bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radical sensitization of acetylene pyrolysis
Authors: Durán R. P. , Amorebieta V. T. , Colussi A. J. 
Published: January 2005

AbstractThe kinetics of acetylene polymerization initiated by neopentane (Np) or acetone (Ac) decompositions has been investigated in a static reactor dynamically coupled to a modulated beam mass spectrometer between 850–950 K. Overall rates follow the expression: R = −d[C2H2]/dt = ks[X]1/2[C2H2] + ku[C2H2]2 (I), where X represents Np or Ac and ks, ku the rate constants of the sensitized and unsensitized reactions, respectively. The rate law of the sensitized reaction clearly suggests a chain polymerization mechanism with ks = kp(ki/kt)1/2 (i, t, and p stand for initiation, termination, and propagation, respectively). Remarkably, the derived values of kp are nearly independent of the sensitizer, although Ac acts as a source of methyl radicals whereas Np also produces hydrogen atoms, and fall in the expected range for the addition of vinylic radicals to acetylene. It is shown that a chain transfer process involving the fast [1,5] intramolecular hydrogen atom shift in 4‐methyl‐buta‐1,3‐dien‐1‐yl radicals (CH3CH  CHCH ĊH) followed by further addition to C2H2 and aromatization, transforms methyl radicals into hydrogen atoms and is able to account for the presence of toluene among the products of the sensitized reactions. Based on current thermochemical data for the but‐1‐en‐3‐yn‐2‐yl radical (CH2ĊCCH) and present rates of propagation it is argued that if the unsensitized polymerization of acetylene also proceeded by a vinyl radical chain, then even the most favorable self‐initiation reaction: 2C2H2 = C4H3 + H (a), would be far too slow. Finally, present results also show that acetone at impurity levels (⩽ 0.1%) can not provide fast enough spurious initiation rates in chain mechanisms for the “unsensitized” acetylene pyrolysis at pressures above 10 torr.
Selectivity–reactivity correlations for thermal Diels–Alder reactions of cyclohexa‐1,3‐diene with substituted Ethenes in the gas phase
Authors: Van Mele B. , Huybrechts G. 
Published: January 2005

AbstractSelectivity–reactivity correlations are shown to support a biradical pathway for the gas phase thermal Diels–Alder reactions of cyclohexa‐1,3‐diene with substituted ethenes except for those involving a carbonyl group.
Kinetics of the reaction of OH radicals with a series of ethers under simulated atmospheric conditions at 295 K
Authors: Wallington Timothy J. , Andino Jean M. , Skewes Loretta M. , Siegl Walter O. , Japar Steven M. 
Published: January 2005

AbstractEthers are being increasingly used as motor fuel additives to increase the octane number and to reduce CO emissions. Since their reaction with hydroxyl radicals (OH) is a major loss process for these oxygenated species in the atmoshpere, we have conducted a relative rate study of the kinetics of the reactions of OH radicals with a series of ethers and report the results of these measurements here. Experiments were performed under simulated atmospheric conditions; atmospheric pressure (≃ 740 torr) in synthetic air at 295 K. Using rate constants of 2.53 × 10−12, and 1.35 × 10−11 cm3 molecule−1 s−1 for the reaction of OH radicals with n‐butane and diethyl ether, the following rate constants were derived, in units of 10−11 cm3 molecule−1 s−1: dimethylether, (0.232 ± 0.023); di‐n‐propylether, (1.97 ± 0.08); di‐n‐butylether, (2.74 ± 0.32); di‐n‐pentylether, (3.09 ± 0.26); methyl‐t‐butylether, (0.324 ± 0.008); methyl‐n‐butylether, (1.29 ± 0.03); ethyl‐n‐butylether, (2.27 ± 0.09); and ethyl‐t‐butylether, (0.883 ± 0.026). Quoted errors represent 2σ from the least squares analysis and do not include any systematic errors associated with uncertainties in the reference rate constants used to place our relative measurements on an absolute basis. The implications of these results for the atmospheric chemistry of ethers are discussed.
FTIR study of the reaction of ethyl radicals with O2 and Cl2 in air at 295 K
Authors: Wallington Timothy J. , Andino Jean M. , Kaiser E. W. , Japar Steven M. 
Published: January 2005

