bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neighboring olefinic double‐bond participation in gas phase pyrolysis of some alkenyl chlorides
Authors: Chuchani Gabriel , Hernandeza. Jose A. , Martin Ignacio 
Published: January 2005

Abstract4‐Chloro‐1‐butene, 5‐chloro‐1‐pentene, and 6‐chloro‐1‐hexene have been shown to decompose, in a static system, mainly to hydrogen chloride and the corresponding alkadienes. In packed and unpacked clean Pyrex vessels the reactions were significantly heterogeneous. However, in a vessel seasoned with allyl bromide these reactions were homogeneous, unimolecular, and follow a first‐order law. The working temperature range was 389.6–480.0°C and with a pressure range of 53–221 Torr. The rate constants for the homogeneous reactions were expressed by the following Arrhenius equations: 4‐chloro‐1‐butene: logk(sec−1) = (13.79 ± 0.17) – (223.8 ± 2.1)kJ/mole/2.303RT; 5‐chloro‐1‐pentene: logk(sec−1) = (14.25 ± 1.20) – (238.4 ± 12.7)kJ/mole/2.303RT; and 6‐chloro‐1‐hexene: logk(sec−1) = (12.38 ± 0.22) – (209.6 ± 2.9)kJ/mole/2.303RT. The olefinic double bond has been found to participate in the rate of dehydrohalogenation of 4‐chloro‐1‐butene. The insulation of the CH2CH in chlorobutene by one or two methylene chains to the reaction center does not indicate neighboring group participation. The three‐membered conformation is the most favored structure for anchimeric assistance of the double bond in gas phase pyrolysis of alkenyl chlorides. The heterolytic nature of these eliminations is also supported by the present work.
The kinetics and the mechanism of the oxidation of carbon monoxide in the presence of hydrogen
Authors: Arustamyan A. M. , Shakhnazaryan I. K. , Philipossyan A. G. , Nalbandyan A. B. 
Published: January 2005

AbstractThe kinetics of the slow oxidation of CO in the presence of H2 have been studied above the second explosion limit for the mixture 2CO + O2 + X% H2 at the temperature range of 530–570°C, pressures from 300 to 530 torr, and hydrogen contents of 1.1, 2.8, and 5.7%. The second explosion limit has been experimentally determined for the mixture of 2CO + O2 containing 1.0, 3.0, and 5.7% H2. On the basis of the oxidation scheme of CO in the presence of H2, which includes the accepted mechanism of oxidation of hydrogen supplemented by the reactions in which CO takes part, the second explosion limit and the profiles of the slow reaction are calculated by computer methods. The agreement found between experimental and calculated values allows one to conclude that the scheme under consideration rather completely described the slow reaction above the second limit and the occurrence of the second explosion limit in the mixture CO–O2–H2. The rate constant for the reaction HO2 + CO → OH + CO2 was calculated from the experimental data and was found to agree with previous determinations.
Oxidation of cyanogen. II. The mechanism of the oxidation
Authors: Lifshitz Assa , Frenklach Michael 
Published: January 2005

AbstractA detailed investigation of the mechanism of cyanogen oxidation is presented. Recent induction time measurements of ignition in cyanogen–oxygen–argon mixtures behind reflected shocks are computer modeled to obtain an agreement between the experimental and calculated values. A 15‐step reaction scheme is suggested to reproduce the parameters E and βi in the experimental parametric relation: τ = 10αexp(E/RT)IICiβi. An explanation is offered to the very strong dependence of the induction time on the cyanogen concentration and the very weak dependence on the oxygen concentration. The sensitivity spectrum shows that the induction time is highly dependent on the O + C2N2 → NCO + CN and NCO + M → N + CO + M reactions (shortened) and the O + NCO → CO + NO and N + NCO → N2 + CO reactions (increased).
The thermal decompositions of carbamates. IV. The ethyl Nmethylcarbamate system
Authors: Daly N. J. , Ziolkowski F. 
Published: January 2005

