bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the interaction of hydroperoxide and inhibitor molecules
Authors: Héberger K. 
Published: January 2005

AbstractDecomposition of 1‐phenylethyl‐hydroperoxide has been studied in the presence of 2,6‐di‐tert‐butyl‐4‐methyl‐phenol inhibitor in ethylbenzene and chlorobenzene both in oxygen and nitrogen. The oxygen consumption and the inhibitor concentrations were measured against the initial inhibitor concentrations. Two methods were applied for the determination of the rate coefficients of the reaction:

Its value is about 3 × 10−4L × mol−1 × S−1, at 120°C. However, large experimental errors we deal with, the existence of a reaction yielding radicals, presumably an interaction between hydroperoxide and inhibitor molecules, can be established emphasizing the importance of measurements carried out with various initial concentrations of the inhibitor.
Disproportionation reactions between alkyl and fluoroalkyl radicals. III. A reassessment of Δ values for CFyH(3−y) radicals (y = 1,2,3) with C2H5 radicals
Authors: Pritchard G. O. , Johnson K. A. , Nilsson W. B. 
Published: January 2005

AbstractNew determinations of the disproportionation and combination ratios between CF2H and C2H5 radicals yield (the hydrogen acceptor radical is given first) Δ(CF2H, C2H5) = 0.068 ± 0.008, and Δ(C2H5, CF2H) = 0.37 ± 0.01. A reevaluation of the existing data on CFH2 and CF3 radicals leads to the following recommended values, Δ(CFH2, C2H5) = 0.038 ± 0.006, and Δ(CF3, C2H5) = 0.11 = ± 0.02.
Reactions of alkoxy radicals with O2. I. C2H5O radicals
Authors: Zabarnick Steven , Heicklen Julian 
Published: January 2005

AbstractC2H5ONO was photolyzed with 366 nm radiation at −48, −22, −2.5, 23, 55, 88, and 120°C in a static system in the presence of NO, O2, and N2. The quantum yield of CH3CHO, Φ{CH3CHO}, was measured as a function of reaction conditions. The primary photochemical act is
equation image
and it proceeds with a quantum yield ϕ1a = 0.29 ± 0.03 independent of temperature. The C2H5O radicals can react with NO by two routes
equation image
The C2H5O radical can also react with O2 via
equation image
Values of k6/k2 were determined at each temperature. They fit the Arrhenius expression: Log(k6/k2) = −2.17 ± 0.14 − (924 ± 94)/2.303 T. For k2 ≃ 4.4 × 10−11 cm3/s, k6 becomes (3.0 ± 1.0) × 10−13 exp{−(924 ± 94)/T} cm3/s. The reaction scheme also provides k8a/k8 = 0.43 ± 0.13, where
equation image
Primary photochemical processes in the photolysis of alkyl nitrites at 366 NM and 23°c in the presence of 15NO
Authors: Morabito Paul , Heicklen Julian 
Published: January 2005

AbstractThe alkyl nitrites, C2H5ONO, n‐C3H7ONO, n‐C4H9ONO, and i‐C4H9ONO were photolyzed at 23°C in the presence of 15NO at 366‐nm incident radiation. The quantum yields of the corresponding isotopically‐enriched alkyl nitrites were measured by mass spectrometry. The results indicated that only part of the absorption leads to photodecomposition. The remainder forms an electronically excited state which isotopically exchanges with 15NO. The indicated reactions of the electronically excited state RONO*, are
equation image
where k3/k2 = 0.50 ± 0.10, 0.62 ± 0.20, 0.42 ± 0.06, and 0.24 ± 0.03 torr, and that k2a/k2 = 1.0, 1.0, 0.64 ± 0.04, and 0.56 ± 0.03, respectively, for C2H5ONO, n‐C3H7ONO, n‐C4H9ONO, and i‐C4H9ONO.
Autocatalysis and bistability in the reaction between nitric acid and thiocyanate
Authors: Bazsa Gyöurgy , Epstein Irving R. 
Published: January 2005

