bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of the iodine atom catalyzed gas phase geometrical isomerization of diiodoethylene. Rotation about a single bond
Authors: Golden David M. , Furuyama Shozo , Benson Sidney W. 
Published: January 2005

AbstractThe spectrophotometric determination of the rate of iodine atom catalyzed geometrical isomerization of diiodoethylene in the gas phase from 502.8 to 609.1°K leads to a rate constant for the bimolecular reaction between I and trans‐diiodoethylene of log kt−c(M−1 sec−1) = 8.85 ± 0.12 − (11.01 ± 0.30)/θ. Estimates of the entropy and enthalpy change for the addition of I atoms to trans‐diiodoethylene (process a.b) lead to log Ka.b(M−1) = −2.99 − 4.0/θ, and thus to log kc (sec−1) = log kt−c – log Kab = 11.8 −7.0/θ for the rate constant for rotation about the single bond in the adduct radical. The theory for calculation of the rotation rate constant is presented and it is shown that while the exact value depends on the barrier height, a value of 6.8 kcal/mole for this quantity leads to log k (sec−1) = 11.8 −6.7/θ. The activation energy points to a better value of the group contribution to heat of formation of the group C‐(I)2(H)(C) than one based on bond additivity.
The rate of addition of hydrogen atoms to olefins: Isobutane and ethylene
Authors: Knox J. H. , Dalgleish D. G. 
Published: January 2005

AbstractThe title reactions have been investigated in a fast flow system at pressures of about 2 torr and temperatures between 12 and 132°C. The following Arrhenius equations are derived for reaction (2)
equation image
where the units of k2 are l/mole sec and of E2, cal/mole, and the limits are the 95% confidence limits assuming random errors.These equations are in good agreement with those which can be derived from previous investigations.
Arrhenius constants for the reactions of ozone with ethylene and acetylene
Authors: DeMore W. B. 
Published: January 2005

AbstractThe kinetics of ozonation of C2H4 and C2H2 have been studied in the gas phase from −40 to −95°C (C2H4) and +10 to −30°C (C2H2). The O3 concentrations were near 10−4 M, and the hydrocarbons were present in 2‐ to 25‐fold excess. A few experiments with propylene were also carried out. The reactions were followed by observing the rate of decay of O3 absorption at 2537 Å. Reaction stoichiometries and effects of added O2 were investigated. The second‐order rate constant for C2H4 was log k(M−1 sec−1) = (6.3 ± 0.2) – (4.7 ± 0.2)/θ (θ = 2.3RT). The rate was independent of the presence of excess O2. Rate measurements for C3H6 were less accurate because of aerosol interference. Combined with room temperature measurements of other workers, the C3H6 rate constant was log k(M−1 sec−1) = (6.0 ± 0.4) – (3.2 ± 0.6)/θ. The C2H2 rate constant was log k(M−1 sec−1) = (9.5 ± 0.4) – (10.8 ± 0.4)/θ. In the case of C3H6 the major product was propylene ozonide. Ethylene did not yield the ozonide, and the products of the O3–C2H4 and O3–C2H2 reactions were not identified. Pre‐exponential factors for the olefin reactions are consistent with a five‐membered ring transition state formed by 1,3 dipolar cycloaddition of O3. For C2H2, however, the much higher observed A factor suggests a different mechanism. Possible transition states for the O3–C2H2 reaction are discussed.
Kinetic studies of the reactions CH2I2 + HI⇄CH3I + I2 and 2 CH3I⇄CH4 + CH2I2 the heat of formation of the iodomethyl radical
Authors: Furuyama Shozo , Golden David M. , Benson Sidney W. 
Published: January 2005

AbstractThe rate of the reaction CH2I2 + HI ⇆ CH3I + I2 has been followed spectrophotometrically from 201.0 to 311.2°. The rate constant for the reaction fits the equation, log (k1/M−1 sec−1) = 11.45 ± 0.18 ‐ (15.11 ± 0.44)/θ. This value, combined with the assumption that E2 = 0 ± 1 kcal/mole, leads to ΔH (CH2I, g) = 55.0 ± 1.6 kcal/mole and DH (HCH2I) = 103.8 ± 1.6 kcal/mole.The kinetics of the disproportionation, 2 CH3I ⇆ CH4 + CH2I2 were studied at 331° and are compatible with the above values.
Reactivities in olefin‐difluorocarbene reactions
Authors: Mitsch Ronald A. , Rodgers Alan S. 
Published: January 2005

AbstractThe relative rates of addition of difluorocarbene to a series of methyl‐substituted olefins have been determined and correlated with similar data for dichlorocarbene, chlorofluorocarbene and ground‐state oxygen atoms. The electrophilic nature and stabilization of difluorocarbene by the fluorine substituents is discussed. Relative activation energies for the difluorocyclopropane‐forming reaction have been estimated and correlated with properties of the olefins as derived from molecular orbital theory.
Some hydrogen atom abstraction reactions of CF2H and CFH2 radicals, and the CH bond dissociation energy in CF2H2
Authors: Pritchard G. O. , Perona M. J. 
Published: January 2005

AbstractBy photolyzing (CF2H)2CO and (CFH2)2CO the hydrogen atom abstraction reactions of CF2H radicals with (CF2H)2CO, H2, D2, CH4, C2H6, nC4H10 and isoC4H10, and the reactions of CFH2 radicals with (CFH2)2CO and nC4H10, have been studied. Arrhenius parameters for these reactions are compared with related systems. From a knowledge of the activation energies for the forward and reverse reactions a value of the bond dissociation energy, D(CF2HH) = 97.4 ± 1.3 kcal mole−1 at a mean temperature of 543°K is
equation image
obtained. This value is subject to much uncertainty due to possible compensation effects in the Arrhenius parameters. These effects are discussed for this and the other reactions, and the data suggest that D(CF2HH) is approximately 100 kcal mole−1, and that D(CFH2H) is very similar. Other literature data tend to confirm these approximate values.
An evaluation of rate data for the reactions of atomic Oxygen (O3P) with methane and ethane
Authors: Herron John T. 
Published: January 2005

AbstractThis review presents in tabular and graphical form rate data on the reactions of atomic oxygen (O3P) with methane and ethane. The reliability of these data is discussed and suggested values of the rate constants are given over specified temperature intervals. Specific values are given for 298 and 1000°K.
Thermal decomposition of benzotrifluoride. The CC bond strength and the heat of formation of the phenyl radical
Authors: Szilágyi I. , Bérces T. 
Published: January 2005

AbstractThe kinetics of the decomposition of benzotrifluoride was studied from 720°c to 859°c in a flow system with and without carrier gas. Consideration of the product distribution made possible the study of the decomposition into CF3 and C6H5 radicals, which appeared to be truly homogeneous in character. The first‐order rate constant of the CC bond fission, log k (sec−1) = (17.9 ± 0.5) (99.7 ± 2.5)/θ, did not change with change of initial concentration, pressure of the carrier gas, or contact time. The Arrhenius parameters have been related to the appropriate thermodynamic data. Assumption of 0 kcal/mole for the activation energy of the reverse combination reaction yielded DH(C6H5CF3) = 103.6 ± 2.5 kcal/mole and ΔH(C6H5) = 77.1 ± 3.0 kcal/mole.Applicability of the simple first‐order formula to calculation of the rate constant has been also dealt with.
The reaction of trifluoromethyl radicals with ammonia
Authors: Morris E. R. , Thynne J. C. J. 
Published: January 2005

AbstractThe reaction of trifluoromethyl radicals with ammonia in the gas phase has been studied in the temperature range 30‐352°. Product formation is not explicable simply in terms of the reactions:

and curvature of the Arrhenius plot at high and low temperatures suggests that there are additional sources of fluoroform.
The elimination of HF from vibrationally excited fluoroethanes. The decomposition of 1,1,1‐trifluoroethane‐d0 and d3
Authors: Pritchard G. O. , Perona M. J. 
Published: January 2005

AbstractThe vibrationally excited molecules CF3CH and CF3CD have been synthesized by radical combination (produced by ketone photolysis), and HF and DF elimination from them studied as a function of temperature and pressure. Using RRK theory many calculations have recently been made of critical energies for the decomposition of "hot" fluoroethane molecules. Taking CF3CH as an example, it is concluded that the empiricism involved in such calculations renders results of doubtful significance. The non‐equilibrium kinetic isotope effect is kH/kD = 3.1 at 470°K. Arrhenius parameters are also presented for radical abstraction reactions from the ketone source molecules.
Some particular aspects of the low‐temperature oxidation of methane initiated by nitric acid
Authors: Iosif Ileana , Lazar D. P. , Schneider I. A. 
Published: January 2005

AbstractDuring methane oxidation initiated by nitric acid or nitrogen dioxide, it is possible to observe, under certain conditions of temperature, initiator content, and flow rates, the formation of an adiabatic “temperature peak.” Because the maximum temperature of the peak does not exceed the initial temperature of the reactor by more than 220°C, the recorded temperature‐increase curves were used for a kinetic interpretation. The obtained kinetic parameters (overall n and E) agree with the values reported in the literature for isothermal methane oxidation and suggest that the overall mechanism does not change in the conditions of “temperature peak.”
Chemically activated 1,1‐dimethylcyclopropane from photolysis of isobutene–neopentane–diazomethane–oxygen mixtures
Authors: Taylor G. W. , Simons J. W. 
Published: January 2005

AbstractA study of the structural isomerization rate of chemically activated 1,1‐dimethylcyclopropane from singlet methylene addition to the double bond of isobutene is reported. Singlet methylenes were produced from the 4358‐ and 3660‐Å photolysis of diazomethane in the presence of added oxygen. Theoretical rates calculated via RRKM theory are in excellent agreement with experiment for calculations utilizing activated complex structures and critical energies consistent with known thermal Arrhenius parameters, and excitation energies consistent with previous determinations of ΔH(CH2) + E*(CH2) = 116.1 and 112.6 kcal/mole for diazomethane photolyses at 3660 and 4358 Å, respectively.
Rates and mechanism of alkyne ozonation
Authors: B. Demore W. 
Published: January 2005

AbstractThe rates and products of the reactions of ozone with acetylene, methylacetylene, dimethylacetylene, and ethylacetylene have been studied in a long‐path infrared cell at 21 ± 1°C. The gas phase reaction gives products formed by cleavage of the carbon–carbon triple bond. A mechanism is proposed that involves formation of a short‐lived acid anhydride intermediate, which is energized by virtue of the reaction exothermicity and undergoes unimolecular decomposition. Formation of an α‐dicarbonyl was observed in every case, but there is evidence that a side reaction on the walls accounted for that product. The general relationship between alkyne and alkene ozonation is discussed. The rate measurements showed that, unlike the alkenes, the rate of alkyne ozonation is not greatly affected by substitution with simple alkyl groups. The rate constant for C2H2 agrees with earlier work and thus provides additional support for the previously derived high A‐factor for acetylene ozonation relative to alkenes.
The vibrational excitation of hydrogen fluoride behind incident shock waves
Authors: Solomon W. C. , Blauer J. A. , Jaye F. C. , Hnat J. G. 
Published: January 2005

AbstractThe vibrational excitation of HF occurring behind incident shock waves has been studied in the temperature range of 1400°K to 4100°K. The extent of excitation was determined as a function of time by continuously monitoring the emission intensity from the 1–0 band of HF centered at 2.5 μ. The data were interpreted in terms of the process

and gave a value of

for M = HF. The corresponding result for (τp)−1Ar was found to be insignificant in comparison to this result. Data were also obtained for the effect of F atoms upon the relaxation rate, i.e., it was found that
The reactions between SO2 and C2H2 (and C2H4) at elevated temperatures. A single‐pulse shock tube investigation
Authors: Fifer R. , Moreau R. , Bauer S. H. 
Published: January 2005

AbstractThe high‐temperature reaction between sulfur dioxide and acetylene in an excess of argon was studied in a 1−in. i.d. single‐pulse shock tube. Mixtures ranging from 1.81% to 5.40% SO2 and 1.60% to 4.90% C2H2 were heated to reflected shock temperatures of 1550°–2150°K, for dwell times of about 0.6 msec and gas dynamically quenched. Total reaction densities were 0.89 to 5.4 × 10−2 moles/1. The reaction products were analyzed by gas chromatography. A technique was developed for separating Ar, C2H4, C2H2, SO2, CO, CO2, H2S, COS, and CS2. The major products of the reaction are CO, H2, CS2, and sulfur. The products observed were compared with those predicted on the assumption that equilibrium was attained. Several preliminary experiments were carried out with ethylene‐sulfur dioxide mixtures, and the results indicated that for this combination the sulfur dioxide probably reacted with the acetylene generated from the decomposition of the ethylene, rather than directly with the ethylene. The rate of decline in the sulfur dioxide content in C2H2‐SO2 mixtures was found to be approximately second order (total) and can be empirically represented by

A mechanism is proposed to account for the overall reaction kinetics.
The reactions of O(3P) with ozone and carbonyl sulfide
Authors: Krezenski Daniel C. , Simonaitis R. , Heicklen Julian 
Published: January 2005

AbstractThe competitive reactions between 2‐trifluoromethylpropene (TMP) and OCS for O(3P) atoms were studied between 300° and 523°K, using the mercury‐senstitized photolysis of N2O as a source of O(3P). From the known value for the rate constant of the O(3P) + TMP reaction, k3 was found to be 1.6 × 10−11 exp (−4500/RT) cm3/particle‐sec, where reaction (3) is

Mixtures of O3 and OCS were photolyzed at 197°, 228°, 273°, and 299°K with radiation above 4300 Å to produce O(3P) from the photolysis of O3, and thus study the competition between reaction (3) and

From the above value of k3, k1 could be computed. When combined with all the previous data, the best espression for k1 is k1 = 1.2 × 10−11 exp (−4300/RT) cm3/particle‐sec.
Disproportionation‐combination ratios of small alkyl radicals formed by the mercury‐photosensitized hydrogenation of olefins in the gas phase
Authors: Falconer W. E. , Sunder W. A. 
Published: January 2005

AbstractDisproportionation‐combination ratios have been obtained for small alkyl radicals produced in the mercury‐photosensitized hydrogenation of ethylene, propylene, butene‐1, butene‐2, and isobutene. For conditions favoring thermalized radicals, kd/kc (ethyl, ethyl) = 0.14, kd/kc (isopropyl, isopropyl) = 0.69, kd/kc (isopropyl, n‐propyl) = 0.41, kd/kc (2‐butyl, 2‐butyl) = 0.77, kd/kc (2‐butyl, n‐butyl) = 0.45, and kd/kc (t‐butyl, t‐butyl) = 3.1. The results are consistent with kd/kc (n‐propyl, n‐propyl) = 0.15 and kd/kc (n‐butyl, n‐butyl) = 0.14. The general agreement between these disproportionation‐combination ratios and those obtained where photolytic radical sources have been used indicates that under appropriate conditions, H atom addition to olefins is a suitable source for the study of thermalized alkyl radicals and may be especially useful for larger alkyl radicals for which clean photolytic precursors are not available.
Bromination of dichloromethane, chlorofluoromethane, and dichlorofluoromethane.
Authors: Copp D. E. , Tedder J. M. 
Published: January 2005

AbstractDichloromethane, chlorofluoromethane, and dichlorofluoromethane have been brominated competitively with each other and with chloroform and methyl chloride. Using the literature values for the rates of bromination of these latter two compounds, the rate constants for the three former compounds have been determined:

where R is taken to be 1.987 cal deg−1 mol−1 (1 cal = 4.186 J).
Kinetics of the thermal reaction of 1,1,2‐trimethylcyclopropane
Authors: O'Neal H. E. , Henfling D. 
Published: January 2005

AbstractThe gas‐phase reaction kinetics of 1,1,2‐trimethylcyclopropane have been studied in the temperature range of 700–755°K. First‐order unimolecular rate constants for over‐all reactant disappearance fit the Arrhenius equation

Reaction products and the relative rates of their formation are found to be reasonably consistent with the biradical mechanism.
Emission studies of the mechanism of gaseous biacetyl photolysis at 3450, 3650, 3880, and 4358 a and 28°C
Authors: Horowitz Abraham , Calvert Jack G. 
Published: January 2005

AbstractThe quantum yields of phosphorescence (Φp) of biacetyl have been determined in pure biacetyl, biacetyl‐SO2, and biacetyl‐c‐C6H12 mixtures in experiments using bands of radiation centered at 3450, 3650, 3880, and 4348 Å. It has been shown that the unexpected effect of gas concentration on the quantum yields of the sulfur dioxide triplet‐sensitized phosphorescence of biacetyl resulted largely from the significant destruction of biacetyl triplets at the wall of the cell. The kinetics of the variation of Φp with [Ac2], wavelength of the absorbed light, and added gases provide new estimates of the energy relations and the rate constants for the decomposition reaction of vibrationally rich biacetyl molecules in the first excited singlet state (1Ac2‡): 1Ac2‡ → products (1), 1Ac2‡ + Ac2 → 1Ac2 + Ac2 (2); the minimum energy necessary in 1Ac2‡ for reaction (1) to occur is estimated to be about 72.8 kcal/mole above the ground state of biacetyl: k1/k2 = (4.3 ± 0.1) × 10−3M at 3450 Å, (4.07 ± 0.04) × 10−4M at 3650 Å, and (5.6 ± 0.4) × 10−5M at about 3800 Å. The variation of the rate constant ratio is shown to be consistent with the expectations of the simple theory of excited molecule decomposition. Biacetyl triplet (3Ac2) rate constants were determined by measurements of Φp in O2 and NO‐containing mixtures: 3Ac2 + S → (Ac2–S, products) (8); for O2 = S, k8 = (5.76 ± 0.40) × 108 (3650 Å experiments), (5.76 ± 0.27) × 108 (4358 Å); for NO = S, k8 = (3.34 ± 0.20) × 109 (3650 Å), (3.33 ± 0.18) × 109 1./mole‐sec (4358 Å). A comparison between these and previous findings of the SO2 triplet (3SO2)‐sensitized excitation of biacetyl [5,6] show that the decomposition of the initial 3Ac2 product of the exothermic energy transfer reaction 3SO2 + Ac2 → SO2 + 3Ac2 is unimportant.
The Reactions of H Atoms with H2S and COS
Authors: Rommel H. , Schiff H. I. 
Published: January 2005

AbstractThe kinetics of the reactions of H atoms with H2S and with COS were measured at 298deg;K in a flow system using mass‐spectrometric detection. The rate constants were found to be 3.8 × 10−13and 2.2 × 10−14cm3part−1sec−1, respectively, with an estimated accuracy of 25%. At high flow rates of H2S, 0.5 molecules of H2S are consumed per H atom originally present. At all flow rates of COS, H2S is a major product, CO production equals COS consumption, and 0.5 molecules of COS are consumed per H atom. The results are consistent with the reaction HS + HS → H2S + S being the dominant process for thiyl radicals, and evidence is presented to indicate that its reaction rate is close to collisional frequency.
Kinetics of the reactions of cyclopropane derivatives, part II. The gas‐phase pyrolysis of cyclopropylamine
Authors: Parry K. A. W. , Robinson P. J. 
Published: January 2005

AbstractAt temperatures of 356‐425°C and pressures of 15–60 Torr, cyclopropylamine reacts to give an equimolar mixture of ammonia and N‐propylidenecyclopropylamine as the initial product. The reaction is first order, homogeneous, and unaffected by the presence of radical inhibitors, and thus proceeds by an initial rate‐determining unimolecular isomerization to give a reactive intermediate, which then reacts with a further molecule of cyclopropylamine to give the observed products. Reaction in the presence of added aliphatic amines gives other imines in addition, and the nature of these indicates that the intermediate is propenylamine or its tautomer propylideneamine:
equation image
A flash photolysis resonance fluorescence kinetics study of ground‐state sulfur atoms. III. Rate parameters for reaction of S(3P) with ethylene episulfide
Authors: Klemm R. B. , Davis D. D. 
Published: January 2005

AbstractAbsolute rate constants for the reaction of S(3P) with ethylene episulfide were measured over a C2H4S concentration range of 5, a total pressure of 20–200 tort, and a flash intensity range of ˜4. Over this range of variables, the bimolecular rate constant was found to be invariant. Because of limitations imposed by the physical properties of the reactant C2H4S, temperature variations were necessarily held to the range 298–355°K. The bimolecular rate constant was found to be invariant over this limited temperature range, having a value of (4.47 ± 0.26) × 10−11 cm3 molec.−1 sec−1. The possible influence of this reaction in studies of the S(3P)–ethylene system are discussed.
The kinetics of biacetyl phosphorescence sensitized in 2875 Å‐irradiated SO2–biacetyl–added gas (CO2, CO, N2) mixtures. The nature of the SO2 excited states formed at high added gas pressures
Authors: Horowitz Abraham , Calvert Jack G. 
Published: January 2005

AbstractThe quantum yields of sensitized biacetyl phosphorescence emission have been determined for SO2–biacetyl–CO2, SO2–biacetyl–N2, and SO2–biacetyl–CO mixtures irradiated at 2875 Å. Series of experiments were made at various SO2, biacetyl, and added‐gas concentrations (up to 4 × 10‐2 M). The kinetic data show an “excess” biacetyl emission which requires the participation of some undefined excited state or isomer of SO2 in addition to the emitting singlet (1SO2) and triplet (3SO2) states of SO2. These results confirm the experimental observations of Cehelnik et al. [12] and Wampler et al. [9] who reported that an “excess” quantum yield of CO2 occurred in 3130 Å‐irradiated SO2‐CO mixtures at high CO pressures. The kinetic analysis of the data is most consistent with the hypothesis of Wampler et al.; the nonreactive, undefined excited state or high‐energy isomer of SO2, designated here as X, is formed in part as 1SO2 is quenched: 1SO2 + M → (SO2M) (1); 1SO2 + M → 3SO2 + M (2); 1SO2 + M → X + M (3). X itself does not transfer energy to biacetyl. It decays largely by a nonradiative first‐order process at low pressures, X → SO2 (5), but it generates 3SO2 by collisional perturbation at high pressures, X + M → 1SO2 + M (4). In terms of this mechanism, the following rate constant ratios are derived from the present study: k2/(k1 + k2 + k3) = 0.020 ± 0.010 (M = CO2), 0.021 ± 0.010 (N2), 0.019 ± 0.010 (CO); k3/(k1 + k2 + k3) = 0.14 ± 0.02 (M = CO2), 0.085 ± 0.012 (CO), 0.11 ± 0.02 (N2); and k5/k4 (mole/l) = 0.020 ± 0.004 (M = CO2), 0.016 ± 0.003 (CO), 0.021 ± 0.005 (N2).
Kinetics of the reactions of cyclopropane derivatives. IV. Kinetic isotope effect in the isomerisation of cyclopropylamine
Authors: Luckraft D. A. , Robinson P. J. 
Published: January 2005

AbstractThe high‐pressure isotopic rate ratio kH/kD for isomerisation of cyclopropylamine and cyclopropylamine‐N‐d2 is 1.06 at 649–678 K, supporting a mechanism which does not involve migration of hydrogen from the amine group in the rate‐determining step.
A flash photolysis–resonance fluorescence kinetics study of ground‐state sulfur atoms. IV. Rate parameters for reaction of S(3P) with propene and 1‐butene
Authors: Klemm R. B. , Davis D. D. 
Published: January 2005

AbstractUsing the technique of flash photolysis‐resonance fluorescence, absolute rate constants have been measured for the reaction of S(3P) with propene and 1‐butene. Variations in experimental conditions included the following: temperature (215–500°K); total pressure a factor of 10; olefin concentration, a factor of 6; flash intensity (S atom concentration), a factor of 10. It was found that over these variations in the experimental conditions only the temperature had a measureable effect on the bimolecular rate constant. The derived Arrhenius rate expressions for the reactions (2) and (3) were as follows:

temperature range 214–500°K

Units are cm3 molec−1 s−1.