bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic isotope effects in the reactions of bromine atoms with CH4 and CD4
Authors: Yokota Toshitsugu , Timmons Richard B. 
Published: January 2005

AbstractThe competitive reactions of Br atoms with CH4 and CD4 were studied over the temperature range of 562° to 637°K. Over this temperature interval, the kinetic isotope effect, kH/kD, varied from 3.05 to 2.47 for the reactions

The rate constant ratio kH/kD, expressed in Arrhenius form, was found to equal (1.10 ± 0.05) exp (1030 ± 60/RT). A comparison is presented between the experimental result and the result obtained theoretically from absolute rate theory using the London‐Eyring‐Polanyi‐Sato (LEPS) method of constructing the potential energy surface of the reaction. The agreement between theory and experiment is very poor, and this is believed to arise from the highly unsymmetrical nature of the potential energy surface involved in these reactions. A comparison is also presented between the kH/kD values obtained in the Br + CH4–CD4 experiments and the available data on the corresponding Cl + CH4–CD4 reactions.
A critical review of the kinetics of the dissociation‐recombination reactions of fluorine and chlorine
Authors: Lloyd Alan C. 
Published: January 2005

AbstractA critical evaluation of the rates of the dissociation and recombination reactions of fluorine and chlorine is given. Data are presented graphically and in tabular form. The effect of various third bodies is discussed. Rate expressions for specified temperature ranges are recommended, while comparison with theoretical values obtained from the Benson and Fueno theory is made where applicable.
Some aspects of theory and experiment in the ethane–methyl radical system
Authors: Waage E. V. , Rabinovitch B. S. 
Published: January 2005

AbstractA critical examination has been made of some aspects of the thermal decomposition of ethane and the reverse recombination reaction. The experimental Arrhenius A‐factors for ethane are, in general, smaller than those which are calculated from thermodynamic quantities together with the observed rate constants for methyl recombination. Theoretical calculations also illustrate a discrepancy between the experimental work on recombination and decomposition. The experimental shapes of k/kα falloff curves and the pressure region of falloff are compared with the predictions of RRKM theory for various models.
Rotating sector study of the gas phase photolysis of the 1,1,1‐trichloro‐2,2,2‐trifluoroethane–cyclohexane system
Authors: Wampler Fred B. , Kuntz Robert R. 
Published: January 2005

AbstractThe rate constant for the combination of 1,1‐dichloro‐2,2,2‐trifluoroethyl radicals in the gas phase has been measured by applying the rotating sector technique to the 1,1,1‐trichloro‐2,2,2‐trifluoroethane–cyclohexane photochemical system. The combination rate constant, k5, was found to be 6.6 × 1012 cc mole−1 sec−1. Arrhenius parameters for the reaction, magnified image are given by the expression log k4 = 11.81 – (9700/2.3RT).
Study of the pyrolysis of H2O2 in the presence of H2and CO by use of UV absorption of HO2
Authors: Kijewski H. , Troe J. 
Published: January 2005

AbstractIn dissociation experiments of H2O2 under shock wave conditions, the spectra of H2O2 and HO2 have been observed in the UV at 2200 ≤ 2800 Å. By the use of these spectra the H2O2 decomposition in the presence of H2 and CO at 870 ≤ T ≤ 1000°K has been analyzed. It was found that in this temperature range, in contrast to low temperature behavior, reactions of H atoms with H2O2 and with HO2 are equally important. The rate of the reaction H + H2O2 ← HO2 + H2 was estimated in comparison with the rate of the reaction between H and HO2. Good agreement between calculated and measured concentration profiles of HO2 and H2O2 was obtained.
Abstraction of hydrogen by methylene
Authors: McNesby J. R. , Kelly R. V. 
Published: January 2005

AbstractThe photolysis of CD2CO at 313 nm in the presence of neopentane was carried out over the temperature range 576–706 K. Analysis of the products and isotopic analysis of the methanes demonstrate abstraction of H from neopentane and D from CD2CO by methylene. The relative kinetics of abstraction of H and D have been measured over the temperature range, and the absolute value for the collision yield of the abstraction of H from neopentane by CD2 at 653 K has been been estimated to be about 1.5 × 1011 mole−1 cm3 sec−1, a value 103 times larger than the corresponding reaction of CH3.
The reactions of O(1D) with ozone and nitrous oxide
Authors: Goldman Charles S. , Greenberg Raymond I. , Heicklen Julian 
Published: January 2005

AbstractOzone was photolyzed at room temperature in the presence of N2O at 2537 Å and 2288 Å to produce O(1D) atoms. These atoms can react with either O3or N2O viamagnified imageFrom the quantum yield of N2, the relative rate constantsk6a/k6andk2/k6could be obtained, wherek6+k6a+k6b. The former rate constant ratio was found to be 0.37 ± 0.03 at 2537 Å and 0.33 ± 0.03 at 2288 Å, in good agreement with an earlier report from our laboratory. The ratiok2/k6was found to be 2.6 at 2537 Å, but 4.1 at 2288 Å. The difference in the two numbers, if real, may reflect differences in reactivity due to different amounts of excess translational energy in the O(1D) atom at the two wavelengths.
Gas and liquid phase kinetics of the unimolecular isomerization of 1‐chloro‐4‐bromobicyclo[2.2.0]hexane: The radical stabilization energy of an α‐bromine atom
Authors: Cain Edward N. , Solly Richard K. 
Published: January 2005

AbstractThe kinetics of the gas phase isomerization of 1‐chloro‐4‐bromobicyclo[2.2.0]hexane to 2‐chloro‐5‐bromohexa‐1,5‐diene have been measured in a static system over the temperature range of 135–215°C, with a variation in the total pressure from 0.6 to 400 torr. For these conditions the rate constants are well represented by the Arrhenius equation:where θ = 2.303RTkcal/mole. Transition state estimates for the biradical mechanism for the isomerization of bicyclo[2.2.0]hexanes are shown to be in good agreement with these Arrhenius parameters. By comparison of the activation energy with that for the isomerization of bicyclo[2.2.0]hexane and 1,4‐dichlorobicyclo[2.2.0]hexane, the radical stabilization energy of an α‐bromine atom is shown to be 1.0 ± 1.8 kcal/mole. Rates are also reported in the liquid phase at temperatures of 155°C and 175°C with diphenyl ether, nitrobenzene, and dimethylsulfoxide as solvents. The observed rate constants are all faster (by a factor of 1.1–1.7) than those measured in the gas phase and display no correlation between rate and solvent polarity.
The SO2‐sensitized phosphorescence of biacetyl vapor in photolyses at 2650 and 2875 Å. The intersystem crossing ratio in sulfur dioxide
Authors: Horowitz Abraham , Calvert Jack G. 
Published: January 2005

AbstractQuantum yields of the triplet sulfur dioxide (3SO2)‐sensitized phosphoresence (Φsens) in biacetyl (Ac2) have been determined in experiments over a wide range of pressures of SO2 and Ac2. Excited singlet sulfur dioxide (1SO2) was generated using 2650‐Å and 28757hyphen;Å light. The values of Φsens were dependent on the [SO2]/[Ac2] ratio, as anticpated theoretically. However, in runs at a fixed [SO2]/[Ac2] ratio, the measured Φsens values were dependent on the total pressure. This theoretically unexpected effect is probably largely the result of biacetyl triplet diffusion with deactivation at the cell wall. Treatment of the quantum yield data in terms of the complete mechanism gave new estimates of the following rate functions: 1SO2 + SO2 → (2SO2) (1), 1SO2 + SO2 → 3SO2 + SO2 (2), k2/(k1 + k2) = 0.082 ± 0.003 (2650 Å), 0.095 ± 0.005 (2875 Å) 3SO2 + Ac2 → SO2 + 3Ac2 (9a), 3SO2 + Ac2 → SO2 + Ac2 (9b), k9a + k9b = (8.4 ± 2.1) × 1010 (2650 Å), (8.1 ± 3.0) × 1010 l./mole‐sec (2875 Å) 3SO2 → SO2 + hvp (6), k6 = (7.3 ± 1.3) × 101 sec−1.
A flash photolysis–resonance fluorescence kinetics study of ground‐state sulfur atoms: I. Absolute rate parameters for reaction of S(3P) with O2(3Σ).
Authors: Davis D. D. , Klemm R. B. , Pilling M. 
Published: January 2005

AbstractThe flash photolysis–resonance fluorescence technique has been used to measure the reaction of ground‐state sulfur atoms with molecular oxygen as a function of both temperature and total pressure. The most suitable source of S(3P) for this study was found to be COS in the presence of CO2, as a diluent gas and with the photolysis flash filtered so as to remove all radiation of wavelengths below 1650 Å. Under these conditions, it was found that over the temperature range of 252–423°K the rate data could be fit to a simple Arrhenius‐type equation of the form

Units are cm3 molec−1 s−1. The small A‐factor for this reaction, the lack of any pressure dependence, and the direct observation of the production of O(3P) with increasing reaction time suggest that the S(3P) atom attacks the O2(3Σ) molecule end‐on forming SOO which rapidly falls apart to form SO (3Σ) and O(3P).
Rate constants for radical recombination. III. The trifluoromethyl radical
Authors: Hiatt R. , Benson S. W. 
Published: January 2005

AbstractProducts of the radical reactions arising from t‐Bu2O2, CF3I, and CH3I at 146°C in the vapor phase have been measured over a 33‐fold range of CH3I/CH3I ratios and shown to be governed by the rapidly established equilibrium

Together with K estimated by thermochemical methods, the results yield, for the rate of recombination for CF3· radicals, kr = 109.7 ± 0.5 M−1 sec−1.
Rates of reaction of atomic oxygen with C2H3F, C2H3Cl, C2H3Br, 1,1‐C2H2F2, and 1,2‐C2H2F2
Authors: Huie Robert E. , Herron John T. , Davis Douglas D. 
Published: January 2005

AbstractRate constants for the reactions of atomic oxygen (O3P) with C2H3F, C2H3Cl, C2H3Br, 1,1‐C2H2F2, and 1,2‐C2H2F2 have been measured at 307°K using a discharge‐flow system coupled to a mass spectrometer. The rate constants for these reactions are (in units of 1011 cm3 mole−1 s−1) 2.63 ± 0.38, 5.22 ± 0.24, 4.90 ± 0.34, 2.19 ± 0.18, and 2.70 ± 0.34, respectively. For some of these reactions, the product carbonyl halides were identified.
Arrhenius parameters for the reactions CH3. + C4H10 → CH4 + C4H9. and C2H5. + C4H10 → C2H6 + C4H9.
Authors: Pacey P. D. , Purnell J. H. 
Published: January 2005

AbstractStudy of n‐butane pyrolysis at high temperature in a flow system allows measurement of the sum of the rate constants of the initiation reactions

and of the Arrhenius parameters of the reactions

Established data for k1/k2 allow estimation of k1 for 951°K and this, with recent thermochemical data, yields the result log k−1 (l.mole s−1) = 8.5, in remarkable agreement with a recent measurement [20] but over si×ty times smaller than conventional assumption. The product k3k4 (l.2mole−2s−2) is found to be associated with the Arrhenius parameters log (A3A4) = 21.90 ± 0.6 and (E3 + E4) = 38.3 ± 2.7 kcal/mole. These values are much higher than would be e×pected on the basis of low temperature estimates. Independent evaluation gives log A4 = 10.5 ± 0.4 (l.mole−1s−1) and E4 = 20.1 ± 1.7 kcal/mole, hence log A3 = 11.4 ± 0.8 (l.mole−1s−1) and E3 = 18.2 ± 3.2 kcal/mole. These values are shown to be entirely consistent with a wide range of results from pyrolytic studies, and it is argued that they further confirm the view that Arrhenius plots for alkyl radical–alkane metathetical reactions are strongly curved, in part due to tunneling and, appreciably, to other as yet unidentified effects. Since there is published evidence that metathetical reactions involving hydrogen atoms show even greater curvature, it is suggested that this may be a characteristic of many metathetical reactions.
The dissociation of 3‐chloro‐1‐butene and the resonance energy of the chloro‐allyl radical
Authors: Trenwith A. B. 
Published: January 2005

AbstractMethane is a primary product of pyrolysis of 3‐chloro‐l‐butene at temperatures in the range 776–835°K, and from its rate of formation values have been obtained for the limiting high‐pressure rate constant of the reaction
equation image
These may be represented by the expression log [(k1)∞/sec−1] = (16.7 ± 0.3) − (71.5 ± 1.5)/θ, where θ = 2.303RT kcal/mole. Assuming a zero activation energy for the reverse reaction and that over the experimental temperature range the rates at which a methyl radical adds on to chlorobutene are comparable to those at which it abstracts hydrogen, the activation energy for the dissociation reaction leads to a value of 83.2 ± 1.9 ckal/mole for D(HCHClCH:CH2) at 298°K. Taking D(HCHClCH2CH 3) = 95.2 ± 1.0 kcal/mole a value of 12.0 ± 2.1 kcal/mole is obtained for the resonance energy of the chloroallyl radical. This value in conjunction with resonance energies obtained in earlier work indicates that substitution of a hydrogen atom on the carbon atom adjacent to the double bond in the allyl radical leads to no significant variation in the allylic resonance energy.
High‐pressure photoionization mass spectrometry. Effect of internal energy and density on the ion–molecule reactions occurring in methyl, dimethyl, and trimethylamine
Authors: Hellner L. , Sieck L. W. 
Published: January 2005

AbstractThe ion–molecule reactions of CH3NH2+, (CH3)2NH+, and (CH3)3N+ with the respective amines have been investigated at thermal kinetic energies in a high‐pressure photoionization mass spectrometer at several wavelengths (energies) in the vacuum ultraviolet. The absolute rate coefficient for proton transfer from (CH3)3N+ to (CH3)3N decreases from 8.2 × 10−10 cm3/molecule · sec at 147.0 nm (8.4 eV) to 4.9 × 10−10 cm3/molecule. sec at 106.7‐104.8 nm (11.7 eV). In dimethylamine, the rate coefficient decreases from 11.6 × 10−10 cm3/molecular. sec at 8 4 eV to 10.2 × 10−10 cm3/molecule osec at 11.7 eV, while no significant effect of energy was detected in methylamine. The reactions of several fragment ions are also reported. Experiments were also carried out at pressures up to 0.5 torr in order to investigate the further solvation of CH3NH2+, (CH3)2NH2+, and (CH3)3NH+. It was found that the maximum proton solvation numbers in methyl‐, dimethyl‐, and trimethyl‐amine are 4, 3, and 2, respectively, under these conditions.
The pyrolysis of hexachloroethane
Authors: White Merle L. , Kuntz Robert R. 
Published: January 2005

AbstractThe thermal decomposition of hexachloroethane in the presence of chlorine has been studied over the temperature range 340‐400°C and a pressure range of 0.5°2.5 atm. The rate of the unimolecular CC bond spliting reaction can be described by the Arrhenius equation

Comparison of these rate data with thermodynamic data suggests a combination rate for CCl3 radicals which is consistent with earlier measurements.
The gas‐phase thermal unimolecular elimination of 1,1‐dimethylketene from 7,7‐dimethylbicyclo[3.2.0]hept‐2‐en‐6‐one
Authors: Egger Kurt W. 
Published: January 2005

AbstractThe gas‐phase thermal decomposition of 7,7‐dimethylbicyclo[3.2.0]hept‐2‐en‐6‐one (DBH) to yield cyclopentadiene and 1,1‐dimethylketene as primary products was studied in the temperature range of 470‐550 °K using a static reaction system. First‐order rate constants for the depletion of DBH based on the internal standard technique and gaschromatographic analyses were independent of the initial starting pressure (7‐68 torr) and of the conversion, ranging between 5% and 89%. (Throughout this paper, 1 torr = (101.325/760) kNm−2, and 1 cal = 4.184J). The reaction is essentially homogeneous, as the nature of the reaction vessel surface (Teflon or glass) had no effect on the observed rate constants which fit the Arrhenius relationship

where θ = 2.303 RT. These activation parameters, when compared with those for similar reactions involving the molecules bicyclo[3.2.0]hept‐2‐en‐6‐one, bicyclo[3.2.0]heptan6‐one, and cyclobutanone, demonstrate a very small effect of the alkyl substituents bonded to the carbon atom adjacent to the carbonyl carbon. Accepting the previously discussed concerted and pronounced polar nature of the mechanism for these retro‐ketene addition reactions, the present data suggest that considerable changes in charge densities between the ground and transition state are only occurring on the two opposite centers of the molecule, with the negative charge residing essentially on the oxygen atom and the positive charge on the opposing bridgehead carbon atom. It then appears that the charge separation in the transition state is more appropriately described as being pseudo‐zwitterionic rather than quadrupolar in nature.
High temperature decomposition of ethane
Authors: Burcat Alexander , Skinner Gordon B. , Crossley Robert W. , Scheller Karl 
Published: January 2005

AbstractMeasurements of the rate of formation of methane in the thermal decomposition of ethane in dilute mixtures with argon were made by the shock tube technique. Derived values of the rate constant of the dissociation reaction are compared with earlier data of the same type and with recent shock tube data on the combination of methyl radicals. An RRKM calculation correlating all the data is described, from which an Arrhenius equation for the range 1000–1500°K, log k∞ = 16.9 − 89,500/2.3RT, is obtained.
Kinetics of the thermal decomposition of CF3CHCL2 in a single‐pulse shock tube
Authors: Sekhar M. V. C. , Millward G. E. , Tschuikow‐Roux E. 
Published: January 2005

AbstractThe pyrolysis of 2,2‐dichloro‐1,1,1‐trifluoroethane was studied over the temperature range of 1120–1260°K at total reflected shock pressures from ∼2800 to 3100 torr. Below 1260°K, the decomposition leads to three reaction products which were identified as CF2CFCl, CF2CFH, and CF3CCl3. The results are interpreted in terms of a parallel CCl bond rupture process which becomes competitive with the molecular HCI elimination. The rate constant for the α,α‐elimination process

has been deduced to be

It was also possible to obtain the overall rate constant for the formation of CF2CFH, which is given by

Some evidence for hydrogen fluoride elimination was found at temperatures above 1260°K. However, at these higher temperatures CC bond scission also occurs and the kinetics of the system become untractable.
Rates of recombination of free radicals. V. The tert‐butyl radical
Authors: Hiatt R. , Benson S. W. 
Published: January 2005

AbstractAnalysis of the products from a vapor‐phase mixture of EtI and t‐BuI, in which free radicals were generated thermally, has yielded a rate constant for the recombination of 2t‐Bu⋅ of 105.4 M−1 sec−1 at 100°C. The close agreement between this and other recent estimations from vapor‐phase work is noted, as is the disparity between these values and those on the order of 109 M−1 sec−1 obtained in solution.
Rotating sector study of the gas phase photochlorination of 2,2‐dichloro‐1,1,1‐trifluoroethane
Authors: Cullison R. F. , Pogue R. C. , White M. L. 
Published: January 2005

AbstractThe rate constant for the combination of 2,2‐dichloro‐1,1,1‐trifluoroethyl radicals has been measured by applying the rotating sector technique to the gas phase photochlorination of 2,2‐dichloro‐1,1,1‐trifluoroethane at 315°K. The observed value is 6.89 × 1012 cc/mole.sec. This value is in excellent agreement with measurements by Wampler and Kuntz which yielded a temperature‐independent value of 6.6 × 1012 cc/mole.sec. The measurement by Wampler and Kuntz was determined from the photochemical system (CF3CCl3 + C‐C6H12 + hν). The Arrhenius parameters for the reaction CF3CCl2· + Cl2 → CF3CCl3 + Cl were found to be given by the expression log k3 = 12.10 − 5830/2.3RT (units in mole, cc, and sec). This is a relatively high activation energy for a chlorination reaction and makes the reaction ever slower than the chlorination of chloroform.
Further studies on the dissociation of HBr behind shock waves
Authors: Cohen N. , Giedt R. R. , Jacobs T. A. 
Published: January 2005

AbstractPreviously reported shock tube studies of the dissociation of HBr in the temperature range of 2100–4200°K have been extended to lower temperatures (1450–2300°K) in pure HBr. The course of reaction was followed by monitoring the radiative recombination emission in the visible spectrum from Br atoms. The results imply that, in the lower range of temperatures, the activation energy of dissociation, E in the expression AT−2e−E/RT, can be approximated by the HBr bond energy (88 kcal/mole). It was also found that, in this temperature range, the rate of HBr dissociation is sensitive to the Br2 dissociation rate and the HBr + Br exchange rate. When these rates were adjusted to bring computed reaction profiles into agreement with experimental ones, it was found that the higher‐temperature data could also be fitted reasonably well with an HBr dissociation activation energy of 88 kcal/mole, contrary to the conclusions of our previous work, which favored an activation energy of 50 kcal/mole. The “best value” for k1Ar, the rate coefficient for HBr dissociation in the presence of Ar as chaperone, appears to be 1021.78 ± 0.3 T−2 10−88/θ cc/mole sec, where θ = 2.3 RT/1000; that for k1HBr, is 1022.66T−210−88/θ. A detailed review is given of the rate coefficients for the other pertinent reactions in the H2–Br2 system, viz., Br2 dissociation and reactions of HBr with H and Br.
Formation of association ions in the photoionization of alkyl halides
Authors: Sieck L. W. , Gorden R. 
Published: January 2005

AbstractThe methyl and ethyl chlorides and bromides, as well as methyl iodide, were photoionized in the vacuum ultraviolet at 300 K in a mass spectrometer over the pressure range 0.5 to approximately 100 millitorr. Under these conditions, stabilized parent ion dimers are found in CH3Br, CH3I, and C2H5Br, but not in the chlorides. Lower limits for the dissociative lifetimes of the ion–molecule collision complexes were estimated and are as follows: (CH3Br)2+, 1.6 μs; (CH3I)2+, 1.9 μs; and (C2H5Br)2+, 5.4 μs. An increase in photon energy (internal energy content of the reactant ion) decreases the dissociative lifetime of the collision complex in CH3I.
A method for computer analysis of kinetics of competing first‐ and second‐order reactions
Authors: Gorman Donald S. , Connolly John S. 
Published: January 2005

AbstractCompeting first‐ and second‐order reactions of transient molecular species (e.g., triplet states and free radicals) are a common occurrence in kinetic studies such as flash photolysis and pulse radiolysis. We have developed a method for analyzing the decay kinetics of any species (Y) whose disappearance is described by −dY/dt = k1Y + k2Y2. The computer program (written in time‐sharing BASIC) employs an iterative technique to obtain the least‐squares estimates of the three parameters in the integrated rate equation.
The methyl radical combination rate constant as determined by kinetic spectroscopy
Authors: Bass Arnold M. , Laufer Allan H. 
Published: January 2005

AbstractThe rate constant for the reaction

has been determined by means of vacuum ultraviolet flash photolysis and time‐resolved kinetic spectroscopic observations of the 1504‐Å absorption band of CH3. The measurements made using three different sources of methyl radicals (azomethane, dimethylmercury, and ketene‐hydrogen) were in accord and yielded a value for the rate constant of k1 = (9.53 ± 1.17) × 10−11 cc molec−1 sec−1. A detailed error analysis is presented. The f‐value for the 1504‐Å band of CH3 is determined to be (2.5 ± 0.7) × 10−2.