bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics and mechanisms of oxidation by metal ions, part XII [1] oxidation of formaldehyde by alkaline osmium(VIII)
Authors: Vishnoi Minakshi , Sharma Kamla , Mehrotra Raj N.
Published: January 2005

The stopped‐flow measurements on the disappearance of alkaline osmium(VIII) at 402 nm indicated a first‐order dependence each in [Os(VIII)] and [HCHO]. The pseudo first‐order rate constant kobs ([HCHO] ≫ [Os(VIII)]) decreased with increasing [OH−]. The ionic strength, however, had no effect on kobs. The rapid scan spectra of the reaction mixture indicated the formation of an inert complex which absorbs at 319 nm. Therefore the rate determining step is considered to involve the bimolecular collision between OsO4(OH) and hydrated formaldehyde. The values of the rate limiting constant k and the equilibrium constant Kha for the formation of the alkoxide ion from the reaction of hydrated formaldehyde with OH− are evaluated. The equilibrium constant Kha, within the experimental limits, is independent of temperature. The pKa value, calculated from Kha, is 13.62 ± 0.05 which is in good agreement with the pKa value 13.27 for formaldehyde. The activation parameters, ΔH‡ = 40 ± 2 kJ mol−1 and ΔS‡ = −51 ± 6 JK−1 mol−1, for the rate limiting constant k are determined.
Are reaction rate coefficients additive? Revised transition state theory calculations for OH + alkane reactions
Authors: Cohen N.
Published: January 2005

Recent shock tube measurements [1,2] of the reactions of OH radicals with various hydrocarbons provide the incentive for revising an earlier model [3] used to carry out thermochemical transition state theory calculations for the reaction rate coefficients of OH radicals with alkanes. In this article, details of the revised model are presented and calculations are described and compared with experiments. Of particular interest is the question of the reliability of an additive formulation for H atom abstraction rate coefficients; i.e., can we evaluate the total rate coefficient as the sum of site‐specific rate coefficients, ktotal = Σinki, where we sum either over primary, secondary, and tertiary H atoms or over some larger number of classes of atoms? It is argued that there are two major reasons for expecting different primary, secondary, or tertiary H atoms to have different rate parameters: (1) activation energies may depend on next‐nearest neighbors and (2) activation entropies can be mass‐dependent. In principle the first factor invalidates the common procedure of treating the total rate coefficient for OH + RH H abstraction processes as the sum of invariant primary, secondary, and tertiary rates multiplied by the respective number of such H atoms in the molecule. The second factor places limits on the accuracy of any additive formulation. A separate question is whether there is sufficient experimental evidence to justify these distinctions, or whether, given experimental and theoretical uncertainties, it is adequate to treat them all as equivalent. It is concluded that (1) mass‐dependent variations are just barely discernible; and (2) there are measurable differences among various primary H atom abstractions, and possibly among secondary atoms, but the data base does not justify distinguishing among tertiary H atoms.
Catalytic effect of anionic micelles on alkaline hydrolysis of N‐hydroxyphthalimide. Evidence for the probable occurrence of the reaction in between Gouy‐Chapman and exterior boundary of Stern layers of the micelles
Authors: Khan M. Niyaz
Published: January 2005

The nucleophilic second‐order rate constant (kOH) for the reaction of ŌH with ionized N‐hydroxyphthalimide (S−) appears to follow a reaction mechanism similar to that for reactions of ŌH with neutral phthalimide and its N‐substituted derivatives. Kinetically indistinguishable terms, k′w[H2O][S−] and kŌH[ŌH][SH] (SH represents nonionized N‐hydroxyphthalimide), which constitute the pH‐independent rate region of the pH‐rate profile, are resolved qualitatively. It is shown that the term kŌH[ŌH][SH], rather than k′w[H2O][S−], is important in these reactions. The rates of ŌH‐catalyzed cleavage of S− were studied at 32° in the presence of micelles of sodium dodecyl sulphate (SDS). At a constant [ŌH], the observed pseudo first‐order rate constants (kobs) increase linearly with [SDS]T (total SDS concentration). These data are explained in terms of the pseudophase model of micellar effects on reactivity. The linear dependence of kobs with [SDS]T (within [SDS]T range of 0.0–0.2 or 0.3 M) is attributed to the occurrence of the reaction between the exterior boundary of Stern layer and Gouy‐Chapman layer.
The use of transition‐state theory to extrapolate rate coefficients for reactions of H atoms with alkanes
Authors: Cohen N.
Published: January 2005

