommended: D,(CF3‐I) = 224, D,(C2F5‐I) = 219, and D,(i,‐C3F7‐I) = 215 kJ/mol.
Hydrogen/deuterium abstraction by chlorine atoms from gaseous ethyl chlorides. Secondary kinetic isotope effects in the system CH3CH2Cl, CH3CHDCl, CH3CD2Cl
Authors: Niedzielski J. , Tschuikow‐Roux E. , Yano T. 
Published: January 2005

AbstractThe abstraction of hydrogen/deuterium from CH3CH2Cl, CH3CHDCl, and CH3CD2Cl by photochemically generated ground‐state chlorine atoms has been investigated over the temperature range of 8–94°C using methane as a competitor. Rate constant data for the following reactions have been obtained:magnified imageThe temperature dependence of the relative rate constants ki/kj was found to conform to the Arrhenius rate law, where the stated error limits are one standard deviation:

and kr is the rate constant for the reference reaction (CH4 + Cl → CH3 + HCl). The β secondary kinetic isotope effects (k2/k3/k4) are close to unity and show a slight inverse temperature dependence. Both preexponential factors and activation energies decrease as a result of deuterium substitution in the adjacent chloromethyl group. The trends are well outside the limits of experimental error.
Thermal decomposition of azoisopropane. II. Secondary decomposition processes
Authors: Péter A. , Ács G. , Huhn P. 
Published: January 2005

AbstractThe thermal decomposition of azoisopropane (AIP) was studied in the presence of various quantities of propylene in the temperature and pressure intervals 498–553 K and 3.33–5.33 kPa. The inhibition functions relating to formation of the products were determined; these proved a good basis for interpretation of the formation of the secondary decompositon products of AIP. The experimental data support the conception that the βμ radical—radical reaction
equation image
occurs. The product of this is not stable; its decomposition is one of the sources of the secondary products. The ratio of the rate constants was determined for the following reactions:magnified image
Efficient production of electronically excited BiF(AO+) via collisions with NF(a1Δ)
Authors: Herbelin John M. , Klingberg Robert A. 
Published: January 2005

AbstractAn efficient process for converting the energy stored in electronically excited NF(a1Δ) into blue‐green BiF (AX) band emissions has been discovered. Bismuth atoms are converted to BiF and then repeatedly pumped to the (AO+) state in two steps via collisions with NF(a1Δ). A model has been formulated that predicts BiF emission intensities that are in excellent agreement with the observed values. Some of the rate coefficients required for this model are estimated by means of charge‐transfer theories. The cyclic nature of this system, along with its other basic properties, suggests that it has a strong potential to be an efficient blue‐green laser system.
Formation of alkyl nitrates from the reaction of branched and cyclic alkyl peroxy radicals with NO
Authors: Atkinson Roger , Aschmann Sara M. , Carter William P. L. , Winer Arthur M. , Pitts James N. 
Published: January 2005

AbstractThe yields of C5 and C6 alkyl nitrates from neopentane, 2‐methylbutane, 2‐methylpentane, 3‐methylpentane, and cyclohexane have been measured in irradiated CH3ONONO‐alkane‐air mixtures at 298 ± 2 K and 735‐torr total pressure. Additionally, OH radical rate constants for neopentyl nitrate, 3‐nitro‐2‐methylbutane, 2‐nitro‐2‐methylpentane, 2‐nitro‐3‐methylpentane, and cyclohexyl nitrate, relative to that for n‐butane, have been determined at 298 ± 2 K. Using a rate constant for the reaction of OH radicals with n‐butane of 2.58 × 10−12 cm3 molecule−1 s−1, these OH radical rate constants are (in units of 10−12 cm3 molecule−1 s−1): neopentyl nitrate, 0.87 ± 0.21; cyclohexyl nitrate, 3.35 ± 0.36; 3‐nitro‐2‐methylbutane, 1.75 ± 0.06; 2‐nitro‐2‐methylpentane, 1.75 ± 0.22; and 2‐nitro‐3‐methylpentane, 3.07 ± 0.08. After accounting for consumption of the alkyl nitrates by OH radical reaction and for the yields of the individual alkyl peroxy radicals formed in the reaction of OH radicals with the alkanes studied, the alkyl nitrate yields (which reflect the fraction of the individual RO2 radicals reacting with NO to form RONO2) determined were: neopentyl nitrate, 0.0513 ± 0.0053; cyclohexyl nitrate, 0.160 ± 0.015; 3‐nitro‐2‐methylbutane, 0.109 ± 0.003; 2‐nitro‐2methylbutane, 0.0533 ± 0.0022; 2‐nitro‐2‐methylpentane, 0.0350 ± 0.0096; 3‐ + 4‐nitro‐2‐methylpentane, 0.165 ± 0.016; and 2‐nitro‐3‐methylpentane, 0.140 ± 0.014. These results are discussed and compared with previous literature values for the alkyl nitrates formed from primary and secondary alkyl peroxy radicals generated from a series of n‐alkanes.
The formation of C3H3 (propynyl) radicals in the reaction of CH2(1A1) with acetylene
Authors: Canosa‐Mas Carlos E. , Ellis Mark , Frey H. Monty , Walsh Robin 
Published: January 2005

