bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal dissociation and recombination of alkyl and haloalkyl peroxynitrates: An SACM modelling study
Authors: Destriau M. , Troe J. 
Published: January 2005

AbstractRecent experimental results on the thermal decomposition and the reverse recombination of alkyl and haloalkyl peroxynitrates are modelled with an SACM formalism. The molecules RO2NO2 with R = CH3, CF3, CF2Cl, CFCl2, CCl3, and C2H5 are considered. Detailed and simplified reduced falloff expressions are compared. Limiting low (𝓀o) and high pressure (𝓀x) rate constants, such as derived from a fit of these falloff expressions to the experiments, are compared with absolute predictions, based on general knowledge about energy transfer (〈ΔE〉 in 𝓀o) and on a recently proposed simple SACM estimate for 𝓀x. The analysis also allows for a derivation of the bond energies of the mentioned molecules.
Disproportionation reactions between alkyl and fluoroalkyl radicals. V. Perfluoro‐n‐propyl and ethyl radicals revisited
Authors: Pritchard G. O. , Abbas S. H. , Kennedy J. M. , Paquette S. J. , Hudson D. B. , Meleason M. A. , Shoemaker D. D. 
Published: January 2005

AbstractA redetermination of the disproportionation/combination ratio for n–C3F7 and C2H5 radicals gives a value of Δ(n–C3F7, C2H5) = 0.13 ± 0.01, independent of the temperature. The radicals were produced by the photolysis of n–C3F7COC2H5. The previous determinations of this ratio are discussed and are found to be largely incorrect. The values for Δ(CF3, C2H5) and Δ(C2F5, C2H5) are also re‐evaluated, and the recommended values are 0.10 ± 0.02 and 0.12 ± 0.02, respectively. Systems involving perfluoroalkyl and ethyl radicals are complicated due to rapid perfluororadical addition to the ethylene formed in the disproportionation process. The extent of this reaction, and its consequences, are discussed and evaluated. The role of the propionyl (C2H5CO) radical in the room temperature photolysis is also assessed. However, it is found that the Δ values determined by the intercept method used in this work are not affected by the secondary reactions that occur. It is concluded that high cross‐combination ratios are general to perfluoroalkyl‐alkyl radical interactions. For C3F7 and C2H5 radicals the ratio is 2.7–2.8. Above 100°C ratios exceed 3 due to secondary reactions.
A study of the reactions of NO3 radicals with organic sulfides: Reactivity trend at 298 K
Authors: Daykin E. P. , Wine P. H. 
Published: January 2005

AbstractA laser flash photolysis‐long path laser absorption technique has been employed to investigate the kinetics of NO3 reactions with CH3SCH3(𝓀1), CD3SCD3(𝓀2), and C2H5SC2H5(𝓀3) in 500 torr air at 298 K. The dependence of 𝓀1 on total pressure (20–500 torr) and oxygen partial pressure (0—100 torr) has also been investigated, with no dependence observed. Measured rate coefficients in units of 10−13 cm3 molecule−1 s−1 are 𝓀1 = 13 ± 3, 𝓀2 = 3.4 ± 0.8, and 𝓀3 = 48 ± 12, where the quoted uncertainties are 2σ estimates of absolute accuracy. The magnitude of NO3 + sulfide rate coefficients and negative activation energies for 𝓀1 (reported by other investigators) suggest that reaction does not proceed via a direct hydrogen abstraction mechanism. However, the reactivity trend observed in this study provides evidence that the reaction mechanism does involve breaking a carbon‐hydrogen bond.
Initiation in hydrocarbon autoxidation at elevated temperatures
Authors: Jensen R. K. , Korcek S. , Zinbo M. , Johnson M. D. 
Published: January 2005