AbstractThe reaction between nitric acid and thiocyanate has been studied both in batch and flow configurations. The batch reaction is autocatalytic with an induction period which is decreased by the addition of HNO2. At the nitric acid concentrations employed (1–10 M), a red NOSCNH+ intermediate is formed. The reaction in a flow reactor exhibits bistability. A model involving competitive reactions of SCN− and NOSCNH+ with NO2 is suggested, and computer simulations with this model give good agreement with both the batch and flow experiments.
Direct comparison of methods for extracting the rate from first order data with background
Authors: McKinnon G. H. , Backhouse C. J. , Kalantar A. H. 
Published: January 2005

AbstractMany methods involving a lag or retardation can linearize A exp(−kt) + Z data, allowing k to be obtained from the slope. A classification scheme is found in which the efficiencies are related to the classes of methods. The methods yielding k with the smallest standard deviations (σk) are compared quantitatively. The resulting error factors for k and the lags are tabulated for each of the four methods compared, for use by the experimenter. This is done for various ranges, backgrounds, and kinds of random noise. Effects on k and σk due to correlation, incorrect weighting, choice of lag, and the distribution of the plotted data are detailed. Effects at high noise levels are discussed for the (usually) best direct method, due to Guggenheim. These include the onset and extent of bias in k and failure of the method to yield any k.
Extent of H‐atom abstraction from the reaction of the OH radical with 1‐butene under atmospheric conditions
Authors: Atkinson Roger , Tuazon Ernesto C. , Carter William P. L. 
Published: January 2005

AbstractProducts of the reaction of OH radicals with 1‐butene have been investigated in the presence of NO in one atmosphere of air at room temperature using gas chromatography and in situ long pathlength Fourier transform infrared absorption spectroscopy. The major product observed was propionaldehyde, with a formation yield (after allowing for its subsequent loss processes) of 0.94 ± 0.12. Minor yields of organic nitrates (RONO2) and of peroxypropionyl nitrate, a secondary product arising from propionaldehyde, were also observed. However, none of the products expected from the reactions subsequent to H‐atom abstraction from 1‐butene by OH radicals were observed, allowing an upper limit of 10% for this process to be derived. These data are compared with the available literature results and the implications are discussed.
Kinetics of reversible recombination of aromatic C‐centered radicals
Authors: Margulis L. A. , Khudyakov I. V. , Kuzmin V. A. , Prokof'ev A. I. , Yasmenko A. I. , Smets G. 
Published: January 2005

AbstractThe kinetics of the reversible recombination of the 2‐phenyl‐ (I), 2‐p‐methoxyphenyl‐(II), and 2‐p‐nitrophenyl‐3‐oxo‐2,3‐dihydrobenzothiophene‐2‐yl (III) radicals
equation image
have been investigated. Recombination rate constants of R(I–III) have been determined in different solvents (2k1 ∼ 109 M−1 s−1). The rate of reaction (I) with R(I–III) decreases with increasing solvent viscosity η. In the toluene‐vaseline oil mixture (2 ≲ η ≲ 120 cP) the recombination of R(I–III) is molecular mobility limited. The thermodynamic parameters of reaction (I) have been determined: ΔH0 = 20–30 kcal/mol. Activation volumes ΔV for recombination of R(II) have been measured. In n‐propanol ΔV is equal to the viscous flow activation volume of the solvent ΔV. In toluene and chloroform ΔV < ΔV. For the last two solvents the activation volumes of the cage reaction have been estimated ΔV = −(2–3) cm3/mol. Visible‐range absorption spectra and ESR spectra have been recorded for R(I–III). The role of cage effect in the reactivity anisotropy averaging of R(I–III) is discussed. The potential of the high‐pressure tests for deriving information about the elementary act of a fast bimolecular reaction is considered.
Pyrolysis of 2‐methylbut‐1‐ene‐3‐yne between 375 and 450°c
Authors: Chanmugathas C. , Heicklen Julian 
Published: January 2005

