bluuebunny/crossref_metadata_2025_split huggingface dataset:
The gas‐phase pyrolysis of alkyl nitrites. VII. Primary and secondary nitrites in the presence of nitric oxide
Authors: Batt L. , Islam T. S. A. , Scott H. 
Published: January 2005

AbstractAlthough our pyrolytic studies of five alkyl nitrites (RONO) have shown that it is possible to determine precise, acceptable values for k1:
equation image
we have been uncertain about the mechanism for the first order production of nitroxyl from primary and secondary nitrites. Nitroxyl could arise either from the direct elimination process (5) or from the disproportionation of the alkoxyl radical concerned and nitric oxide:
equation image
Thus kexp = k5 or k1k6/[k2 + k6]. If the route is reaction (6), Eexp should be identical to E1, since the ratio k6/k2 is temperature independent. We preferred the elimination process because Eexp < E1 and Aexp was in agreement with transition‐state calculations for such elimination processes. This study was concerned with the pyrolyses of ethyl and i‐propyl nitrites in the presence of nitric oxide. The results show that nitroxyl is produced via the disproportionation of the alkoxyl radical and nitric oxide, as originally suggested by Levy. This is supported by the wealth of particularly photochemical data in the literature. Our and other previous spuriously low Arrhenius parameters are attributed to heterogeneous effects.
EPR kinetic study of the reactions of CF3Br with H atoms and OH radicals
Authors: Le Bras G. , Combourieu J. 
Published: January 2005

AbstractReactions of CF3Br with H atoms and OH radicals have been studied at room temperature at 1–2 torr pressures in a discharge flow reactor coupled to an EPR spectrometer. The rate constant of the reaction H + CF3Br → CF3 + HBr (1) was found to be k1 = (3.27 ± 0.34) × 10−14 cm3/molec·sec. For the reaction of OH with CF3Br (8) an upper limit of 1 × 10−15 cm3/molec·sec was determined for k8. When H atoms were in excess compared to NO2, used to produce OH radicals, a noticeable reactivity of OH was observed as a result of the reaction OH + HBr → H2O + Br, HBr being produced from reaction (1).
Competitive unimolecular reactions at low pressures. The pyrolysis of cyclobutyl chloride
Authors: King Keith D. , Gaynor Brendan J. , Gilbert Robert G. 
Published: January 2005

AbstractThe thermal decomposition of cyclobutyl chloride has been investigated over the temperature range of 892–1150 K using the technique of very low‐pressure pyrolysis (VLPP). The reaction proceeds via two competitive unimolecular channels, one to yield ethylene and vinyl chloride and the other to yield 1,3‐butadiene and hydrogen chloride, with the latter being the major reaction under the experimental conditions. With the usual assumption that gas‐wall collisions are «strong,» RRKM calculations, generalized to take into account two competing pathways, show that the experimental unimolecular rate constants are consistent with the high‐pressure Arrhenius parameters given by log k1(sec−1) = (14.8 ± 0.3) − (61.1 ± 1.0)/Θ for vinyl chloride formation and log k2(sec−1) = (13.6 ± 0.3) − (55.7 ± 1.0)/Θ for 1,3‐butadiene formation, where Θ = 2.303 RT kcal/mol. The A factors were assigned from previous high‐pressure low‐temperature data of other workers assuming a four‐center transition state for 1,2‐HCl elimination and a chlorine‐bridged biradical transition state for vinyl chloride formation. The activation energies are in good agreement with the high‐pressure results which were obtained with a conventional static system. The difference in critical energies is 4.6 kcal/mol.
Pressure saturation of SO2(3B1 0,0,0) lifetimes
Authors: Wampler Fred B. , Oldenborg Richard C. , Rice Walter W. 
Published: January 2005