AbstractEthyl Nmethylcarbamate decomposes thermally over the temperature range of 600–650 K by competing first‐order reactions, one forming methylamine, carbon dioxide, and ethylene, the other forming methyl isocyanate and ethanol. The first‐order rate constants are described in S1 units by the equations
equation image
where R = 1.986 cal/deg mol. The appareance of symdimethylurea among the products raised the possibility of gas‐phase transesterifications. These were ruled out by the study of the reactions of sym‐dimethylurea at 604 K which showed its behavior to be well explained by the rapid decomposition in the gas phase
equation image
which is reversed in the condensation stage in the analysis.
Study of the ethane oxidation reaction by the kinetic tracer method
Authors: Moshkina R. I. , Polyak S. S. , Sokolova N. A. , Masterovoi I. F. , Nalbandyan A. B. 
Published: January 2005

AbstractThe kinetics of ethane oxidation was studied at 320, 340, 353 and 380°C, mixture composition 2 C2H6 + 1 O2, and total pressure 609 torr. It was found that at 320°C CH2O and CH3CHO were branching agents. A series of experiments was conducted on 2C2H6 + O2 oxidation in the presence of 0.7% 14C‐labeled ethylene. The ethylene oxide was found to form only from C2H4, formaldehyde formed from C2H4 and C2H6; and CH3CHO, C2H5OH, and CH3OH formed only from ethane. The formation rates of C2H4, C2H4O, and CH2O were calculated by the kinetic tracer method. At 320°C the fraction of oxygen‐containing products formed from C2H4 was 16–18%, and at 353 and 380°C it was 30–40%.
Carbon kinetic isotope effect in the oxidation of methane by hydroxyl
Authors: Rust Fleet , Stevens C. M. 
Published: January 2005

AbstractThe carbon kinetic isotope effect in the reaction of CH4 with OH has an experimentally measured value of 1.003. The measurement was performed using a static system in which the source of OH was the gas‐phase photolysis of H2O2 with ultraviolet light produced by a high‐pressure mercury arc lamp. Implications for the tropospheric cycle of CH4 are considered briefly.
Thermal decomposition of ammonia in shock waves
Authors: Yumura M. , Asaba T. , Matsumoto Y. , Matsui H. 
Published: January 2005

AbstractThe thermal decomposition of ammonia was studied by means of the shock‐tube and vacuum ultraviolet absorption spectroscopy monitoring the concentration of atomic hydrogen. The rate constants of both the initiation reaction
equation image
and the consecutive reaction
equation image
were determined directly as

and

respectively.
Kinetics and mechanism of the autoxidation of pentaerythrityl tetraheptanoate at 180–220°C
Authors: Hamilton Edwin J. , Korcek Stefan , Mahoney Lee R. , Zinbo Mikio 
Published: January 2005

AbstractA kinetic and mechanistic study of the autoxidation of liquid pentaerythrityl tetraheptanoate (PETH) at 180–220°C has been carried out utilizing a stirred‐flow reactor. The results are consistent with the occurrence of a chain reaction scheme similar to that proposed for n‐hexadecane autoxidation, namely, the formation of monohydroperoxides by the intermolecular abstraction reaction (3), the formation of α,γ‐ and α,δ‐dihydroperoxides and α,γ‐ and α,δ‐hydroperoxyketones by intramolecular peroxy radical abstraction reactions (4) and (4*), the bimolecular termination of peroxy radicals, reaction (6), and the rapid conversion of α,γ‐hydroperoxyketones to the corresponding cleavage acids and methyl ketones, reaction (7). Comparisons of various rate parameters for the n‐hexadecane and PETH systems reveal that the values of k7 and (k3/H atom)/(2 k6)1/2 are within experimental uncertainties identical for the two systems at 180°C. The proposed reaction scheme includes the concurrent formation of hydroxy radicals and hydroperoxyketone species. The results of kinetic analysis and the experimentally observed isomer distributions of primary and secondary monohydroperoxide products at high and low oxygen pressures suggest that ≈60% of the hydrogen abstractions from PETH at high oxygen pressures occur by hydroxy radicals.
Rate constants for self‐ and cross terminations of transient radicals in solution by effect modulated electron spin resonance spectroscopy
Authors: Paul H. , Segaud C. 
Published: January 2005

