bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of reactions between methoxycarbonyl, methyl, and methoxy radicals formed in flash photolysis of dimethyl oxalate in gas phase
Authors: Hassinen E. , Riepponen P. , Blomqvist K. , Kalliorinne K. , Evseev A. M. , Koskikallio J. 
Published: January 2005

AbstractFlash photolysis of dimethyl oxalate produced the radicals CH3, CH3O, and COOCH3. Thermally equilibrated methoxycarbonyl radicals did not decompose during radicalradical reactions in the presence of 40‐torr cyclohexane in the temperature range 298–448 K. Cyclohexyl radicals were also generated during the flash photolysis of the reaction mixture. Rate coefficients of radical–radical reactions were calculated from the amounts of stable products determined by gas chromatography: CO, CO2, CH4, C2H4, C2H6, CH2O, CH3OH, CH3OCH3, HCOOCH3, CH3COOCH3, CH3OCOOCH3, CH3C6H11, and CH3OC6H11. Calculations were performed using an iterative computer integration program. Absolute values of rate coefficients were based on the rate coefficient of the reaction between methyl radicals, k1 = 2.7 × 1010 dm3 mol−1 s−1, measured with the same equipment.
equation image
The rate coefficients for reactions (5)–(8) are:
Studies on the composition and kinetics of chromium(III)‐alanine system
Authors: Khan Iqrar A. , Kabir‐Ud‐Din  
Published: January 2005

AbstractKinetics of the complex formation of chromium(III) with alanine in aqueous medium has been studied at 45, 50, and 55°C, pH 3.3–4.4, and μ = 1 M (KNO3). Under pseudo first‐order conditions the observed rate constant (kobs) was found to follow the rate equation:

Values of the rate parameters (kan, k, KIP, and K) were calculated. Activation parameters for anation rate constants, ΔH≠(kan) = 25 ± 1 kJ mol−1, ΔH≠(k) = 91 ± 3 kJ mol−1, and ΔS≠(kan) = −244 ± 3 JK−1 mol−1, ΔS≠(k) = −30 ± 10 JK−1 mol−1 are indicative of an (Ia) mechanism for kan and (Id) mechanism for k routes (‥substrate Cr(H2O) is involved in the k route whereas Cr(H2O)5OH2+ is involved in k′ route). Thermodynamic parameters for ion‐pair formation constants are found to be ΔH°(KIP) = 12 ± 1 kJ mol−1, ΔH°(K) = −13 ± 3 kJ mol−1 and ΔS°(KIP) = 47 ± 2 JK−1 mol−1, and ΔS°(K) = 20 ± 9 JK−1 mol−1.
Quenching of O2(1Δg) by aliphatic amines
Authors: Raja Nalini , Arora P. K. , Chatha J. P. S. , Vohra K. G. 
Published: January 2005

AbstractThe quenching rate constants of O2(1Δg) with n‐butylamine, diethylamine, dipropylamine, dibutylamine, and tripropylamine have been determined in a discharge flow system. The rate constants are found to be (1.6 ± 0.2) × 103, (8.5 ± 0.6) × 104, (9.8 ± 0.5) × 104, (2.1 ± 0.1) × 105, and (8.6 ± 0.5) × 105 1 mol−1 s−1, respectively. The rate constants are found to increase in the order, tertiary amine → secondary amine → primary amine. The “inductive effect” of alkyl substitution is also found to increase the rate constant in a given series of amines.
Determination of absolute rate data for the reactions of atomic sodium, Na(32S1/2), with CH3F, CH3Cl, CH3Br, HCl, and HBr as a function of temperature by time‐resolved atomic resonance spectroscopy
Authors: Husain David , Marshall Paul 
Published: January 2005