AbstractResults obtained from the photolysis of ketene with acetylene strongly support the formation of C3H3 radicals in the title reaction. Stationary state studies are interpreted in terms of the reaction

with a rate constant (109.8 s−1) which is compared to RRKM predictions. In pulsed laser induced decomposition experiments, recombination products involving C3H3 have been detected (some for the first time) and their formation modeled using step (3) with the same rate constant.
The kinetics of the addition of alkyl radicals to carbonyl groups. I. The kinetics of the gas phase decomposition reactions of the trifluoro‐t‐butoxy radical
Authors: Kerr J. Alistair , Wright J. Paul 
Published: January 2005

AbstractTrifluoro‐t‐butoxy radicals have been generated by reacting fluorine with 2‐trifluoromethyl propan‐2‐ol:

Over the temperature range 361‐600 K the trifluoro‐t‐butoxy radical decomposes exclusively by loss of the CF3 group [reaction (−2)] rather than by loss of CH3 group [reaction (−1)]:
equation image
The limits of detectability of the product CF3COCH3, by gas‐chromatographic analysis, place a lower limit on the ratio k−2/k−1 of ca. 75. The implications of these results in relation to the reverse radical addition reactions to the carbonyl group are discussed along with the thermochemistry of the reactions.
UV absorption study of the dissociation of SO2 and SO in shock waves
Authors: Plach H. J. , Troe J. 
Published: January 2005

AbstractThe thermal decomposition of SO2 and of the primary dissociation product SO have been studied in shock waves by the uv absorption technique. The controversy about SO2 dissociation data from uv absorption signals was resolved and attributed to the extensive overlap of SO2 and SO uv absorption spectra. The derived rate coefficients are k1/[Ar] = 1015.6 exp(‐420 kJmol−1/RT) cm3mol−1 s−1 (temperature range 3000–5000 K) for SO2 dissociation, and k3/[Ar] = 1014.6 exp(‐448 kJmol−1/RT) cm3 mol−1 s−1 (temperature range 4000–6000 K) for SO dissociation. Anomalously high values of the apparent collision efficiencies βc in SO2 dissociation are attributed to marked contributions from excited electronic states.
High temperature determination of the rate coefficient for the reaction H2O + CN → HCN + OH
Authors: Szekely Attila , Hanson Ronald K. , Bowman Craig T. 
Published: January 2005

AbstractThe rate coefficient, k, of the reaction

has been determined in the temperature range 2460–2840 K using a shock tube technique. C2N2H2OAr mixtures were heated behind incident shock waves and the CN and OH concentration time histories were monitored simultaneously using broad‐band absorption near 388 nm (CN) and narrow‐line laser absorption at 306.67 nm (OH). The rate coefficient expression providing the best fit to the data was

with uncertainty limits of about ±45% in the temperature range 2460–2840 K. The rate coefficient of the reverse reaction was calculated using detailed balancing, and its extrapolation to lower temperatures was compared with previously published results.
Decomposition of di‐tert‐butyl nitroxide in aqueous solutions
Authors: Cáceres T. , Urzúa C. , Lissi E. A. 
Published: January 2005