AbstractIt is shown how electron spin resonance spectroscopy with modulated radical initiation can be used to analyze by purely spectroscopic means the second‐order termination kinetics of systems containing two different kinds of radicals. The technique is applied to species generated by photoreduction of acetone in tetraethoxy silane. The bimolecular self‐ and cross reactions of\documentclass{article}\pagestyle{empty}\begin{document}${\rm (CH}_{\rm 3} {\rm CH}_{\rm 2} {\rm O)}_{\rm 3} {\rm SiO\dot CHCH}_{\rm 3} (\dot R_1 )\,and\,(CH_3 )_2 \dot COH(\dot R_2 )$\end{document}are found to be encounter‐controlled processes. For the cross termination the often used relationk12= (4k1k2)1/2is verified experimentally.
Rate data for O + OCS → SO + CO and SO + O3 → SO2 + O2 by a new time‐resolved technique
Authors: Robertshaw John S. , Smith Ian W. M. 
Published: January 2005

AbstractPulsed laser photolysis of O3 in a large excess of N2 has been used to generate O(3P) atoms in the presence of OCS. By observing chemiluminescence from the small fraction of electronically excited SO2 formed in the reaction of SO with O3, rate constants of (1.7 ± 0.2) × 10−14 and (8.7 ± 1.6) × 10−14 cm3/molecule sec have been determined at 296 ± 4 K for the reactions
equation image
and
equation image
In addition, it has been shown that any reaction between SO and OCS has a rate constant 10−14 cm3/molecule sec.
Kinetics and mechanism of the bromination of aromatic compounds by N‐bromosuccinimide in solution
Authors: Sivakamasundari S. , Ganesan R. 
Published: January 2005

AbstractThe kinetics of bromination of several aromatic compounds (anilides, anisoles, and phenols) was investigated in 80% aqueous acetic acid (v/v) in the temperature range 20–50°C using N‐bromosuccinimide (NBS) as the reagent. The reaction was found to be first order in the aromatic substrate (ArH), and zero order in NBS, the overall order being 1. Stoichiometry of the reaction was 1:1. An increase in solvent polarity increased the reaction rate, and chloride ions were found to be specific catalysts for the reaction. Arrhenius activation energy remained almost constant for all the substrates. A probable mechanism explaining all these observed facts was proposed. The mechanism involved an attack by Br+ or more probably by a solvated Br+ ion on the aromatic substrate.
Photooxidation of 1,3‐butadiene containing systems: Rate constant determination for the reaction of acrolein with ⋅OH radicals
Authors: Maldotti Andrea , Chiorboli Claudio , Bignozzi Carlo A. , Bartocci Carlo , Carassiti Vittorio 
Published: January 2005

AbstractThe photooxidation of the 1,3‐butadiene–NO–air system at 298 ± 2 K was investigated in an environmental chamber under simulated atmospheric conditions. The irradiation gave rise to the formation of acrolein in a 55% yield, based on 1,3‐butadiene initial concentration for all the experimental runs.The rate of formation of acrolein was the same as that of 1,3‐butadiene consumption, indicating that acrolein is the major product of the 1,3‐butadiene oxidation in air.The dependence of acrolein concentration on irradiation time showed thata secondary process, identified as an oxidation of acrolein by ⋅OH radicals, was occurring during the photochemical runs. The rate constant of this secondary process was determined by measuring the relative rates of disappearance of acrolein and n‐butane during the irradiation of acrolein‐n‐butane‐NO‐air mixtures. The so obtained relative rate constant value was placed on an absolute basis using a reported rate constant for the n‐butane + ⋅OH reaction; a value of (1.6 ± 0.2) × 1010 M−1 sec−1 was obtained.
Cerium (IV) oxidation rate of p‐chloromandelic acid in perchlorate and sulfate media
Authors: Calvaruso Giuseppe , Cavasino F. Paolo , Sbriziolo Carmelo 
Published: January 2005

