bluuebunny/crossref_metadata_2025_split huggingface dataset:
The formation of the complex pentacyano(3‐pyrazincarboxylate)ferrate(II) in various water‐cosolvent mixtures
Authors: Rodríguez Amalia , Moyá M. Luisa , López Pilar , Muñoz Ernestina 
Published: January 2005

AbstractThis article presents the kinetic of formation of pentacyano(3‐pyrazincarboxylate)ferrate(II) from pyrazincarboxylate and pentacyanoaquoferrate(II) ions in various isodielectric water‐cosolvent mixtures at 298 K. The rate law is in the form d[Fe(CN)5(3‐pzCO2)4−]/dt = 𝓀f[Fe(CN)5H2O−3] [pzCO2−]. Plots of log(𝓀f/dm3 mol−1 s−1) vs. D (where Dm is the bulk dielectric constant of the medium) and log(𝓀f/dm3 mol−1 s−1) vs. the Grunwald‐Winstein parameter are nonlinear for some of the mixtures and to each mixture corresponds a different behavior in respect to the above parameters. The plots of log(𝓀f/dm3 mol−1 s−1) vs. the mol fraction of water are straight lines over the entire composition range studied, except for the water‐methanol mixture. It is evident that the solvation phenomenon plays a dominant role and that the rate of formation is mediated by the dual solvent vectors, the overall basicity and acidity of the solvent mixtures.
Absolute and relative rate constants for the reactions of hydroxyl radicals and chlorine atoms with a series of aliphatic alcohols and ethers at 298 K
Authors: Nelson Linda , Rattigan Oliver , Neavyn Ruaidhri , Sidebottom Howard , Treacy Jack , Nielsen Ole John 
Published: January 2005

AbstractRate constants for the gas‐phase reactions of hydroxyl radicals and chlorine atoms with aliphatic alcohols and ethers have been determined at 298 ± 2 K and at a total pressure of 1 atmosphere. The OH radical rate data were obtained using both the absolute technique of pulse radiolysis combined with kinetic UV spectroscopy and a conventional photolytic relative rate method. The Cl atom rate constants were measured using only the relative rate method. Values of the rate constants in units of 10−12 cm3 molecule−1 s−1 are:
equation image
The above relative rate constants are based on the values of 𝓀(OH + c‐C6H12) = 7.49 × 10−12 cm3 molecule−1 s−1 and 𝓀(Cl + c‐C6H12) = 311 × 10−12 cm3 molecule−1 s−1. Attempts to corre late the trends in the rate constant data in terms of the bond dissociation energies and inductive effects are discussed.
Effect of solvents and effect of nucleophiles in nucleophilic substitution on benzyl bromide—A kinetic study
Authors: Manikyamba P. , Sundaram E. V. 
Published: January 2005

AbstractThe kinetics of the reaction of benzyl bromide with thiourea was studied in different pure (protic and aprotic) solvents and the rate data was correlated using linear multiple regression analysis. From the regression coefficients which describe the susceptibility of rate to different solvent parameters, information regarding the solvent‐reagent, and the solvent‐intermediate interactions was obtained and solvation models were proposed.Applicability of the Swain‐Scott free energy relationship was tested using different sulphur nucleophiles in acetonitrile solvent and the nucleophilicity constant of N‐acetylthiourea was computed as 2.74 from the regression line.
A flash photolysis investigation of the gas phase uv absorption spectrum and self‐reaction kinetics of the neopentylperoxy radical
Authors: Dagaut Philippe , Kurylo Michael J. 
Published: January 2005

AbstractThe ultraviolet absorption spectrum of the neopentylperoxy radical, (CH3)3CCH2O2 (or C5H11O2), and the kinetics of its self‐reaction have been studied in the gas phase using a flash photolysis technique. The room temperature absorption cross‐section at 250 nm was determined to be

and was used to normalize the radical absorption spectrum between 210 and 300 nm. Detailed modeling of the self‐reaction system was used to interpret the transient absorption kinetic decay curves over the temperature range 228–380 K, at total pressures between 25 and 100 torr. The results are discussed in relation to previous measurements of alkylperoxy radical spectra and kinetics.
The atmospheric chemistry of Oxygenated fuel additives: t‐Butyl alcohol, dimethyl ether, and methylt‐butyl ether
Authors: Japar S. M. , Wallington T. J. , Richert J. F. O. , Ball J. C. 
Published: January 2005