The thermochemical kinetics formulation of conventional transition state theory has been applied to metathesis reactions of H atoms with a series of alkanes in order to provide a sound framework for the intercomparison of experimental data, and also to extrapolate rate coefficients to temperature regimes that may lie beyond the range of experiments. The calculations require a value for the rate coefficient at some temperature, necessitating a discussion of the extant experimental data and their reliability. The procedures are described, the results of the calculations are presented, and their agreement with experimental data (for methane, ethane, propane, butane, pentane, isobutane, cyclopropane, cyclohexane, neopentane, neooctane, and 2,2,3‐trimethylbutane) is discussed. A general expression for reactions of H with large (more than 4 carbons) alkanes is proposed:

where np, ns, and nt are the numbers of primary, secondary, and tertiary H atoms available for abstraction.
THERM: Thermodynamic property estimation for gas phase radicals and molecules
Authors: Ritter Edward R. , Bozzelli Joseph W.
Published: January 2005

We have developed a computer code for an IBM PC/XT/AT or compatible which can be used to estimate, edit, or enter thermodynamic property data for gas phase radicals and molecules using Benson's group additivity method. The computer code is called THERM (THermo Estimation for Radicals and Molecules). All group contributions considered for a species are recorded and thermodynamic properties are generated in old NASA polynomial format for compatibility with the CHEMKIN reaction modeling code. In addition, listings are created in a format more convenient for thermodynamic, kinetic, and equilibrium calculations. Polynomial coefficients are valid from 300–5000 K using extrapolation methods based upon the harmonic oscillator model, an exponential function, or the Wilhoit polynomials. Properties for radical and biradical species are calculated by applying bond dissociation increments to a stable parent molecule to reflect loss of H atom. THERM contains a chemical reaction interpreter to calculate thermodynamic property changes for chemical reactions as functions of temperature. These include equilibrium constant, heat release (required heat, ΔHr), entropy change (ΔSr), Gibbs free energy change (ΔGr), and the ratio of forward to reverse Arrhenius A‐factors (for elementary reactions). This interpreter can also process CHEMKIN input files. A recalculation procedure is incorporated for rapid updating of a database of chemical species to reflect changes in estimated bond dissociation energies, heats of formation, or other group values. All input and output files are in ASCII so that they can be easily edited, expanded, or updated.
Thermal unimolecular decomposition of 1,3,5‐trioxane: Comparison of theory and experiment
Authors: Aldridge H. K. , Liu X. , Lin M. C. , Melius C. F.
Published: January 2005

The unimolecular decomposition of 1,3,5‐trioxane into three formaldehyde molecules has been studied thermally at eight temperatures between 523 and 603 K using mixtures highly diluted with Ar. Under these conditions, the only decomposition product detected by means of FTIR analysis was formaldehyde. At 588 K, the effect of total pressure was examined between 25 and 800 torr; a noticeable decline in the first‐order rate constant was observed only at pressures below 500 torr. A least‐squares analysis of the measured high‐pressure, first‐order rate constants leads to

This result differs significantly from earlier data on the reaction, but it compares closely with the theoretical value:

computed with the transition‐state theory using the molecular and TST parameters predicted by the BAC–MP4 method.
Products of the gas‐phase reaction of methyl tert‐butyl ether with the OH radical in the presence of NOx
Authors: Tuazon Ernesto C. , Carter William P. L. , Aschmann Sara M. , Atkinson Roger
Published: January 2005

