bluuebunny/crossref_metadata_2025_split huggingface dataset:
Disproportionation reactions between alkyl and fluoroalkyl radicals. VII. Difluoromethyl with perfluoro‐n‐propyl and methyl radicals
Authors: Pritchard G. O. , Follmer D. W. , Meleason M. A. , Shoemaker D. D. , Perkins J. C. , Leupp S. L. 
Published: January 2005

AbstractMixtures of 1,1,3,3‐tetrafluoroacetone and perfluorodi‐n‐propyl ketone have been photolyzed together over the temperature range 50° to 200°C, and the disproportionation/combination ratio for n‐C3F7 and CF2H radicals has been determined to be Δ(n‐C3F7, CF2H) = 0.072 ± 0.003. A reevaluation of existing data on CH3 and CF2H radicals leads to a value of Δ(CH3, CF2H) = 0.35. The large variations in Δ for the reactions of alkyl and perfluoroalkyl radicals with CF2H radicals are discussed. © John Wiley & Sons, Inc.
Correlation analysis of kinetic parameters of the free radical polymerization of alkylphenyl methacrylates
Authors: Vrhovac Ljubica , Filipović Dragoljub , Misić‐vuković Milica , Veličković Jovan 
Published: January 2005

AbstractData from previous articles on the initial polymerization rates of a series of monoalkyl substituted phenyl methacrylates were found to depend strongly on the size and position of the monoalkyl substituent in the phenyl ring. In order to investigate the possibility of correlation of all the rate data obtained, all those for phenyl methacrylate and ten other alkylphenyl substituted methacrylate monomers were fitted into empirical linear free energy relationships (LFER). Assuming steady‐state kinetics and separating out the initiator decomposition contribution to the initial overall rate Rp, it was demonstrated that k′ = kp/kt½ can be successfully correlated with LFER equations containing predominantly steric parameters. The steric influence is more pronounced in the o‐ than in the p‐substitution, due to the proximity of the o‐substituent to the reaction propagation site. The results are corroborated by the existence of an isokinetic relationship of ΔH‡ vs. ΔS‡, providing the proportionality of electronic effects, however small, and the predominating steric effects. The treatment is based on the assumption that the initiator efficiency ƒ equals 1 and that the termination rate constants kt are equal for monomers of similar structure, what might represent an approximation of the true situation in the system investigated. © John Wiley & Sons, Inc.
OH radical reaction rate constants for polycyclic alkanes: Effects of ring strain and consequences for estimation methods
Authors: Atkinson Roger , Aschmann Sara M. 
Published: January 2005

AbstractUsing a relative rate method, rate constants for the gas‐phase reactions of the OH radical with trans‐pinane [(1R, 2R)‐2, 6, 6‐trimethylbicyclo[3.1.1]heptane], tricyclene (1, 7, 7‐trimethyltricyclo[2.2.1.02, 6]heptane), and quadricyclane (quadricyclo[2.2.1.02, 6.03, 5]heptane) of (1.34 ± 0.29) × 10−11 cm3 molecule−1 s−1, (2.86 ± 0.62) × 10−12 cm3 molecule−1 s−1 and (1.83 ± 0.41) × 10−12 cm3 molecule−1 s−1, respectively, have been determined at 296 ± 2 K. These rate constants are compared with values calculated from an empirical estimation method and used to refine this estimation technique for the calculation of OH radical reaction rate constants for polycyclic systems. © John Wiley & Sons, Inc.
Reactions of halogenated organic peroxyl radicals with various purine derivatives, tyrosine, and thymine: A pulse radiolysis study
Authors: Kapoor Sudhir Kumar , Gopinathan C. 
Published: January 2005

AbstractAbsolute rate constants for the one electron oxidation of guanine, guanosine, uric acid, xanthine, hypoxanthine, tyrosine, and thymine by various halogenated peroxyl radicals in aqueous solutions have been determined using the technique of pulse radiolysis. Roughly, linear correlations have been observed between the logarithm of these rate constants and Taft's inductive parameter (σ*) for the radicals. However, the rate constants for the radical CBr3O are slightly higher than those for CCl3O for most of these compounds. © John Wiley & Sons, Inc.
Kinetics of the solvolysis of chloropentacyanocobaltate (III) ions in mixtures of ethane‐1,2‐diol or ethanonitrile with water
Authors: Halawani Kamal H. , Wells Cecil F. 
Published: January 2005