AbstractLifetime data have been obtained for the decay of SO2(3B1 0,0,0) at 25°C over the pressure range of 1–762 torr. The 3B1 state was populated by direct absorption to eliminate any possible complications in interpretation due to the participation of excited‐singlet manifolds. At pressures greater than about 10 torr, the measured lifetimes are longer than predicted from low‐pressure Stern–Volmer parameters. This deviation can be interpreted in terms of Freed's theory on collisionally induced intersystem crossing and provides unequivocal evidence to support earlier speculations that the lengthening of the lifetimes at high pressures is due to saturation in depopulation of the 3B1 state.
Kinetics of oxidation of some amino acids by KMNO4 in a moderately concentrated H2SO4 medium in the presence and absence of Ag+
Authors: Surender Rao V. , Sethuram B. , Navaneeth Rao T. 
Published: January 2005

AbstractThe kinetics of oxidation of glycine, alanine, phenylalanine, serine threonine, aspartic, and glutamic acid by acid permanganate were investigated to elucidate the mechanism of the reactions. The rate law was found to be

The reactions were found to be acid catalyzed, and the kinetic data indicate the participation of the water molecules in the rate‐determining step as a proton‐abstracting agent from the substrate, as per Bunnett's hypothesis. As Ag+ was found to catalyze these reactions, the oxidation of glycine and glutamic acid was studied, and the rate law was found to be

A probable mechanism consistent with the observed results is discussed.
Evidence for production of the hydroxycarbonyl radical in the decomposition of formic acid on platinum
Authors: Tevault D. E. , Lin M. C. , Umstead M. E. , Smardzewski R. R. 
Published: January 2005

AbstractFormic acid molecules highly diluted in argon were passed through a clean platinum screen at 420–730 K and condensed onto an 8‐K CsI window. The well‐known decomposition products, CO2, CO, and H2O, were observed in the infrared spectra of the resulting matrices. In addition, new absorptions which are attributed to the OCOH free radical were also observed. Experiments with partially deuterated formic acids confirmed that the carbon‐hydrogen bond of the formic acid was lost in the formation of the new intermediate species. The activation energy for CO2 production, Ea = 3.5 ± 0.2 kcal/mol, was determined by monitoring its appearance rate at several different catalyst temperatures.
The reactions of methyl radicals with chloromethanes
Authors: Macken Kenneth V. , Sidebottom Howard W. 
Published: January 2005

AbstractThe reaction of methyl radicals with CCl4 and CCl3Br have been reinvestigated in the gas phase over a wide range of temperatures and pressures using both the photolysis of acetone and the pyrolysis of di‐tertiary butyl peroxide (dtBP) as the methyl radical sources. The results are in essential agreement with previous work; however, these new studies provide evidence that at higher pressures the major source of HCl in the reactions is due to methyl radical attack on CH3CCl3, formed via the combination of methyl and trichloromethyl radicals.From these investigations Arrhenius parameters for the reactions
equation image
have been determined:

Pyrolysis of dtBP in the presence of relatively high‐pressure mixtures of CCl4 and CCl3Br resulted in no enhanced methane formation, since, under these conditions, the only termination product is C2Cl6, and the HCl precursor CH3CCl3 is not formed. A competitive technique has been used in which dtBP was pyrolysed in the gas phase in the presence of high‐pressure mixtures of CCl3Br and a chloromethane. Arrhenius parameters were obtained for the reactions
equation image
and the results were used to provide information on the importance of polar effects for hydrogen abstraction from halogenated methanes.
Very‐low‐pressure pyrolysis (VLPP) of group IV (A) tetramethyls: Neopentane and tetramethyltin
Authors: Baldwin Alan C. , Lewis Karan E. , Golden David M. 
Published: January 2005

AbstractThe decomposition of neopentane was studied using the very‐low‐pressure pyrolysis (VLPP) technique at temperatures from 1000 to 1260 K. The derived Arrhenius parameters

are consistent with δHf0(t‐butyl) = 8.4 kcal/mol. Using the above A factor, data on the decomposition of tetramethyltin yield DH0(Sn(CH3)3 ‐ CH3) = 69 ± 2 kcal/mol.
Effect of substituents in the gas‐phase elimination kinetics of β‐substituted ethyl acetates
Authors: Chuchani Gabriel , Martin Ignacio , Avila Irama 
Published: January 2005

