bluuebunny/crossref_metadata_2025_split huggingface dataset:
A structure‐activity relationship for the estimation of rate constants for the gas‐phase reactions of OH radicals with organic compounds
Authors: Atkinson Roger 
Published: January 2005

AbstractA previous technique for the calculation of rate constants for the gas‐phase reactions of the OH radical with organic compounds has been updated and extended to include sulfur‐ and nitrogen‐containing compounds. The overall OH radical reaction rate constants are separated into individual processes involving (a) H‐atom abstraction from CH and OH bonds in saturated organics, (b) OH radical addition to >CC< and CC unsaturated bonds, (c) OH radical addition to aromatic rings, and (d) OH radical interaction with NH2, >NH, >N, SH, and S groups. During its development, this estimation technique has been tested against the available database, and only for 18 out of a total of ca. 300 organic compounds do the calculated and experimental room temperature rate constants disagree by more than a factor of 2. This suggests that this technique has utility in estimating OH radical reaction rate constants at room temperature and atmospheric pressure of air, and hence atmospheric lifetimes due to OH radical reaction, for organic compounds for which experimental data are not available. In addition, OH radical reaction rate constants can be estimated over the temperature range ca. 250–1000 K for those organic compounds which react via H‐atom abstraction from CH and OH bonds, and over the temperature range ca. 250–500 K for compounds containing >CC< bond systems.
Kinetics of the gas‐phase reactions of Cl atoms with chloroethenes at 298 ± 2 K and atmospheric pressure
Authors: Atkinson Roger , Aschmann Sara M. 
Published: January 2005

AbstractUsing a relative rate technique, rate constants have been determined for the gas‐phase reactions of Cl atoms with the cholorethenes and ethane at 298 ± 2 K and 735 torr total pressure of air. Using a rate constant of 1.97 × 10−10 cm3 molecule−1 s−1 for the reaction of Cl atoms with n‐butane, the following rate constants (in units of 10−11 cm3 molecule−1 s−1) were obtained: vinyl chloride, 12.7 ± 0.2; 1,1‐dichloroethene, 14.0 ± 0.2; cis‐1,2‐dichloroethene, 9.65 ± 0.10; trans‐1,2‐dichloroethene, 9.58 ± 0.18; trichloroethene, 8.08 ± 0.10; tetrachloroethene, 4.13 ± 0.23; and ethane, 6.17 ± 0.08 (where the indicated error limits do not include the uncertainties in the rate constant for n‐butane). A small amount of cis‐trans isomerization was observed for the reactions involving the cis‐ and trans‐1,2‐dichloroethenes. These data are compared and discussed with the available literature data.
The kinetics and mechanism of the pyrolysis elimination of methyl 4‐bromocrotonate
Authors: Chuchani Gabriel , Martin Ignacio 
Published: January 2005

AbstractThe pyrolysis of methyl 4‐bromocrotonate in the temperature range 300–340°C and pressure range 74–170 torr has been shown to be homogeneous, unimolecular, and to follow a first‐order rate law. The reaction was carried out in a static system, seasoned with allyl bromide, and in the presence of the radical chain exhibitor toluene. The rate coefficients are represented by the Arrhenius expression: log k1(s−1) = (13.30 ± 0.66) − (185.2 ± 7.5) kJ mol−1 (2.303RT)−1. The carbomethoxy group appears to provide anchimeric assistance in the process of dehydrobromination and lactone products formation. The partial rates for the parallel reaction have been estimated, reported, and discussed. The pyrolysis elimination is explained in terms of an intimate ion pair‐type of mechanism.
Reactions of N2(A3Σ)
Authors: Golde Michael F. 
Published: January 2005