AbstractThe mechanisms for the Cl‐initiated and OH‐initiated atmospheric oxidation of t‐butyl alcohol (TBA), methyl t‐butyl ether (MTBE), and dimethyl ether (DME) have been determined. For TBA the only products observed are equimolar amounts of H2CO and acetone, and its atmospheric oxidation can be represented by (7),
equation image
The mechanism for the atmospheric oxidation of DME is also straight forward, with the only observable product being methyl formate,
equation image
The mechanism for the atmospheric oxidation of MTBE is more complex, with observable products being t‐butyl formate (TBF) and H2CO. Evidence is presented also for the formation of 2‐methoxy‐2‐methyl propanal (MMP), which is highly reactive and presumably oxidized to products. The atmospheric oxidation of MTBE can be represented by (9) and (10),
equation image

equation image
In terms of atmospheric reactivity, DME, TBA, and MTBE all compare favorably with methanol. In terms of rate of reaction in the atmosphere, DME, MTBE, and TBA are 1.4, 0.40, and 0.28 times as reactive as CH3OH towards OH on a per carbon basis. With regard tochemistry, atmospheric oxidation of CH3OH yields highly reactive H2CO as the sole carbon‐containing product. In contrast, only 25% of the carbon in TBA is converted to H2CO, with the balance yielding unreactive acetone. For DME, all the carbon is converted to methyl formate which is unreactive. Finally, for MTBE, 60% is converted to unreactive TBF while the remaining 40% produces highly reactive MMP.Final assessment of the impact of these materials on the atmospheric reactivity of vehicle emissions requires the determination of their emissions rates under realistic operating conditions.
Thermal decomposition of chlorofluoromethyl peroxynitrates
Authors: Köppenkastrop D. , Zabel F. 
Published: January 2005

AbstractThe thermal decomposition of CCl3O2NO2,CCl2FO2NO2, and CClF2O2NO2 was studied in a temperature‐controlled 420 l reaction chamber using in situ detection of peroxynitrates by long‐path IR absorption. The temperature dependence of the unimolecular dissociation rate constants was determined at total pressures of 10 and 800 mbar in nitrogen as buffer gas, and the pressure dependence was measured at 273 K between 10 and 800 mbar. In Troe's notation, the data are represented by the following values for the limiting low and high pressure rate constants k0/[N2] and k∞ and the fall‐off curvature parameter Fc (in units of cm3 molecule−1 s−1, s−1): CCl3O2NO2,k0/[N2] = 6.3 × 10−3 exp(−85.1 kJ · mol−1/RT), k∞ = 4.8 × 1016 exp(−98.3 kJ · mol−1/RT), Fc = 0.22; CCl2FO2NO2, k0/[N2] = 1.01× 10−2 exp(−90.3 kJ · mol−1/RT), k∞ = 6.6 × 1016 exp(−101.8 kJ · mol−1/RT), Fc = 0.28; and CClF2O2NO2, k0/[N2] = 1.80 × 10−3 exp(−87.3 kJ · mol−1/RT), k∞ = 1.60 × 1016exp(−99.7 kJ · mol−1/RT), Fc = 0.30. From these dissociation rate constants and recently measured rate constants for the reverse reaction (see Caralp, Lesclaux, Rayez, Rayez, and Forst [19]), bond energies (=ΔH) of 100, 103, and 104 kJ/mol were derived for the RO2–NO2 bonds in CCl3O2NO2, CCl2FO2NO2, and CClF2O2NO2, respectively. The kinetic and thermochemical parameters of these decomposition reactions are compared with those of the dissociation of other peroxynitrates. Atmospheric implications of the thermal stability of chlorofluoromethyl peroxynitrates are briefly discussed.
A combined stability‐sensitivity analysis of weak and strong reactions of hydrogen/oxygen mixtures
Authors: Yetter R. A. , Rabitz H. , Hedges R. M. 
Published: January 2005