AbstractDi‐tert‐butyl nitroxide (DTBN) decomposes in aqueous solutions producing 2‐methyl‐2‐nitroso propane (MNP) and tert‐butanol. The process is acid catalyzed, it is of second order in DTBN, and takes place with a rate constant of (1.0 ± 0.1) M−2 s−1. The reaction is also catalyzed by the anionic surfactant sodium dodecyl sulfate and by Fe(II) and Fe(III) ions. The catalysis by Fe(III) involves a very fast reduction of Fe(III) ions with concomitant formation of 2‐methyl‐2‐nitroso propane. The reaction catalyzed by Fe(II) also produces 2‐methyl‐2‐nitroso propane with a formation rate given by: d[MNP]/dt = (0.25 ± 0.10) [Fe(II)] [DTBN]. This reaction rate is nearly pH independent.
An outdoor smog chamber and modeling study of toluene–NOx photooxidation
Authors: Leone Joseph A. , Flagan Richard C. , Grosjean Daniel , Seinfeld John H. 
Published: January 2005

AbstractAn experimental investigation of the gas‐phase photooxidation of toluene–NOx–air mixtures at part‐per‐million concentrations has been carried out in a 65‐m3, outdoor smog chamber to assess our understanding of the atmospheric chemistry of toluene. In addition, six CONOx–air irradiations were conducted to characterize the chamber with regard to any wall radical sources. Measured parameters in the toluene–NOx experiments included O3, NO, NO2, HNO3, peroxyacetyl nitrate (PAN), CO, toluene, benzaldehyde, o‐cresol, m‐nitrotoluene, peroxybenzoyl nitrate (PBZN), temperature, relative humidity, aerosol size distributions, and particulate organic carbon. Predictions of the reaction mechanism of Leone and Seinfeld [7] are found to be in good agreement with the data under a variety of initial conditions. Additional simulations are used to investigate various mechanistic pathways in areas where our understanding of toluene chemistry is still incomplete.
Kinetics of the reactions of hydroxyl radical with aliphatic aldehydes
Authors: Semmes D. H. , Ravishankara A. R. , Gump‐Perkins C. A. , Wine P. H. 
Published: January 2005

AbstractRate coefficients for OH reactions with the 2–5 carbon aliphatic aldehydes have been measured under pseudo first‐order conditions in OH. OH was generated by flash photolysis of H2O at wavelengths greater than 165 nm and its concentration monitored using time‐resolved resonance fluorescence spectroscopy. Two reactions were studied only at 298 K while five reactions were studied over the temperature range 250–425 K; negative activation energies were observed for all five reactions. Aldehyde reactivity toward OH is nearly independent of the identity of the hydrocarbon side chain. Our results are compared with those obtained in previous studies of OH‐aldehyde reaction kinetics and their mechanistic implications are discussed.
Model study of synchronization and other phenomena in light perturbation of the Briggs–Rauscher reaction
Authors: Kumpinsky Enio , Epstein Irving R. , De Kepper Patrick 
Published: January 2005

AbstractCalculations are performed to model several phenomena observed when a photosensitive oscillating chemical reaction, the Briggs–Rauscher (BR) reaction, is subject to irradiation in a continuous‐flow stirred‐tank reactor. The BR mechanism proposed earlier by De Kepper and Epstein is supplemented by additional steps involving the photogeneration and subsequent reaction of iodine atoms. The calculations show qualitative agreement with the following experimentally observed phenomena: (a) change in the period and amplitude of oscillation as a function of the intensity of constant illumination, (b) synchronization between periodically varying illumination and the period of chemical oscillation, (c) phase shifts induced by single light pulses, and (d) dark steady states which are excitable by single light pulses and become oscillatory at appropriate levels of constant illumination.
The reactions of alkoxy radicals with O2. II. n‐C3H7O radicals
Authors: Zabarnick Steven , Heicklen Julian 
Published: January 2005