AbstractThe kinetics of the solvolysis of [Co(CN)5Cl]3− ions have been investigated in mixtures formed by the addition of ethane‐1,2‐diol or ethanonitrile to water where the physical properties indicate little enhancement of structure in water‐rich conditions. The effect on the kinetics of this solvolysis of this lack of structural change in the solvent shows in the linearity of the variation of log (rate constant) with the reciprocal of the dielectric constant for the addition of ethane‐1,2‐diol to water and the absence of any prominent extrema in the enthalpy or entropy of activation using either co‐solvent. However, the effect of changes in solvation on the solvolysis with these two co‐solvents appears to operate in a similar manner to the effects found when the hydrophobic co‐solvent propan‐2‐ol is added to water. The application of a free energy cycle to the process of the initial state going to the transition state for this dissociative process suggests that, with both co‐solvents, [Co(CN)5]2− in the transition state is more stable than [Co(CN)5Cl]3− in the initial state. © John Wiley & Sons, Inc.
Kinetic salt effects on the outer sphere electron transfer reaction between hexacyanoferrate(II) and 4‐pyridinecarboxylatopentammine cobalt(III)
Authors: LÓPez P. , Muñ;Oz E. , SáNchez F. , Galán M. 
Published: January 2005

AbstractA study is made of the kinetic salt effects upon the outer‐sphere electron transfer reaction between hexacyanoferrate(II) and 4‐pyridinecarboxylatopentaamminecobalt(III). The observed salts effects are analyzed, taking into account the possible association of the reactants with the ions of the supporting electrolyte, though no conclusive results could be obtained. A correlation has been established between the logarithm of the observed second‐order rate constants and the logarithm of the rate constants for a related innersphere electron transfer reaction. From this correlation the conclusion can be drawn that the observed salt effects in concentrated electrolyte solutions are mainly due to the effects on the electron transfer step. © John Wiley & Sons, Inc.
Determination of the gas‐phase reactivity of hydroxyl with chlorinated methanes at high temperature: Effects of laser/thermal photochemistry
Authors: Taylor Philip H. , Jiang Zhen , Dellinger Barry 
Published: January 2005

AbstractAtmospheric pressure absolute rate coefficients have been determined for the gas phase reaction of OH radicals with methyl chloride (k1), methylene chloride (k2), and chloroform (k3) over an extended temperature range using a laser photolysis/laser‐induced fluorescence technique. The rate coefficients are best described by the following modified Arrhenius equations:

Measurements were obtained as a function of excimer photolysis intensity and are compared with previous results and extended to higher temperatures. Photolysis intensities in excess of 12 mJ‐cm−2 were found to measurably increase (up to a factor of 2) the rate coefficients for k3 between 400–775 K, with the effect increasing with increasing temperature. A similar, yet much smaller (ca. 20–35%) increase was observed for k2 between 675–955 K. No effect was observed for k1 at any temperature. Relative absorption coefficient measurements at 193.3 nm indicated that chlorinated methane photolysis increases with both increasing temperature and increasing chlorine substitution. These measurements suggest that reactant photolysis may be responsible for the observed dependence of k2 and k3 on photolysis intensity at elevated temperatures. The puzzling and disconcerting discrepancy between previously published high temperature measurements of k3 and transition state model predictions is reconciled with these latest measurements. © 1993 John Wiley & Sons, Inc.
Kinetics and mechanism of the oxidation of thiourea by chlorine dioxide
Authors: Rábai Gyula , Wang Robert T. , Kustin Kenneth 
Published: January 2005

AbstractThe stoichiometry and kinetics of the oxidation of thiourea (SC(NH2)2) by chlorine dioxide (ClO2) have been studied by uv‐vis spectrophotometry using conventional and stopped‐flow mixing techniques at 25.0 ± 0.1°C, pH 0.3–4.8. In high acid and initial 10:1 molar ratio of thiourea to chlorine dioxide, thiourea is oxidized relatively rapidly to dithiobisformamidine ion ((NH2)2CSSC(NH2)22+), which slowly decomposes to thiourea, sulfur, and cyanamide (NCNH2). In high acid and excess ClO2, thiourea is oxidized to relatively stable formamidine sulfinic acid ((NH) (NH2)CSO2H). In high acid and molar ratios of ClO2 to thiourea of 5:1 and higher, some oxidation to formamidine sulfonic acid ((NH) (NH2)CSO3H) occurs. At lower acidity, along with Cl−, the major ClO2 reduction product, byproduct sulfate is detected and, at pH < 3, ClO2−, also, appears. Kinetics data were collected for high excess thiourea with varying pH. The [ClO2]‐time curves are straight lines with negative slopes that increase in magnitude with increasing [thiourea]. The dependence on [thiourea] is first‐order; the dependence on [ClO2] is zero‐order for 90% of reaction. With decreasing pH, the rate increases and the disappearance of ClO2 becomes autocatalytic. Studies of the effects of reaction products on the rate of reaction lead to the conclusion that autocatalysis at low pH is due to the greater reactivity of HClO2 compared with ClO2−. A 10‐step mechanism incorporating a slow one‐electron transfer from thiourea to ClO2 to generate the (NH) (NH2)CS · radical and subsequent more rapid reactions has been constructed and implemented in a computer simulation which provides a reasonably accurate fit to the observed kinetics curves. © 1993 John Wiley & Sons, Inc.
Kinetics and mechanism of pyrogallol autoxidation: Calibration of the dynamic response of an oxygen electrode
Authors: Doona Christopher J. , Kustin Kenneth 
Published: January 2005