AbstractKinetic and mechanistic investigations of liquid phase autoxidation of hexadecane at 120 to 190°C have shown that, in the early stages of oxidation, the initiation process involves homolytic decomposition of hydroperoxides. The values of a composite first order rate constant for this decomposition, 𝓀1, have been determined in stirred flow reactor experiments from the rate of formation of termination products and in batch reactor studies using inhibitor methods. Arrhenius parameters derived from these studies (log (A/s−1) = 8.5 and Ea = 26 kcal mol−1) allow calculation of 𝓀1 as a function of temperature. This permits determination of the rate of initiation as a function of hydroperoxide concentration and facilitates determination of absolute rate constants for other oxidation reactions occurring in this system.
Substituent effects in the gas‐phase thermolysis of aryl tert‐butyl ethers and sulfides
Authors: Martin Gonzalo , Martinez Henry , Ascanio Julian 
Published: January 2005

AbstractThe pyrolyses of p‐nitrophenyl t‐butyl ether, p‐methoxyphenyl t‐butyl ether, p‐aminophenyl t‐butyl ether, p‐nitrophenyl t‐butyl sulfide, and propargyl t‐butyl sulfide have been studied in a stirred‐flow reactor over the temperature range 430–530°C and pressures in the range 7–14 torr, using toluene as carrier gas. The reactions yielded between 90 and 99% isobutene plus the corresponding phenol, thiophenol, or thiol as products. The first order rate coefficients for reactant consumption, based on isobutene production, followed the Arrhenius equationsp‐nitrophenyl t‐butyl ether

p‐methoxyphenyl t‐butyl ether

p‐aminophenyl t‐butyl ether:

p‐nitrophenyl t‐butyl sulfide

propargyl t‐‐butyl sulfide:

The results support a unimolecular elimination of the isobutene involving polar, four‐center cyclic transition states.
A kinetic study of the decomposition of N‐bromoserine
Authors: Antelo Juan M. , Arce Florencio , Crugeiras Juan , Franco Julia , Rodriguez Pilar , Varela Angel 
Published: January 2005

AbstractThis article reports the kinetics of the decomposition of N‐bromoserine formed rapidly by bromation of serine by BrO−. The main decomposition products are glycolaldehyde, ammonia, carbon dioxide, and bromide ions at pH < 11.5, and β‐hydroxypyruvic acid, ammonia, and bromide ions at pH > 11.5. The reaction is of order one with respect to N‐bromoserine, and is independent of ionic strength and excess serine. The rate constant increases with increasing pH at pH > 11 and with decreasing pH at pH < 8, and over the range pH 8–11 has the constant value 1.67 × 10−3 s−1 at 298 K.
Rate constant and products of the BrO + BrO reaction at 298 K
Authors: Lançar I. T. , Laverdet G. , Bras G. Le , Poulet G. 
Published: January 2005

AbstractThe overall rate coefficient k of the self recombination of BrO radicals has been measured at 298 K with use of the discharge flow/mass spectrometry technique. The rate coefficient k2 for the reaction channel forming Br2 has been also determined. The results are: k = (3.2 ± 0.5) × 10−12 and k2 = (4.7 ± 1.5) × 10−13 (in cm3 molecule−1 s−1). These results are discussed with respect to previous literature data.
The mechanism of thermal eliminations. Part XXVIII [1]: Thermal decomposition of benzoylformic acid
Authors: Taylor Roger 
Published: January 2005

AbstractThe thermal decomposition of benzoylformic acid into carbon dioxide and benzaldehyde is a unimolecular first‐order reaction which takes place according to the rate equation log k = 15.3–42,500/4.575 K. At 600 K the reaction takes place 18 times faster than the corresponding decomposition of pyruvic acid into carbon dioxide and acetaldehyde. This is consistent with the 4‐center process proposed previously for pyruvic acid, in which a partial negative charge develops on the carbon of the α‐carbonyl group in the transition state. Benzoylformic acid is considerably less reactive towards thermal elimination than is oxalic acid, which also accords with the proposed mechanism.
Pd(II) complexes of amino alcohols and their reaction with chloramine‐T: A kinetic study
Authors: Shukla Anju , Gupta Sushma , Upadhyay Santosh K. 
Published: January 2005