The products of the reaction of the hydroxyl (OH) radical with methyl tert‐butyl ether (MTBE) in NOx‐air systems were identified and measured by Fourier transform infrared absorption spectroscopy and gas chromatography. The products observed, and their yields, were as follows: t‐butyl formate, 76 ± 7%; formaldehyde, 37%; methyl acetate, 17 ± 2%, and acetone, 2.1 ± 0.9%, where the stated error limits represent both random (two standard deviations) and estimated systematic uncertainties. These products account for ca. 95% of the MTBE carbon reacted. Infrared absorption bands which may be due to small amounts of organic nitrate formation were observed, but organic nitrate yields could not be quantified. These data allow a chemical mechanism for the reaction of MTBE with the OH radical in the presence of NOx to be formulated.
Rate constants for the gas‐phase reactions of OH radicals and Cl atoms with n‐alkyl nitrites at atmospheric pressure and 298 K
Authors: Nielsen Ole J. , Sidebottom Howard W. , Donlon Michael , Treacy Jack
Published: January 2005

Rate constants for the reactions of OH radicals and Cl atoms with CH3ONO, C2H5ONO, n‐C3H7ONO, n‐C4H9ONO, and n‐C5H11ONO have been determined at 298 ± 2 K and a total pressure of approximately 1 atm. The OH rate data were obtained using both the absolute rate technique of pulse radiolysis combined with kinetic spectroscopy and a relative rate method involving simultaneous measurement of the loss of the nitrite and the reference compound. The Cl rate constants were measured using the relative rate method. Values of the rate constants in units of 10−13 cm3 molecule−1 s−1 are:

Relative Cl
Relative OH
Absolute OH

CH3ONO
94.4 ± 7.4
3.0 ± 1.0
2.6 ± 0.5

C2H5ONO
295 ± 13
7.0 ± 1.5
7.0 −1.1

n‐C3H7ONO
646 ± 58
11.0 ± 1.5
12.0 ± 0.5

n‐C4H9ONO
1370 ± 58
22.7 ± 0.8
27.2 ± 6.0

n‐C5H11ONO
2464 ± 444
37.4 ± 5.0
42.5 ± 8.0

When compared to rate data for the corresponding alkanes the results show that the ‐ONO group decreases the rate constant for H atom abstraction by the OH radical from groups bonded to the ‐ONO group and also decreases that for groups in the β position. Similar results were found for the reaction of Cl atoms with these compounds. The results are discussed in terms of reactivity trends.
Surface chemkin: A general formalism and software for analyzing heterogeneous chemical kinetics at a gas‐surface interface
Authors: Coltrin Michael E. , Kee Robert J. , Rupley Fran M.
Published: January 2005

This article describes a general kinetic formalism for treating the details of heterogeneous reactions at a gas‐solid interface. We develop a nomenclature for treating reactions between the gas phase and surface species residing on any number of surface site types and bulk‐phase species residing in bulk‐phase mixtures or in pure bulk phases. The rate of progress of surface reactions follows the law of mass‐action. We discuss the relationship between macroscopic conservation laws for mass and energy and the microscopic surface reaction rates as they might appear in boundary conditions for a chemically reacting flow. The formalism developed has been implemented in a general package of Fortran computer codes for the evaluation of complex surface‐reaction kinetics called Surface Chemkin.
Schiff bases between pyridoxal 5′‐phosphate and dodecylamine. Kinetic study
Authors: Vázquez M. A. , Muñoz F. , Donoso J. , Blanco F. García
Published: January 2005

We studied the formation and hydrolysis of the Schiff base of pyridoxal‐5′ ‐phosphate (PLP) and n‐dodecylamine (DOD) by kinetic methods and found the formation rate constants to be much larger than those reported for related systems. This can be ascribed to the occurrence of local concentration of charges in the vicinity of the carbinolamine, which stabilizes the corresponding transition state of the dehydration reaction. On the other hand, the hydrolysis rate constants of our system were considerably smaller as a result of the 12‐atom hydrocarbon chain acting as a bulky hydrophobic rest protecting the imine bond from attack by water.
Radical processes in the pyrolysis of acetylene
Authors: Benson Sidney W.
Published: January 2005