AbstractThe rate of the cerium (IV) oxidation of p‐chloromandelic acid has been studied in perchlorate media at an ionic strength of 1.50 mol/dm3 by the stopped‐flow technique and in H2SO4MHSO4 (M+ = Li+, Na+, K+) and H2SO4MClO4 (M+ = H+, Li+, Na+) mixtures at constant total electrolyte concentrations of 1.00 and 2.00 mol/dm3 using the conventional spectrophotometric method. In perchlorate media the kinetic data indicate the formation of two intermediate complexes between cerium (IV) and the organic substrate, but only one is significantly involved in the intramolecular electron‐transfer process. The oxidation rate is markedly lower in sulfate media, where two reaction paths have been found to contribute to the overall redox reaction. The univalent cations examined exhibit negative specific effects upon the overall oxidation rate increasing in the order H+ < Li+ < Na+ < K+. Activation parameters have been also estimated.
A quantitative study of alkyl radical reactions by kinetic spectroscopy. IV. The flash photolysis of azopropanes
Authors: Adachi Hiroyuki , Basco Norman 
Published: January 2005

AbstractThe flash photolysis of azo‒n‒propane and of azoisopropane has been studied by kinetic spectroscopy. Transient absorption spectra in theregion of 220–260 nm have been assigned to the n‐propyl and isopropyl radicals. For the n‐propyl radical, ϵmax = 744 ± 39 l/mol cm at 245 nm and the rate constants for the mutual reactions were measured to be kc = (1.0 ± 0.1) × 1010 l/mol sec (combination) and kd = (1.9 ± 0.2) × 109 l/mol sec (disproportionation). For the isopropyl radical, ϵmax = 1280 ± 110 l/mol cm at 238 nm, with kc = (7.7 ± 1.6) × 109 l/mol sec and kd = (5.0 ± 1.2) × 109 l/mol secThe rate constant for the dissociation of the vibrationally excited triplet state of the azopropanes into radicals was measured from the variation in the quantum yield of radicals with pressure. For azo‐n‐propane k = (6.6 ± 1.3) × 107 sec−1, and for azoisopropane k = (1.6 ± 0.4) × 108 sec−1. Collisional deactivation of the vibrationally excited singlet and triplet states was found to occur on every collision for n‐pentane; but nitrogen and argon were inefficient with a rate constant of 1.1 × 1010 l/mol sec.Spectra observed in the region of 220–260 and 370–400 nm areattributed to the cis isomers of the parent trans‐azopropanes. These are formed, as permanent products, in increasing amounts as the pressure is increased.
Analytical solution of vibrational–rotational energy transfer in the dissociation and relaxation of N2, Br2, and CO at high temperature
Authors: Forst Wendell 
Published: January 2005

AbstractAn approximate analytical solution of relaxation in a low‐pressure system with exponential transition probabilities is given for vibrational–rotational energy transfer in the dissociation of diatomics. The main assumption is that the rotational degrees of freedom are in thermal equilibrium at all times, and that the barrier to dissociation in the vibrational–rotational plane is linear and asymmetric. The theory is applied to high‐temperature dissociations of N2, Br2, and CO in excess argon, with satisfactory agreement with available experimental data.
Reaction of hydrogen atoms with diethyldisulfide and ethylmethyldisulfide
Authors: Ekwenchi M. M. , Safarik I. , Strausz O. P. 
Published: January 2005

AbstractH atoms react with C2H5SSC2H5 to give C2H5SH as the sole retrievable product with ϕ = 2.32 at 25°C and 2.84 at 145°C. The primary reaction is postulated to be H + C2H5SSC2H5 ← C2H5SH + C2H5S with k1 = (4.73 ± 0.64) × 1013 exp [−(1710 ± 69)/RT] cm3/mol·s relative to the rate constant of the H + C2H4 ← C2H5 reaction. The high value of the entropy of activation suggests the presence of partial hydrogen bonding in diethyldisulfide which is broken in the transition state.Ethylmethyldisulfide reacts similarly: H + C2H5SSCH3 ← C2H5SH + CH3S or CH3SH + C2H5S. The thiyl radicals propagate a chain of radical exchange reactions forming the symmetrical disulfides with exposure‐time‐dependent quantum yields. The overall kinetics conform to a 16‐step mechanism from which the rate constants of the elementary reactions could be established by computer modeling. Thiyl radicals react considerably more slowly with disulfides than H atoms.
Arrhenius parameters for the alkoxy radical decomposition reactions
Authors: Choo Kwang Yul , Benson Sidney W. 
Published: January 2005