AbstractThe kinetics of reaction of amino alcohols viz. 2‐aminoethanol, 3‐aminopropanol, and triethanolamine with chloramine‐T have been studied in perchloric acid medium with palladous chloride as catalyst. The formation of {Pd(II)‐(aminoalcohol)} and {Pd(II)‐(aminoalcohol)2} complexes and resistance of {Pd(II)‐(aminoalcohol)2} complex to react with chloramine‐T have been observed. A suitable mechanism consistent with the kinetic data is proposed and discussed.
Atmospheric oxidation of reduced sulfur species
Authors: Tyndall Geoffrey S. , Ravishankara A. R. 
Published: January 2005

AbstractThe kinetics of elementary gas phase reactions involved in the oxidation of reduced sulfur species, H2S, CS2, OCS, CH3SH, CH3SCH3, and CH3SSCH3, to SO2 (or other products) are reviewed. The reactions with OH and NO3 which are the processes that initiate the degradation of the above compounds have been evaluated. Reactions of key intermediates, HS, HSO, CH3S, and CH3SO, are discussed. Whenever possible, recommendations for the rate coefficients are made and the need for further work indicated. The review has been carried out with the atmospheric chemistry in mind by looking at the laboratory based kinetics data. This review also provides information that will help model the Earth's sulfur cycle.
Kinetics and mechanisms of the oxidation by permanganate of L‐Phenylalanine
Authors: Insausti M. J. , Mata‐Perez F. , Alvarez‐Macho M. P. 
Published: January 2005

AbstractThe oxidation of L‐Phenylalanine by permanganate ion in aqueous phosphate buffers is autocatalized by the inorganic reaction product, which is stabilized in solution by adsorption of phosphate ions on its surface. This product is a soluble form of colloidal manganese dioxide. The rate of the noncatalytic reaction pathway is first‐order in both the oxidizing and reducing agent. It is not affected by potassium chloride addition to the solution, but by phosphate addition. The rate increases with the pH of the medium. The autocatalytic pathway is first‐order in both permanganate ion and colloidal manganese dioxide, (the permanganate ion according to the Langmuir isotherm). The autocatalytic rate increases with reductant concentration (follows the Langmuir adsorption isotherm). It is not affected by potassium chloride addition to the solution, whereas an increase in the phosphate concentration results in an increase in the rate with the same pH of the medium. Mechanisms consistent with the experimental data are proposed.
Activation energy barriers in the molecular relaxation dynamics of Li+ interacting with acyclic and cyclic polyethers in acetonitrile
Authors: Xu Meizhen , Eyring Edward M. , Petrucci Sergio 
Published: January 2005

AbstractUltrasonic relaxation spectra of LiClO4 plus the open chain polyether triglyme (TG) at CLiClO4 ≃ 0.8 M, molar ratio R = [TG]/[LiClO4] = 1, and at temperatures of 15, 25, 35, and 45°C in dry acetonitrile are reported. Corresponding spectra for LiClO4 plus the macrocycle 12‐crown‐4 (12C4) at R = [12C4]/[LiClO4] = 1, at 10, 15, 20, 25, 30, and 40°C, and CLiClO4 = 0.32 M in acetonitrile are also reported.Both relaxation envelopes, for the two systems, have been fitted by two Debye relaxation processes and interpreted by the Eigen‐Winkler reaction scheme:

where “PE” symbolizes the polyether, Li+ … PE is a solvent separated species and LiPE+ and (LiPE)+ are two complex species. The temperature dependence of the relaxation spectra permits the calculation of the activation parameters for the forward and reverse processes for the system LiClO4 + TG and for one of the two processes for the LiClO4 + 12C4 system.Comparisons between the two sets of data lead to the conclusion that the much slower second relaxation process, in the case of the macrocycle, is attributable to a combination of an enthalpic and an entropic effect on the energy barrier for the present systems.
Minor processes in the photolysis of azomethane at low pressure: An upper limit for the rate of the unimolecular elimination of H2 from vibrationally excited ethane
Authors: Roscoe J. M. , Blatt C. , Back R. A. 
Published: January 2005