AbstractThe kinetics of gas‐phase elimination of 3‐methyl‐1‐butyl acetate and 3,3‐dimethyl‐1‐butyl acetate into acetic acid and the corresponding substituted butenes have been measured over the temperature range of 360–420°C and the pressure range of 63–250 Torr. The reactions are homogeneous in both clean and seasoned vessels, obey first‐order law, and are unimolecular. The temperature dependence of the rate constants is given by the Arrhenius equation3‐methyl‐1‐butyl acetate:

3,3‐dimethyl‐1‐butyl acetate:

The points in a plot of log (k/k0) of β‐alkyl and several β‐substituted ethyl acetates against Es values appear aligned in an approximate linear relationship. These results may be interpreted as a consequence of steric effects, namely, steric accelerations.
Bimolecular self‐reactions of 2‐arylindandione‐ 1,3‐yl radicals studied by flash photolysis
Authors: Khudyakov I. V. , Yasmenko A. I. , Kuzmin V. A. 
Published: January 2005

AbstractKinetic and thermodynamic data for reaction (1) of certain C‐centered aromatic radicals (referred to in this paper by the numbers I to X) in chlorobenzene:
equation image
have been obtained. The k1 values of radicals varied between (1.1 ± 0.2) × 106M−1·sec−1 (radical VIII) and (3.6 ± 0.7) × 109M−1 sec−1 (radical VI) at 20°C. An investigation of the relationship between the recombination rates of radicals I–VIII and X and the solvent viscosity (mixture of toluene and dibutylphthalate, 0.6 < η < 18.4 cP) has shown that the recombination reactions involving radicals I–IV are limited by diffusion in solvents having a viscosity η> 10 cP and are activation reactions in solvents having a viscosity η < 10 cP. The recombination of radicals VIII and IX is an activation reaction, while that of radicals V–VII is diffusion‐controlled in the entire viscosity range. The recombination of radical X is limited, in the viscosity range of 18.4 to 2 cP, by intrusion into the first coordination sphere of the partner, the effect of viscosity on the radical X recombination rate in the specified range being the same as its effect on diffusion‐controlled reactions. The possible reasons of the discrepancies between the experimental fast recombination rate constants and the theoretical values calculated by the Debye–Smoluchowski theory are discussed. The equilibrium constant depends strongly on the nature of the substituent in the phenyl fragment: the substituents which increase unpaired electron delocalization in the radical intensify the dissociation of the respective dimer. Long‐wave absorption bands have been recorded for radicals I–X and their extinction coefficients obtained. Dimers I–V are thermo‐ and photochromic compounds.
Rate constants for the termination of benzyl radicals in solution
Authors: Lehni M. , Schuh H. , Fischer H. 
Published: January 2005

AbstractThe rate constant for the bimolecular combination of benzyl radicals in cyclohexane and toluene is determined as a function of temperature. Further, it is studied in cyclohexane–toluene mixtures of different compositions. In the entire range covered, 9.8 × 108 ⩽ 2kt ⩽ 9.0 × 109M−1·sec−1, the data are very well described by the Smoluchowski equation for a diffusion‐controlled reaction to ground‐state products using a spin statistical factor of 1/4, a temperature‐ and solvent‐independent reaction distance, and the known diffusion coefficient of toluene.
Absolute rate constants for the reaction of bromine atoms with ozone from 234 to 360 K
Authors: Michael J. V. , Payne W. A. 
Published: January 2005

AbstractThe rate constant for the reaction of Br + O3 → BrO + O2 has been measured at four temperatures from 234 to 360 K by the technique of discharge flow coupled with resonance‐fluorescence detection of bromine atoms. The measured rate constants obey the Arrhenius expression k = (9.45 ± 2.48) × 10−12 exp(‐659 ± 64/T) cm3/molec·sec (one standard deviation). The results are compared with two previous studies, one of which utilized the flash‐photolysis–resonance‐fluorescence technique and the other utilized the discharge‐flow–mass‐spectrometric technique. The result is also discussed from a theoretical point of view.
Kinetics and mechanism of palladium (II) chloride catalyzed oxidation of allyl alcohol by potassium hexacyanoferrate (III)
Authors: Ahmad Iftikhar , Muhammad ashraf C. 
Published: January 2005