Abstractn‐C3H7ONO was photolyzed with 366 nm radiation at −26, −3, 23, 55, 88, and 120°C in a static system in the presence of NO, O2, and N2. The quantum yields of C2H5CHO, C2H5ONO, and CH3CHO were measured as a function of reaction conditions. The primary photochemical act is
equation image
and it proceeds with a quantum yield ϕ1 = 0.38 ± 0.04 independent of temperature. The n‐C3H7O radicals can react with NO by two routes
equation image
The n‐C3H7O radical can decompose via
equation image
or react with O2 via
equation image
Values of k4/k2 ≃ k4b/k2 were determined to be (2.0 ± 0.2) × 1014, (3.1 ± 0.6) × 1014, and (1.4 ± 0.1) × 1015 molec/cm3 at 55, 88, and 120°C, respectively, at 150‐torr total pressure of N2. Values of k6/k2 were determined from −26 to 88°C. They fit the Arrhenius expression:

For k2 ≃ 4.4 × 10−11 cm3/s, k6 becomes (2.9 ± 1.7) × 10−13 exp{−(879 ± 117)/T} cm3/s. The reaction scheme also provides k4b/k6 = 1.58 × 1018 molec/cm3 at 120°C and k8a/k8 = 0.56 ± 0.24 independent of temperature, where
equation image
Temperature coefficients for reactions of OH radicals with alkanes between 300 and 1000 K
Authors: Walker R. W. 
Published: January 2005

AbstractRecently, Atkinson et al. have developed a more sophisticated approach than simple additivity to determine group rate constants at room temperature for reactions of OH radicals with alkanes. In this article, use is made of reliable experimental data at room temperature and at 753 K to determine temperature coefficients for these reactions. Evidence based on experiment is cited in support of the expression k = AT1e−E/RT as a suitable quantitative expression for the variation of k with temperature between 300 and 1000 K for OH attack at any particular specific group in an alkane. Values are given for A and E for a number of groups found in both linear and branched alkanes. With highly branched alkanes, steric effects may limit the use of even the more sophisticated additivity approach used here. Use of the group values permits the calculation of both the overall rate constant for OH + alkane, the agreement with the limited amount of experimental data available being very good, and the proportions of each species of alkyl radical formed in the overall attack. Such information is vital to quantitative modeling of combustion processes currently being carried out extensively. The values given in the article are recommended for use over the temperature range 300–1000 K.
Bovine serum albumin and alizarin yellow G — a model system for positive cooperative binding to macromolecules
Authors: Nissani E. , Perlmutter‐Hayman B. 
Published: January 2005

AbstractThe kinetics of the binding of alizarin yellow G to six nonequivalent binding sites on bovine serum albumin were investigated, using the stopped flow and T‐jump techniques. The first step in the reaction sequence is very fast, and is followed by a slower step which is suggested to be an internal rearrangement of the collision complex formed in the first step. This temporal sequence shows that the strong cooperativity between the first and second binding sites is not due to the existence of different conformations in equilibrium in free albumin, but rather to a ligand‐induced change. Next, an additional, still slower transformation is observed. From the fact that this transformation is not rate‐determining for the formation of higher complexes we conclude that it corresponds to a branch reaction. The higher complexes are again formed with very high rate constants. The first complex has a high negative value of both ΔH and ΔS° of formation. For the second and higher complexes, the heat of formation is much lower, and the standard entropy of formation is positive. The formation of these complexes is thus largely entropy‐driven. The difference between the thermodynamic parameters of the first and subsequent ligands is in accordance with the assumption that only the binding of the first ligand entails significant structural changes.
The OH(v = 9) + O3 reaction pathway
Authors: Slanger T. G. , Huestis D. L. 
Published: January 2005

AbstractThe oxygen‐hydrogen system, including the reactive species H, O, H2, O2, O3, OH, and HO2, is very complex, and contains numerous reactions whose kinetics and branches have been insufficiently explored. In the present study we use computer modeling to simulate observations made in a 300‐K ozone‐hydrogen mixture, in which a critical H2 pressure leads to rapid ozone decomposition, and generation of high concentrations of atomic oxygen. Initiation of the reaction chain involves heterogeneous O and/or H atom production, and the chain branching step is the reaction OH(v) + O3 → OH + O + O2, which is shown to be the predominant pathway for these reactants. The critical H2 pressure (ca. 3 torr) sets important constraints upon the system kinetics.
Separation of polar and steric effects on absolute rate constants and arrhenius parameters for the reaction of tert‐butyl radicals with alkenes
Authors: Münger K. , Fischer H. 
Published: January 2005