AbstractWe present a kinetic study of the reactions of ground‐state sodium atoms with the molecules CH3F, CH3Cl, CH3Br, HCl, and HBr at elevated temperatures (537–966 K). Na(32S1/2) was generated by the pulsed irradiation of various sodium halide vapors and monitored by time‐resolved atomic resonance absorption of the unresolved D‐lines at λ = 589 nm [Na(32PJ) ← Na(32S1/2)] in the “single‐shot mode.” The photoelectric signals were amplified without distortion, captured, and digitized in a transient recorder interfaced to a microcomputer for data analysis. Absolute second‐order rate constants were measured at various temperatures in each case, yielding the following Arrhenius parameters (kRX = A exp(–E/RT), errors 1σ):
magnified image
which constitute, to the best of our knowledge, the first direct measurements of these quantities. The reaction between Na and HBr demonstrated anomalous behaviour which is discussed in terms of potential surfaces that have been calculated previously for this type of collisional process. The data are compared with analogous results for Na + CF4, CF3Cl, and CF3Br and with single‐temperature measurements on diffusion flames.
Quantum mechanical reactive scattering theory
Authors: Kouri D. J. 
Published: January 2005

AbstractIn this article we briefly discuss a number of promising approaches to the formulation of a general, numerically exact, quantum mechanical theory of fully three‐dimensional reactive atom‐diatom collisions. It is noted that the ability to treat the three‐dimensional H + H2 exchange reactions is pre‐requisite to any demonstration of the success of a general quantum mechanical formalism for reactivescattering. However, it is also noted that the time has come for any such theory to further demonstrate the ability to go beyond this basic, elementary atom‐diatom exchange reaction. It is speculated that there now exist a number of approaches which can potentially provide such a general framework for quantum reactive scattering theory. Finally, a new generalizationof the Faddeev formalism for such systems, which is capable of inclusion ofthree body forces with a completely general form for the potential surface, is presented.
Kinetics and mechanism of the decomposition of N‐bromoalcoholamines in aqueous solution
Authors: Antelo J. M. , Arce F. , Franco J. , Forneas M. J. , Sanchez M. E. , Varela A. 
Published: January 2005

AbstractThe decomposition reactions of N‐bromodiethanolamine, N‐bromoethylethanolamine, and N‐bromomethylethanolamine in aqueous solution have been studied kinetically under various experimental conditions. The results support a proposed reaction mechanism in which the rate controlling step is assumed to be the formation of an imine which is then hydrolyzed to the final decomposition products.
Gas phase thermal isomerization of 4‐acetyl−5‐methyl‐isoxazole
Authors: Perez Jorge Daniel , Wunderlin Daniel A. 
Published: January 2005

AbstractThe gas phase thermal isomerization of 4‐acetyl−5‐methyl‐isoxazole affords 3‐cyano−2,4‐pentanedione as the only product in good agreement with previous proposed isomerization mechanism for isoxazoles. On the other hand, kinetic parameters and MO theoretical calculations do not agree with those previously reported. An alternative reaction mechanism which explains this fact is discussed.
Neighboring group participation in the pyrolysis kinetics of 4‐chloro‐1‐butanol in the gas phase
Authors: Chuchani Gabriel , Martin Ignacio 
Published: January 2005

AbstractThe pyrolysis of 4‐chloro‐1‐butanol has been studied in a static system, seasoned with allyl bromide, and in the presence of the free radical suppressor toluene. The working temperature and pressure ranges were 400–450°C and 43–164 Torr, respectively. The reaction is homogeneous, unimolecular, and follows a first‐order rate law. The temperature dependence of the rate coefficients is given by the following Arrhenius equation: log k1(s−1) = (13.34 ± 0.50) − (221.1 ± 6.7) kJ mol−1 (2.303RT)−1. The products tetrahydrofuran, formaldehyde, and propene, arise by the participation of the neighboring OH group in 4‐chloro‐1‐butanol pyrolysis. The reaction is best explained in terms of an intimate ion pair type of mechanism.
Disproportionation‐combination rate constant ratios for haloalkyl radicals: Evidence for heterogeneous disproportionation
Authors: Holmes Bert E. , Rakestraw David J. 
Published: January 2005

AbstractDisproportionation‐combination rate constant ratios, kd/kc, have been determined for R + RCH2CHCl and for the auto disproportionation‐combination of RCH2CHCl radicals, R = CF3, C2F5, and C3F7. The kd/kc for R = CF3 and to a lesser degree for R = C2F5 and C3F7 were very sensitive to the surface/volume ratio of the reaction vessel suggesting a heterogeneous component for disproportionation.
FTIR study of the DMS/NO2/I2/N2 photolysis system: The reaction of IO radicals with DMS
Authors: Barnes I. , Becker K. H. , Carlier P. , Mouvier G. 
Published: January 2005