AbstractA kinetic study of the oxidation of allyl alcohol by potassium hexacyanoferrate (III) in the presence of palladium (II) chloride is reported. The reaction was observed by measuring the disappearance of the potassium hexacyanoferrate (III) spectrophotometrically. The reaction is first order with respect to allyl alcohol and palladium (II) chloride, inverse second order with respect to [Cl−], and zero order with respect to potassium hexacyanoferrate (III). The rate is found to increase linearly with hydroxyl ion concentration.
The reaction of CH3O2 with SO2
Authors: Sanhueza Eugenio , Simonaitis R. , Heicklen Julian 
Published: January 2005

AbstractMixtures of Cl2, CH4, and O2 were flash photolyzed at room temperature and pressures of ∽60–760 Torr to produce CH3O2. The CH3O2 radicals decay by the second‐order process
equation image
with k6 = (3.7 ± 0.3) × 10−13 cm3/sec in good agreement with other studies. This value ignores any removal by secondary radicals produced as a result of reaction (6), and therefore the true value might be as much as 30% lower. The value is independent of total pressure or the presence of H2O vapor. With SO2 also present, the CH3O2 decay becomes pseudo first order at sufficiently high SO2 pressure which indicates the reaction
equation image
The value of (8.2 ± 0.5) × 10−15 cm3/sec at about 1 atm total pressure (mostly CH4) was found for CH3O2 removal by SO2, in good agreement with another recent measurement. This value can be equated with k1, unless the products rapidly remove another CH3O2 radical, in which case k1 would be a factor of 2 smaller.
Kinetic flash spectroscopic study of the CH3O2CH3O2 and CH3O2SO2 reactions
Authors: Kan Charles S. , McQuigg Robert D. , Whitbeck Michael R. , Calvert Jack G. 
Published: January 2005

AbstractMethylperoxy radicals were generated by the flash photolysis of azomethane–oxygen mixtures. The observed broadband spectrum of the CH3O2 radical is similar, but not identical to those reported previously. The CH3O2 decay followed second‐order kinetics at high CH3O2 concentrations with k4' = (2.5 ± 0.3) × 108 liter/mol·sec (23 ± 2°C); 2CH3O2 → products (4). Because of the potential loss of CH3O2 through the reactions with HO2 and CH3O radicals subsequently formed in this system, simulations suggest that the true k4 is in the range: 2.5 × 108 ≥ k4 ≥ 2.3 × 108 liter/mol·sec. Deviations from linearity of the plot of the reciprocal of the CH3O2 absorbance versus time were seen at long times and were attributed to the reaction (5) with an apparent rate constant k5' ⋍ (1.6 ± 0.4) × 105 liter/mol·sec; CH3O2 + Me2N2 → product (5). The CH3O2–SO2 reaction, CH3O2 + SO2 → products (16), was studied by observing CH3O2 decay in flashed mixtures of Me2N2, O2, and SO2. The results gave the apparent second‐order rate constant k16' ⋍ (6.4 ± 1.4) × 106 liter/mol·sec. It appears likely that each occurrence of reaction (5) and (16) is followed by the loss of an additional CH3O2 radical and that k5 ⋍ k5'/2 and k16 ⋍ k16'/2. Our findings suggest that a significant fraction of the SO2 oxidation in a sunlight‐irradiated NOx−RH‐polluted atmosphere, may occur by reaction with CH3O2 as well as from the HO and HO2 reactions.
Kinetics of the thermal decomposition of bis‐pentafluorosulfur trioxide(SF5O3SF5) in the presence of carbon monoxide
Authors: Czarnowski J. , Schumacher H. J. 
Published: January 2005

AbstractThe thermal decomposition of SF5O3SF5 in the presence of CO has been investigated between ‐9.8°C and + 9.9°C. Besides traces of S2F10, equimolecular amounts of SF5O2SF5 and CO2 are formed.

The reaction is homogeneous. Its rate is proportional to the pressure of the trioxide and in dependent of the total pressure, the pressure of inert gases and of carbon monoxide:

where k = k1∞ = 1016.32±0.40 exp(−25,300 ± 500 cal)/RT sec−1. Consequently,

In the presence of oxygen a sensitized CO2 formation is observed. A mechanism is given which explains the experimental results.
Pyrolytic production of Se (3P) from carbon diselenide. II. Rate of CSe2decay
Authors: Belford R. L. , Marquart J. R. , Fraenkel H. A. , Cross A. J. , Lenhardt T. M. , Wei G. J. 
Published: January 2005

AbstractPyrolytic decay of carbon diselenide was monitored by ultraviolet absorption spectroscopy in reflected shock waves in the temperature range of 1600–2600°K. The temperature dependence of the absorption coefficient of CSe2at 2308 Å was determined and was used to provide kinetic information along with a deconvolution procedure which accounted for and removed systematic distortions of the fast time‐resolved absorbance profile. For temperatures of 1600–2600°K and argon densities of 1.5–7.0 × 10−5mol/cm3dilute (1.0–9.0 × 10−9mol/cm3) CSe2pyrolyzed with measured first‐order decay rates in the range of log10k1(sec−1) = 3.0−5.7; at midrange (2100°K and 4.3 × 10−5mol/cm3in Ar)k1≈ 3 × 104sec−1. The decay probably occurs via a unimolecular low‐pressure process, first order in both CSe2and Ar, for whichk2± 109cm3/mol·sec at 2100°K. The deconvoluted data yield Arrhenius activation energies of 53.2 kcal/mol under second‐order treatment, but the activation energy is less reliable than the general magnitude of the rate constant. A comparison of CSe2with other molecules which are isoelectronic in their valence shells (CO2, CS2, OCS, and N2O) is made.
Kinetics of the thermal dimerization and isomerization of cis, trans‐1,5‐cyclooctadiene in the gas phase and of related reactions. A simple algorithm to determine the rate constants of competing first‐ and second‐order reactions
Authors: Leitich J. 
Published: January 2005

AbstractIn the gas phase, cis,trans‐1,5‐cyclooctadiene (\documentclass{article}\pagestyle{empty}\begin{document}$ {\mathop 1\limits_\sim} $\end{document}) undergoes a unimolecular rearrangement to cis,cis‐1,5‐cyclooctadiene (\documentclass{article}\pagestyle{empty}\begin{document}$ {\mathop 2\limits_\sim} $\end{document}) and bimolecular formation of dimers \documentclass{article}\pagestyle{empty}\begin{document}$ {\mathop 3\limits_\sim}-{\mathop 5\limits_\sim} $\end{document} $\end{document}. The Arrhenius parameters are EA = 135.7 ± 4.4 kJ mole−1 and log(A/sec−1) = 12.9 ± 0.6 for the first reaction and EA = 66.1 ± 6.0 kJ mole−1 and log[A/(liter mole−1 sec−1)] = 5.5 ± 0.8 for the second reaction. Using thermochemical kinetics, the first reaction is shown to proceed via a rate determining Cope rearrangement of \documentclass{article}\pagestyle{empty}\begin{document}$ {\mathop 1\limits_\sim} $\end{document} to cis1,2‐divinylcyclobutane (\documentclass{article}\pagestyle{empty}\begin{document}$ {\mathop 6\limits_\sim} $\end{document}), EA = 136.2 ‐ 4.4 kJ mole−1 and log(A/sec−1) = 13.0 ± 0.6. The corresponding back reaction, \documentclass{article}\pagestyle{empty}\begin{document}$ {\mathop 6\limits_\sim}{\rightarrow}{\mathop 1\limits_\sim} $\end{document}, which was investigated separately, shows EA = 110.2 ± 1.2 kJ mole−1 and log(A/sec−1) = 10.9 ± 0.2. The heat of formation of \documentclass{article}\pagestyle{empty}\begin{document}$ {\mathop 6\limits_\sim} $\end{document} is determined to 188 ± 5.5 kJ mole−1. The mechanism of formation of dimers \documentclass{article}\pagestyle{empty}\begin{document}$ {\mathop 3\limits_\sim}-{\mathop 5\limits_\sim} $\end{document} is discussed. To allow the formal analysis of the kinetic problem, a simple algorithm to obtain the rate constants of competing first‐ and second‐order reactions was developed.
The vacuum UV photolysis of various C4 and C5 olefins: The energy content of the α‐ and β‐methallyl fragments
Authors: Collin Guy J. , Deslauriers Hélène 
Published: January 2005