AbstractThe photolysis of azomethane in the near UV has been studied at room temperature and pressures from 10 mtorr to 10 torr. The main products, C2H6 and N2, accounted for more than 99% of the reaction. Minor hydrocarbon products observed were (with quantum yields) C3H8 (3.5 × 10−3), C2H4 (3.2 × 10−4), CH4 (3 × 10−3), and n‐C4H10 (trace). Quantum yields of H2 of 4 × 10−5 and 2 × 10−5 were measured at azomethane pressures of 0.1 and 1.0 torr, respectively.The minor hydrocarbon products can be accounted for by reactions of CH3 and C2H5 radicals following hydrogen abstraction from azomethane by CH3. The H2 product observed represents an upper limit for the H2 elimination from vibrationally excited C2H6 formed by CH3 combination in the system, corresponding to a rate of elimination ca. 5 × 10−5 times the competing rate of dissociation to 2CH3. Assuming a frequency factor of 1013 s−1 for the H2 elimination, a lower limit of about 90 kcal mol−1 was estimated for the energy barrier.
Hydrolysis of schiff bases, 1: Kinetics and mechanism of spontaneous, acid, and base hydrolysis of N‐(2/4‐hydroxybenzylidene)‐2‐aminobenzothiazoles
Authors: Misra Pramila , Mishra Bijaya K. , Behera Gopa B. 
Published: January 2005

AbstractThe rate of hydrolysis of title schiff bases was studied in the pH range 4–13 in 10% dioxanewater system, CTAB, NaLS micellar solutions. The hydrolysis was found to be due to ‘water’ and ‘hydroxide’ reactions and hence the rate constants in different pH were computed and analyzed with an intermediate involving a water molecule being positioned with the help of 2‐OH group and the thiazolyl C–N pi bond. The ‘hydroxide’ reaction was due to a direct nucleophilic attack of hydroxide ion at the aldimine linkage of the reactant. The influence of cationic and anionic micelles supports the mechanistic picture in the entire pH range.
A shock tube study of H + HNCO → NH2 + CO
Authors: Mertens John D. , Kohse‐Höinghaus Katharina , Hanson Ronald K. , Bowman Craig T. 
Published: January 2005

AbstractThe reaction of atomic hydrogen with isocyanic acid (HNCO) to produce the amidogen radical (NH2) and carbon monoxide,
equation image
has been studied in shock‐heated mixtures of HNCO dilute in argon. Time‐histories of the ground‐state NH2 radical were measured behind reflected shock waves using cw, narrowlinewidth laser absorption at 597 nm, and HNCO time‐histories were measured using infrared emission from the fundamental v2‐band of HNCO near 5 μm. The second‐order rate coefficient of reaction (2(a)) was determined to be:

cm3 mol−1 s−1, where f and F define the lower and upper uncertainty limits, respectively.An upper limit on the rate coefficient of
equation image
was determined to be:
The kinetics and mechanisms of methyl 2‐bromopropionate and 2‐bromopropionic acid pyrolyses under maximum inhibition
Authors: Chuchani Gabriel , Dominguez Rosa M. , Rotinov Alexandra 
Published: January 2005

