bluuebunny/crossref_metadata_2025_split huggingface dataset:
The homogeneous gas phase H2D2 metathesis at room temperature: Reaction induced by specific vibrational excitation
Authors: Bauer S. H. , Lederman D. M. , Resler E. L. , Fisher E. R. 
Published: January 2005

AbstractWe have demonstrated that reactions for which substantial activation energies are needed can be induced to occur at room temperature via specific vibrational excitation. Indeed, the indications are that the atom‐switching reactions for which Ea > 25 kcal take place with high probability only when the activation energy is localized in the vibrational mode. In this preliminary report on the utilization of the stimulated Raman effect to generate substantial populations in the critical vibrational states required for the homogeneous atom exchange between H2 and D2, we first summarized the historical development of the concept. The experimental arrangement is then described and the analytical results tabulated; the observed dependence on relative concentrations is semiquantitatively rationalized on the basis of a model proposed in 1964. Independent shock tube and molecular beam investigations were similarly accounted for. Attention is called to the discrepancy between the generally concordant experimental results and the ab initio quantum mechanical calculations of the potential energy surface for 4H atoms.
The liquid‐phase oxidation of 2,4‐dimethylpentane
Authors: Mill Theodore , Montorsi Giorgio 
Published: January 2005

AbstractThe initiated oxidation of 2, 4‐dimethylpentane in the neat liquid phase at 100°C with 760 torr O2 gives more than 90% of a mixture of 2,4‐dihydroperoxy‐2,4‐dimethylpentane and 2‐hydroperoxy‐2, 4‐dimethylpentane in a ratio of 7:1. The rate of oxidation depends closely on the [initiator]1/2, consistent with a mechanism in which chain termination occurs mostly by interactions of two 2‐hydroperoxy‐2, 4‐dimethyl‐4‐pentylperoxy radicals. 2, 4‐Dimethylpentane oxidizes only one sixth as fast as isobutane at the same rate of initiation at 100°C. In cooxidations of the same hydrocarbons, it is 0.71 as reactive as isobutane toward any of the peroxy radicals involved. 2, 4‐Dimethylpentane oxidizes 7.5 times as fast at 1.25°C as at 50°C for the same rate of initiation, but the ratio of dihydroperoxide to monohydroperoxide increases only from 5 to 7, corresponding to a difference in activation energy between intramolecular and intermolecular abstraction of 1 kcal/mole. The overall activation energy (Ep – Et/2) is 10.7 kcal/mole, close to the value of 12 kcal/mole found for isobutane. Absolute values for Ep, Et, kp, kr, and kt were derived. Ring closure of 2‐hydroperoxy‐2, 4‐methyl‐4‐pentyl radicals to oxetane, not detected during oxidation, was observed when this radical was generated at 100°C in the near‐absence of oxygen. The ratio of rate constants for oxetane formation and addition of oxygen to the 2, 4dimethyl‐2‐hydroperoxy‐4‐pentyl radical is about 5.4 × 10−5 M at 100°C. Thus, ring closure to oxetane is too slow to compete with addition of oxygen above ˜200 torr. At 100°C, 2, 3‐dimethylbutane gave no evidence of any intramolecular abstraction. However, 2, 3‐dimethylpentane did give at least 12% 2, 4‐glycol or hydroxyketone.
Kinetics of the reactions of cyclopropane derivatives. III. Gas‐phase unimolecular isomerization of cyclopropyl cyanide to the cyanopropenes
Authors: Luckraft D. A. , Robinson P. J. 
Published: January 2005

AbstractCyclopropyl cyanide isomerizes in the gas phase at 660°–760°K and 2–89 torr to give mainly cis‐ and trans‐crotonitrile and allyl cyanide, with traces of methacrylonitrile. The reactions are first order, homogeneous, and unaffected by the presence of radical‐chain inhibitors. The rate constants are given by Overall:

cis‐Crotonitrile:

trans‐Crotonitrile:

Allyl cyanide:

where the error limits are standard deviations. On the basis of a biradical mechanism, it is deduced that the CHCN radical center is resonance stabilized by ca. 30 kJ mole−1. Approximate equilibrium data are given for interconversion of the 1‐ and 3‐cyanopropenes.
Kinetics of the I2‐catalyzed isomerization of allyl chloride to cis‐ and trans‐1‐chloro‐1‐propene. The stabilization energy of the chloroallyl radical
Authors: Alfassi Ze'ev B. , Golden David M. , Benson Sidney W. 
Published: January 2005