AbstractN2(A3Σ), the lowest electronically excited state of N2, has a long and distinguished history due to its role in nitrogen discharges and the nitrogen afterglow. Recently, the production of N2(A) via photolysis and chemiluminescent reactions has been newly explored, and new facets of its reactivity have been uncovered. N2(A) is unusual, in that its deactivation probability in collision with small molecules spans many orders of magnitude, and is frequently strongly dependent on the vibrational content of N2(A). This behavior and the observed product channels can be understood in terms of a simple model for the energy transfer process. Brief comparison with reactions of related species is made.
Measurement of absolute rate data for the reaction of atomic potassium, K(42S½), with CH3F, C2H5F, C6H5F, CH3Br, C2H5Br, HCl and HBr by time‐resolved atomic resonance absorption spectroscopy at λ = 404 nm (K(52PJ) ← K(42S½))
Authors: Husain D. , Lee Y. H. 
Published: January 2005

AbstractWe present a kinetic study of atomic potassium in its electronic ground state, K(42S½), generated in the “single‐shot mode” by pulsed irradiation at elevated temperatures and monitored by time‐resolved atomic resonance absorption spectroscopy using the Rydberg doublet at λ = 404 nm (K[52PJ]←K[42S½]). Profiles for the decay of atomic potassium in the presence of various halogenated reactants were recorded at different temperatures, yielding the following Arrhenius parameters (kR = A exp(−E/RT), errors 1σ):

R
A/10−10 cm3 molecule−1s−1
E/kJ mol−1
Temp. Range

CH3F
1.93+1.1−0.7
59±3.3
822–922 K

C2H5F
1.40+2.5−0.9
62±6.6
694–807 K

C6H5F
2.0+1.6−0.9
41±3.9
705–812 K

CH3Br
1.7+0.3−0.2
15.9±1.2
798–903 K

HCl
5.6+3.5−2.1
34.7±3.5
828–902 K

HBr
1.9+0.3−0.3
34±1.2
836–925 K

A limited body of data is reported for k(K + C2H5Br) = 3.6 × 10−11 cm3 molecule−1 s−1 for the temperature range 704–733 K. These results for atomic potassium constitute a new body of absolute rate data which are compared with some previous results for reactions of atomic potassium with other reactants, and for reactions of atomic sodium, also determined by time‐resolved atomic resonance absorption spectroscopy. The data for HCl and HBr are finally compared with early estimates reported using diffusion flames.
Kinetics of the gas‐phase reactions of the OH radical with (C2H5)3PO and (CH3O)2P(S)Cl at 296 ± 2 K
Authors: Atkinson Roger , Aschmann Sara M. , Goodman Mark A. , Winer Arthur M. 
Published: January 2005

AbstractThe kinetics of the gas‐phase reactions of the OH radical with (C2H5O)3PO and (CH3O)2P(S)Cl and of the reactions of NO3 radicals and O3 with (CH3O)2P(S)Cl have been studied at room temperature. Using a relative rate technique, the rate constants determined for the reactions of the OH radical with (C2H5O)3PO and (CH3O)2P(S)Cl at 296 ± 2 K and 740 torr total pressure of air were (5.53 ± 0.35) × 10−11 and (5.96 ± 0.38) × 10−11 cm3 molecule−1 s−1, respectively. Upper limits to the rate constants for the NO3 radical and O3 reactions with (CH3O)2P(S)Cl of <3 × 10−14 cm3 molecule−1 s−1 and <2 × 10−19 cm3 molecule−1 s−1, respectively, were obtained. These data are compared and discussed with previous literature data for organophosphorus compounds.
The kinetics of the reaction: Br + C3H6 ⇌ HBr + C3H5
Authors: Kondo Osamu , Marshall Roger M. , Benson Sidney W. 
Published: January 2005