AbstractThe kinetics of the reaction between 1,2,3‐trihydroxybenzene (pyrogallol) and O2 (autoxidation) have been determined by monitoring the concentration of dissolved dioxygen with a polarographic oxygen electrode. The reaction is carried out in pseudo‐first‐order excess pyrogallol, 25°C, 0.08 M NaCl, and 0.04 M phosphate buffer in the pH range 6.9–10.5. Data collection precedes reaction initiation, but only the data recorded after the estimated 3.2 s dead time are used in kinetics calculations. Observed rate constants are corrected for incomplete mixing, which is treated as a first‐order process that has an experimentally determined mixing rate constant of 4.0 s−1. The rate law for the reaction is −d[O2]/dt=kapp[PYR]tot[O2], in which [PYR]tot is the total stoichiometric pyrogallol concentration. A mechanism is presented which explains the increase in rate with increasing [OH−] by postulating that H2PYR− (k2) has greater reactivity with dissolved dioxygen than does H3PYR (k1). The data best fit the equation kapp=(k1 + k2KH[OH−])/(1 + KH[OH−]) when the value of the hydrolysis constant KH (the quotient of the pyrogallol acid dissociation and water autoprotolysis constants) for this medium equals 3.1×104 M−1. The resulting values of k1 and k2, respectively, equal (0.13 + 0.01) M−1 s−1 and (3.5 plusmn; 0.1) M−1 s−1. This reaction is recommended as a test reaction for calibrating the dynamic response of an O2‐electrode. © 1993 John Wiley & Sons, Inc.
The formaldehyde decomposition chain mechanism
Authors: Irdam Erwin A. , Kiefer John H. , Harding Lawrence B. , Wagner Albert F. 
Published: January 2005

AbstractA kinetic mechanism for the chain decomposition of formaldehyde consistent with recent theoretical and experimental results is presented. This includes new calculations and measurements of the rate constant for the abstraction reaction

The calculation uses a multi‐reference configuration interaction wavefunction to construct the potential energy surface which is used in a tunneling‐corrected TST calculation of the rate constant. The rate constant for the bond fission

at high temperatures was determined by an RRKM extrapolation of direct low temperature measurements. This mechanism has been successfully tested against laser‐schlieren measurements covering the temperature range 2200–3200 K. These measurements are insensitive to all but the above two reactions and they confirm the large, non‐Arrhenius rate for the abstraction reaction derived here from theory. Modeling of previous experiments using IR emission, ARAS, and CO laser absorption with this mechanism is quite satisfactory. The branching ratio of the rate of the faster molecular dissociation (CH2O + (M) → CO + H2 + (M)), to that of the bond fission reaction, was estimated to be no more than 2 or 3 over 2000 to 3000 K. Such a ratio is consistent with one recent theoretical estimate and most of the experimental observations. © 1993 John Wiley & Sons, Inc.
Analysis of a model scheme incorporating reactant inhibition: Instability of homogeneous solution and formation of spatio–temporal structures
Authors: Rajani P. , Bandyopadhyay J. K. , Inamdar S. R. , Kulkarni B. D. 
Published: January 2005

AbstractA model scheme incorporating reactant inhibition in the rate process has been analyzed with a view to study the instability of homogeneous solution due to diffusion. Conditions for the occurrence of Turing as well as phase instability are derived and show the existence of multiplicity in the parameter space. The Ginzburg‐Landau equation for the system is developed and solved numerically in various regions of the parameter space. The simple model system shows the existence of very rich behavior including normal and inverted bifurcations in the super and subcritical regimes. The various results are analyzed and discussed. © 1993 John Wiley & Sons, Inc.
The thermal decomposition of the new energetic material ammoniumdinitramide (NH4N(NO2)2) in relation to Nitramide (NH2NO2) and NH4NO3
Authors: Rossi Michel J. , Bottaro Jeffrey C. , McMillen Donald F. 
Published: January 2005