AbstractThe pyrolysis of 2‐methylbut‐1‐ene‐3‐yne (C5H6) has been studied from 375 to 450°C in a quartz reaction vessel in the absence and presence of O2 or NO. From 375 to 425°C, the rates of disappearance of reactant and of formation of dimers are second order in C5H6. The major product is polymer, with the dimers accounting for about 3% of the C5H6 consumed. In addition, toluene and p‐xylene are produced, their production coming, at least in part, from decomposition of the C5H6 dimers (C10H12). Also, trace amounts of CH4, C2H4, C2H6, are formed. The rate coefficients for C5H6 removal and C10H12 formation in the absence of O2 or NO are

where the uncertainties are one standard deviation. The reaction mechanism for dimer formation is analogous to that in vinyl acetylene (C4H4) pyrolysis (5), except that in the C4H4 system cyclooctatetraene is seen as an unstable product that isomerizes to styrene, whereas in the C5H6 system, the dimethylcyclooctatetraene apparently is too unstable to be detected. The dimers detected were 2,6‐dimethylstyrene (P4), p‐isopropenyltoluene (P5), and two other unidentified dimers (P3) with nearly identical gas chromatographic retention times. From the effect of the radical scavengers and by comparison of the C4H4 and C5H6 systems, the following mechanistic characteristics were determined: (1) The direct formation of styrene in the C4H4 system comes from a head‐to‐head modified Diels‐Alder six‐member cycloaddition that proceeds through a diradical intermediate. (2) There is no positive evidence for a direct head‐to‐tail modified Diels‐Alder six‐member cycloaddition. However, if it does occur, it does not involve diradicals but must be concerted. (3) Cyclooctatetraene is formed in concerted, non‐free‐radical mechanisms that may proceed both by head‐to‐head and head‐to‐tail eight‐member cycloadditions. For the C5H6 system, the head‐to‐head adduct isomerizes to P3, whereas the head‐to‐tail adduct isomerizes to P3, P4, and/or P5. and/or P5. Kinetic data suggest that P3 is not produced from the cyclooctatetraene intermediate, in which case, head‐to‐head addition would not occur. It appears that the head‐to‐head additions are free radical in nature and proceed mainly through a six‐membered ring intermediate, while head‐to‐tail additions are a concerted molecular process and proceed mainly through an eight‐membered ring intermediate.
On the mechanism of thermal oxidation of methane
Authors: Vardanyan I. A. , Nalbandyan A. B. 
Published: January 2005

AbstractUsing the method of freezing radicals in conjunction with ESR spectroscopic measurements, the kinetics of the thermal oxidation of methane has been studied under atmospheric pressure depending on the temperature, composition of the mixture, and nature of the surface of the reaction vessel. It has been shown that in a reactor treated with boric acid, the intermediates methylhydroperoxide and hydrogen peroxide are responsible for chain branching. It has been established that the leading active centers of the reaction are the HO2 radicals, while chain branching occurs as a result of the decomposition of peroxy compounds—methylhydroperoxide and hydrogen peroxide. In reactors treated with potassium bromide, the concentrations of radicals and peroxy compounds were found to be lower than the sensitivity of the method of measurement. Computations were performed for the scheme of methane oxidation at 738 K for a reactor treated with boric acid. Satisfactory agreement was found between the experimental and computed kinetic curves of accumulation of main intermediates CH2O, H2O2, CH3OOH. The influence of their addition on the kinetics of the reaction has been considered. It has been shown that the addition of formaldehyde does not lead to chain branching, however; it contributes to the formation of those peroxy compounds that bring about chain branching. Mathematical modeling confirmed conclusions made on the basis of experimental data concerning the nature of the leading active centers and the products that are responsible for the degenerate chain branching.
A continuous stirred tank reactor investigation of the gas‐phase reaction of hydroxyl radicals and toluene
Authors: Gery Michael W. , Fox Donald L. , Jeffries Harvey E. , Stockburger Leonard , Weathers Walter S. 
Published: January 2005