AbstractStability and sensitivity analysis are used to examine the ignition/reaction characteristics of dilute hydrogen‐oxygen mixtures. The analysis confirms the existence of two distinct regions of ignition and fast reaction previously labeled “weak” and “strong” ignition, both of which are located in the explosive pressure‐temperature domain and separated by a region related to the “extended” classical second limit. The stability analysis is based on an eigenanalysis of the Green's function matrix of the governing kinetic equations. The magnitudes of the largest (and system controlling) eigenvalue allow the strengths of the two processes to be quantified, giving a clear definition to the terms “weak” and “strong.” The sensitivities of the largest eigenvalue to the reaction rate constants of the mechanism pinpoint the elementary steps controlling the two ignition processes and the subsequent reaction. The associated eigenvectors yield the direction of change in species concentrations and temperature during the course of reaction. These vectors are found to be nearly constant during the induction period of both “weak” and “strong.” ignition, thus producing constant overall stoichiometric reactions. The subsequent reaction of major reactants associated with “weak” ignition also has a constant overall reaction vector, although, different than that during the induction period. However, the vector describing the reaction of major reactants associated with “strong.” ignition is found never to be constant, but continuously changing beyond the induction period.
Kinetics and mechanisms of chlorine transfer from chloramine to amines in aqueous medium
Authors: Ferriol Michel , Gazet Josette , Adad Marie‐thérèse Saugier‐cohen 
Published: January 2005

AbstractThe kinetics and the equilibrium constant of the chlorine transfer reaction between monochloramine NH2Cl and the amines: C2H5NH2, (CH3)2CHNH2, (CH3)2NH, and (C2H5)2NH are investigated by spectrophotometry in aqueous medium at 25°C, in the pH range from 8 to 13 and for an ionic strength equal to 1.03 ± 0.05M. For a concentration of total ammonia equal to 1M, the observed rate constant is pH independent below 8 and above 12.8 and reaches a maximum located between the pKas of NH4+ and RR'NH2+. From these results and those obtained earlier for NH2Cl and CH3NH2, the reaction is shown to involve an interaction between neutral molecules NH2Cl and RR'NH, subject to general acid catalysis. The ability of an interaction corresponding to a specific catalysis and involving NH3Cl+ and RR'NH rather than NH2Cl and RR'NH2+ is also discussed. The activation parameters are given for each reaction.
Isotopic study of the mechanism of ozone formation
Authors: Larsen N. Wessel , Pedersen T. , Sehested J. 
Published: January 2005

AbstractThe mechanism of ozone formation has been studied using 16O and 18O2. High‐resolution microwave spectroscopy was used to measure the amounts of the isotopomeric ozone species formed. The study is hampered by the very rapid exchange process between the reactants, that tends to scramble the isotopes and hence give a 2:1 statistical ratio between the two possible isotopomers. We have found a strategy to come around this difficulty and conclude that the mechanism is a simple end‐on‐addition.
Experimental study on the reactions of vibrationally excited 1,1‐difluorocyclopropane
Authors: Lauterwald H. , Heydtmann H. 
Published: January 2005

AbstractVibrationally excited 1,1‐difluorocyclopropane, generated by addition of singlet methylene to 1,1‐difluoroethene, reacts according to four reaction channels by isomerization as well as by elimination of difluoromethylene. Identification of the products leads to a critical view on an early study dealing with this reaction system. The pressure dependence of the reaction is investigated. The apparent rate‐constants of the reaction paths were determined.
Preliminary observations on the high temperature oxidation of ethyl tert‐butyl ether
Authors: Dunphy Mary P. , Simmie John M. 
Published: January 2005

AbstractThe high temperature oxidation of ethyl tert‐butyl ether (ETBE) with oxygen in argon diluent has been studied in reflected shock waves over the temperature range 1160 to 1830 K, with pressures of 3.5 bar and with varying equivalence ratios from 0.3 to 2.4. Measurements of the ignition delay times, characterized by chemiluminescence and pressure rise, show that the rate of oxidation is very similar to that of methyl tert‐butyl ether.
An investigation of temperature and pressure dependence of the reaction of CF2ClO2 radicals with nitrogen dioxide by flash photolysis and time resolved mass spectrometry
Authors: Wu Fuxiang , Carr Robert W. 
Published: January 2005