AbstractThe I2‐catalyzed isomerization of allyl chloride to cis‐ and trans‐ l‐chloro‐l‐propene was measured in a static system in the temperature range 225–329°C. Propylene was found as a side product, mainly at the lower temperatures. The rate constant for an abstraction of a hydrogen atom from allyl chloride by an iodine atom was found to obey the equation log [k,/M−1 sec−1] = (10.5 ± 0.2) −; (18.3 ± 10.4)/θ, where θ is 2.303RT in kcal/mole. Using this activation energy together with 1 ± 1 kcal/mole for the activation energy for the reaction of HI with alkyl radicals gives DH0 (CH2CHCHClH) = 88.6 ± 1.1 kcal/mole, and 7.4 ± 1.5 kcal/mole as the stabilization energy (SE) of the chloroallyl radical. Using the results of Abell and Adolf on allyl fluoride and allyl bromide, we conclude DH0 (CH2CHCHFH) = 88.6 ± 1.1 and DH0 (CH2CHCHBrH) = 89.4 ± 1.1 kcal/ mole; the SE of the corresponding radicals are 7.4 ± 2.2 and 7.8 ± 1.5 kcal/mole. The bond dissociation energies of the CH bonds in the allyl halides are similar to that of propene, while the SE values are about 2 kcal/mole less than in the allyl radical, resulting perhaps more from the stabilization of alkyl radicals by α‐halogen atoms than from differences in the unsaturated systems.
The thermal decomposition of biacetyl
Authors: Knoll H. , Scherzer K. , Geiseler G. 
Published: January 2005

AbstractThe thermal decomposition of biacetyl has been studied at small percentage conversion over the temperature range 375‐417°C. For these conditions, an almost quantitative mass balance was obtained by gas‐chromatographic analysis. The following equation was obtained for the overall reaction
equation image
Between 240° and 277°C, the decomposition of biacetyl initiated by methyl radicals has also been studied. As source of radicals, the thermolysis of azomethane was used. Moreover, the Arrhenius parameters of the following reactions were determined:
equation image
where A is in sec−1 for reaction (1) and in cm3mole−1 sec−1 for reactions (3) and (4); E is in kcal/mole. Evidence is provided that the displacement reaction (4) proceeds by a two step mechanism.
The radiolysis of mixtures of carbon monoxide and hydrogen
Authors: Beattie W. H. 
Published: January 2005

AbstractThe self‐radiolysis of mixtures of CO and tritium (3H2) has been studied at pressures of 0.25 to 1.0 atmospheres, temperatures of −198° to +100°C, and in the presence of added H2O or CO2. The products of decomposition are CO2, 3H2O, C3H4, C23H4, and a white polymer believed to be polyformaldehyde. Initial rates and G values were measured and compared with rates of ion pair formation. The rates of formation of both CO2 and C3H4 are independent of temperature and proportional to the energy absorbed in the 3H2.
A thermal initiation correction to Shepp's rotating sector theory
Authors: Arthur N. L. , Donchi K. F. , de Martinis C. 
Published: January 2005

AbstractShepp's rotating sector theory for determining radical recombination rate constants, kb, has been modified to take account of radical production by a concurrent thermal reaction. A theoretical sector curve expression has been derived which gives the average radical concentration under intermittent illumination as a function of α, the ratio of first‐to second‐order radical removal rates, n, the ratio of thermal initiation to photoinitiation, and β, the ratio of the flash time to the half time of second‐order radical removal. Analysis of the sector curves generated by the modified theory shows that n has a greater effect on kb than α and that the rotating sector method should be applied only to those photochemical systems in which termination by first‐order processes is less than 34% (α = 0.52) and thermal initiation is less than 2% (n = 0.02).
Kinetic solvent isotope effect for aromatic nucleophilic substitution in mixtures of EtOH and EtOD
Authors: Cattania M. G. , Beltrame P. 
Published: January 2005

AbstractRate coefficients for the ethoxydechlorination of 1‐chloro‐2,4‐dinitrobenzene were measured in mixtures of EtOH and EtOD of different deuterium atom fraction n (n = 0., 0.259, 0.377, 0.581, 0.767, 0.958), at 25°C. The extreme solvent isotope effect, obtained by different extrapolation procedures, is (kD/kH) = 1.90 ± 0.02. The curved variation of kn/kH with n is interpreted by fractionation factor theory in terms of hydrogen‐bonding solvation of ethoxide ion and transition state.
The self‐inhibited pyrolysis of isobutane
Authors: Konar R. S. , Marshall R. M. , Purnell J. H. 
Published: January 2005