The literature on the pyrolysis of acetylene below 1000 K is reviewed and it is shown that the reaction is a radical chain polymerization initiated by H atoms. The induction period is examined and shown to arise from a rapid autocatalysis produced by the very first product, vinyl acetylene. Data from studies of acetylene polymerization induced by vinyl acetylene and styrene are examined and shown to be in good qualitative agreement with the radical chain process presented. Measured and where needed, estimated rate constants are given to produce numerical estimates of chain length, rates of polymerization, induction period, and rates of initiation. It is further shown that all the products of the polymerization are capable of efficiently initiating chains in the system. An examination of the possible kinetics of vinylidene shows that it does not play any role in acetylene chemistry.
A shock tube study of reactions of atomic oxygen with isocyanic acid
Authors: Mertens John D. , Chang Albert Y. , Hanson Ronald K. , Bowman Craig T.
Published: January 2005

Reactions of atomic oxygen with isocyanic acid (HNCO) have been studied in incident and reflected shock wave experiments using HNCO/N2O/Ar mixtures. Quantitative time‐histories of the NH(X3Σ−) and OH(X2Πi) radicals were measured behind the shock waves using cw, narrow‐linewidth laser absorption at 336 nm and 307 nm, respectively. The second‐order rate coefficients of the reactions:

equation image

and

equation image

were determined from early‐time NH and OH formation rates, with least‐squares two‐parameter fits of the results given by:

and

cm3 mol−1 s−1. The minimum and maximum rate constant factors (ƒ,F) define the lower and upper uncertainty limits, respectively.

An upper limit on the rate coefficient of

equation image

was determined to be:

.
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

Mixtures 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

Data 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

Using 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

Absolute 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

The 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

A 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

Atmospheric 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

The 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

The 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

A 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

A 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

This 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

In 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

The 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

The 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

The 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

The 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

The 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

A 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.
Role of resin‐manganese(II) complexes in hydrogen peroxide decomposition
Authors: Salem Ibrahim A.
Published: January 2005

The kinetics of hydrogen peroxide decomposition has been investigated in the presence of Wofatit KPS (4% DVB, 40–80 μm) resin in the form of mono (mea), di (dea), triethanolamine (tea), ethylenediamine (eda), and N,N′‐diethylethylenediamine (deeda)‐ Mn(II) complexes. The rate constant k (per g dry resin) was evaluated over the temperature range 25–40°C. The reaction was first‐order with respect to [H2O2]. The rate constant, k, with the three ethanolamines decreased in the following order mea > dea > tea which is the same order of basicity. Also, k value with deeda is lower than eda as a result of steric hindrance. The peroxo metal complex which formed at the beginning of the reaction, was found to contain the catalytic active species. The rate of reaction was proportional to [Mn‐complex], [H2O2] and [H+]−1. The activation parameters were calculated and a probable reaction mechanism is proposed. © 1994 John Wiley & Sons, Inc.
Gas‐phase thermal decomposition of peroxy‐N‐butyryl nitrate
Authors: Grosjean Daniel , Williams Edwin L. , Grosjean Eric
Published: January 2005

The gas‐phase thermal decomposition rate of peroxy‐n‐butyryl nitrate (n‐C3H7C(O)OONO2, PnBN) has been measured at ambient temperature (296 K) and 1 atm of air relative to that of peroxyacetyl nitrate (CH3C(O)OONO2, PAN) using mixtures of PAN (14–19 ppb), PnBN (22–46 ppb), and nitric oxide (1.35–1.90 ppm). The PnBN/PAN decomposition rate ratio was 0.773 ± 0.030. This ratio, together with a literature value of 3.0 × 10−4 s−1 for the thermal decomposition rate of PAN at 296 K, yields a PnBN thermal decomposition rate of (2.32 ± 0.09) × 10−4 s−1. The results are briefly discussed by comparison with data for other peroxyacyl nitrates and with respect to the atmospheric persistence of PnBN. © 1994 John Wiley & Sons, Inc.
A shock tube study of the OH + OH → H2O + O reaction
Authors: Wooldridge Margaret S. , Hanson Ronald K. , Bowman Craig T.
Published: January 2005