AbstractUsing Fourier transform infrared spectroscopy, the ethene yield from the reaction of C2H5 radicals with O2 has been determined to be 1.50 ± 0.09%, 0.85 ± 0.11%, and <0.1% at total pressures of 25, 50, and 700 torr, respectively. Additionally, the rate constant of the reaction of C2H5 radicals with molecular chlorine was measured relative to that with molecular oxygen.
equation image
A ratio k6/k7 = 1.99 ± 0.14 was measured at 700 torr total pressure which, together with the literature value of k7 = 4.4 × 10−12 cm3 molecule−1s−1, yields k6 = (8.8 ± 0.6) × 10−12 cm3 molecule−1s−1. Quoted errors represent 2σ. These results are discussed with respect to previous kinetic and mechanistic studies of C2H5 radicals.
The mechanism of the elimination kinetics of 2‐bromo‐2‐butene in the gas phase
Authors: Chuchani Gabriel , Dominguez Rosa M. 
Published: January 2005

AbstractThe kinetics of the gas phase elimination of 2‐bromo‐2‐butene were determined in a static system over the temperature range of 340–380°C and pressure range of 37–134 torr. The reaction in seasoned vessels, even in the presence of a free radical inhibitor, is catalyzed by hydrogen bromide. Under maximum catalysis of HBr, the kinetics were found to be of order 1.0. The reaction, when maximally catalyzed with HBr, appears to undergo a molecular elimination of HBr which follows first‐order kinetics. The products are 1,2‐butadiene and hydrogen bromide. The rate coefficients. under maximum catalysis, are given by the Arrhenius equation log 𝓀1(s−1) = (13.57 ± 0.56) − (200.4 ± 6.8) kJ mol−1 (2.303RT)−1. The catalyzed pyrolysis of 2‐bromo‐2‐butene appears to proceed through a six‐membered cyclic transition‐state type of mechanism.
Kinetic study of the bromine‐catalyzed alcoholysis of butoxytriethylsilane: n‐Butoxy group–s‐butoxy group exchange reaction
Authors: Ito Katsuko , Ibaraki Takeshi 
Published: January 2005

AbstractIn order to compare the catalytic activity of bromine with those of iodine and iodine monohalides, kinetic studies on the reaction, Et3SiOBun + BusOH ⇌ Et3SiOBus + BunOH, were undertaken. Pseudo first‐order rate constants were determined at 0°, 10°, 15°, 20°, and 30°C by means of gas chromatography on the reaction mixtures containing both butanols in excess. From the observed rate constants, the catalytic coefficients of bromine were evaluated as follows:

The enthalpies and entropies of activation were estimated to be (42.0 – 42.2) kJ/mol, −(103 – 104) J/K (forward reaction), and (40.4 − 40.7) kJ/mol, − (101 − 102) J/K (reverse reactions). These data suggest that bromine is much more active than iodine and iodine monohalides, and its high activity was interpreted on the basis of the structure of the reaction intermediate.
Kinetics of the reactions of Cl(2PJ) and Br(2P3/2) with O3
Authors: Nicovich J. M. , Kreutter K. D. , Wine P. H. 
Published: January 2005

AbstractA laser flash photolysis‐resonance fluorescence technique has been employed to study the kinetics of the important stratospheric reactions Cl(2PJ) + O3 → ClO + O2 and Br(2P3/2) + O3 → BrO + O2 as a function of temperature. The temperature dependence observed for the Cl(2PJ) + O3 reaction is nonArrhenius, but can be adequately described by the following two Arrhenius expressions (units are cm3 molecule−1 s−1, errors are 2σ and represent precision only): 𝓀1(T) = (1.19 ± 0.21) × 10−11 exp [(−33 ± 37)/T] for T = 189–269K and 𝓀1(T) = (2.49 ± 0.38) × 10−11 exp[(−233 ± 46)/T] for T = 269–385 K. At temperatures below 230 K, the rate coefficients determined in this study are faster than any reported previously. Incorporation of our values for 𝓀1(T) into stratospheric models would increase calculated ClO levels and decrease calculated HCl levels; hence the calculated efficiency of ClOx catalyzed ozone destruction would increase. The temperature dependence observed for the (2P3/2) + O3 reaction is adequately described by the following Arrhenius expression (units are cm3 molecule−1 s−1, errors are 2σ and represent precision only): 𝓀2(T) = (1.50 ± 0.16) × 10−1 exp[(−775 ± 30)/T] for T = 195–392 K. While not in quantitative agreement with Arrhenius parameters reported in most previous studies, our results almost exactly reproduce the average of all earlier studies and, therefore, will not affect the choice of 𝓀2(T) for use in modeling stratospheric BrOx chemistry.
Rate constants for Hydrogen abstraction reactions of NO3 in aqueous solution
Authors: Shastri L. V. , Huie Robert E. 
Published: January 2005