AbstractIn recent publications from this laboratory, we have shown that the fragmentation of photoexcited olefinic molecules in the vacuum UV region leads mainly to the cleavage of a C—C bond located in the ß position relative to the double bond. The allyl fragment bears away part of the excess energy of the photon. At low pressure, this excited radical is capable of undergoing further decomposition. From the pressure effect, we were able to measure the first order rate constant for this secondary fragmentation. In this paper we shall use RRKM calculations in order to get a better idea on how the energy is distributed among the primary fragments. In cases where α‐ and β;‐methallyl radicals were involved, the results show that an important part of the excess energy is located in the methallyl fragment in the 7.1 and 7.6 eV photolysis of 3‐methyl‐1‐butene, 2‐methyl‐1‐butene, and cis‐2‐pentene.
A dual‐path sequence of first‐order reactions the protiodeacylation of acetylpropionylmesitylene
Authors: Gore Peter H. , Nassar Ahmed M. G. , Waters David N. , Moxon Gerry F. 
Published: January 2005

AbstractAn example of a sequence of competing first‐order reactions, leading to a common product, has been found for the sulfodeacylation of acetylpropionylmesitylene. The basic reaction scheme is Scheme l
equation image
and a kinetic analysis of the component rate constants allows an estimate to be made of the concentrations of the reactant and products as a function of time. In the present system the total concentration of the intermediates B, C, and D never exceeds 0.26% at 25°C, and therefore the kinetics, which were followed spectrophotometrically, were essentially of the conversion of substrate A to the final product E.The kinetics of protiodeacylation have been measured, over a range of temperatures, of propionyl‐, dipropionyl‐, and acetylpropionylmesitylenes in 89.8% (w/w) sulfuric acid.
Evaluation of the rate coefficients and arrhenius parameters of hydrogen atom transfer reactions. II. Application of the method
Authors: Bérces Tibor , Dombi József 
Published: January 2005

AbstractThe bond‐strength–bond‐length (BSBL) method was used to estimate Arrhenius parameters and rate coefficients for various hydrogen atom transfer reactions of the type A + BC → AB + C. In most cases predicted activation energies agreed within 1.2 kcal/mol with the experimental values (average error = 1.12 and standard deviation = 1.42), and the calculated logAagreed within 0.55 log units with the literature data (average error = 0.47 and standard deviation = 0.57). Predicted activated complex properties were shown to agree very well with potential energy surface properties obtained fromab initioquantum mechanical calculations. Detailed comparison of the BSBL results and the results of bond‐energy–bond‐order (BEBO)‐type calculations are presented.
Atmospheric photodissociation lifetimes for nitromethane, methyl nitrite, and methyl nitrate
Authors: Taylor W. D. , Allston T. D. , Moscato M. J. , Fazekas G. B. , Kozlowski R. , Takacs G. A. 
Published: January 2005

AbstractAtmospheric photodissociation rate coefficients and photodissociation lifetimes for nitromethane, methyl nitrite, and methyl nitrate were calculated as a function of altitude from their measured visible and near ultraviolet photoabsorption cross sections at 298 K. The lifetime of methyl nitrite is nearly independent of altitude and is approximately 2 min. From 0 to 50 km the lifetime of nitromethane varies from 10 to 0.5 hr, while that of methyl nitrate changes from 5.3 to 0.09 days, respectively.