The rate coefficient for the reaction
equation image
has been determined in mixtures of nitric acid (HNO3) and argon in incident shock wave experiments. Quantitative OH time‐histories were obtained by cw narrow‐linewidth uv laser absorption of the R1(5) line of the A2 σ+ ← X2 Πi (0,0) transition at 32606.56 cm−1 (vacuum). The experiments were conducted over the temperature range 1050–2380 K and the pressure range 0.18–0.60 atm. The second‐order rate coefficient was determined to be

with overall uncertainties of +11%, −16% at high temperatures and +25%, −22% at low temperatures. By incorporating data from previous investigations in the temperature range 298–578 K, the following expression is determined for the temperature range 298–2380 K

© 1994 John Wiley & Sons, Inc.
Kinetics and mechanisms of the gas‐phase reactions of the NO3 radical with aromatic compounds
Authors: Kwok Eric S. C. , Atkinson Roger , Arey Janet
Published: January 2005

The kinetics and nitrated products of the gas‐phase reactions of the NO3 radical with methoxybenzene, 1,2‐, 1,3‐, and 1,4‐dimethoxybenzene, dibenzofuran and dibenzo‐p‐dioxin have been investigated at 297 ± 2 K and in the presence of one atmosphere of air. A relative rate method was used for the kinetic measurements. No reactions of methoxybenzene or dibenzofuran with the NO3 radical were observed. The dimethoxybenzenes were observed to react by H‐atom abstraction and NO3 radical addition to the aromatic ring, while dibenzo‐p‐dioxin reacted by NO3 radical addition to the aromatic rings. For these compounds, the NO3 radical addition pathways were observed to be reversible. At the NO2 concentrations employed, the NO3‐aromatic adducts reacted with NO2 and the observed rate constants increased with increasing NO2 concentration. However, for dibenzo‐p‐dioxin the observed rate constant became independent of the NO2 concentration for concentrations ≥ 4.8 × 1013 molecule cm−3, and under these conditions the rate constant of 6.8 × 10−14 cm3 molecule−1 s−1 was taken to be that for addition of the NO3 radical to the aromatic rings. The proposed NO3 radical reaction mechanisms are discussed. © 1994 John Wiley & Sons, Inc.
Base hydrolysis of (αβ S)‐(o‐methoxy benzoato) (tetraethylenepentamine) cobalt(III) ion: A comparative study of the role of ion pairs and micelles
Authors: Acharya Achyuta N. , Dash Anadi C.
Published: January 2005

The kinetics of base hydrolysis of (αβ S)‐(o‐methoxy benzoato) (tetraethylenepentamine)cobalt(III) obeyed the rate law: kobs = kOH[OH−], in the range 0.05 ⩽ [OH−]T, mol dm−3 ⩽ 1.0, I = 1.0 mol dm−3, and 20.0–40.0°C. At 25°C, kOH = 13.4 ± 0.4 dm3 mol−1 s−1, ΔH≠ = 93 ± 2 kJ mol−1 and ΔS≠ = 90 ± 5 JK−1 mol−1. Several anions of varying charge and basicity, CH3CO2−, SO32−, SO42−, CO32−, C2O42−, CH2(CO2)22−, PO43−, and citrate3− had no effect on the rate while phthalate2−, NTA3−, EDTA4−, and DTPA5− accelerated the process via formation of the reactive ion pairs. The anionic (SDS), cationic (CTAB), and neutral (Triton X‐100) micelles, however, retarded the reaction, the effect being in the order SDS> CTAB > Triton X‐100. The importance of electrostatic and hydrophobic effects of the micelles on the selective partitioning of the reactants between the micellar and bulk aqueous pseudo‐phases which control the rate are discussed. © 1994 John Wiley & Sons, Inc.
Reactions of cobalt(III) complexes with free radicals derived from thymine
Authors: Chakrabarti S. , Mandal P. C. , Bhattacharyya S. N.
Published: January 2005