AbstractThis qualitative study examines the response of the novel energetic material ammonium dinitramide (ADN), NH4N(NO2)2, to thermal stress under low heating rate conditions in a new experimental apparatus. It involved a combination of residual gas mass spectrometry and FTIR absorption spectroscopy of a thin cryogenic condensate film resulting from deposition of ADN pyrolysis products on a KCl window. The results of ADN pyrolysis were compared under similar conditions with the behavior of NH4NO3 and NH2NO2 (nitramide), which served as reference materials. NH4NO3 decomposes into HNO3 and NH3 at 182°C and is regenerated on the cold cryostat surface. HNO3 undergoes presumably heterogeneous loss to a minor extent such that the condensed film of NH4NO3 contains occluded NH3. Nitramide undergoes efficient heterogeneous decomposition to N2O and H2O even at ambient temperature so that pyrolysis experiments at higher temperatures were not possible. However, the presence of nitramide can be monitored by mass spectrometry at its molecular ion (m/ℯ 62). ADN pyrolysis is dominated by decomposition into NH3 and HN(NO2)2 (HDN) in analogy to NH4NO3, with a maximum rate of decomposition under our conditions at approximately 155°C. The two vapor phase components regenerate ADN on the cold cryostat surface in addition to deposition of the pure acid HDN and H2O. Condensed phase HDN is found to be stable for indefinite periods of time at ambient temperature and vacuum conditions, whereas fast heterogeneous decomposition of HDN at higher temperature leads to N2O and HNO3. The HNO3 then undergoes fast (heterogeneous) decomposition in some experiments. Gas phase HDN also undergoes fast heterogeneous decomposition to NO and other products, probably on the internal surface (ca. 60°C) of the vacuum chamber before mass spectrometric detection. © 1993 John Wiley & Sons, Inc.
Application of various methods of nonisothermal kinetic analysis to magnesium hydroxide decomposition
Authors: Halikia Iliana , Economacou Antonia 
Published: January 2005

AbstractIn the present study the determination of the mechanism of the thermal decomposition of magnesium hydroxide from thermogravimetric experiments is attempted. For this purpose nonisothermal kinetic analysis of the dynamic experimental data is applied, using different methods, which are based on the best linearization of a functional form of the Arrhenius equation. The experiments were carried out under nonisothermal conditions in a thermogravimetric analyzer with nitrogen atmosphere, at five different heating rates, i.e., 3, 8, 15, 20, and 35 deg/min. The nonisothermal methods used for the kinetic analysis of the experimental data were the Coats‐Redfern method, the Romero et al., the improved Coats‐Redfern method, the differential method, the differential by Jerez et al., and a method using the heating rate as a variable. Applying each of these methods, the kinetic parameters and, in most cases, the form of the conversion function (kinetic model) which governs the dehydroxylation process of Mg(OH)2 were determined. From the comparative study of the results of the above methods and using criteria about the credibility of each method, it was concluded that the kinetic model which represents the mechanism of the dehydroxylation of magnesium hydroxide, is that corresponding to the two dimensions nucleation with a reference value of activation energy 117.67 kJ/mol. © 1993 John Wiley & Sons, Inc.
The photo‐oxidation of diethyl ether in smog chamber experiments simulating tropospheric conditions: Product studies and proposed mechanism
Authors: Eberhard Jürg , MüLler Claudia , Stocker David W. , Kerr J. Alistair 
Published: January 2005

AbstractThe products formed by the hydroxyl radical initiated photo‐oxidation of diethyl ether have been investigated by irradiating synthetic air mixtures containing diethyl ether and nitrous acid in amounts approaching ppbv levels in a smog chamber. The decay of reactants and formation of products were monitored by gas chromatography, HPLC, and by chemiluminescent analysis. The major products are ethyl formate and formaldehyde, minor products include ethyl acetate, acetaldehyde, peroxyacetyl nitrate, methyl nitrate, and ethyl nitrate. The products observed arise from the decomposition reactions of the 1‐ethoxyethoxy radical and its reaction with oxygen. One molecule of nitric oxide appears to be oxidized per molecule of diethyl ether reacted. This is lower than would be expected on the basis of the proposed mechanism and possible reasons for the discrepancy are discussed. © 1993 John Wiley & Sons, Inc.
Rate constants for the gas‐phase reactions of ozone with unsaturated alcohols, esters, and carbonyls
Authors: Grosjean Daniel , Grosjean Eric , Williams Edwin L. 
Published: January 2005