AbstractA steady‐state system involving the photolysis of NO2 in an excess of I2 as a source of IO radicals has been used to study the reaction IO + DMS in 760 Torr N2 at 296 K. IO radicals were found to react rapidly with DMS, one molecule of DMSO being produced for each molecule of DMS consumed. Numerical analysis of the experimental results yielded a rate constant of (3.0 ± 1.5) × 10−11 cm3 s−1 for the reaction IO + DMS → DMSO + I.
A reinvestigation of the rate constants for the reactions of ozone with cyclopentene and cyclohexene under atmospheric conditions
Authors: Bennett Paul J. , Harris Stephen J. , Kerr J. Alistair 
Published: January 2005

AbstractThe rates of decay of ozone in a large excess of the cycloalkene have been re‐measured by an improved experimental procedure, and the following second‐order rate constants (cm3 molecule−1 s−1) have been determined in synthetic air at atmospheric pressure:

The results are discussed in relation to existing literature data on the kinetics of ozonecycloalkene reactions.
The decomposition kinetics of disilane and the heat of formation of silylene
Authors: Martin J. G. , Ring M. A. , O'Neal H. E. 
Published: January 2005

AbstractThe static system decomposition kinetics of disilane (\documentclass{article}\pagestyle{empty}\begin{document}${\rm Si}_{\rm 2} {\rm H}_{\rm 6} \mathop {\longrightarrow}\limits^1 {\rm SiH}_{\rm 2} + {\rm SiH}_{\rm 4}$\end{document}, 538–587 K and 10–500 Torr), are reported. Reaction rate constants are weakly pressure dependent, and best fits of the data are realized with RRKM fall‐off calculations using logA1,∞ = 15.75 and E1,∞ = 52,200 cal. These parameters yield AHf0(SiH2)298 = (63.5 − Eb, c) kcal mol,−1 where Eb, c is the activation energy for the back reaction at 550 K, M = 1 std state. Five other silylene heat‐of‐formation values (ranging from 63.9 – Eb, c to 66.0 ‐ Eb, c kcal mol−1) are deduced from the reported decomposition kinetics of trisilane and methyldisilane, and from the reported absolute and relative rate constants for silylene insertions into H2 and SiH4. Assuming Eb, c = 0, an average value of ΔHf0(SiH2) = 64.3 ± 0.3 kcal mol−1 is obtained. Also, a recalculation of the activation energy for silylene insertion into H2, based in part on the new disilane decomposition Arrhenius parameters, gives (0.6 + Eb, c) kcal mol−1, in good agreement with theoretical calculations.
High‐temperature collisional energy transfer in highly vibrationally excited molecules II: Isotope effects in isopropyl bromide systems
Authors: Brown Trevor C. , King Keith D. , Gilbert Robert G. 
Published: January 2005

AbstractValues for 〈ΔEdown〉, the average downward energy transferred from the reactant to the bath gas upon collision, have been obtained for highly vibrationally excited undeuterated and per‐deuterated isopropyl bromide with the bath gases Ne, Xe, C2H4, and C2D4, at ca. 870 K. The technique of pressure‐dependent very low‐pressure pyrolysis (VLPP) was used to obtain the data. For C3H7Br, the 〈ΔEdown〉 values (cm−1) are 490 (Ne), 540 (Xe), 820 (C2H4), and 740 (C2D4), and for C3D7Br, 440 (Ne), 570 (Xe), 730 (C2H4), and 810 (C2D4). The uncertainties in these values are ca. ±10%. The 〈ΔEdown〉 values for the inert bath gases Ne and Xe show excellent agreement with the theoretical predictions of the semi‐empirical biased random walk model for monatomic/substrate collisional energy exchange [J. Chem. Phys., 80, 5501 (1984)]. The relative effects of deuteration of the reactant molecule on 〈ΔEdown〉 also compare favorably with the predictions of this theoretical model. Extrapolated high‐pressure rate coefficients (s−1) for the thermal decomposition of reactant are 1013.6±0.3 exp(−200 ± 8 kJ mol−1/RT) for C3H7Br and 1013.9±0.3 exp(−207 ± 8 kJ mol±1/RT) for C3D7Br, which are consistent with previous studies and the expected isotope effect.
Isomerization of n‐hexyl and s‐octyl radicals by 1,5 and 1,4 intramolecular hydrogen atom transfer reactions
Authors: Dóbé S. , Bérces T. , Réti F. , Márta F. 
Published: January 2005