AbstractArrhenius parameters for the decomposition reactions of various alkoxy radicals are evaluated. The recommended values for tert‐butoxy radical decomposition reaction are log A (s−1) = 14.1, Ea = 15.3 kcal/mol. magnified image The parameters give reasonably self‐consistent results with related rate constants, product distributions of hydrocarbon oxidation reactions, and the values reported in different laboratories in different environments.A reworking of data by Batt et al. on RO + NO and RO + NO2 leads to a lowering of his A factors for these reactions by a factor of 5. It also leads to a similar lowering of the A factors for RO decompositions. The intrinsic activation energies E for the addition of alkyl radicals R to the carbonyl group are not only found to be a function of the exothermicity of reaction, but they are also dependent on the nucleophilicity of the alkyl radicals. For each radical R (Me, Et, i‐Pr) the data can be fit to an Evans–Polanyi plot E = a + b (δH), where a uniform slope b = 0.58 can be found for all R. The intercepts a are then found to decrease nearly linearly with the decreasing ionization potential of R, namely, a = 2.1 [IP] – 6.2 (kcal/mol), with the ionization potential given in electron volts.
Modeling of biological reactions
Authors: Ma Shao‐mu , Eyring Henry , Ueda Issaku , Kaneshina Shoji 
Published: January 2005

AbstractCell membranes consist of lipid bilayers in which proteins are embedded. Many cell functions are carried out at the cell boundary which interface with water. Here we describe the response to an anesthetic of a lipid bilayer and of an enzyme separately. While both systems are markedly affected by anesthetics at appropriately high concentrations, the result at the clinical concentrations seems best explained as principally an effect on the protein somewhat accentuated by its presence in the lipid bilayer. Thus the lipoprotein complex seems to have the properties of the protein alone, except with somewhat greater induced sensitivity due to the lipid matrix in which it is immersed.
Kinetic investigation of the bromate–ascorbic acid–malonic acid system
Authors: Rábai Gy. , Bazsa Gy. , Beck M. T. 
Published: January 2005

AbstractAccording to our experiments the bromide ion concentration exhibits in the bromate–ascorbic acid–malonic acid–perchloric acid system three extrema as a function of time. To describe this peculiar phenomenon, the kinetics of four component reactions have been studied separately. The following rate equations were obtained:Bromate–ascorbic acid reaction:

Bromate–bromide ion reaction:

Bromide–ascorbic acid reaction:

Bromine–malonic acid reaction:

k4 = 6 × 10−3 s−1, k‐4 ≥ 1.7 × 103 s−1, k5 ≥ 1 × 107M−1 · s−1Taking into account the stoichiometry of the component reactions and using these rate equations, the concentration versus time curves of the composite system were calculated. Although the agreement is not as good as in the case of the component reactions, it is remarkable that this kinetic structure exhibits the three extrema found.
Kinetics and mechanism of Os(VIII)‐catalyzed hexacyanoferrate(III) oxidation of α amino acids in alkaline medium
Authors: Acharya R. C. , Saran N. K. , Rao S. R. , Das M. N. 
Published: January 2005