AbstractStudies of the reaction of Br + propylene to produce HBr and allyl radical were made using VLPR (Very Low Pressure Reactor) over the range 263–363 K. Apparent bimolecular rate constants k were found to vary in an inverse manner with the initial concentration of bromine atoms introduced into the reactor. Plots of k against [Br] give straight lines whose intercepts were taken to be the true bimolecular, metathesis rate constant k1. The reaction scheme is

where k2 ≫ k1 and k−1 [HBr] is negligibly small under our conditions.Arrhenius parameters for k1 were assigned for linear and bent transition states and shown to give excellent fits to the observed intercepts.

where θ = 2.303 RT (kcal mol−1).The dependence of k on [Br] is accounted for in terms of the reactivity of Br* (2P1/2) produced in the microwave discharge. The activation energy for the metathesis reaction of Br* with propylene is shown to be very small.
Angular momentum conservation in unimolecular and recombination reactions
Authors: Smith Sean C. , Gilbert Robert G. 
Published: January 2005

AbstractIt is shown that the master equation describing fall‐off effects in unimolecular and recombination reactions, with angular momentum (J) conservation taken into account, can be solved exactly if the assumption is made that the probability of collisional energy transfer in J is independent of initial state; this assumption is shown to be physically acceptable (from general conservation considerations and from trajectory calculations) for typical neutral radical recombination and decomposition reactions. This leads to a J‐averaged master equation which can be readily solved by standard means. Illustrative computations using this treatment are presented.
Kinetics of the gas‐phase thermal elimination of (β‐bromo ethyl)‐pyrazole
Authors: Perez Jorge Daniel , Phagouapé Leonardo Miguel 
Published: January 2005

AbstractPyrazole elimination and vinyl bromide were found as products in the Flash Vacuum Pyrolysis of (β‐Bromo ethyl)‐pyrazole. To obtain kinetic parameters (Ea) we carried out competitive reactions using (β‐chloro ethyl)‐pyrazole as an internal standard. A thermochemical study to calculate Δ(ΔH) for this reaction was carried out.
Production and decomposition of highly excited 2‐butyl radicals by the addition of hot hydrogen atoms to but‐2‐ene. Cross section for the addition reaction
Authors: Al‐Niami Kisma , Holbrook Kenneth A. , Oldershaw Geoffrey A. 
Published: January 2005

AbstractHighly excited 2‐butyl radicals have been generated by addition of hot hydrogen atoms to but‐2‐ene. Atoms of initial energy 130 kJ mol−1 and 161 kJ mol−1 were produced by photolysis of H2S. Rates of decomposition of the highly excited 2‐butyl radicals were monitored by analysis of stabilization and decomposition products, and the extent of energy‐loss of the hydrogen atoms in nonreactive collisions assessed by measuring the effect of added xenon on product yields. A model involving the cross‐section for the addition reaction, energy transfer in nonreactive collisions between hydrogen atoms and but‐2‐ene, RRKM rate constants for decomposition of excited 2‐butyl radicals, and collisional energy transfer from the radicals, has been used to calculate product yields for comparison with experimental values. It is concluded that the cross‐section for addition of hydrogen atoms of energy about 130 kJ mol−1 to but‐2‐ene is 0.055 ± 0.028 nm2. This value is compatible with the A factor for the thermal addition reaction.
Angular momentum conservation in multichannel unimolecular reactions
Authors: Smith Sean C. , Gilbert Robert G. 
Published: January 2005

AbstractA recently developed solution of the master equation for unimolecular and recombination reactions is extended to give new means for incorporating angular momentum (J) conservation in the fall‐off regime for multichannel reactions. The calculated pressure dependence of a typical multichannel unimolecular dissociation reaction (thermal dissociation of 1‐iodopropane) shows that if one of the channels has a transition state with a moment of inertia (I†) significantly different from that of the parent molecule (I) (e.g., a “simple‐fission” type), neglect of angular momentum conservation causes the predicted branching ratio to be grossly in error at lower pressures. Specifically, if I† > I the rate coefficient is underestimated whereas if I† < I the rate coefficient is overestimated.
The mechanism of the reversible reaction: 2C2H2 ⇌ vinyl acetylene and the pyrolysis of butadiene
Authors: Benson Sidney W. 
Published: January 2005