AbstractA continuous stirred tank reactor (CSTR) was used to study the gas‐phase reaction between HO⋅ and toluene. HO⋅ was generated by the in situ photolysis of nitrous acid. Flow reactor operation at steady‐state conditions with a residence time of 20 min allowed investigation of primary and very rapid secondary reactions. CSTR and batch reactor experiments were also performed with selected products. Both gas‐phase and aerosol products were identified by chromatography and mass spectroscopy, with total product yields between 55 and 75% of reacted carbon. Toluene reaction products included cresols, nitrocresols, nitrotoluenes, 3,5‐dinitrotouluene, benzaldehyde, benzyl nitrate, nitrophenols, methyl‐p‐benzoquinone, glyoxal, methylglyoxal, formaldehyde, methyl nitrate, PAN, and CO. The fraction of HO⋅ methyl hydrogen abstraction was calculated to be 0.13 ± 0.04. The ratio of reaction rate constants for nitrotoluene versus cresol formation from the HO⋅‐adduct was calculated to be about 3.3 × 104. Also, the ratio of cresol formation versus O2 addition to the HO⋅‐adduct was estimated to be ≥0.5 for atmospheric conditions. Comparisons of these measurements with previous values and the implications with respect to photochemical kinetics modeling of the atmosphere are discussed.
Mechanism and kinetics of the silane decomposition in the presence of acetylene and in the presence of olefins
Authors: Erwin J. W. , Ring M. A. , O'Neal H. E. 
Published: January 2005

AbstractKinetic data and product studies are reported for the silane pyrolysis in the presence of olefins and acetylene. The kinetics of silane loss in the presence of acetylene was found to be identical to the initial gas phase silane decomposition step (SiH4 + M → SiH2 + H2 + M) when corrected for pressure fall‐off effects. This result and the absence of methane or ethane from the pyrolysis of SiH4 in the presence of 1‐butene or 1‐pentene demonstrate that silyl radicals and H atoms are not involved in silane‐olefin or silane‐acetylene reactions. Qualitative aspects and kinetic data from the SiH4 pyrolysis in the presence of propylene are in accord with propylsilane formation via propylsilylene formed by silylene addition to propylene.
Comments on the linear relation between reaction rate and affinity
Authors: Boudart Michel , Löffler Daniel G. , Gottifredi Juan Carlos 
Published: January 2005

AbstractIn the case of catalytic dehydrogenation of cyclohexane, the linear relation between reaction rate and affinity holds at an appreciable distance away from equilibrium on both sides. In fact, in order to explain this observation, it is necessary to invoke a high value of three for the stoichiometric number of the rate determining step. This in turn can be explained by a reasonable mechanism for the reaction.
Kinetics and mechanism of electron transfer via bridge metal‐ion
Authors: Maletin Y. A. , Strizhakova N. G. 
Published: January 2005

AbstractThe kinetics and mechanism of electron transfer between stable verdazyl radicals via bridge Mn(II), Co(II), Ni(II), Cu(I), and Zn ions have been studied in the range 280–330 K using the stopped‐flow technique. It was found that the kinetic features of the reactions could be described in terms of the Marcus theory. The reorganization energy of the inner coordination sphere (ICS) of intermediate complexes was estimated from the reported data on the energy of release of various ligands from the ICS of similar complexes. The rest of the kinetic parameters (solvent reorganization energy, transmission coefficients, enthalpy, and entropy of activation) were determined from Marcus equations and from plots of rate constant versus temperature, “standard” free energy, and polarity of the medium. It was also found that the reactions under consideration are nonadiabatic and the transmission coefficient value depends on the mean lifetimes of ligands in the ICS.
Kinetics of the gas phase reaction of OH radicals with pyrrole and thiophene
Authors: Wallington Timothy J. 
Published: January 2005