AbstractThe kinetics of the Os(VIII)‐catalyzed oxidation of glycine, alanine, valine, phenylalanine, isoleucine, lycine, and glutamic acid by alkaline hexacyanoferrate(III) reveal that these reactions are zero order in hexacyanoferrate(III) and first order in Os(VIII). The order in amino acid as well as in alkali is 1 at [amino acid] ⩽2.5 × 10−2M and [OH−] ⩽1.3 × 10−M, but less than unity at higher concentrations of amino acids or alkali. The active oxidizing species under the experimental conditions is OsO4(H2O) (OH)−. The ferricyanide is merely used up to regenerate the Os(VIII) species from Os(VI) formed during the reaction. The structural influence of amino acids on the reactivity has been discussed. The amino acids during oxidation are shown to be degraded through intermediate keto acids. The kinetic data are accommodated by considering the interaction between the conjugate base of the amino acids and the active oxidizing species of Os(VIII) to form a transient complex in the primary rate‐determining step. The catalytic effect of hexacyanoferrate(II) has been rationalized.
Kinetics and energetics of the criegee intermediate in the gas phase. II. The criegee intermediate in the photooxidation of formaldehyde, in alkyldioxy disproportionation and O + oxoalkane addition reactions
Authors: Herron John T. , Martinez Richard I. , Huie Robert E. 
Published: January 2005

AbstractThe gas‐phase kinetics and energetics of the Criegee intermediate, deduced from studies of O3‐alkene systems, suggest that a hydroxy‐substituted Criegee intermediate probably participates in the photooxidation of formaldehyde. In contradistinction, the existing evidence suggests that the Criegee intermediate and its isomers are probably not involved in alkyldioxy disproportionation reactions. In the case of O + oxoalkane addition reactions, the Criegee intermediate and its isomers are discussed in terms of a complex equilibrium: .
Analysis of the unimolecular reaction N2O5 + M ⇌ NO2 + NO3 + M
Authors: Malko M. W. , Troe J. 
Published: January 2005

AbstractRecent experimental results on the thermal decomposition of N2O5 in N2 are evaluated in terms of unimolecular rate theory. A theoretically consistent set of fall‐off curves is constructed which allows to identify experimental errors or misinterpretations. Limiting rate constants k0 = [N2] 2.2 × 10−3 (T/300)−4.4 exp(−11,080/T) cm3/molec·s over the range of 220–300 K, k∞ = 9.7 × 1014 (T/300)+0.1 exp(−11,080/T) s−1 over the range of 220–300 K, and broadening factors of the fall‐off curve Fcent = exp(‐T/250) + exp(−1050/T) over the range of 220–520 K have been derived. NO2 + NO3 recombination rate constants over the range of 200–300 K are krec,0 = [N2] 3.7 × 10−30 (T/300)−4.1 cm6/molec2·s and krec,∞ = 1.6 × 10−12 (T/300)+0.2 cm3/molec·s.
Direct detection of CF2 and computer modeling of its appearance in the fluorination of CH2F2
Authors: Seeger C. , Rotzoll G. , Lübbert A. , Schügerl K. 
Published: January 2005

AbstractThe branched chain reaction between CH2F2 and F2 is studied in a miniature tubular reactor having a diameter of 1.1 mm. The gases at the end of the tube expand into a low‐pressure chamber and are analyzed by molecular beam detection. The branching intermediate CF2 is detected directly at low ionization energies. An approximate quantitative reaction model for the fluorination of CH2F2 is proposed and discussed. The influence of the unknown rate constants in this scheme on the course of the reaction is examined. For the most reasonable set of rate constants the unknown rate constant for the branching reaction CF2 + F2 → CF3 + F at 550 K is found to be log k = 10.7 [cm3/mol·s].
A kinetic study of the reaction between formic acid and HoBr
Authors: Brusa M. A. , Colussi A. J. 
Published: January 2005

AbstractThe reaction between formic acid and HOBr in strongly acid aqueous media was studied by absorption spectrophotometry at 298 K. Bromine, the monitored species, displays a transient behavior, gradually rising up to a maximum and then decaying with first‐order kinetics. Reaction rates, expressed as R = ‐dCBr2/dt, depend on the concentrations of HCOOH (0.1–1.4M), HOBr (0.3–1.5 × 10−3 M), and H+ (0.1–1.0M). The mechanism
equation image
with k1 =1.04 ± 0.20M−1· s−1, k3 = 20.2M−1, quantitatively accounts for all observations within experimental error.