AbstractRate coefficients of the termolecular reaction

were determined over the temperature range of 248–324 K and at pressures from 1 to 10 torr by time resolved mass spectrometry. CF2ClO2 radicals were generated by flash photolysis of CF2ClBr in the presence of oxygen. Their rate of decay was measured by following (CF2O2)+ fragment ions formed in the ion source. With 2 to 40 mtorr of NO2 present the dominant removal pathway is addition to form the peroxynitrate. The third order rate coefficients are wholly within the falloff over the experimental pressure range, and have a negative temperature coefficient. Rate constants for the reverse reaction, the unimolecular dissociation of CF2ClO2NO2, D. Koppenkastrop and F. Zabel, Int. J. Chem. Kinet., 23, 1 (1991) were employed to calculate equilibrium constants, from which a 600 torr value of the combination rate coefficient was obtained at each temperature. From the temperature dependence of the equilibrium constants, the average enthalpy of reaction over the experimental temperature range was found to be 106.1 ± 0.3 kJ/mol. Extrapolation of the combination rate constants to lower and higher pressures, and estimates of low and high pressure limiting rate coefficients, k0 and k∞ were done by nonlinear least squares fit of the experimental data, using the empirical Fc equations developed by Troe.
Shock tube pyrolysis of pyrrole and kinetic modeling
Authors: Mackie John C. , Colket Meredith B. , Nelson Peter F. , Esler Michael 
Published: January 2005

AbstractThe kinetics of pyrolysis of pyrrole dilute in argon have been studied in a single pulse shock tube, using capillary column GC, together with GC/MS and FTIR for product identification, over the temperature range 1200–1700 K, total pressures of 7.5–13.5 atm and nominal mixture compositions of pyrrole of 5000 and 700 ppm (nominal concentrations of 5 × 10−7 and 7 × 10−8 mol cm−3). Time‐resolved measurements of the rate of disappearance of pyrrole behind reflected shock waves have been made by absorption spectroscopy at 230 nm, corresponding to the lowest 1π* ← 1π transition of pyrrole at pressures of 20 atm and mixture compositions between 1000–2000 ppm pyrrole (1.7–3.0 × 10−7 mol cm−3) over the temperature range of 1300 to 1700 K. At the lower end of the studied temperature range, the isomers of pyrrole, allyl cyanide and cis‐ and trans‐crotononitrile, were the principal products, together with hydrogen cyanide and propyne/allene. At elevated temperatures, acetylene, acetonitrile, cyanoacetylene, and hydrogen became important products.The rate of overall disappearance of pyrrole, as measured by absorption spectrometry, was found to be first order in pyrrole concentration, with a rate constant kdis(pyrrole) = 1014.1±0.7 exp(−74.1 ± 3.0 kcal mol−1/RT) s−1 between 1350–1600 K and at a pressure of 20 atm. First order dependence of pyrrole decomposition and major product formation was also observed in the single pulse experiments over the range of mixture compositions studied.A 75‐step reaction model is presented and shown to substantially fit the observed temperature profiles of the major product species and the reactant profile. In the model the initiation reaction is postulated to be the reversible formation of pyrrolenine, (2H‐pyrrole). Pyrrolenine can undergo ring scission at the C2N bond forming a biradical which can rearrange to form allyl cyanide and crotononitrile or undergo decomposition to form HCN and C3H4 or acetylene and a precursor of acetonitrile. The model predicts an overall rate of disappearance of pyrrole in agreement with the experimental measurements.
UV absorption spectra and kinetics of the self reaction of CFCl2CH2O2 and CF2ClCH2O2 radicals in the gas phase at 298 K
Authors: Wallington Timothy J. , Nielsen Ole J. 
Published: January 2005