AbstractRate constants have been measured by pulse radiolysis for the reactions of the NO3 radical with five cyclic ethers and a series of alcohols. Rate constants ranged from 3.5 × 104 M×1 s×1 for deuterated methanol to 1.1 × 107 M−1 s−1 for tetrahydrofuran. The rate constants for the reactions of NO3 with the alcohols 1‐propanol to 1‐heptanol were found to be linearly dependent on the number of CH3 groups with a group reactivity of 6.4 × 105 M−1 s−1.
High temperature reaction rate coefficients derived from N‐atom ARAS measurements and excimer photolysis of NO
Authors: Davidson D. F. , Hanson R. K. 
Published: January 2005

AbstractMixtures of NO and NO/H2 in Ar were shock‐heated and photolyzed with an ArF excimer laser. Measurements in these experiments of N‐atom profiles using atomic resonance absorption spectrophotometry (ARAS) permitted the determination of two rate coefficients. The rate coefficient for the reaction
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was found to be 4.29 × 1013 exp(−787/T) cm3 mol−1 sec−1 (±20% at 1400 K to ±10% at 3500 K). This is the first direct high temperature measurement of this rate coefficient in the exothermic direction. The rate coefficient for the reaction
equation image
was found to be 1.60 × 1014 exp(−12650/T) (±35% from 1950 to 2850 K). To our knowledge, this is the first direct measurement of this rate coefficient.A study of the N‐atom ARAS absorption behavior revealed a noticeable pressure dependence, as well as a weak temperature dependence, in the Beer‐Lambert law absorption coefficient. Proper consideration of these effects is important when the N‐atom ARAS diagnostic is used for absolute concentration measurements.
Kinetics and nitro‐products of the gas‐phase OH and NO3 radical‐initiated reactions of naphthalene‐d8, Fluoranthene‐d10, and pyrene
Authors: Atkinson Roger , Arey Janet , Zielinska Barbara , Aschmann Sara M. 
Published: January 2005

AbstractThe kinetics and nitroarene product yields of the gas‐phase reactions of naphthalene‐d8, fluoranthene‐d10, and pyrene with OH radicals in the presence of NOx and in N2O5NO3NO2air mixtures have been investigated at 296 ± 2 K and atmospheric pressure of air. Using a relative rate method, naphthalene‐d8 was shown to react in N2O5NO3NO2air mixtures a factor of 1.22 ± 0.10 times faster than did naphthalene, with the 1‐ and 2‐nitronaphthalene‐d7 product yields being similar to those of 1‐ and 2‐nitronaphthalene from naphthalene. From the measured PAH concentrations and the nitroarene product yields, formation yields of 2‐, 7‐, and 8‐nitrofluoranthene‐d9 and 2‐ and 4‐nitropyrene of 0.03, 0.01, 0.003, 0.005, and 0.0006, respectively, were determined from the OH radical‐initiated reactions. Effective rate constants for the reactions of fluoranthene‐d10 and pyrene with N2O5 in N2O5;NO3NO2air mixtures of ca. 1.8 × 10−17 cm3 molecule−1 s−1 and ca. 5.6 × 10−17 cm3 molecule−1 s−1, respectively, were derived. Formation yields of 2‐nitrofluoranthene‐d9 and 4‐nitropyrene of ca. 0.24 and ca. 0.0006, respectively, were estimated for these reaction systems. 2‐Nitropyrene was also observed to be formed in these N2O5NO3NO2 reactions, but was found to be a function of the NO2 concentration and, therefore, would be a negligible product under ambient NO2 concentrations. These product and kinetic data are consistent with ambient air measurements of the nitroarene concentrations.
Kinetic study of the reaction OH + HI by laser photolysis‐resonance fluorescence
Authors: Leod H. Mac , Balestra C. , Jourdain J. L. , Laverdet G. , Bras G. Le 
Published: January 2005