AbstractIt is shown that kinetic data on the polymerization of acetylene to vinyl acetylene and benzene can be reconciled with the formation of a 1,4 biradical which can isomerize by a 1‐3, H‐atom shift to the molecular product. Since the biradicals have a negligibly small life‐time in the system the overall process appears to be a concerted bimolecular reaction. The labile isomer CH2  C: which had been suggested as being the reactive intermediate, is argued on energy considerations not to be a plausible intermediate.Data on the reverse pyrolysis of vinyl acetylene to acetylene are consistent with the model. Extending the model to butadiene explains the observed molecular nature of its decomposition to ethylene and acetylene.Reactions of other oligomers of acetylene are discussed.
Kinetics and mechanism of osmium (VIII) and ruthenium(III) catalyzed oxidation of aliphatic amines by chloramine‐T in alkaline and perchloric acid media
Authors: Gupta Sushma , Ali Vazid , Upadhyay Santosh K. 
Published: January 2005

AbstractThe kinetics of oxidation of aliphatic amines viz., ethylamine, n‐butylamine, isopropylamine (primary amines), diethylamine (secondary amine), and triethylamine (tertiary amine) by chloramine‐T have been studied in NaOH medium catalyzed by osmium (VIII) and in perchloric acid medium with ruthenium(III) as catalyst. The order of reaction in [Chloramine‐T] is always found to be unity. A zero order dependence of rate with respect to each [OH−] and [Amine] has been observed during the osmium(VIII) catalyzed oxidation of diethylamine and triethylamine while a retarding effect of [OH−] or [Amine] on the rate of oxidation is observed in case of osmium(VIII) catalyzed oxidation of primary aliphatic amines. The ruthenium(III) catalyzed oxidation of amines follow almost similar kinetics. The order of reactions in [Amine] or [Acid] decreases from unity at higher amine or acid concentrations.The rate of oxidation is proportional to {k′ and k″ [Ruthenium(III)] or [Osmium(VIII)]} where k′ and k″ (having different values in case of ruthenium(III) and osmium(VIII)) are the rate constants for uncatalyzed and catalyzed path respectively. The suitable mechanism consisting with the kinetic data is proposed in each case and discussed.
Hydrogen transfer from 9,10‐dihydrophenanthrene to anthracene
Authors: Billmers R. , Brown R. L. , Stein S. E. 
Published: January 2005

AbstractKinetic studies of the transfer of hydrogen from 9,10‐dihydrophenanthrene to anthracene were done at 350°C in the liquid phase. Principal products were phenanthrene and 9,10‐dihydroanthracene. Autocatalysis occurred at low extents of reaction, where H‐transfer from 9,10‐dihydroanthracene to anthracene caused an increase in free radical concentrations. At higher extents of reaction, 9,10‐dihydroanthracene inhibited rates by diverting intermediate 9‐hydrophenanthryl radicals back to reactants. A quantitative kinetic model based on literature rate and thermodynamic data fits the observations well. A key net reaction is the transfer of an H‐atom from a radical (9‐hydrophenanthryl) to a molecule (anthracene). It is shown that this process does not involve a free H‐atom intermediate. The derived rate constant for this exothermic process (7.5 × 103 M−1 s−1) is considerably greater than that for the related, but thermoneutral H‐transfer between anthracene moieties (120 M−1 s−1).
Kinetics and mechanism of indigo carmine‐acidic iodate reaction. An indicator reaction for catalytic determination of Ru(III) ion
Authors: Muthakia G. K. , Jonnalagadda S. B. 
Published: January 2005