AbstractThe ultraviolet absorption spectra of the peroxy radicals derived from hydrochlorofluorocarbons 141b and 142b, (CFCl2CH2O2 and CF2ClCH2O2, respectively), and the kinetics of their self reactions have been studied in the gas phase at 298 K using a pulse radiolysis technique. Absorption cross sections were quantified over the wavelength range 220–300 nm. Measured absorption cross sections at 250 nm were indistinguishable within the experimental uncertainties (≈10%) and yield;

Errors represent the sum of statistical uncertainty and our estimate of potential systematic errors. Our absorption cross section data were then used to derive the observed self reaction rate constants for reactions (1) and (2), defined as −d[RO2]/dt = 2k[RO2]2 (R = CFCl2CH2 or CF2ClCH2),
equation image
of k1obs = (4.36 ± 0.64) × 10−12 and k2obs = (4.13 ± 0.58) × 10−12 cm3 molecule−1 s−1, quoted errors represent 2σ. These results are discussed with respect to previous studies of the absorption spectra and kinetics of peroxy radicals.
The reaction of 2,5‐dimethylpyrrole with O2(a1Δg) in the gas phase
Authors: Fiedler E. , Hack W. 
Published: January 2005

AbstractThe chemical reaction of 2,5‐dimethylpyrrole (C6H9N) with O2(1Δg)
equation image
was studied in the gas phase in an isothermal flow reactor at room temperature and low pressures. The C6H9N concentration profiles were studied under pseudo‐first order conditions [C6H9N]∘ ≪ [O2(1Δg)] with mass‐spectrometric detection of C6H9N. O2(1Δg) was produced either in a microwave discharge or in a chemical reaction. The value for the rate constant:

was measured.The rate constant is compared to the value obtained for the quenching process. The primary product C6H9NO2 was detected by mass spectrometry and the reaction mechanism is proposed. The possibility of using this reaction as a gas phase titration reaction for O2(1Δg) is discussed.
Kinetic model of liquid B2O3 gasification in a hydrocarbon combustion environment: I. Heterogeneous surface reactions
Authors: Brown R. C. , Kolb C. E. , Rabitz H. , Cho S. Y. , Yetter R. A. , Dryer F. L. 
Published: January 2005

AbstractAs part of an ongoing program to model hydrocarbon assisted boron combustion, a kinetic model has been developed to describe gasification of the ubiquitous boron oxide coating that inhibits particulate boron ignition. This model includes homogeneous gas phase oxidation reactions, multi‐component gas phase diffusion, heterogeneous surface reactions, and oxide vaporization. The kinetic processes are treated using a generalized kinetics code, with embeded sensitivity analysis, for the combustion of a one‐dimensional (particle radius), spherical particle.This article presents the heterogeneous surface reactions used to describe oxide gasification and presents selected model results for a spherical boron oxide droplet which illustrate the dependence of the oxide gasification rates on the ambient temperature and particle diameter.
Shock tube measurements of the reactions of CN with O and O2
Authors: Davidson D. F. , Dean A. J. , Dirosa M. D. , Hanson R. K. 
Published: January 2005

AbstractThe rate coefficients of the reactionsequation imageandequation imagewere determined in a series of shock tube experiments from CN time histories recorded using a narrow‐linewidth cw laser absorption technique. The ring dye laser source generated 388.44 nm radiation corresponding to the CN B2Σ+(v= 0) ←X2Σ+(v= 0) P‐branch bandhead, enabling 0.1 ppm detection sensitivity.Reaction (1) was measured in shock‐heated gas mixtures of typically 200 ppm N2O and 10 ppm C2N2in argon in the temperature range 3000 to 4500 K and at pressures between 0.45 and 0.90 atm.k1was determined using pseudo‐first order kinetics and was found to be 7.7 × 1013(±20%) [cm3mol−1s−1]. This value is significantly higher than reported by earlier workers. Reaction (2) was measured in two regimes. In the first, nominal gas mixtures of 500 ppm O2and 10 ppm C2N2in argon were shock heated in the temperature range 2700 K to 3800 K and at pressures between 0.62 and 1.05 atm.k2was determined by fitting the measured CN profiles with a detailed mechanism. In the second regime, gas mixtures of 500 ppm O2and 1000 ppm C2N2in argon were shock heated in the temperature range 1550 to 1950 K and at pressures between 1.19 and 1.57 atm. Using pulsed radiation from an ArF excimer laser at 193 nm, a fraction of the C2N2was photolyzed to produce CN. Pseudo‐first order kinetics were used to determinek2. Combining the results from both regimes,k2was found to be 1.0 × 1013(±20%) [cm3mol−1s−1].
A spectroscopic study of the equilibrium NO2 + NO3 + M 2 N2O5 + M and the kinetics of the O3/N2O5/NO3/NO2/ air system
Authors: Hjorth J. , Notholt J. , Restelli G. 
Published: January 2005