Abstractn‐Hexyl and s‐octyl radical isomerizations by intramolecular hydrogen atom shift have been studied in the presence of high methyl radical concentration where isomerized alkyl radicals reacted predominantly by combination and disproportionation reactions with methyl radicals.By assuming the rate coefficient of 1‐hexyl radical recombination to be equal to that of ethyl self‐combination, the rate coefficient of log(k1/s−1) = (9.5 ± 0.3) – (11.6 ± 0.3) kcal mol−1/RT ln 10 has been derived for the 6sp isomerization of n‐hexyl radicals, 1‐hexyl → 2‐hexyl (1).Investigation of s‐octyl radical isomerization was complicated by fast interconversion between 3‐octyl, 2‐octyl, and 4‐octyl radicals. Use of the methyl trapping technique and systematic variation of methyl radical concentration made possible the determination of log(k2/s−1) = (9.4 ± 0.7) − (11.2 ± 1.0) kcal mol−1/RT ln 10 for the 6ss isomerization of 3‐octyl and the estimation of log(k3/s−1) = 10.5–17 kcal mol−1/RT ln 10 for the 5ss isomerization of 2‐octyl radicals, where 3‐octyl → 2‐octyl (2), and 2‐octyl → 4‐octyl (3).
Pressure and temperature dependence of reactions proceeding via a bound complex. An approach for combustion and atmospheric chemistry modelers. Application to HO + CO → [HOCO] → H + CO2
Authors: Larson C. W. , Stewart P. H. , Golden D. M. 
Published: January 2005

AbstractElementary bimolecular processes that involve formation of a chemically activated intermediate species are common. We address the general problem of modeling these processes and describe the necessary and sufficient information that must be specified to assure that a kinetics model will extrapolate the rate constants for those reactions over wide ranges of temperature and pressure. The approach is illustrated for the system centered around the HOCO intermediate. Here, specification of the temperature and pressure dependence of three rate constants, k(T,P) and the temperature dependence of two equilibrium constants, K(T), is necessary and sufficient, viz:

equation image

Rate constants are cast in the form of an analytical expression, suggested by Troe, and appropriate parameters are tabulated.
Kinetics of the reaction of hydroxyl radicals with 2‐(dimethylamino)ethanol from 234–364 K
Authors: Anderson Larry G. , Stephens Robert D. 
Published: January 2005

AbstractThe temperature dependence of the rate of the reaction of OH with 2‐(dimethylamino)‐ethanol, (CH3)2NCH2CH2OH (DMAE) was investigated over the temperature range, 234 to 364 K. The reaction was studied using the flash photolysis‐resonance fluorescence technique. The room temperature rate constant determined for this reaction was (10.3 ± 2.0) × 10−11 cm3 molecule−1 s−1, with essentially no temperature dependence evident within the uncertainty in the experiments. A value of (9.0 ± 2.0) × 10−11 cm3 molecule−1 s−1 is believed to best describe the reaction over the entire temperature range. The room temperature rate constant is about twice the value reported previously for this reaction. The overall reaction of OH with DMAE was apportioned to the reactivity of OH for abstracting individual H‐ atoms from different types of CH bonds and the OH bond within the molecule. This technique predicts the overall rate constant for the OH‐DMAE reaction to within about 15% of the experimental value and makes it possible to estimate the yields of the initial radical products of the OH attack on DMAE. A mechanism is proposed for the subsequent atmospheric reactions that would occur in the photooxidation of DMAE.
Formation of H and D atoms in pyrolysis of 1,3‐butadiene and 1,3 butadiene‐1,1,4,4,‐d4 behind shock waves
Authors: Rao V. S. , Takeda Kunio , Skinner Gordon B. 
Published: January 2005