AbstractThe kinetics of the gas phase pyrolyses of methyl 2‐bromopropionate and 2‐bromopropionic acid were studied in a seasoned, static reaction vessel and under maximum inhibition of the free radical suppressor toluene. The working temperature and pressure range was 310–430°C and 26.5–201.5 torr, respectively. The reactions proved to be homogeneous, unimolecular, and obeys a first‐order rate law. The rate coefficients are expressible by the following equations: for methyl 2‐bromopropionate, log k1(s−1) = (13.10 ± 0.34) − (211.4 ± 4.4)kJ mol−1(2.303RT)−1; for 2‐bromopropionic acid, log k1(s−1) = (12.41 ± 0.29) − (180.3 ± 3.4)kJ mol−1(2.303RT)−1. The bromoacid yields acetaldehyde, CO and HBr. Because of this result, the mechanism is believed to proceed via a polar five‐membered cyclic transition state.
Electron transfer. 109. The reaction of dimeric molybdenum(V) with carboxylato‐bound chromium(V). A third mechanistic variation
Authors: Ghosh M. C. , Gould E. S. 
Published: January 2005

AbstractThe bridged dimer of molybdenum(V), Mo2O42+ (aq) is oxidized to Mo(VI) by carboxylato‐bound chromium(V). Reaction of bis(chelated) Cr(V) with excess (MoV)2 yields a chelated Cr(III) complex, but this conversion proceeds through a pink Cr(IV) intermediate, indicating that the oxidation of (MoV)2 entails a series of le− steps, passing through a reactive transient, the mixed valence complex, MoVMoVI. When experiments are carried out in buffers of the ligating acid, 2‐ethyl‐2‐hydroxybutanoic acid, two stages of ligation of (MoV)2 by the ligand anion, characterized by rate constants near 104 and 0.14 M−1 s−1 (19°C; pH 3.0; μ = 0.6 M) must be considered. In quick mixing experiments, the first, but not the second, of these proceeds before the redox reaction gets under way, and autocatalytic redox profiles are observed. If the slower ligation is allowed to reach completion before Cr(V) is added, reduction to Cr(IV) is greatly accelerated and conforms to the superposition of two processes, whereas the reduction of Cr(IV) to Cr(III) is slow and exhibits a rate independent of [CrIV]. A proposed sequence applicable to the latter conditions includes reductions of Cr(V) at two ligation levels, slow unimolecular conversion of (MoV)2 to an activated form, and rapid reduction of the latter with Cr(IV). Here Cr(IV) has assumed the role of a scavenger for the reactive form of (MoV)2.
Kinetics of the gas‐phase reactions of β‐phellandrene with OH and NO3 radicals and O3 at 297 ± 2 K
Authors: Shorees Basima , Atkinson Roger , Arey Janet 
Published: January 2005

AbstractRate constants for the gas‐phase reactions of the biogenically emitted monoterpene β‐phellandrene with OH and NO3 radicals and O3 have been measured at 297 ± 2 K and atmospheric pressure of air using relative rate methods. The rate constants obtained were (in cm3 molecule−1 s−1 units): for reaction with the OH radical, (1.68 ± 0.41) × 10−10; for reaction with the NO3 radical, (7.96 ± 2.82) × 10−12; and for reaction with O3, (4.77 ± 1.23) × 10−17, where the error limits include the estimated uncertainties in the reference reaction rate constants. Using these rate constants, the lifetime of β‐phellandrene in the lower troposphere due to reaction with these species is calculated to be in the range of ca. 1–8 h, with the OH radical reaction being expected to dominate over the O3 reaction as a loss process for β‐phellandrene during daylight hours.
Decomposition of hydrogen peroxide in aqueous solutions at elevated temperatures
Authors: Lin C. C. , Smith F. R. , Ichikawa N. , Baba T. , Itow M. 
Published: January 2005

AbstractDecomposition of hydrogen peroxide in high‐purity water has been measured at temperatures ranging 100 to 280°C in a laboratory test loop. A first‐order decomposition kinetics has been observed in all cases, but the decomposition rates were found to vary widely, depending on the material used in the reaction chamber. In a 4 mm ID stainless steel tubing, the decomposition rate constant is determined to be k = 2 × 105 exp(−14800/RT). This decomposition rate is approximately 100 times faster than that observed in a Teflon tubing.The variation of decomposition rate in different reaction chambers is attributed to the heterogeneous catalytic effects. There is no evidence of reaction between H2 and H2O2 in the highpurity water at temperatures up to 280°C.
A shock tube study of the reaction of methyl radicals with hydroxyl radicals
Authors: Bott J. F. , Cohen N. 
Published: January 2005