AbstractAbsolute rate constants for the gas phase reaction of OH radicals with pyrrole (k1) and thiophene (k2) have been measured over the temperature ranges 298–440 and 274–382 K, respectively, using the flash photolysis‐resonance fluorescence technique. The rate constants obtained were independent of the total pressure of argon diluent over the range 25–100 torr andwere fit by the Arrhenius expressions

and

with rate constants at 298 ± 2 K of k1 = (1.03 ± 0.06) × 10−10 cm3 molecule−1 s−1 and k2 = (8.9 ± 0.7) × 10−12 cm3 molecule−1 s−1. [These errors represent two standard deviations (systematic errors could constitute an additional ca. 10% uncertainty)]. These results are discussed with respect to the previous literature data and the atmospheric lifetimes of pyrrole and thiophene.
Temperature dependence of the quasiclassical reactivity for vibrationally excited hydrogen molecules colliding with hydrogen atoms
Authors: Laganà A. 
Published: January 2005

AbstractA discussion of reactants vibrational energy and temperature dependence of reactive rate constants for the hydrogen atom hydrogen molecule reaction is presented for a matrix of values calculated at 0 < v <10 and temperatures in the range from 300 K to 4000 K. A parametrization ofthe results is attempted. A comparison with rate constant values obtained from an approximate quantum treatment is also reported.
The Heterogeneous Reaction of Ozone on Carbonaceous Surfaces
Authors: Stephens Sherry , Rossi Michel J. , Golden David M. 
Published: January 2005

AbstractOzone, O3, reacts with a carbon sample at room temperature. Clean carbon samples show a half to one and a half order of magnitude increased initial rate constant (k0) for O3 loss relative to repetitively exposed carbon samples. The ozone loss rate and therefore the rate constant reaches steady state (kss) on the time scale of tens of minutes, upon exposure to a characteristic dose of 8 × 1017 molecules for a 30‐mg carbon sample independent of the flow rate. This characteristic dose closely corresponds to a monolayer of adsorbed ozone molecules on the carbon sample. Both k0 and kss decrease with increasing flow rate of O3 into the reactor, and the loss rate is found to depend on [O3]. When the loss rate is plotted against the steady state concentration of O3, a saturation plot results which is proportional to the surface coverage, θ, at a given [O3].This interpretation rests upon a Langmuir type kinetics model with an assumed first‐order dependence of the loss rate constant. The “sticking coefficients” track the rate constants and are on the order of 10−3 to 10−5 depending on the carbon sample, dose, and flow rate. Furthermore, ko depends on the length of the dark period (absence of O3 exposure) and is larger the longer time the sample has had to recuperate from previous O3 exposures up to a period of 150 s. This surface relaxation is thought of as a time‐dependent change in surface coverage taking place in the dark period and is therefore an indication of a slow surface diffusion/reaction that can be separated from the adsorption‐desorption kinetics. The mass balance shows that for every ozone molecule that is lost on the surface, an oxygen molecule is found. This adsorbed odd oxygen is then responsible for product formation, which comprises the volatile components CO and CO2 to an extent of 20 to 40% of the odd oxygen deposited on the surface. The difference is thought to be in a preoxidized state on the carbon sample, which evolves CO and CO2 upon heat treatment.
Kinetic evidence for the occurrence of trianionic tetrahedral intermediate in the hydroxide ion‐catalyzed cleavage of 1, 2‐benzisothiazolin‐3‐one‐1, 1‐dioxide (saccharin)
Authors: Khan M. Niyaz , O M. S. O. 
Published: January 2005

AbstractThe kinetics of hydrolytic cleavage of saccharin has been studied at 60°C within the [ŌH] range of 0.1 to 3.0 M. The observed pseudo first‐order rate constants, kobs, follow an empirical relationship: kobs = B[ŌH] + [C[ŌH]]2. The B and C terms are attributed to the formation of dianionic and trianionic tetrahedral intermediates on the reaction path. It is concluded that the ionized form of saccharin is the major reacting species under the present experimental conditions. The positive ionic strength effect and the negative effect of 1,4‐dioxan on the rate of hydrolysis favor the proposed reaction mechanism. The analysis of the observed activation parameters indicates that the increase in the contribution of C term to kobs causes the slight increase in both ΔH* and ΔS*. A significantly large negative value of ΔS* favors the proposed mechanism.
Transient kinetic studies involving exciplex formation. Methods of analysis
Authors: Richer Jacques , Lessard Ginette , Belletěte Michel , Durocher Gilles 
Published: January 2005