AbstractHighly dilute mixtures of 1,3‐butadiene and 1,3‐butadiene‐1,1,4,4‐d4 were pyrolyzed behind reflected and incident shock waves, respectively. Concentrations of H and D atoms were measured by resonance absorption spectroscopy. In the early stages of the reaction, nearly equal amounts of H and D were formed from CD2CHCHCD2, indicating that loss of H from C2 followed by loss of D from C1 is a more important reaction than breaking of the central CC bond. Overall, rate constants for atom‐forming reactions are much slower than rate constants for disappearance of butadiene in earlier experiments, suggesting that most of the butadiene disappears by processes that do not involve H or D atoms or by radicals that produce them rapidly.
The gas phase reactions of hydroxyl radicals with a series of esters over the temperature range 240–440 K
Authors: Wallington Timothy J. , Dagaut Philippe , Liu Renzhang , Kurylo Michael J. 
Published: January 2005

AbstractAbsolute rate constants were determined for the gas phase reactions of OH radicals with a series of esters using the flash photolysis resonance fluorescence technique. Experiments were performed over the temperature range 240–440 K at total pressures (using Ar diluent gas) between 25–50 torr. The kinetic data for methyltrifluoroacetate (k1) over the complete temperature range, and for methylacetate (k2), and ethylacetate (k3) over the range 296–440 K were used to derive the Arrhenius expressions;

At 296 K, the measured rate constants (in units of 10−13 cm3 molecule−1 s−1) were: k1 = (0.52 ± 0.08), k2 = (3.41 ± 0.29), and k3 = (15.1 ± 1.4). Room temperature rate constants for the OH reactions with several other aliphatic esters were also measured. These were (in the above units): methylformate, (2.27 ± 0.34); ethylformate, (10.2 ± 1.4); n‐propylformate, (23.8 ± 2.7); n‐butylformate, (31.2 ± 3.3); n‐propylacetate, (34.5 ± 3.4); i‐propylacetate, (37.2 ± 2.9); n‐butylacetate, (41.5 ± 3.0); s‐butylacetate, (56.5 ± 5.9); methylpropionate, (10.3 ± 0.4); ethylpropionate, (21.4 ± 3.0); n‐propylpropionate, (40.2 ± 3.2); methylbutyrate, (30.4 ± 3.3); ethylbutyrate, (49.4 ± 3.8); n‐propylbutyrate, (74.1 ± 3.2), and n‐butylbutyrate, (106 ± 13), error limits represent 2σ from linear least‐squares analyses. The results are discussed in terms of the reaction mechanisms and are compared to previous literature data.
On the ion contamination of atoms produced in a microwave discharge
Authors: Nelson T. O. , Tardy D. C. 
Published: January 2005

AbstractThe present study was undertaken to quantitatively measure the concentration of ions produced by a microwave discharge source commonly used in the production of atomic species. Using a double floating probe to monitor the ion content, the results indicate that the flow of ions was less than 1.8 × 10−6 times the total flow of particles from the discharge cavity. Due to the low ion mole fraction, it is concluded that ion‐molecule reactions are not competitive with previousry reported atom‐molecule reactions.
Rate constants for the gas phase reactions of OH with C5 through C7 aliphatic alcohols and ethers: Predicted and experimental values
Authors: Wallington Timothy J. , Dagaut Philippe , Liu Renzhang , Kurylo Michael J. 
Published: January 2005

AbstractAbsolute rate constants were determined at 298 K for the gas phase reactions of hydroxyl radicals with several C5 through C7 aliphatic alcohols and ethers using the flash photolysis resonance fluorescence technique. The values obtained (in units of 10−12 cm3 molecule−1 s−1) were: 3‐methyl‐2‐butanol, (12.4 ± 0.7); 2‐pentanol, (11.8 ± 0.8); 3‐pentanol, (12.2 ± 0.7); cyclopentanol, (10.7 ± 0.7); 1‐hexanol, (12.4 ± 0.7); 2‐hexanol, (12.1 ± 0.7); 1‐heptanol, (13.6 ± 1.3); methyl‐n‐butylether, (16.4 ± 0.6); ethyl‐n‐butylether, (22.8 ± 0.9); ethyl‐t‐butylether, (8.12 ± 0.32); and methyl‐t‐amylether, (7.91 ± 0.42). These results are discussed in terms of group reactivities in such molecules and are compared with values estimated from an additive structure‐reactivity index.
The formation of hydrogen in ethylene pyrolysis at 900 K
Authors: Jayaweera Indira S. , Pacey Philip D. 
Published: January 2005

AbstractEthylene at concentrations of 2.7 × 10−3 to 1.0 × 10−2 mol L−1 has been pyrolyzed at 900 K in a flow system. The products ethane and hydrogen have been analyzed by gas chromatography. The results are consistent with a mechanism in which these products are initially formed as follows:

equation image

Reaction [1] occurs only 1 to 2% as often as the addition reaction,

equation image

The latter reaction is close to equilibrium. Taking the rate constant, k4, and the equilibrium constant, K2, from the literature and making small adjustments for minor processes, k1 is found to be (9 ± 3) × 107 L mol−1 s−1. Here the uncertainty is intended to encompass errors in the present work and in the literature parameters.A secondary source of hydrogen was also observed. Its dependence on ethylene concentration was consistent with formation from an intermediate with six carbon atoms, such as cyclohexene.
A kinetics study of the reaction of Cl with NO2
Authors: Ravishankara A. R. , Smith G. J. , Davis D. D. 
Published: January 2005

AbstractThe third order rate coefficients for the addition reaction of Cl with NO2, Cl + NO2 + M → ClNO2 (ClONO) + M; k1, were measured to be k1(He) = (7.5 ± 1.1) × 10−31 cm6 molecule−2 s−1 and k1(N2) = (16.6 ± 3.0) × 10−31 cm6 molecule−2 s−1 at 298 K using the flash photolysis‐resonance fluorescence method. The pressure range of the study was 15 to 500 torr He and 19 to 200 torr N2. The temperature dependence of the third order rate coefficients were also measured between 240 and 350 K. The 298 K results are compared with those from previous low pressure studies.
Heterogeneous recombination of O + CO on solid CO2 at 77 K
Authors: Sharpe Steven , Boiani James A. , Sethi Dhanwant S. 
Published: January 2005

AbstractHeterogeneous recombination of O + CO → CO2 over a solid CO2 surface at 77 K was investigated. A modified discharge flow setup was used to generate low O atom concentrations by the reaction N + NO → N2 + O(3P). The O atom concentrations were measured upstream and downstream of the solid CO2 substrate using resonance fluorescence by monitoring the unresolved 130.3 nm triplet transition 3S1 − 3P2,1,0 at the two fixed points. CO2 formed was determined by measuring the β activity from C14O2 produced from CO containing C14O as a reactant gas. The CO2 formation was found to be first order in CO and independent of O atom concentration over the entire range of 4.3 × 1012 to 1.9 × 1014 cm−3 and 1.2 × 1011 to 5.6 × 1012 cm−3 for CO and O respectively. The first order recombination coefficient, λCO was found to be 1.4 (±.38) × 10−5.
Kinetics of the formation and hydrolysis of the schiff's base of 4‐pyridinecarboxaldehyde with N‐hexylamine in water‐dioxan mixtures
Authors: Llor Juan , Asensio Salvador , Sanchez‐ruiz Jose Manuel 
Published: January 2005

AbstractWe have carried out a kinetic study of the 4‐pyridinecarboxaldehyde plus n‐hexylamine system, at 25°C, in water‐dioxan mixtures (0–60% v/v) and in the pH range pKa + 1.5 > pH > pKa − 1.5, where pKa is the pK value of the conjugate acid of the amine. The results obtained could be interpreted in terms of a rate constant for Schiff's base hydrolysis and a rate constant for the reaction between the nonprotonated n‐hexylamine and the nonhydrated form of 4‐pyridinecarboxaldehyde. Both constants decrease sharply as the dioxan content of the solvent increases, in a manner consistent with Marshall's model [J. Phys. Chem., 74, 346 (1970)]. It is suggested that the transition state of the rate‐limiting step (carbinolamine dehydration) is highly solvated by water molecules and has a high separation of charges.