AbstractThe reaction of CH3 with OH has been studied near 1200 K and 1 atmosphere pressure in shock tube experiments in which UV absorption was used to monitor [OH]. A rate coefficient of (1.1 ± 0.3) × 1013 cm3/mol‐s was measured for removal of OH by CH3. This measured value is compared with previous experimental data and calculations. Several possible reaction channels are discussed, and although products were not monitored, it seems probable, on the basis of other work and theoretical estimates, that the primary mechanism (≃75%) for the removal of OH by CH3 at these conditions is their combination to form CH3OH. Rate coefficients of (5.3 ± 0.8) × 1012 and (9.0 ± 1.4) × 1012 cm3/mol‐s were measured for the reactions of OH with acetone and ethane, respectively, at the same temperature and pressure.
Time resolved kinetic studies of the gas‐phase reactions of dimethylsilylene with some O‐Donor molecules: Part I. Room temperature studies
Authors: Baggott J. E. , Blitz M. A. , Frey H. M. , Lightfoot P. D. , Walsh R. 
Published: January 2005

AbstractThe reactions of dimethylsilylene, SiMe2, generated by laser flash photolysis from pentamethyldisilane and octamethyltrisilane, and detected via its 457.9 nm absorption, have been investigated with a number of oxygen containing molecules, including oxygen itself, carbon monoxide, water, alcohols, and ethers at 295 K. Some substrate molecules were deuterated. Apart from CO, all molecules reacted with SiMe2 with second order rate constants (in cm3 molecule−1 s−1) in the range 7.7 ± 10−14 to 4.7 ± 10−11.While most of the reactions of SiMe2 studied went to completion those with dimethylether and tetrahydrofuran were partially reversible. The reaction of SiMe2 with oxirane was pressure dependent.The data are generally consistent with a mechanism involving initial formation of a donoracceptor, zwitterionic complex. In the case of reaction with alcohols, there is a small overall isotope effect, suggesting formation of a complex followed by rapid H‐transfer, which only marginally affects the rate. In the case of ethers, complexes are formed which (i) may react further (Me2Si…oxetane), (ii) may react further but also reversibly decompose (Me2Si…oxirane), or (iii) do not seem to react further (Me2Si…OMe2, Me2Si…THF) but partially redissociate. The donor‐acceptor bond strength has been estimated in these last cases to be ca. 40 kJ mol−1. Supporting arguments and mechanistic details of all reactions investigated are presented.
Effect of solvent on the reactions of coordination complexes: Part 16. Kinetics and mechanism of complexation of oxalatopentaammine‐cobalt(III) with nickel(II) in methanol‐water medium
Authors: Dash Anadi C. , Pradhan Jyotshamayee 
Published: January 2005

AbstractThe kinetics of reversible complexation of oxalatopentaammine cobalt(III) with Ni2+ has been investigated in MeOH + water media (0–50 (v/v) % MeOH) at 15.0–35.0°C and I = 0.10 mol dm−3. Analysis of rate data indicates that the monobonded complex [(NH3)5 · CoOCOCO2Ni]3+ in which Ni2+ is bound to the end carboxylate group is the possible reaction intermediate. The formation and dissociation rates of such a species are rate limiting for the overall formation and dissociation of the binuclear species, in which Ni2+ is chelated by the oxalate moiety. The rate and activation parameters for formation and dissociation of the binuclear species are moderately solvent sensitive and solvent structural effects are discernible in the nonlinear variations of ΔH≠ and ΔS≠ with solvent composition. The log kr vs. Grunwald Winstein parameter (Y) plot for the dissociation of the binuclear species is markedly nonlinear.