AbstractA kinetic study of uncatalyzed and Ru(III) catalyzed oxidation of indigo carmine(IC) (disodium 3,3′‐dioxobi‐indolin‐2,2′‐ylidene‐5,5′‐disulphonate) by iodate ion in aqueous sulphuric acid solution is reported. The uncatalyzed reaction order was found to be four; one each with respect to IC and iodate ion and second order with H+ion. The Ru(III) catalyzed reaction was of fifth order, second order with respect to H+and first order with respect to reductant, oxidant, and catalyst. Stoichiometric ratios of both reactions were the same with a 3:2 reductant‐oxidant ratio. In both uncatalyzed and catalyzed reactions isatin‐5‐monosulphonic acid (2,3‐dioxoindoline‐5‐sulphonic acid) was observed as the oxidation product. Rate constants for both the reactions are reported. Reaction mechanisms consistent with the experimental data are suggested.Further, a fixed time method is described for the determination of Ru(III), based on its ability to catalyze the oxidation of IC by acidic iodate. Using [H+] 2.25M, [iodate] 1.00 × 10−3Mand [IC] 5.0 × 10−5M, in presence of Ru(III), the reaction followed first order kinetics with respect to IC. The interference of various cations, neutral salts, and potassium iodide on the determination of Ru(III) was studied using synthetic mixtures. The selectivity of the method and the recommended procedure are described.
Decomposition of the t‐butoxy radical: II. Studies over the temperature range 303—393 K
Authors: Batt L. , Hisham M. W. M. , Mackay M. 
Published: January 2005

AbstractThe near U‐V photolysis of t‐butyl nitrite has been studied over the temperature range 303–393 K. Under these conditions t‐butyl nitrite was shown to be a very clean photochemical source of t‐butoxy radicals. This allows a study of the decomposition of the t‐butoxy radical to be made over this temperature range (3).
equation image
Extrapolation of the rate constants k3 to high pressure and combination with our previous thermal data give the results:
The gas phase pyrolysis of phenol
Authors: Lovell A. B. , Brezinsky K. , Glassman I. 
Published: January 2005

AbstractPhenol pyrolysis has been studied in a turbulent flow reactor by analyzing concentration‐time profiles of three major decomposition products: carbon monoxide, cyclopentadiene, and benzene. Experimental conditions were P = 1 atm, T = 1064 − 1162 K, and initial phenol concentrations of 500−2016 ppm. The major experimental observations were that the decomposition product profiles were nearly linear as a function of time and that the overall rate of carbon monoxide production was greater than that of cyclopentadiene. The rate difference is explained by a mechanism which includes a radical combination reaction of cyclopentadienyl and phenoxy. With literature and approximate rate coefficient data, the mechanism reproduced the experimental observations very well. The mechanism and data provide estimates of rate coefficients for the phenol decomposition initiation step, abstraction of hydrogen from phenol by cyclopentadienyl, and the phenoxy‐cyclopentadienyl combination, all of which have not been available in the literature.
Flash photolysis study for reactions of NO3· with sulfur compounds in acetonitrile solution
Authors: Akiho Seiji , Ito Osamu , Iino Masashi 
Published: January 2005

AbstractThe rate constants for the reaction of NO3· with sulfur compounds in acetonitrile have been determined by the flash photolysis method. The rate constant for dimethyl sulfone (2.7 × 104 M−1s−1 at −10°C) is larger than that of the deuterium derivative, indicating that NO3· abstracts the hydrogen atom from dimethyl sulfone. In the case of dimethyl sulfide, the rate constant was evaluated to be 1.5 × 109 M−1 s−1 at −10°C; the transient absorption band attributable to the cation radical was observed after the decay of NO3·, suggesting the electron transfer reaction from the sulfide to NO3·. For diphenyl sulfide and dimethyl disulfide, the electron transfer reactions were also confirmed. For dimethyl sulfoxide, the reaction rate constant of 1.2 × 109 M−1 s−1 (at −10°C) was not practically affected by the deuterium substitution, suggesting that NO3· adds to sulfur atom forming (CH3)2Ṡ(O)‐ONO2. On the other hand, for diphenyl sulfoxide, the electron transfer reaction occurs. By the comparison of these rate constants in acetonitrile solution with the reported rate constants in the gas phase, the change of the reaction paths was revealed.
Study of the reaction of MoOS2(S2CNR2)2 with PPh3 in 1,2‐dichloroethane: Part I. Kinetics of the teaction of MoOS2(S2CNR2)2 with triphenylphosphine PPh3
Authors: Xiaoqing Song , Huixing Yang , Degang Han 
Published: January 2005