AbstractIn this paper, rate parameters are extracted from fluorescene decay data in the framework of Feedback‐Type Kinetics (k8 < k4). The exciplex dissociation (k4) and fluorescene decay rate constants (k8) have been obtained for the five following systems:
equation image
For this task we have added to the straight line method of Ware which is valid in certain cases only at high perturber concentrations, a new but similar Taylor series method applicable at low concentrations. Thereafter, a safer and more general method of kinetic analysis based on a quasi‐linear χ2 minimization procedure has been developed and applies to data in any range of concentration.
An FTIR spectroscopic study of the kinetics and mechanism for the NO2‐initiated oxidation of tetramethyl ethylene at 298 K
Authors: Niki H. , Maker P. D. , Savage C. M. , Breitenbach L. P. , Hurley M. D. 
Published: January 2005

AbstractThe kinetics and mechansim for the NO2‐initiated oxidation of tetramethyl ethylene (TME) have been studied using the FTIR spectroscopic method in mixtures containing NO2 and TME (0.1−1.0 Torr) and N2O2 (700 Torr) at 298 ± 2 K. While TME decayed according to ‐d[TME]/dt = kobs[NO2][TME], NO2 exhibited a complex kinetic behavior. Furthermore, values of kobs were dependent on [O2]. Among the products were (CH3)2CO and at least three NO2‐containing compounds. These results indicate the formation of a nitro‐alkylperoxy radical via reactions (1), (−1), and (2), and its subsequent reactions leading to the observed products.
equation image
The [O2]‐dependence of kobs yielded k1 = (1.07 ± 0.15) × 10−20 cm3 molecule−1 S−1 and k−1/k2 = (3.54 ± 0.61) × 1018 molecule cm−3.
Kinetics and mechanism of electron transfer from phenolate anion to hexacyanoferrate (III) in aqueous alkaline media
Authors: Panda Pradeepta K. , Panda Rama Krushna , Murti P. S. Radhakrishna 
Published: January 2005

AbstractA kinetic reinvestigation of the title redox system in aqueous alkaline media at 35°C and an ionic strength of 0.5 mol dm−3shows that the reaction follows a pseudosecond‐order Fe(CN)disappearance. While varying [phenol]0and [OH−] exhibit a linear influence on the pseudo‐second‐order rate constant, varying[Fe(CN)]0and [Fe(CN)]0, initially taken, have a complicated inhibitory effect on the same. The major phenoloxidation products isolated under a chosen condition are 2,2′‐ and 4,4′‐ dihydroxydiphenyl. Results are interpreted in terms of a probable mechanism which envisages a reversible formation, by the first one‐electron transfer, of a reactive phenoxy radical (PhO˙) which on the second one‐electron transfer forms a less reactive ion‐pair intermediate (stabilized by the Fe(CN)produced) to decompose rate‐determiningly to phenoxonium cation (PhO+) and Fe(CN), the product‐formation steps being very rapid and kinetically indistinguishable.
Investigation of the gas phase reaction of dinitrogen pentoxide with water vapor
Authors: Sverdrup George M. , Spicer Chester W. , Ward Gerald F. 
Published: January 2005

AbstractThe gas phase reaction of N2O5 with water vapor was investigated in a 17.3‐m3 Teflon lined chamber. Temporal concentration profiles for ozone, total nitrogen oxides, and nitrogen dioxide were measured. Concentration profiles for N2O5 and HNO3 were calculated from a combination of measurements of nitrogenous species. A kinetic mechanism with an adjustable value for the rate constant of N2O5 + H2O was used to model the experiments. From this analysis an upper limit value of k ⩽ 4 × 10−7 ppm−1 min−1 for the gas phase reaction N2O5 + H2O → 2HNO3 was derived.