AbstractThe equilibrium constant, Keq of the reaction NO2 + NO3 + M 2 N2O5 + M has been determined for a small range of temperatures around room temperature in air at 740 torr by direct spectroscopical measurements of NO2, NO3, and N2O5. At 298 K, Keq was determined as (3.73 ± 0.61) × 10−11 cm3 molecule−1. Averaging this and 11 other independent evaluations of Keq yields Keq = (3.31 ± 0.82) × 10−11 cm3 molecule−1, where the uncertainty is given as one standard deviation. The kinetics of the O3/NO2/N2O5/NO3/ air system was studied in a static chamber at room temperature and 740 torr total pressure. Evidence of a unimolecular decay reaction of NO3, NO3 → NO + O2, was found and its rate coefficient was estimated as (1.6 ± 0.7) × 10−3 s−1 at 295 ± 2 K.
Oxidation by Permanganate in strong alkaline medium. Oxidation of ethane‐1,2‐diol, glycol aldehyde, glycollic acid, and glyoxylic acid
Authors: Szammer J. , Jáky M. , Gerasimov O. V. 
Published: January 2005

AbstractA study was made on the kinetics and mechanism of the reaction

in aqueous solutions of 0.10 to 2.0 mol dm−3 alkaline concentrations. The substrates (S) applied were ethane‐1,2‐diol (ethylene glycol), glycol aldehyde, glycollic acid, and glyoxylic acid. Glycol aldehyde and glyoxylic acid were present in the form of dihydrate. In each case alkoxy anion is the reactive form and the KB constant of deprotonation can be calculated from the kinetic data. A mechanism based on electron abstraction is suggested. Manganate reacts with these substrates much slower than permanganate.
Study of mechanistic features of tetrahedral‐octahedral interconversion of tetracyanozincate (II) to bis(4‐(2hyphen;Pyridylazo)hyphen;resorcinol)zincate(II) by stopped‐flow technique
Authors: Prasad Surendra , Nigam Prem C. , Phull Madhu 
Published: January 2005

AbstractThe present study examines the kinetics and mechanism of the formation of [Zn(CN)4]2− from ZnR22− (R represents 4‐(2‐Pyridylazo)resorcinol, short named as Par) and vice versa. The reactions have been followed at 494 nm (λmax of [Zn(Par)2]2−, ε = 7.8 × 104 M−1 cm−1) using stopped‐flow spectrophotometer in presence of excess of incoming ligand. The data show that the formation of [Zn(CN)4]2− complex is first order in [ZnR22−] and the order with respect to [CN−] varies from one at higher cyanide concentration to zero at low [CN−]. These observations suggest a slow dissociation of [ZnR2]2− to ZnR and R2− and a cyanide assisted rapid dissociation of [ZnR2]2− to [ZnR(CN)x]x− followed by their rapid conversion to [Zn(CN)4]2−. The reaction of Zn(Par) with cyanide ions also follow first order kinetics at higher as well as lower cyanide concentrations. The reverse reaction exhibits first order dependence each in [Zn(CN)42−] and [Par2−], but an inverse first order dependence in [CN−] at low Par concentrations. However, at higher Par concentration the reaction rate tends to be independent of [Par2−]. On the basis of forward and reverse rate studies, a five step mechanism consistent with these results has been proposed. The activation parameters and the effect of ionic strength have been used in further support to the proposed mechanism. The effect of pH on the rates of forward and reverse reaction has also been investigated.