AbstractAbsolute rate constants and their temperature dependencies were measured for the reaction of tert‐butyl radicals with 24 substituted ethenes and several other compounds in 2‐propanol solution by time‐resolved electron spin resonance. At 300 K the rate constants cover the range from 60 M−1 s−1 (1,2‐dimethylene) over 16,500 M−1 s−1 (vinyl‐chloride) to 460,000 M−1 s−1 (2‐vinylpyridine). For the mono‐ and 1,1‐disubstituted ethenes log k300 increases and the activation energy decreases with increasing electron affinity of the olefins. The frequency factors are in the range log A/M−1 s−1 = 7.5 ± 1.0 as typical for addition reactions, with minor exceptions. Electron affinity (polar) and steric effects on reactivity are separated for the addition of tert‐butyl to chloro‐ and methyl‐substituted ethylenes. A comparison with rate data for methyl, ethyl, 2‐propyl, and other radicals indicates both polar and steric effects on radical substitution.
Termolecular reaction of nitrogen monoxide and oxygen: A still unsolved problem
Authors: Olbregts J. 
Published: January 2005

AbstractThe oxidation of nitrogen monoxide has been studied extensively between 226 and 758 K at pressures of NO and O2 ranging from about 0.2 to 30 torr. It has been shown that (i) the reaction is properly first order against oxygen and second order against nitrogen monoxide, as well under initial conditions as during the course of the reaction; (ii) the termolecular rate constant, k, first decreases with increasing temperature and reaches a minimum value at 600 K; (iii) the transition state theory is unable to describe this behavior correctly, (iv) under the present experimental conditions k can be represented either by

or by

The latter equation is compatabile with a multiple‐step mechanism.
Thermal decomposition of methane: Autocatalysis
Authors: Roscoe John M. , Thompson Marla J. 
Published: January 2005

AbstractThe origin of autocatalysis in the pyrolysis of methane has been investigated by kinetic modeling. A mechanism is presented that provides good agreement with experimental data at 1038 K and 433 torr into the autocatalytic region. The main causes of autocatalysis are secondary initiation by hydrocarbon products larger than C2H6 and chain radical methylation sequences.
Excimer laser perturbations of methane flames: High temperature reactions of OH and CH
Authors: Chou Mau‐Song , Dean Anthony M. 
Published: January 2005

AbstractAn ArF excimer laser was used to perturb radical concentrations and a tunable dye laser was used to follow the rise and subsequent decay of OH and CH in rich (ϕ = 1.6–1.8) atmospheric pressure methane flames. The excimer beam is only slightly focussed to minimize temperature excursions and the influence of diffusion and convection on the decay rates. The observed OH decay is consistent with that predicted using a detailed kinetic mechanism. The observed CH decay is much faster than predicted. The effects of equivalence ratio and height above burner suggests that a major CH decay channel involving an intermediate with higher concentration in rich flames is not properly treated in the mechanism.
Variational sensitivity analysis of a photochemical smog mechanism
Authors: Gautier Olivier , Carr Robert W. , Seigneur Christian 
Published: January 2005

AbstractThe variational method of sensitivity analysis is applied to a recent chemical kinetic mechanism for photochemical smog. It is demonstrated that the variational method is capable of readily handling a large mechanism. The analysis can be applied to a single chemical species or to an arbitrarily large group of species contained in an objective function. Examples of the use of different objective functions are given. The variational method provides temporally distributed sensitivity coefficients. Therefore, the results are presented as a time‐dependent ranking of reactions in orderof decreasing importance with respect to the objective function species. This ranking permits the time‐dependent relative influence of each reaction to be readily determined by inspection. Particular attention is paid to reactions governing daytime O3 formation and nighttime NO3 and HONO formation.
Reaction of CF3 radicals with C2H6
Authors: Arican Haluk , Arthur Neville L. 
Published: January 2005

AbstractThe hydrogen transfer reaction between C2H6 and CF3 radicals, generated by the photolysis of CF3I, has been studied in the temperature range 298–617 K. The rate constant, based on the value of 1013.36 cm3 mol−1 s−1 for the recombination of CF3 radicals, is given by

where k2 is in cm3 mol−1 s−1 and E is in J mol−1. These results are compared with those previously reported, and the following best value for k2 is recommended: