bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics and mechanisms of the oxidation of sulfur dioxide over titanium dioxide and nickel oxide
Authors: Choi Jae Shi , Kim Keu Hong , Choi Sung Rack 
Published: January 2005

AbstractThe reactions between SO2 and O2 were carried out in the presence of TiO2 and NiO under various partial pressures of SO2 and O2 at temperatures from 240 to 330°C. TiO2 and NiO were pretreated by applying an annealing effect from which the catalysts would have the different activity. The rates are the highest for TiO2 pretreated at high temperature in the region of 400 to 600deg;C in vacuum, 1.21 × 10−4 mmHg. In contrast, the rates are the lowest for NiO pretreated at high temperaturefrom 350 to 550°C. The data have been correlated with 1.4 and first‐order kinetics for TiO2 and NiO, respectively. A reaction mechanism to explain the data was suggested.The quantities of anionic vacancies in TiO2 surfaces and of positive holes in NiO appeared to be paramount in determining the type of kinetics.
Substituent effects in the gas‐phase eliminations of alpha;‐substituted alkyl chlorides the pyrolyses of 2‐chloro‐3‐methylbutane and pinacolyl chloride
Authors: Chuchani Gabriel , Martin Ignacio , Alonso Miguel E. 
Published: January 2005

AbstractThe gas‐phase pyrolyses of 2‐chloro‐3‐methylbutane and pinacolyl chloride in the temperature range of 345‐390°C and pressure range of 60‐220 mm Hg are homogeneous and unimolecular in a seasoned reaction vessel. The temperature dependence of the rate constants is given by the Arrhenius equations

and

respectively. The Wagner‐Meerwein rearrangement was not observed in these eliminations. Some correlations for the pyrolysis of α‐substituted alkyl chlorides are presented and discussed. These facts are consistent with the heterolytic nature of the cyclic transition state mechanisms for these reactions.
Shock‐tube studies of the reactions of NO2 with NO2, SO2, and CO
Authors: Freund H. , Palmer H. B. 
Published: January 2005

AbstractThe thermal decomposition of NO2 and its atom‐transfer reactions with SO2 and CO have been studied behind incident shock waves using photometric detection methods. From the decomposition study it is possible to obtain information on the rate of the reaction 2NO2 → antisymmetric‐NO3 + NO. The results on the reaction, NO2 + SO2 → NO + SO3 extend the earlier work of Armitage and Cullis to about 2000°K. The reaction with CO [NO2 +] [CO NO + CO2] at shock temperatures is somewhat faster than predicted from available low‐temperature data and provides a modification of the rate‐constant expression that is applicable over a wide temperature range.
Very low‐pressure pyrolysis (VLPP) of 3,3‐dimethylbut‐1‐yne (tert‐butyl acetylene). The heat of formation and stabilization energy of the dimethylpropargyl radical
Authors: King Keith D. 
Published: January 2005

AbstractThe unimolecular decomposition of 3,3‐dimethylbut‐1‐yne has been investigated over the temperature range of 933°‐1182°K using the technique of very low‐pressure pyrolysis (VLPP). The primary process is CC bond fission yielding the resonance stabilized dimethylpropargyl radical. Application of RRKM theory shows that the experimental unimolecular rate constants are consistent with the high‐pressure Arrhenius parameters given by log (k/sec−1) = (15.8 ± 0.3) ‐ (70.8 ± 1.5)/θ where θ = 2.303RT kcal/mol. The activation energy leads to DH0[(CH3)2C(CCH)CH3] = 70.7 ± 1.5, θH0f((CH3)2ċCCH,g) = 61.5 ± 2.0, and DH0[(CH3)2C(CCH)H] = 81.0 ± 2.3, all in kcal/mol at 298°K. The stabilization energy of the dimethylpropargyl radical has been found to be 11.0±2.5 kcal/mol.
The Kinetics of the thermal oxidation of NO in solid oxygen between 13 and 29 K; direct observation of the reaction of (NO)2 and oxygen
Authors: Smith George R. , Guillory William A. 
Published: January 2005

AbstractThe kinetics of the reaction of cis‐(NO)2 with solid oxygen to form iso‐N2O4 have been studied between 13 and 29 K. The overall reaction is pseudo first order in cis‐(NO)2, and solid oxygen serves both as a reactant and the matrix. The pseudo‐first‐order rate constants are calculated to be k(14N) = 4.25 × 10−2 exp(‐103/RT), and k(15N) = 3.00 × 10−2 exp(‐105/RT) sec−1, based on temperature measurements from a thermocouple junction which may be at most three degrees lower than the actual reacting film. Most significantly, however, 14k/15k = 1.55 at∼13 K. The condensed phase reaction has been compared to that observed in the gas phase, and the extremely small pre‐exponential factors and large isotope effects have been discussed in terms of tunneling corrections and orientational constraints. It is suggested that the form of the crystal plays an integral role in the observed process.
A program system for computer integration of multistep reaction rate equations using the gear integration method
Authors: Stabler Robert N. , Chesick John P. 
Published: January 2005

AbstractA program system is described for the integration of the rate equations resulting from large systems of elementary reactions. The Gear integration method is used for this problem, which frequently may exhibit stiffness instability when other integration methds are employed. No usage of the quasi‐steady‐state approximation is necessary. Ease in varying the reaction mechanism and simplicity of input structure are coupled with efficient execution and minimal demands for program storage as key features. The input–output structure, method of operation, and implementation are summarized, along with core storage requirements and execution times for trials using an IBM 360/44 computer.
The kinetics of the thermal gas‐phase reaction Br2 + C6F5I → BrI + C6F5Br. An attempt to determine the bond dissociation energy D(C6F5‐I)
Authors: Okafo Ernest N. , Whittle Eric 
Published: January 2005

AbstractThe kinetics of the thermal bromination reaction
equation image
have been studied in the range of 261°–391°C. The observed rate law is compatible with initiation by the step
equation image
for which we obtain

where Θ = 2.303RT cal/mol. Using the above value of E6, we have

This result disagrees with values of D(C6F5‐I) obtained in other ways and we conclude that reaction (3) probably does not involve initiation by reaction (6). Instead, initiation may involve an addition of Br to the ring in C6F5I followed by decomposition of the adduct to give C6F5Br. If correct, this implies that the Arrhenius parameters above refer to the addition reaction rather than to reaction (6).
Thermal decomposition of cyclopentane and related compounds
Authors: Tsang Wing 
Published: January 2005

AbstractCyclopentane has been decomposed in comparative‐rate single‐pulse shock‐tube experiments. The pyrolytic mechanism involves isomerization to 1‐pentene and also a minor pathway leading to cyclopropane and ethylene. This is followed by the decomposition of 1‐pentene and cyclopropane. The rate expressions over the temperature range of 1000°–1200° K are

Details of the cyclopentane decomposition processes are considered, and it appears that if the trimethylene radical is an intermediate, then ΔHf(trimethylene) ≤ 280 kJ/mol at 300°K.
Radiation‐induced dechlorination of carbon tetrachloride in cyclohexane and n‐hexane mixtures. III. The kinetics of liquid‐phase reactions of trichloromethyl radicals
Authors: Katz M. G. , Baruch G. , Rajbenbach L. A. 
Published: January 2005

AbstractThe kinetics of gamma‐radiation‐induced free‐radical chain reactions in solutions of carbon tetrachloride in mixtures of varying composition of cyclohexane and n‐hexane was investigated in the temperature range of 296°–413°K. Trichloromethyl radicals were produced by the reaction of radiolytically generated alkyl radicals with the solute. The kinetics of the following reactions were studied:
equation image
The following rate expression was obtained:

The error limits are the standard deviation from the least mean‐square Arrhenius plots. The present results, combined with previously measured activation parameters for hydrogen‐atom abstraction from c‐C6H12 and n‐C6H14 by CCl3 radicals relative to CCl3 combination, afford experimental evidence that the decay of trichloromethyl species in alkane solutions is a diffusion‐limited process. The thesis that activation energies of reactions (4) and (5) in the liquid phase are equal to their respective values in the gas phase is confirmed.
Correlation of activation energies of radical–molecule metathesis reactions with enthalpic, polar, and steric parameters
Authors: Katz M. G. , Rajbenbach L. A. 
Published: January 2005

AbstractIt is shown that the activation energies E oF chlorine atom abstraction by cyclohexyl radicals and hydrogen atom abstraction by Cl atoms from polychloroalkanes can be correlated with the bond dissociation energies D and the Taft polar and steric substituent constants σ* and Es by the expression:

where ΔE and ΔD represent the differences between the E and D values of a given substrate and those of a reference compound (CH3 substituted substrate) and α, ρ, and δ are the corresponding correlation coefficients. The use of this expression allows quantitative evaluation of the relative contribution of the various factors affecting the activation energies of these reactions and estimation of related thermochemical data.
Very‐low‐pressure pyrolysis of N‐methyl aniline and N,N‐dimethyl aniline. Enthalpy of formation of the anilino and N‐methyl anilino radicals
Authors: Colussi A. J. , Benson S. W. 
Published: January 2005

AbstractThe kinetics of the thermal unimolecular decompositions of N‐methyl aniline and N,N‐dimethyl aniline into anilino and N‐methyl anilino radicals, respectively, have been studied under very low‐pressure conditions. The enthalpies of formation of both radicals, ΔH°f,298°K(PhṄH,g) = 55.1 and ΔH°f,298°K(PhṄMe,g) = 53.2 kcal/mol, which have been derived from the experimental data, lead to BDE(PhNH‐H) = 86.4 ± 2, BDE[PhN(Me)‐H] = 84.9 ± 2 kcal/mol and to a value of 16.4 kcal/mol for the stabilization energy of the PhNH radical (relative to MeNH). These results are discussed in connection with earlier work. At high temperatures, the anilino radical loses HNC and forms the very stable cyclopentadienyl radical, a decomposition comparable to that of the phenoxy radical.
Chemical actinometry at 147.0 nm
Authors: Powell Gerard R. , Sethi Dhanwant S. 
Published: January 2005

AbstractHexafluoroacetone (HFA) and O2 were photolyzed at 147.0 nm to investigate their use in chemical actinometry. The products, CO for the former and O3 in the latter case, were monitored. For accurate comparison, both of these substances were irradiated by a single light source with two identical reaction cells at 180° to each other. The light intensities I were measured under the same integrated as well as instantaneous photon flux based on ϕ and ϕCO (quantum yield) as 2 and 1, respectively. Optimum conditions for maximum product yield were 5.0 torr HFA pressure and an O2 flow rate of 200 ml/min at 1 atm pressure for a 20‐minute photolysis period. For light intensity variations between 1.09 × 1014 and 2.10 × 1015 photons absorbed/sec, the ratio I/IHFA was found to be unity. Calibration with the commonly used N2O actinometer for a ϕ value of 1.41 showed that I/IHFA and I/I are unity. Both HFA and O2 are suitable chemical actinometers at 147.0 nm with ϕCO and ϕ of 1 and 2, respectively. The light intensity determination in the first case involves the measurement of only one product which is noncondensible at 77°K, whereas wet analysis for O3, the only product, in the second actinometer is necessary. Both of these determinations are quite simple and are preferable over product analysis in N2O actiometry, wherein N2 separation from other noncondensibles at 77°K is required.
Autooxidation of diethyl hydroxylamine
Authors: Cáceres T. , Lissi E. A. , Sanhueza E. 
Published: January 2005

AbstractThe autooxidation of diethyl hydroxylamine (DEHA) has been studied both in solution and in the gas phase between 0° and 60°C. The results obtained are interpreted in terms of a nonchain free radical mechanism in which reaction (1)
equation image
is the rate‐determining step. This reaction is followed by the reaction of HO2 radicals with DEHA to give hydrogen peroxide. The initial stoichiometry is given by

which implies that the hydrogen peroxide reacts with DEHA to give water and diethyl nitroxide radicals.The activation energy of reaction (1) is 16.5 ± 2 kcal/mol, leading to a dissociation energy of 69.5 ± 2 kcal for the OH bond in DEHA.The oxidation of DEHA in the gas phase is nearly ten times slower than that observed in chlorobenzene solution under similar experimental conditions. This result is related to the stabilization of the free radicals produced by the solvent.
Gas‐phase pyrolysis of 2,2,3,3‐tetramethylbutane using a wall‐less reactor
Authors: Taylor Jay E. , Milazzo Thomas S. 
Published: January 2005

AbstractThe pyrolysis of 2,2,3,3‐tetramethylbutane (TMB) has been studied using the wall‐less reactor. Under homogeneous conditions up to 670°C, the activation energy is 43.2 kcal/mol and log A is 10.70. The products are 2‐methylpropene, hydrogen, propene, 2‐methyl‐2‐butene, ethane, ethene, methane, neopentane, and 2,3‐dimethyl‐2‐butene in order of abundance. Addition of toluene, cyclopentadiene, or nitrous oxide to the system increases both the activation energy and the A factor; whereas oxygen decreases both the activation energy and the A factor. Incorporation of stainless‐steel rods to provide surface has only a modest effect upon the rate. In view of this evidence, it appears that the homogeneous pyrolysis of TMB at higher pressures is a chain reaction under the described conditions.
Quenching of *UF6 (A state) by alkanes
Authors: Wampler Fred B. , Rice Walter W. , Oldenborg Richard C. 
Published: January 2005

AbstractThe removal of *UF6 (A state) molecules by selected alkanes has been investigated at 25°C. The following rate constants (units of 1011 l/mol·sec) were evaluated: iso‐C4F10, 0.0432 ± 0.0115; n‐C4F10, 0.0764 ± 0.020; C2F6, 0.0192 ± 0.0052; CH4, 0.0612 ± 0.0061; C2H6, 3.78 ± 0.60; C3H8, 5.08 ± 0.60; n‐C4H10, 5.05 ± 0.78; iso‐C4H10, 4.17 ± 1.15; neo‐C5H12, 6.59 ± 0.93; CF3CH3, 0.0385 ± 0.0056; CF2HCF2H, 0.0729 ± 0.0074; and CF2HCFH2, 0.149 ± 0.015. The perfluoro‐alkane quenching of *UF6 proceeds via a physical mechanism. The other alkane quenching reactions are consistent with a chemical mechanism also contributing in varying degrees which may involve removal of two hydrogens from the alkane.
Shock‐tube study of thermal decomposition of nitric oxide between 2700 and 3500 K
Authors: Koshi Mitsuo , Asaba Tetsuro 
Published: January 2005

AbstractThe decomposition of nitric oxide at temperatures ranging from 2700 to 3500 K was studied by means of the shock tube. The experimental data were reduced by the method described in a preceding paper and explained consistently by a set of the elementary reactions. The rate constant of the initiation reaction 2NO → N2O + O, which was not well known in this temperature range, was deduced precisely. k1 was one order of magnitude lower than that reported previously in similar shock‐tube experiments, and was consistent with results obtained below 2000 K and from the reverse reaction.
The interpretation of pressure‐dependent very‐low‐pressure pyrolysis experiments
Authors: Gilbert Robert G. , Gaynor Brendan J. , King Keith D. 
Published: January 2005

AbstractUnimolecular rate data from systems such as very‐low‐pressure pyrolysis (steady‐state flow) and static experiments where gas‐gas collisions compete with gas‐wall collisions must be interpreted in terms of reactant inhomogeneity arising from finite diffusion rates, rather than using the usual assumption of a well‐stirred reactor. An integrodifferential equation describing this process is derived, and a numerical variational solution applicable to weak gas‐gas collisions is presented. This gives a powerful method for obtaining collisional energy transfer probabilities from such experiments. Previously reported data (on cyclobutane and cycloheptatriene reactions) are reinterpreted to give conventional values for average energy transfer, replacing the anomalously low collisional efficiencies proposed previously.
Mechanism of catalytic ascorbic acid oxidation system Cu2+–ascorbic acid–O2
Authors: Shtamm E. V. , Purmal A. P. , Skurlatov Yu. I. 
Published: January 2005

AbstractAnalysis is made of reported results on the kinetics and mechanism of ascorbic acid oxidation with oxygen in the presence of cupric ions. The diversities due to methodological reasons are cleared up. A kinetic study of the mechanism of Cu2+ anaerobic reaction with ascorbic acid (DH2) is carried out. The true kinetic regularities of catalytic ascorbic acid oxidation with oxygen are established at 2.7 ≤ pH < 4, 5 × 10−4 ≤ [DH2] ≤ 10−2M, 10−4 ≤ [Cu2+] ≤ 10−3M, and 10−4 ≤ [O2] ≤ 10−3M:

where𝔨1 (25°C) = 0.13 ± 0.01 M−0.5˙sec−1. The activation energy for this reaction is E1 = 22 ± 1 kcal/mol. It is found by means of adding Cu+ acceptors (acetonitrile and allyl alcohol) that the catalytic process is of a chain nature. The Cu+ ion generation at the interaction of the Cu2+ ion with ascorbic acid is the initiation step. The rate of the chain initiation at [Cu2+] ± 10−4M, [DH2] ± 10−2M, 2.5 < pH < 4, is

where𝔨i,1 (25°C) = (1.8 ± 0.3)M−1˙sec−1, Ei,1 = 31 ± 2 kcal/mol. The reaction of the Cu+ ion with O2 is involved in a chain propagation, so that the rate of catalytic ascorbic acid oxidation for the system Cu2+DH2O2 is

where𝔨1 (25°C) = (5 ± 0.5) × 104 M−1˙sec−1. The Cu+ ion and a species interacting with ascorbate are involved to quadratic chain termination. By means of photochemical and flow electron spin resonance methods we obtained data characteristic of the reactivities of ascorbic acid radicals and ruled out their importance for the catalytic chain process. A new type of chain mechanism of catalytic ascorbic acid oxidation with oxygen is proposed:
equation image
.
The kinetics of dimerization of chlorotrifluoroethene
Authors: Atkinson Bernard , Tsiamis Christos 
Published: January 2005

AbstractRate constants determined for the thermal dimerization of chlorotrifluoroethene to dichlorohexafluorocyclobutane at 404–672 K have been correlated with previously published results. For the temperature range of 404–800 K,

The dependence of the preexponential factor on temperature corresponds to a value of 17 J/K·mol for the difference in heat capacity (ΔCp±) between the activation complex and the reactant.
The kinetics and the mechanism of the thermal decomposition of bis‐pentafluorosulfurtrioxide (SF5OOOSF5)
Authors: Czarnowski J. , Schumacher H. J. 
Published: January 2005

AbstractThe thermal decomposition of SF5O3SF5 has been investigated between 5 and 25°C. In the presence of sufficient high pressures of O2 the only products formed are SF5O2SF5 and O2:

The reaction is homogeneous. Its rate is strictly first order with respect to the trioxide pressure and independent of the total pressure of the reaction products and of oxygen above a certain limiting pressure:

The experimental results can be explained with the following mechanism:
equation image
In the presence of O2 > 100 Torr the concentration of SF5 is insignificantly small. Therefore reactions (5) and (6) do not have to be considered any more, and steps (2) and (2′) will be of no importance. From reactions (1)–(4) it follows:

The numerical value of the factor [1 + (k′12/2k3k4)1/2] is small. It can be estimated that E3 ≃ 2 ± 1 kcal; therefore, E – E1 ≤ 1 kcal, and D = (26 – 1) ± 1.0 kcal.
Oxidation of fluorenes by ammonium meta vanadate—a kinetic study
Authors: Narasimhan S. , Venkatasubramanian N. 
Published: January 2005

AbstractThe oxidation of fluorene by vanadium(V) in aqueous acetic acid containing sulfuric acid (1.0M) at 50°C produces fluorenone and 2‐hydroxy diphenyl 2′‐carboxaldehyde. The order with respect to each reactant is found to be 1. The order dependence on sulfuric acid concentration is 4, indicating that V(OH)23+ could be the active species. An increase in the acetic acid percentage in the solvent medium increases the rate of the reaction. The effect of solvent variation has been discussed in the light of the acidity function and the polarity of the medium. The effect of substituents on the rate has been studied for seven substituted fluorenes, and a linear relationship exists between log k versus σ values with the slope ρ = ‐3.2. A small isotope effect is observed for the oxidation of the parent compound (kH/kD = 1.2). The effect of temperature on the rate of the reaction has been studied, and the activation parameters are discussed. A mechanism involving the rate‐limiting formation of a cation‐radical intermediate is proposed.
A computational algorithm for the Green's function method of sensitivity analysis in chemical kinetics
Authors: Dougherty Eugene P. , Rabitz Herschel 
Published: January 2005

AbstractThe recent interest in numerical modeling of chemical kinetics has generated the need for proper analysis of the system sensitivities in such models. This paper describes the logic for a program developed by the authors to implement the Green's function method of sensitivity analysis in complex kinetic schemes. The relevant equations and numerical details of the algorithm are outlined, two flow charts are provided, and some special programming considerations are discussed in some detail. Computer storage and computational time considerations are also treated. Finally, applications of sensitivity information to understanding complex kinetic system behavior and analyzing experimental results are suggested.
Aluminium monoacetate complex formation reaction studied by the pressure‐jump method
Authors: Hiraishi M. , Harada S. , Uchida Y. , Kuo H. L. , Yasunaga T. 
Published: January 2005

AbstractOne of two pressure‐jump relaxation processes observed in Al(III) acetate aqueous solution, the slow one, was studied kinetically. The relaxation was ascribed to the Al(III) monoacetate complex formation reaction. The detailed reaction mechanism, including the hydrolysis process, was revealed, and the rate constants were obtained.
Titration of oxygen chemisorbed on platinum: Experiment and simulation
Authors: Tseng Fu‐hsiang , White J. M. 
Published: January 2005

AbstractThe titration of chemisorbed oxygen by carbon monoxide to form carbon dioxide has been studied from 373 to 673 K over polycrystalline platinum. The pressure transients for CO and CO2 have been measured and simulated numerically. A complex Langmuir–Hinshelwood mechanism is found which fits all the data, and it is not necessary to invoke Eley–Rideal kinetics. The results fall into two temperature regimes, above and below 473 K, which are characterized by different Arrhenius parameters. A change in activation energy with oxygen coverage is also found below 473 K.
The rate constant of NO + O3 → NO2 + O2 in the temperature range of 283–443 K
Authors: Lippmann H. H. , Jesser Barbara , Schurath Ulrich 
Published: January 2005

AbstractThe reaction NO + O3 → NO2 + O2 has been studied in a 220‐m3 spherical stainless steel reactor under stopped‐flow conditions below 0.1 mtorr total pressure. Under the conditions used, the mixing time of the reactants was negligible compared with the chemical reaction time. The pseudo‐first‐order decay of the chemiluminescence owing to the reaction of ozone with a large excess of nitric oxide was measured with an infrared sensitive photomultiplier. One hundred twenty‐nine decays at 18 different temperatures in the range of 283–443 K were evaluated. A weighted least‐squares fit to the Arrhenius equation yielded k = (4.3 ± 0.6) × 10−12 exp[‐(1598 ± 50)/T] cm3/molecule sec (two standard deviations in brackets). The Arrhenius plot showed no curvature within experimental accuracy. Comparison with recent results of Birks and co‐workers, however, suggests that a nonlinear fit, as proposed by these authors, is more appropriate over an extended temperature range.