AbstractThe pyrolysis of isobutane was investigated in the ranges of 770° to 855°K and 20 to 150 Torr at up to 4% decomposition. The reaction is homogeneous and strongly self‐inhibited. A simple Rice‐Herzfeld chain terminated by the recombination of methyl radicals is proposed for the initial, uninhibited reaction. Self‐inhibition is due to abstraction of hydrogen atoms from product isobutene giving resonance‐stabilized 2‐methylallyl radicals which participate in termination reactions. The reaction chains are shown to be long. It is suggested that a previously published rate constant for the initiation reaction (1)

is incorrect and the value k1 = 1016.8 exp (−81700 cal mol−1/RT)s−1 is recommended. The values of the rate constants for the reactions (4i)

(4t)

(8)

are estimated to be

and

From a recalculation of previously published data on the pyrolysis of isobutane at lower temperatures and higher pressures, the value k11c, = 109.6 cm3 mol−1 s−1 is obtained for the rate constant of recombination of t‐butyl. A calculation which is independent of any assumed rate constants or thermochemistry shows that the predominant chain termination reaction is the recombination of two methyl radicals in the conditions of the present work and the recombination of two t‐butyl radicals in those of our previous study at lower temperatures and higher pressures.
ESR studies on the formation of p‐benzosemiquinone anions over manganese dioxide
Authors: Fukuzumi Shun‐Ichi , Ono Yoshio , Keii Tominaga 
Published: January 2005

AbstractThe reaction between a hydroquinone aqueous solution and manganese dioxide has been investigated by electron paramagnetic resonance spectroscopy. A very stable p‐benzosemiquinone anion is formed when an aqueous solution of hydroquinone is passed through a column of manganese dioxide. The kinetics for the reaction between hydroquinone and manganese dioxide follow the equation

where A0 is the initial concentration of hydroquinone, C is the concentration of p‐benzosemiquinone anions, W is the amount of manganese dioxide, F is the feed rate of a hydroquinone aqueous solution, and k10 and k20 are constants; k10 = 3.1 × 10−2 (cm3/g MnO2· min), k20 = 3.2 (cm3/g MnO2·min).A mechanism for the reaction is proposed such that Mn(IV) in manganese dioxide is reduced to Mn(II) with hydroquinone from which the semiquinone anion is formed via a neutral semiquinone. The formation of semiquinone anions from several substituted hydroquinones is also discussed.
The role of solvent in some oxygen‐transfer reactions of peroxy compounds
Authors: Ibne‐Rasa Khairat M. , Edwards John O. 
Published: January 2005

AbstractSolvent–solute interactions in the peroxyacid oxidations are believed to be specific rather than electrostatic in nature. The kinetic solvent effects reported for the oxidations of organic sulfides, olefins, acetylenes, nitrosobenzenes, thioketones, and aryl sulfines reveal that in each case the rates are fast in nonbasic solvents (e.g., benzene, nitrobenzene, and halogenated hydrocarbons) relative to those in basic solvents such as DMF, dioxane, and alcohols. The rates in CF3CH2OH and aqueous or partially aqueous media are again higher than those in the basic solvents. This remakably similar pattern of sensitivity of rates to changes in the solvent nature appears to be characteristic of these oxidations as demonstrated by the existence of linear free‐energy relationship. The behavior is best understood in terms of cyclic transition states for these oxidations in which charge separation is avoided by intra‐ or intermolecular hydrogen bonding depending on the nature of the solvent. Solvent effects on sulfoxide oxidation and on oxidations by hydrogen peroxide and t‐butylhydroperoxide are also briefly discussed.
Rate constants of the combination of methyl radicals with nitric oxide and oxygen
Authors: Laufer Allan H. , Bass Arnold M. 
Published: January 2005

AbstractRate constants for the combination of methyl radicals with NO and O2 have been measured by flash photolysis of azomethane coupled with product analysis by gas chromatography. Values of the rate constants have been obtained over the pressure region from 50 to 700 torr with He, N2, and Ar as quenching molecules.The high‐pressure limits were obtained through an RRKM model calculation and were found to be

The rate constants were measured relative to the methyl combination reaction k1 with k1 = 9.5 × 10−11 cm3/molec · sec. The RRKM model suggests D0(CH3O2) = 32 ± 3 kcal/mole.
Model for a three‐center decomposition reaction. I. Perfluorodiazirine
Authors: Tschuikow‐Roux E. , Jung K. H. 
Published: January 2005

AbstractA semiempirical approach has been used to evaluate rate parameters for a three‐center decomposition reaction from the point of view of transition state theory, with perfluorodiazirine serving as the prototype molecule. Several activated complex models are considered in which the reaction coordinate is chosen as the ∡ NCN bending mode. The constraints imposed include the principle of concerted bond‐order conservation in passing from the initial to the final state, and use is made of empirical bond order–bond length and bond order–force constant relationships. The geometric configuration of the transition state sought is one which conforms with the lowest energy path and is also consistent with the observed entropy of activation. The potential energy of activation is taken as the optimum difference in binding energies (based on the INDO method) between the transition and initial states, and the critical energy is obtained by applying a correction for the zero‐point energy difference, derived from normal coordinate analysis. Satisfactory agreement is found in the case of the activated complex model for which the total bond order is conserved and bonds undergoing rupture are assigned a fractional bond order (FBO) of 2/3, derived from the postulate (FBO) = α/β whe re α(=2) is the number of bonds breaking, and β(=3) is the number of bonds undergoing change in the ring opening.
Thermal decomposition of trimethylene sulfone and 3‐methyl sulfolane
Authors: Cornell Douglas , Tsang W. 
Published: January 2005

AbstractTrimethylene sulfone and 3methyl sulfolane have been pyrolyzed using a modification of the toluene flow method and a comparative rate technique. The main decomposition reactions are
equation image
where k1=1016.1±0.3 exp(−28,100±500/T) sec−1 and k2=1016.1±0.4 exp(−33,200±750/T) sec−1.
The kinetics of the decarboxylation of n‐butylmalonic acid in alkanols and amines
Authors: Clark Louis Watts 
Published: January 2005

AbstractRate constants and activation parameters are reported for the decarboxylation of n‐butylmalonic acid in four normal alkanols (hexanol1, octanol1, decanol1, and dodecanol1) and in five amines (aniline, N‐methylaniline, N‐ethylaniline, N‐n‐propylaniline, and N‐n‐butylaniline). Both ΔH‡ and ΔS‡ of the reaction in both homologous series decrease regularly with increasing length of the hydrocarbon chain of solvent. If we compare data for the reaction in alkanol–amine pairs containing the same total number of carbon atoms in the molecule, we find that the ΔH‡ values are identical, but that the value of ΔS‡ is 0.8 eu/mole higher for the reaction in the amines as compared with the alcohol. The rate constant, at all temperatures, is 1.5 times as large in the amine as it is in the corresponding alcohol. Empirical equations are deduced relating the parameters ΔH‡ ΔS‡ ΔG‡ and k of the reaction to the parameters n and T, where n is the total number of carbon atoms in the solvent molecule and T is the absolute temperature. The results reported herein are compared with previously reported data for malonic acid.
The homogeneous reaction CD4 + NH3 → CD3H + NH2D: The effect of ethane impurities
Authors: Lifshitz Assa , Schechner Pinhas 
Published: January 2005

AbstractThe homogeneous exchange reaction between tetradeutero methane and ammonia was studied behind reflected shocks in a single‐pulse shock tube over the temperature range of 1300–1800°K. The rate of production of CD3H at the early stages of the reaction in mixtures ranging between 1‐4.5% NH3 and 1–4.3% CD4 in argon is given by d[CD3H]/dt=kb [CD4]0[NH3]0, where kb=8 × 1016 exp (−65.3 × 103/RT) cm3/mole·sec. This activation energy is considerably lower than the one that may be expected on the basis of a pure free radical mechanism. It is rationalized by C2D6 impurities in the methane. No clear answer can be obtained regarding the role of a four‐center intermediate in this reaction.
A study of the mechanism and kinetics of the reaction of O(3P) atoms with propane
Authors: Harker Alan B. , Burton C. S. 
Published: January 2005

AbstractThe mechanism and kinetics of the reaction of O(3P) atoms with propane were investigated using molecular modulation spectroscopy, with the O(3P) atoms being generated by the Hg photosensitized decomposition of N2O. The absorption spectrum of the X2II3/2 state of OH was observed in the ultraviolet between 307 and 309 nm, and it was confirmed that OH was the product of the O(3P) reaction with propane. The rate constants for the reactions of O(3P) and OH with propane were determined to be 3.9±0.7±1010 and 1.19±0.05±1012 cm3/mole·sec, respectively, at T=56±5°C.
VLPP unimolecular rate theory
Authors: Barker John R. 
Published: January 2005

AbstractThe exact theory is derived for the thermal unimolecular decomposition of gas‐phase molecules activated and deactivated exclusively through heterogeneous collisions with the walls of a spherical vessel. This theory is appropriate for the treatment of very‐low‐pressure pyrolysis (VLPP) experiments and other experiments carried out at very low pressures. It is shown, however, that the exact theory is closely approximated by ordinary gas‐phase unimolecular rate theory and that for practical application to experiments the results of both theories are indistinguishable.
The thermal unimolecular decompositions of C2H5Cl, i‐C3H7Cl, and t‐C4H9Cl
Authors: Heydtmann Horst , Dill Bernd , Jonas Reinhard 
Published: January 2005

AbstractThe thermal decompositions of ethyl chloride, iso propyl chloride, and tertiary butyl chloride were studied in a static system in the pressure range of 0.1–300 torr. The following Arrhenius equations for the high‐pressure limit were obtained:
equation image
The pressure dependence of the first‐order rate constant (falloff) for these three unimolecular dehydrochlorination reactions, starting with approximately equal kω values, by proper choice of temperature, is shifted to lower pressures with increasing molecular size:
equation image
Thermal isomerization of cis‐ or trans‐2‐butene. The unimolecular elimination of hydrogen from cis‐2‐butene around 500°C
Authors: Masson D. , Richard C. , Martin R. 
Published: January 2005

AbstractAn analytical and kinetic study of the thermal reaction of cis‐ or trans‐2‐butene has been performed in a static system over the temperature range of 480–550°C and at a low extent of reaction and initial pressures of 10–100 torr.The rate constant of the unimolecular cis–trans isomerization of cis‐2‐butene, determined under the conditions

(2.3 RT in cal/mole) is in good agreement with previous measurements made at lower pressures.A comparison between the formation rates of hydrogen from the thermal reactions of cis‐ and trans‐2 butene around 500°C leads to the rate constant value

(2.3 RT in cal/mole) for the unimolecular 1,4hydrogen elimination from cis2butene.
Thermal stability of alcohols
Authors: Tsang Wing 
Published: January 2005

Abstract3,3‐Dimethylbutanol‐2 (3,3‐DMB‐ol‐2) and 2,3‐dimethylbutanol‐2 (2,3‐DMB‐ol‐2) have been decomposed in comparative‐rate single‐pulse shock‐tube experiments. The mechanisms of the decompositions are
equation image
The rate expressions are

They lead to D(iC3H7H) – D((CH3)2(OH) CH) = 8.3 kJ and D(C2H5H) – D(CH3(OH) CHH) = 24.2 kJ.These data, in conjunction with reasonable assumptions, give

and
equation image
The rate expressions for the decomposition of 2,3‐DMB‐1 and 3,3‐DMB‐1 are

and
Comparison between experimental and calculated results on the decomposition of chemically activated alcohols
Authors: Tsang Wing 
Published: January 2005

AbstractThe life times of chemically activated alcohols have been determined using the high‐pressure unimolecular rate parameters for thermal decomposition of alcohols from shocktube studies and RRKM calculations. They are compared with literature numbers (from insertion of 0(1D) into hydrocarbons). It is suggested that in some cases singlet oxygen carries excess energy into the hydrocarbon. The consequences of such an assumption are explored and discrepancies with previously published conclusions discussed.
Reactions of methyl radicals with acetaldehyde and acetaldehyde‐d1. I. relative rates of atom abstraction reactions at 785°K
Authors: Bárdi I. , Bérces T. , Szilágyi I. 
Published: January 2005

AbstractThe role of ethenoxy radicals in the pyrolysis of CH3CDO was studied by mass spectrometric analysis of the isotopic composition of the methane, ethane, and recovered aldehyde. Experimental evidence was obtained for the formation of ethenoxy radicals and for their reaction with acetaldehyde.Mixtures of CH3CHO and CH3CDO were pyrolyzed in order to minimize H‐D scrambling in the methyl group of the aldehyde. A kinetic treatment of the methyl radical reactions

equation image

and

equation image

furnished the rate constant ratios (k2a + k2b)/k1a = 2.7 and k1b/k1a = 0.62 at 785°K. It is concluded that at the usual temperatures of CH3CHO pyrolysis the rate of alkyl hydrogen capture is comparable to that of formyl hydrogen abstraction.The results and conclusions are discussed and compared with previous work.
Kinetics of bimolecular chemical reaction by a modified diffusion equation
Authors: Kondo Shingo , Takano Yo 
Published: January 2005

AbstractIn order to describe the kinematical behavior of the bimolecular chmical reaction in a dilute solution of species characterized by a single diffusion coefficient and by some nonuniform spatial distribution of the active site, a diffusion equation with a simple sink term is derived by reducing the many‐body problem to a one‐body problem. The equation is normalized with the concentration of unreacted particles. The so‐called second‐order reaction rate constant can be calculated from the solution of the equation. The equation is applied to the intermolecular termination reaction of polymer radicals on the assumption of free draining. The reaction rate constant gradually decreases with time.