bluuebunny/crossref_metadata_2025_split huggingface dataset:
The free‐radical reaction of tri‐n‐butyltin hydride with peroxides
Authors: Brokenshire J. L. , Ingold K. U. 
Published: January 2005

AbstractRate constants for the tri‐n‐butyltin radical (Sn ·) induced decomposition of a number of peroxides have been measured in benzene at 10°C. The values range from ∼100 M−1 sec−1 for di‐t‐butyl peroxide to 2.6 × 107 M−1 sec−1 for di‐t‐butyl diperoxyisophthalate. The majority of the peroxides, including diethyl peroxide, diacetyl peroxide, and t‐butyl peracetate, have rate constants of ∼105 M−1 sec−1. It is shown that di‐n‐alkyl disulfides are ten times as reactive toward Sn · as di‐n‐alkyl peroxides, although the exothermicities of these reactions are ∼15 and ∼39 kcal/mole, respectively. The enhanced reactivity of the disulfides is attributed to the easier formation of an intermediate or transition state with 9 electrons around sulfur, compared with an analogous species with 9 electrons around oxygen.The following bond strengths (kcal/mole) have been estimated: D[SnOR] = 77; D[SnH] = 82; D[SnSR] = 83; and D[SnOC(O)R] = 86, where R = alkyl. Rate constants for reaction of Sn · with some benzyl esters have also been measured. It has been found that t‐butoxy radicals can add to benzene and abstract hydrogen from benzene at ambient temperatures.
Reactions of radicals. XXVI. On the use of activation parameters as a test for concerted decomposition of initiators
Authors: Pryor William A. , Smith Kennedy 
Published: January 2005

AbstractIn 1958, Bartlett and Hiatt [1] suggested that the number of bonds which are rotationally “frozen” at the transition state for decomposition of peresters can be determined from the magnitude of the values of ΔH‡ and ΔS‡. In recent years, other workers have extended this hypothesis to include the use of the magnitude of ΔH‡ and ΔS‡ values to determine the number of bonds which undergo synchronous scission in the decomposition of initiators. This criterion for separating one‐bond from two ‐or three‐bond initiators is discussed in the light of all of the data now reported in the literature. It is probable that the correlation of ΔH‡ and ΔS‡ in an isokinetic plot cannot be used to distinguish either the number of bonds which are rotationally frozen at the transition state or the number that are undergoing scission, except in limited and rather imprecise ways. However, the insights and principles of Bartlett and Hiatt still are extremely useful as qualitative tools.
The rate of dissociation of allyl iodide in shock waves
Authors: Maloney K. L. , Palmer H. B. , Seery D. J. 
Published: January 2005

AbstractThe rate of decomposition of allyl iodide has been measured from 742plusmn;K to 1068±K and from 169 to 1429 torr using a shock tube method in which the disappearance of allyl iodide and the appearance of iodine are followed simultaneously. The kinetics are first order in allyl iodide and probably are slightly dependent upon total pressure. Mathematical modeling shows that they are compatible with a mechanism consisting of three reactions:

equation image

The experiments yield the rate constant k1, the high‐pressure limiting value of which is found to be

in reasonable agreement with that predicted using the methods of Benson and O'Neal [1].
Very low‐pressure pyrolysis. VII. The decomposition of methylhydrazine, 1,1‐dimethylhydrazine, 1,2‐dimethylhydrazine, and tetramethylhydrazine. Concerted deamination and dehydrogenation of methylhydrazine
Authors: Golden D. M. , Solly R. K. , Gac N. A. , Benson S. W. 
Published: January 2005

AbstractThe rate constants (kuni) for the first‐order disappearance of the title molecules have been determined under VLPP conditions. The kuni are not the rate constants of ultimate interest since they reflect the fact that energy transfer competes with the chemical decomposition. Use of the Rice‐Ramsperger‐Kassel‐(Marcus) [RRK(M)] theory allows the determination of the high‐pressure rate constants (kα), if the mode of decomposition is known. The heats of formation of the radicals NH2, CH3NH, and (CH3)2N are known. These values should be usable for prediction of the activation energy for NN bond homolysis in the hydrazines. Measured rate constants for UDMH and TMH bear this out, but the rate constant for MMH does not. This and other evidence lead to the conclusion that MMH decomposes via molecular concerted elimination of NH3 and H2 not and by NN bond scission. The following values are preferred from this work (θ = 2.303RT in kcal/mole). Mode of decomposition is N—N bond scission unless noted otherwise in parenthesis:

.
The rate of the gas phase iodination of cyclobutane. The heat of formation of the cyclobutyl radical
Authors: McMillen D. F. , Golden D. M. , Benson S. W. 
Published: January 2005

AbstractThe gas phase iodination of cyclobutane was studied spectrophotometrically in a static system over the temperature range 589° to 662°K. The early stage of the reaction was found to correspond to the general mechanism

where the Arrenius parameters describing k1 are given by log k1/M−1 sec−1 = 11.66 ± 0.11 – 26.83 ± .31/θ, θ = 2.303RT in kcal/mole. The measured value of E1, together with the fact that E−1 = 1 ± 1 kcal/mole, provides ΔH(c‐C4H7.) = 51.14 ± 1.0 kcal/mole, and the corresponding bond dissociation energy, D(c‐C4H7H) = 96.8 ± 1.0 kcal/mole. A bond dissociation energy of 1.8 kcal/mole higher than that for a normal secondary CH bond corresponds to one half of the extra strain energy in cyclobutene compared to cyclobutane and is in excellent agreement with the recent value of Whittle, determined in a completely different system. Estimates of ΔH and entropy of cyclobutyl iodide are in very good agreement with the equilibrium constant K12 deduced from the kinetic data. Also in good agreement with estimates of Arrhenius parameters is the rate of HI elimination from cyclobutyl iodide.
Reaction of methyl radicals with atomic oxygen
Authors: Morris E. D. , Niki H. 
Published: January 2005

AbstractThe reaction of hydrogen atoms with diazomethane was used as a source of methyl radicals to study the reaction of oxygen atoms with methyl radicals. This investigation verifies directly the earlier results that formaldehyde is a major product and that the rate constant is greater than 3×10−11cm3 molecule−1 sec−1.
The compilation and evaluation of chemical kinetics data; a descriptive survey of current efforts
Authors: Gevantman Lewis H. , Garvin David 
Published: January 2005

AbstractA description of the current range of activities being pursued in the compilation and evaluation of chemical kinetic data is given. The roles of individual scientists, professional groups, and national and international programs are detailed. The special problems attending on kinetic parameters are enumerated and discussed. An appendix is included which gives a comprehensive list of compilations and evaluations extant in the field of chemical kinetics.
The very low‐pressure dehydrogenation of cis‐2‐butene. The activation energy for 1,4‐H2 elimination
Authors: Alfassi Ze'ev B. , Golden David M. , Benson Sidney W. 
Published: January 2005

AbstractPyrolysis of cis‐butene‐2 under conditions of very low pressure (VLPP) has been studied in the range of 1100–1300°K. The principal products are butadiene and H2, obtained in a unimolecular reaction. A competing reaction to form butene‐l accounts for from 10% to 40% of the overall decomposition over the range. Using a «tight» model for the transition state and RRKM theory yields a high‐pressure, unimolecular rate constant for the 1,4‐H2 elimination of

where θ = 2.303RT in kcal/mol. There is some surface reaction of butadiene at these temperatures to yield H2 + nonvolatile residue. Butene‐l proceeds to decompose irreversibly to allyl + methyl radicals which have been observed directly. Comparison with related reactions leads to the conclusion that orbital symmetry‐forbidden, 1,2‐H2 elimination from saturated organic compounds will have activation energies too high to observe.
Kinetic isotope effect in the protonation of anthracenide salts by MeOH and MeOD role of counterions and solvents
Authors: Rainis A. , Szwarc M. 
Published: January 2005

AbstractKinetics of protonation of Li+, Na+, K+, and Cs+ salts of anthracene radical anions (A−·,Cat+) and dianions (A2−, 2Cat+) by MeOH and MeOD in tetrahydrofuran (THF) and dimethoxyethane (DME) led to the determination of the isotope effect (kH/kD) in the following reactions:

Studies of cation and solvent influence on the rate constants of these reactions and on the magnitude of the isotope effect permitted us to draw some conclusions about the structure of the pertinent transition states. It seems that only the tight A−·,Na+ pairs participate in the protonation, and on this basis the fraction of tight ion paris of A−·,Na+ in DME was estimated. Our results have been compared with data reported in the literature.
The reaction of OH with NO
Authors: Sie B. K. T. , Simonaitis R. , Heicklen J. 
Published: January 2005

AbstractMixtures of N2O, CO, and NO in excess H2 were photolyzed at 213.9 nm and 298°K. The initially formed O(1D) atoms from the photolysis of N2O abstract an H atom from H2 permitting a study of the competition:

equation image

From the CO2 yield the relative rate coefficient k1/k2 is obtained. It is found to be slightly dependent on pressure for total pressures (mainly H2) of 95.5 to 768 torr. However, the values are near the high‐pressure limiting value which is found by extrapolation to give k1∞ = 1.2 × 10−11 cm3/sec based on k2∞ = 3.55 × 10−13 cm3/sec.
H2 formation in the reaction of O(1D) with CH4
Authors: Jayanty R. K. M. , Simonaitis R. , Heicklen Julian 
Published: January 2005

AbstractThe reaction of O(1D) with CH4 was studied to determine the efficiency of H2 production in a direct process, and it was found to be 0.11 ± 0.02. Thus the two channels which account for all of the reaction between O(1D) and CH4 in the gas phase are

equation image
Gas‐phase hydrogen abstraction from asymmetrically halogenated ethanes by chlorine atoms
Authors: Martens G. J. , Godfroid M. , Delvaux J. , Verbeyst J. 
Published: January 2005

AbstractThe hydrogen abstraction from asymmetrically fluorinated and chlorofluorinated ethanes by chlorine atoms has been investigated in the gas phase between 264 and 333°K using the competition method. Arrhenius parameters for the reaction on both sites of the molecules are discussed.
Quenching of N2(A3Σu+) by O2, O, N, and H
Authors: Dunn O. J. , Young R. A. 
Published: January 2005

AbstractMetastable N2(A3Σu+), υ = 0, υ = 1, molecules are produced by a pulsed Tesla‐type discharge of a dilute N2/Ar gas mixture. Rate coefficients for quenching these metastable levels by O2, O, N, and H were obtained by time‐resolved emission measurements of the (0, 6) and (1, 5) Vegard–Kaplan bands. In units of cm3/mole · sec at 300°K and with an experimental uncertainty of ±20%, these rate coefficients for N2(A3Σu+) are

Within the limits of error these coefficients apply to quenching N2(A3Σu+) υ′ = 1 as well.
Rate constants of elementary reactions in the high temperature system of nitric oxide and hydrogen
Authors: Ando H. , Asaba T. 
Published: January 2005

AbstractThe consumption of nitric oxide in the shock‐heated nitric oxide, hydrogen, and argon system had been studied and modeled as the chain‐branching process containing the reaction H + NO ⇀ N + OH (k3) as a slow‐branching step. Through the computer simulation method the authors clarified the role of the initiation reaction H2 + NO ⇀ HNO + H (k1) in the system and obtained the rate constants of k1 and k3 as k1 = 1013.5±0.15 exp (−55.2 kcal/RT) and k3 = 1013.7±0.15 exp (−48.7 kcal/RT) (cm3/mole·sec), respectively. k1 was one order larger than the value obtained in the flame experiment by Halstead and Jenkins.
The effect of alkyl group substitution on the rate of thermal isomerization of small ring compounds
Authors: Solly Richard K. , Cain Edward N. 
Published: January 2005

AbstractThe thermal isomerization of 1‐chloro‐4‐methylbicyclo[2.2.0]hexane and 1‐chloro‐4‐lthylbicyclo[2.2.0]hexane has been studied in the gas phase and in tetrachloroethylene and o‐dichlorobenzene solvents over the temperature range of 409–512°K. Good first‐order kinetics yield the following Arrhenius equations: log kg/(sec−1) = (13.86 ± 0.03) − (36.90 ± 0.07)/middot; log ka/(sec−1) = (13.55 ± 0.31) − (35.50 ± 0.13)/θ log kb/(sec−1) = (13.55 ± 0.15) − (35.87 ± 0.06)/θ for the 4‐methyl derivative, and log ka/(sec−1) = (13.68 ± 0.29) − (36.19 ± 0.13)/· log kb/(sec−1) = (13.55 ± 0.15) − (35.87 ± 0.06)/θ for the 4‐ethyl derivative. The subscripts g, a, and b refer to the gas phase, tetrachloroethylene, and o‐dichlorobenzene as solvents, respectively, θ = 2.303 RT kcal/mole, and the error limits are least squares deviations. The activation energy is increased by 1.2 ± 0.5 kcal/mole for a methyl group and 1.5 ± 0.5 kcal/mole for an ethyl group with respect to the unsubstituted bridgehead compound. With reference to the reported Arrhenius parameters for all bicyclo[2.2.0]hexane isomerizations, it is shown that this increase in activation energy with alkyl substitution is not due to the steric interaction in the transition complex. It is postulated that the ground‐state reactant bicyclo[2.2.0]hexane molecules are stabilized by alkyl substitution. This ground‐state alkyl stabilization of small ring compounds may also account for an increase in the activation energy on pyrolysis of alkyl substituted cyclopropanes and cyclobutanes.
Kinetics of the heterogeneous electron transfer reaction of triplet pyrene in micelles to Br2− radicals in aqueous solution
Authors: Frank A. J. , Grätzel M. , Henglein A. , Janata E. 
Published: January 2005

AbstractA combined flash photolysis and pulse radiolysis experiment was carried out to produce triplet pyrene (P) molecules in micelles of cetyltrimethylammonium bromide and Br2− in the surrounding aqueous medium. The reaction 3Pmic + Br
→ P + 2 Br− was followed by optical absorption measurements in the 10−8−10−4–sec range. This reaction possesses a “fast” and a “slow” component with respective rate constants of 2.3 × 106 sec−1 and 1 × 109M−1 · sec−1.The fast component is related to the probability of a Br2− radical meeting a triplet pyrene containing micelle on the first encounter (only 16% of the micelles contained a triplet molecule). Reactions involving more than one Br2− radical–micelle encounter are ascribed to the slow component. The presence of two components reflects the fact that the residence time of a Br2− radical in the vicinity of a cationic micelle is substantially longer than the diffusion time of the radical between micelles. Thus the conditions met in micellar chemistry differ dramatically from those in ordinary solution kinetics where the encounter time is generally much shorter than the time between encounters. Some considerations on the energetics of this electron transfer reaction are also presented.
An investigation of nonequilibrium kinetic isotope effects in chemically activated vinyl radicals
Authors: Keil D. G. , Lynch K. P. , Cowfer J. A. , Michael J. V. 
Published: January 2005

AbstractNew experimental data have been obtained for H + C2H2, D + C2H2, H + C2D2, and D + C2D2 at room temperature. Two previously described apparatus were used in order to measure the pressure dependence of the reactions. The absolute rate constants are compared to results from other laboratories. The present results and those of Payne and Stief are used to obtain the high‐pressure limiting rate constant at room temperature. When the activation energy from the work of Payne and Stief is considered, it is shown that the A factor for H + C2H2 is too low by a factor of ∼20. If a transmission coefficient is introduced which is constant for all isotopic variations, the pressure dependence can be explained in terms of the randomly energized radicals. RRKM theory is then invoked to explain the observed statistical nonequilibrium kinetic isotope effects.
Kinetics and mechanism of the gas‐phase reaction of O(3P) atoms with acetone
Authors: Lee J. H. , Timmons Richard B. 
Published: January 2005

AbstractThe kinetics of the reaction of O(3P) atoms with acetone were investigated using fast flow methods. The reaction was studied over a temperature range of 298 to 478°K. The specific rate constant obtained was (1.9 ± 0.4) × 1012 exp(—5040 ± 180/1.987 T) cm3/mol·sec. The observation of a sizable primary H/D kinetic isotope effect in comparing rates of CH3COCH3 and CD3COCD3 led to the conclusion that the major reaction channel involves H atom abstraction, namely,

The rather low Arrhenius preexponential factor obtained in this reaction is compared and contrasted with those reported for other reactions of O(3P) with low molecular weight compounds.
The very low‐pressure pyrolysis of phenyl ethyl ether, phenyl allyl ether, and benzyl methyl ether and the enthalpy of formation of the phenoxy radical
Authors: Colussi A. J. , Zabel F. , Benson S. W. 
Published: January 2005

AbstractA value of the enthalpy of formation of the phenoxy radical in the gas phase, ΔH°,298K (ϕO·, g) = 11.4 ± 2.0 kcal/mol, has been obtained from the kinetic study of the unimolecular decompositions of phenyl ethyl ether, phenyl allyl ether, and benzyl methyl etherTrivial names for ethoxy benzene, 2‐propenoxy (allyloxy) benzene, and α‐methoxytoluene, respectively
at very low pressures. Bond fission, producing phenoxy or benzyl radicals, respectively, is the only mode of decomposition in each case. The present value leads to a bond dissociation energy BDE(ϕO—H) = 86.5 ± 2 kcal/mol,1 kcal = 4.18674 kJ (absolute)
in good agreement with recent estimates made on the basis of competitive oxidation steps in the liquid phase. A comparison with bond dissociation energies of aliphatic alcohols, BDE(RO—H) = 104 kcal/mol, reveals that the stabilization energy of the phenoxy radical (17.5 kcal/mol) is considerably greater than the one observed for the isoelectronic benzyl radical (13.2 kcal/mol). Decomposition of phenoxy radicals into cyclopentadienyl radicals and CO has been observed at temperatures above 1000°K, and a mechanism for this reaction is proposed.
Kinetics of the Fe3+ ion–H2O2 reaction: Steady‐state and terminal‐state analysis
Authors: Kremer Mordechai L. , Stein Gabriel 
Published: January 2005

AbstractComputer calculations of the kinetics of the ferric ion catalyzed decomposition of H2O2 by Walling and Weil are not in contradiction to the “complex mechanism.” The examination of their results reveals that their simulations correspond to the terminal state of the system in which the secondary complex between Fe3+ and H2O2 becomes stabilized.
Kinetics of gas‐phase addition reactions of methyl radicals. I. Addition to ethylene, acetylene, and benzene
Authors: Holt Pauline M. , Kerr J. Alistair 
Published: January 2005

AbstractThe reactions have been studied by a mass‐balance method involving the photolysis of small amounts of biacetyl in the presence of a large excess of isobutane containing a small proportion of the unsaturated substrate. The following Arrhenius parameters have been derived:

Temperature

E
log A
range

Reaction
(kcal/mol)
(1./mol·sec)
(°K)

ĊH3 + C2H4 → Ċ3H7
7.3 ± 1.0
8.32 ± 0.5
350 – 500

ĊH3 + C2H2 → Ċ3H5
7.7 ± 1.5
8.79 ± 0.8
379 – 487

ĊH3 + C6H6 → C7H9
7.6 ± 1.0
8.79 ± 0.5
372 – 484

The results for methyl addition to ethylene are based on previous determinations by other techniques as well as the present studies. The results for methyl addition to acetylene and benzene are derived solely from the present experiments and are calculated relative to a rate constant of log k2(l./mol·sec) = 7.42 ‐ (7.1/θ) for the reference reaction (2), ·H3 + (CH3)3CH → CH4 + ·4H9.
Kinetics and mechanism of the reaction H + CH3ONO
Authors: Moortgat G. K. , ŠSlemr F. , Warneck P. 
Published: January 2005

AbstractThe reaction of hydrogen atoms with methyl nitrite was studied in a fast‐flow system using photoionization mass spectrometry and excess atomic hydrogen. The associated bimolecular rate coefficient can be expressed by

in the temperature range of 223‐398°K. NO, CH3OH, CH4, C2H6, CH2O, and H2O are the main products; OH and CH3 radicals were detectable intermediates. The mechanism was deduced from the observed product yields using normal and deuterated reactants. The primary reaction steps were identified as
equation image
followed by a rapid unimolecular decomposition of CH2ONO into CH2O and NO. Since the extent of reaction channel (1b) could not be determined independently, only extreme limits could be obtained for the individual contributions of the two channels of reaction (3) which follows the generation of CH3O radicals:
equation image
The most probable values, k3a/k3 = 0.31 ± 0.30 and k3b/k3 = 0.69 ± 0.30, support the previous results on this reaction, although the range of uncertainties is much greater here.
The very low‐pressure pyrolysis of phenyl methyl sulfide and benzyl methyl sulfide. The enthalpy of formation of the methylthio and phenylthio radicals
Authors: Colussi A. J. , Benson S. W. 
Published: January 2005

AbstractThe kinetics and mechanisms of the unimolecular decompositions of phenyl methyl sulfide (PhSCH3) and benzyl methyl sulfide (PhCH2SCH3) have been studied at very low pressures (VLPP). Both reactions essentially proceed by simple carbon‐sulfur bond fission into the stabilized phenylthio (PhS·) and benzyl (PhCH2·) radicals, respectively. The bond dissociation energies BDE(PhS‐CH3) = 67.5 ± 2.0 kcal/mol and BDE(PhCH2‐SCH3) = 59.4 ± 2 kcal/mol, and the enthalpies of formation of the phenylthio and methylthio radicals ΔH° ,298K(PhS·, g) = 56.8 ± 2.0 kcal/mol and ΔH°f, 298K(CH3S·, g) = 34.2 ± 2.0 kcal/mol have been derived from the kinetic data, and the results are compared with earlier work on the same systems. The present values reveal that the stabilization energy of the phenylthio radical (9.6 kcal/mol) is considerably smaller than that observed for the related benzyl (13.2 kcal/mol) and phenoxy (17.5 kcal/mol) radicals.
Primary processes in the 147‐nm photolysis of 1,1‐dichloroethane
Authors: Salomon D. , Kirk A. W. , Tschuikow‐Roux E. 
Published: January 2005

AbstractThe room temperature photolysis of 1,1‐dichloroethane at 147 nm in the pressure range of 1.34‐196.2 torr is characterized almost entirely by the molecular elimination of HCl, Cl2, and small quantities of H2. Acetylene is also produced. While it is possible that the C2H2 arises, in part, from the decomposition of vibrationally excited ground states of C2H3Cl and/or C2H4, in this particlar case serious consideration has to be given to alternative explanations where the products of the primary processes are formed in electronically excited states. The ±, elimination of molecular chlorine is not inconsistent with an increased degree of ClCl interaction predicted for a «Rydberg «state of 1,1‐C2H4Cl2. Varying small yields of CH4 are observed in the presence and absence of NO. The effect of large pressures of CF4 on the quantum yields of the major products is extremely small. The extinction coefficient for 1,1‐C2H4Cl2 at 147 nm and 296°K is 246 ± 29 cm−1 ± atm−1.
Kinetics of the gas‐phase elimination of isopropyl α‐halo acetates and the taft correlation
Authors: Chuchani Gabriel , Hernandez Jose A. , Yepez Magdalia , Alonso Miguel E. 
Published: January 2005

AbstractThe gas‐phase pyrolysis of three secondary acetates in the temperature range of 290‐350°C and the pressure range of 40‐236 mm Hg reveals a homogeneous first‐order law and unimolecular elimination. The rate constants are given by the following Arrhenius equations: isopropyl fluoroacetate:

isopropyl chloroacetate:

isopropyl iodoacetate:

The differences in rates I > Br > Cl > F apparently question previous assumptions where the pyrolyses of esters follow the same sequence as acid strength. The experimental data give a good correlation with σ* values, where ρ* = ‐1.85 at 330°C. Some kind of discrete bond polarization at the CαO bond of the acetate in the cyclic transition state seems to be involved in this type of reactions.