AbstractThe kinetics of the reaction of MoOS2(S2CNR2)2 (R = CH3, C2H5, n‐C3H7) with PPh3 have been studied using a Stopped‐flow method. It was found that these MoOS2(S2CNR2)2 complexes react with PPh3 in the form of an irreversible second‐order reaction. The rate constants at 25°C are respectively 48.4, 23.8, and 20.8 mol−1 dm3 s−1 and the activation energies are 4.8, 4.9, and 5.0 Kcal/mol with R = CH3, C2H5, and n‐C3H7.
Kinetics of CH radical reactions with N2O, SO2, OCS, CS2, and SF6
Authors: Zabarnick S. , Fleming J. W. , Lin M. C. 
Published: January 2005

AbstractPulsed laser photolysis/laser‐induced fluorescence (LIF) is utilized to measure absolute rate constants of CH radical reactions as a function of temperature and pressure. Multiphoton dissociation of CHBr3 at 266 nm is employed for the generation of CH (X2Π) radicals. The CH radical relative concentration is monitored by exciting fluorescence on the R1(2) line of the (A2Δ – X2Π) transition at 429.8 nm. A resistively heated cell allows temperature studies to be performed from room temperature to ≈︂670 K. The following Arrhenius equations are derived:

With the exception of SF6, the reactions of sulfur containing species proceed at rates that are near the theoretical gas kinetic collision frequency. Additionally, these reactions all have activation energies that are near zero or slightly negative. These observations are consistent with an insertion‐decomposition mechanism being dominant under these conditions.
Laser photolysis/laser‐induced fluorescence studies of reaction rates of OH with CH3Cl, CH2Cl2, and CHCl3 over an extended temperature range
Authors: Taylor Philip H. , D'angelo Joe A. , Martin Marc C. , Kasner James H. , Dellinger Barry 
Published: January 2005

AbstractA modified laser photolysis/laser‐induced fluorescence technique has been used to measure atmospheric pressure absolute rate coefficients for the reaction of hydroxyl (OH) radicals with the chlorinated methanes (CH3Cl, CH2Cl2, and CHCl3). Data have been obtained for these compounds over the widest temperature range (292–800 K) that has been reported in the literature using a single experimental apparatus. The temperature dependence of the rate data is best represented by the following three‐parameter expressions:

Uncertainties in the pre‐exponential and exponential term are expressed as 95% confidence intervals. For the temperature exponent, error limits represent a ±10% change in the total error of best fit.The degree of curvature in the Arrhenius plots appeared to increase with increasing Cl substitution of the reactant. However, the uncertainty in the temperature exponent for the CH3Cl data was large in comparison with the other chlorinated methanes. Thus, data of greater precision at elevated temperatures are necessary to further explore this relationship. The rate coefficients were compared with recent semiempirical and transition state theory models for haloalkane‐OH hydrogen transfer reactions over a temperature range of 250–800 K. The transition state model of Cohen and Benson was in excellent agreement with the CH3Cl and CH2Cl2 data. The semiempirical structure activity relationship developed by Atkinson represented the best fit of the CHCl3 data, although it underestimated the experimental data by more than a factor of 2 at 800 K. The extreme care used to remove and alayze for reactive impurities along with the agreement with other experimental studies suggests that transition state and semi‐empirical models for CHCl3 must be modified to account its reaction behavior at high temperature.