AbstractThe gas phase reaction of OH radicals with hydrogen iodide (HI) has been studied using a Laser Photolysis‐Resonance Fluorescence (LP‐RF) apparatus, recently developed in our group. The measured rate constant at 298 K was (2.7 ± 0.2) × 10−11 cm3 molecule−1 s−1. This rate constant is compared with the ones of the reactions OH + HCl and OH + HBr. The role of the reaction OH + HI in marine tropospheric chemistry is discussed.In addition, the LP‐RF apparatus was tested and validated by measuring the following rate constants (in cm3 molecule−1 s−1 units): 𝓀(OH + HNO3) = (1.31 ± 0.06) × 10−13 at p = 27 and 50 Torr of argon and 𝓀(OH + C3H8) = (1.22 ± 0.08) × 10−12. These rate constants are in very good agreement with the literature data.
On the mechanism of C2F5I photolysis in the presence of trifluoroacetic acid
Authors: Lane S. I. , Oexler E. V. , Staricco E. H. 
Published: January 2005

AbstractThe photolysis of C2F5I with CF3COOH in the temperature range 473–533 K was studied in the gas phase.Evidence is presented that supports a complex mechanism for the formation of C2F5H through the H‐atom abstraction reaction from CF3COOH by C2F5 radicals as well as the participation of I(2P½).
Chemical effects of radical vibrational energy content on the abstraction reaction: CF3 + Br2 → CF3Br + Br
Authors: Young Mark A. , Pimentel George C. 
Published: January 2005

AbstractWe have studied the effect of vibrational mode activation in the CF3 radical on the bromine abstraction reaction; CF3 + Br2 → CF3Br + Br. Excess vibrational energy resides in the symmetric modes of the radical after 248 nm photolysis of the parent molecule, CF3I. Our data indicate that the hot radicals react no faster than thermalized CF3, and may actually have a lower cross‐section for reaction. Dynamical factors that result in poor coupling of the vibrational energy to the reaction coordinate, as well as other similar considerations, could be responsible for the experimental observations. In addition, we have made an independent determination of the rate for the bromine abstraction reaction of (1.08 ± .13) × 1012 s−1 cm3 mol−1.
Formation of ring‐retaining products from the OH radical‐initated reactions of o‐, m‐, and p‐xylene
Authors: Atkinson Roger , Aschmann Sara M. , Arey Janet 
Published: January 2005

AbstractThe ring‐retaining products formed from the OH radical‐initiated reactions of o‐, m‐, and p‐xylene in the presence of NOx have been identified and their formation yields determined. Experiments were carried out at 298 ± 2 K and in the presence of 740 torr total pressure of air. The products observed, and their yields, were: from o‐xylene, o‐tolualdehyde, 0.0453; 2‐methylbenzyl nitrate, (0.0135 + 5.5 × 10−17 [NO2]); 2,3‐dimethylphenol, 0.097; 3,4‐dimethyl‐phenol, 0.064; 3‐nitro‐o‐xylene, 0.0059; 4‐nitro‐o‐xylene, (0.0111 + 9.9 × 10−17 [NO2]); from m‐xylene, m‐tolualdehyde, 0.0331; 3‐methylbenzyl nitrate, 0.0061; 2,4‐dimethylphenol, 0.099; 2,6‐dimethylphenol, 0.111; 4‐nitro‐m‐xylene, 0.0018; 5‐nitro‐m‐xylene, (0.0032 + 1.6 × 10−17 [NO2]); from p‐xylene, p‐tolualdehyde, 0.0701; 4‐methylbenzyl nitrate, 0.0082; 2,5‐dimethylphenol, 0.188, 2‐nitro‐p‐xylene, (0.0120 + 2.8 × 10−17 [NO2]), where the NO2 concentration is in molecule cm−3 units. The nitro‐xylene data are consistent with our recent product study of the corresponding reactions of benzene and toluene and indicate that under the experimental conditions employed the dimethylhydroxycyclohexadienyl radicals reacted with NO2 and not with O2. When combined with literature ring‐cleavage product yields, these data show that ca. 55–80% of the reaction pathways are accounted for.
The oxidation of 3,3′‐dimethoxy benzidine with potassium bromate in acidic solutions
Authors: Jonnalagadda S. B. , Munkombwe N. M. , Hensman P. , Mushinga T. 
Published: January 2005