AbstractThe kinetics of the gas‐phase reaction of ozone with unsaturated alcohols, carbonyls, and esters in air have been investigated at atmospheric pressure, ambient temperature (285–295 K), and in the presence of sufficient cyclohexane to scavenge the hydroxyl radical which forms as a product of the ozone‐unsaturated compound reaction. The reaction rate constants, in units of 10−18 cm3 molecule−1 s−1, are 0.26 ± 0.05 for acrolein, 1.07 ± 0.05 for 2‐ethyl acrolein, 6.0 ± 0.4 for ethyl vinyl ketone, 4.9 ± 0.4 for 3‐buten‐1‐ol, 14.4 ± 2.0 for allyl alcohol, 105 ± 7 for cis‐3‐hexen‐1‐ol, 7.5 ± 0.9 for methyl methacrylate, 2.9 ± 0.3 for vinyl acetate, 4.4 ± 0.3 for methyl crotonate, and 8.1 ± 0.3 for the 1,1‐disubstituted alkene 2‐ethyl‐1‐butene. Substituent effects on reactivity are discussed by comparison with alkenes and indicate that the reactivity of unsaturated alcohols is the same as that of alkene structural homologues and that the —C(O)OR, —C(O)R, and —CHO groups decrease the reactivity towards ozone as compared to alkyl groups. Estimates are made of the atmospheric persistence of these unsaturated compounds using the kinetic data obtained in this study as input to structure‐reactivity and linear free‐energy relationships. © 1993 John Wiley & Sons, Inc.
Thermal reaction of HNCO with NO2 at moderate temperatures
Authors: He Y. , Liu Xiaoping , Lin M. C. , Melius C. F. 
Published: January 2005

AbstractThe thermal reaction of HNCO with NO2 has been studied in the temperature range of 623 to 773 K by FTIR spectrometry. Major products measured are CO2 and NO with a small amount of N2O. Kinetic modeling of the time resolved concentration profiles of the reactants and products, aided by the thermochemical data of various likely reactive intermediates computed by means of the BAC‐MP4 method, allows us to conclude that the reaction is initiated exclusively by a new bimolecular process:
equation image
with a rate constant, k1 = 2.5 × 1012e−13,100/T cm3/mols. The well‐known bimolecular reaction
equation image
is the only strong competitive process in this important reactive system throughout the temperature range studied. Kinetic modeling of NO formation and NO2 decay rates gave rise to values of k10 which were in close agreement with literature data. © 1993 John Wiley & Sons, Inc.
Kinetics of the reaction of C6H5 with HBr
Authors: Lin M. C. , Yu T. 
Published: January 2005

AbstractThe rate constant for the reaction of phenyl radical with hydrogen bromide has been measured with the cavity‐ring‐down method at six temperatures between 297 and 523 K. The Arrhenius expression for the H abstraction reaction can be effectively given by:

. The values of these parameters are similar to those for the H + HBr reaction, but are in sharp contrast to those for alkyl radical reactions. The gross difference between the alkyl radical reactions and the phenyl and H‐atom reactions could be rationalized in terms of the inductive effects of these radicals as measured by Taft's σ* (polar) constants. © 1993 John Wiley & Sons, Inc.
On the importance of specific solvent effects in electron trransfer reactions
Authors: Moyá María Luisa , Sánchez Francisco , Burgess John 
Published: January 2005

AbstractThe intramolecular electron transfer reaction within the binuclear complex formed between tetraamminepyrazinecarboxylatocobalt(III) and aquopentacyanoferrate(II) ions is studied in various binary aqueous media at different temperatures. Results could not be explained on the basis of a primitive model. Experimental data were fitted by using a multiparameter regression which shows the important role played by specific interactions on reactivity. © 1993 John Wiley & Sons, Inc.
The reaction of fluorine atoms with formyl fluoride and the CFO self‐reaction at 293 K
Authors: Behr Peter , Goldbach Karin , Heydtmann Horst 
Published: January 2005

AbstractA fast‐flow apparatus with mass spectrometric detection was used to study the system F + CHFO between 2 and 3.5 mbar total pressure. The rate constant of the primary reaction was evaluated directly to yield at 298 K k(1) = (8.8 ± 1.4) * 10−13 cm3 * molecule−1 * s−1. Numerical modelling was used to determine the rate constant at 298 K of the subsequent reaction CFO + CFO → CF2O + CO: k(2) = (4.9 ± 2.0) * 10−11 cm3 * molecule−1 * s−1. The possible occurrences of secondary reactions, CFO + F + M → CF2O + M, and CFO + F2 → CF2O + F, can be excluded under the present conditions. © 1993 John Wiley & Sons, Inc.