AbstractThe kinetics and mechanism of the oxidation of 3,3′‐dimethoxybenzidine (oda, o‐dianisidine) by potassium bromate in aqueous acidic medium were studied by monitoring the formation rate of the reaction product, 3,3′‐dimethoxy 4,4′‐diphenoquinone at 447 nm. The reaction is, first order with respect to both the substrate and oxidant, and second order with respect to H+. The oda: bromate stoichiometric ratio is 1:1. Plausible mechanism and rate laws are proposed accounting the experimental findings. Computer simulations were done using the proposed mechanism.
Rate of the retro‐Diels‐Alder dissociation of 1,2,3,6‐tetrahydropyridine over a wide temperature range
Authors: Sidhu S. S. , Kiefer J. H. , Lifshitz A. , Tamburu C. , Walker J. A. , Tsang W. 
Published: January 2005

AbstractRate constants for the retro‐Diels‐Alder dissociation of 1,2,3,6‐tetrahydropyridine, to 1,3‐butadiene and methanimine, have been measured over 650–1450 K. To cover this range, three separate techniques were used at three laboratories: laser schlieren and single pulse shock tube methods, and a comparative rate flow system technique. The derived rate constants are extrapolated to the high‐pressure limit with an RRKM model parameterized to fit the falloff observed in the laser‐schlieren measurements. The resulting high‐pressure rate constants show a reduction in activation energy of about 10 kcal/mol, comparing the isoelectronic cyclohexene, but little change in A‐factor. There is an apparent increase in activation energy of 4 kcal/mol over the temperature range of these experiments, which is just outside probable error. Such a rise in activation energy is in marked contrast to the drop usually seen in simple bond fission, and may reflect a change from a concerted to a stepwise, biradical mechanism at high temperatures.
Kinetics of ethane oxidation
Authors: Dagaut Philippe , Cathonnet Michel , Boettner Jean‐claude 
Published: January 2005

AbstractEthane oxidation in jet‐stirred reactor has recently been investigated at high temperature (800–1200 K) in the pressure range 1–10 atm and molecular species (H2, CO, CO2, CH4, C2H2, C2H4, C2H6) concentration profiles were obtained by probe sampling and GC analysis. Ethane oxidation was modeled using a comprehensive kinetic reaction mechanism including the most recent findings concerning the kinetics of the reactions involved in the oxidation of C1C4 hydrocarbons. The proposed mechanism is able to reproduce experimental data obtained in our high‐pressure jet stirred reactor and ignition delay times measured in shock tube in the pressure range 1–13 atm, for temperatures extending from 800 to 2000 K and equivalence ratios of 0.1 to 2. It is also able to reproduce atoms concentrations (H,O) measured in shock tube at ≈2 atm. The same detailed kinetic mechanism can also be used to model the oxidation of methane, ethylene, propyne, and allene in similar conditions.
Temperature dependence of the rate constants for reactions of the carbonate radical with organic and inorganic reductants
Authors: Huie R. E. , Shoute L. C. T. , Neta P. 
Published: January 2005

AbstractRate constants have been measured by pulse radiolysis for the reactions of the carbonate radical, CO3·−, with a number of organic and inorganic reactants as a function of temperature, generally over the range 5 to 80°C. The reactants include the substitution‐inert cyano complexes of FeII, MoIV, and WIV, the simple inorganic anions SO32−, ClO2−, NO2−, I−, and SCN−, several phenolates, ascorbate, tryptophan, cysteine, cystine, methionine, triethylamine, and allyl alcohol. The measured rate constants ranged from less than 105 to 3 × 109 M−1 s−1, the activation energies ranged from −11.4 to 18.8 kJ mol−1, and the pre‐exponential factors ranged from log A = 6.4 to 10.7. The activation energies for the metal complexes and inorganic anions generally decrease with increasing driving force for the reaction, as expected for an outer sphere electron transfer. For highly exothermic reactions, however, the activation energy appears to increase, probably reflecting the temperature dependence of diffusion. For many of the organic reactants, the activation energies were low and independent of driving force, suggesting that the oxidation is via an inner sphere mechanism.
Salt effects in the aqueous alkaline hydrolysis of N‐hydroxyphthalimide. Kinetic evidence for the ion‐pair formation
Authors: Khan M. Niyaz 
Published: January 2005

AbstractThe effects of the concentrations of LiCl, NaCl, KCl, CsCl, Na2CO3, BaCl2, and Me4NCl on the rates of reactions of hydroxide ion with ionized N‐hydroxyphthalimide (NHP) at 30°C and in a H2O–MeCN solvent containing 98%, v/v, H2O reveal a nonlinear increase in observed rate constants with increase in salt concentrations. The observed rate constants are highly sensitive to the valence state of cations and almost insensitive to the valence state of anions of the salts. These observations are explained in terms of ion‐pair formation between cations and NHP−.
The photooxidation of methyl tertiary butyl ether
Authors: Smith D. F. , Kleindienst T. E. , Hudgens E. E. , McIver C. D. , Bufalini J. J. 
Published: January 2005

AbstractMethyl tertiary butyl ether (MTBE) has been proposed and is being used as an additive to increase the octane of gasoline without the use of tetraethyl lead and alkylbenzenes. The present experiments have been performed to examine the kinetics and mechanisms of the atmospheric removal of MTBE. The kinetics of the reaction of OH with MTBE was examined by using a relative rate technique in which photolysis of methyl nitrite was used as the source of OH. With n‐butane as the reference compound a value of (2.99 ± 0.12) × 10−12 cm3 molecule−1 s−1 at a temperature of 298 K was obtained for the rate constant. The products (and product yields) for the OH reaction with MTBE in the presence of NOx were also determined and found to be t‐butyl formate (0.68 ± 0.05), methyl acetate (0.14 ± 0.02), acetone (0.026 ± 0.003), t‐butanol (0.062 ± 0.009), and formaldehyde (0.48 ± 0.05) in mols/mol MTBE converted. The OH rate constant for the major product formed, t‐butyl formate was also measured and found to be (7.37 ± 0.05) × 10−13 cm3 molecule−1 s−1. Mechanisms to rationalize the formation of the products are presented.
Oxidative pyrolysis of CH2Cl2, CHCl3, and CCl4‐I: Incineration implications
Authors: Taylor Philip H. , Dellinger Barry , Tirey Debra A. 
Published: January 2005

AbstractThe oxidative pyrolysis of methylene chloride, chloroform, and carbon tetrachloride has been investigated using a micro‐bore, fused silica, tubular flow reactor operating under laminar flow conditions coupled to in‐line GC‐MS detection. Data were obtained over the temperature range 573–1273 K for the following conditions: chlorocarbon/oxygen equivalence ratios of 3.0, chlorocarbon concentrations of 2.7 ± 0.1 × 10−5 mols/L, gas‐phase residence times of 2.0 s, and reactor pressures of 1.15 ± 0.05 atm. The parent stability (defined by the temperature required for 99% destruction) was evaluated as:

Chemically activated recombination of chlorinated C1 radicals are proposed as important pathways to chlorinated ethane and olefin products. The most significant finding from analysis of product distributions containing ≥2 carbon atoms was the observation of ca. 1 mol% yields of higher‐molecular‐weight perchlorinated aromatic species from the decomposition of chloroform and carbon tetrachloride. Implications with respect to the controlled high‐temperature incineration of these chlorinated methanes are briefly discussed.
A kinetic approach for the mechanism of malachite green‐peroxydisulphate reaction in aqueous solution
Authors: Mushinga T. , Jonnalagadda S. B. 
Published: January 2005

AbstractThe oxidation kinetics of malachite green (MG) with peroxydisulphate ion (PDS) were investigated by monitoring the absorbance change at 618 nm, in aqueous solutions under buffered and unbuffered conditions. Under both conditions, the reaction had first order dependence on reductant and a fractional order (one half) dependence on the oxidant. The stoichiometric ratio between MG and PDS was 1:2. The reaction had a negative salt effect. Reaction rates were enhanced under both high or low pH relative to neutral conditions. A plausible mechanism is proposed.