The nature of interaction of Co(III) complexes such as Co(III)EDTA and Co(III)NTA with transient adducts of thymine such as TOH˙, T˙−, and TH˙ formed in the gamma radiolysis of thymine were studied. The study shows that TOH radicals do not undergo electron transfer reaction with Co(III) complexes whence no radiosensitization of thymine by Co(III) complexes was observed. Electron transfer however, takes place from T˙− and TH˙ to Co(III) complexes. A plausible mechanism of radiolysis of thymine in presence of Co(III) complexes is discussed. © 1994 John Wiley & Sons, Inc.
Methyl isocyanide is an RRKM molecule after all
Authors: Shen Delin , Pritchard Huw O.
Published: January 2005

Classical trajectory calculations on the methyl isocyanide molecule at energies above 25,000 cm−1 confirm that the rate of reaction to methyl cyanide is bimodal, with a very fast rate before 0.1 ps, and a slower rate from then on. We conclude that before 0.1 ps, the reacting molecules are unrandomized, but thereafter, they are essentially randomized, with decay to products being, to a good approximation, pure exponential. We estimate that the time for randomization is roughly 0.3 ps at energies near the reaction threshold of 13,500 cm−1. © 1994 John Wiley & Sons, Inc.
Kinetics of the reaction of C6H5 with HBr and DBr
Authors: Yu T. , Lin M. C.
Published: January 2005

The rate constants for the reaction of C6H5 with HBr and DBr have been measured with the cavity–ring–down method in the temperature range of 297 to 523 K and 297 to 500 K, respectively. These rate constants can be effectively represented, in units of cm3/s, by

Both activation energies are similar and positive, contrary to those of alkyl radical reactions, all of which exhibit negative temperature dependencies. The difference, as pointed out before [1], could be accounted for by the electron‐withdrawing effect of the phenyl vis‐à‐vis the electron‐donating ability of the alkyls. © 1994 John Wiley & Sons, Inc.
CO2 laser excitation of triethylsilane: Time resolved luminescence of diethylsilyl radical
Authors: Papagiannakopoulos Panos , Lazarou Yannis G.
Published: January 2005

The infrared multiphoton excitation of triethylsilane in the gas phase, with a pulsed CO2 laser at high intensities (I > 700 MW/cm2), produced an intense luminescence. The spectrum and time profile of this luminescence was studied as a function of pressure, and laser frequency. The radiative lifetime of this emission was 357 ± 10 ns, and the quenching rates by Cl2 and NO were determined from lifetime measurements. A reasonable mechanism for the interpretation of this luminescence involves the initial infrared multiphoton decomposition of triethylsilane, followed by the secondary infrared multiphoton excitation of the primary photofragment diethylsilyl radical, which subsequently undergoes relaxation to an excited electronic state. The addition of O2 resulted in a new chemiluminescence at shorter wavelengths, which corresponds to the SiO* chromophore group. © 1994 John Wiley & Sons, Inc.
General base catalysis in the decomposition of N‐Cl‐Valine in aqueous solution
Authors: Abia Ll , Armesto X. L. , Canle L. M. , García M. V. , Losada M. , Santaballa J. A.
Published: January 2005

This article analyzes the kinetics of the decomposition of N‐Cl‐Valine in aqueous solution, which is formed rapidly by chlorination of Valine with sodium hypochlorite. A general‐base catalyzed process not yet described is reported. The experimental evidence shows two competitive decomposition paths: an unimolecular concerted fragmentation process (k = (1.8 ± 0.1) · 10−4 s−1 at 298 K) and the other one is an E2 elimination process whose importance increases with pH and depends on the nature and the concentration of the bases present in the medium. © 1994 John Wiley & Sons, Inc.
Rate constants for the gas‐phase reactions of Ozone with unsaturated Aliphatic Alcohols
Authors: Grosjean Eric , Grosjean Daniel
Published: January 2005

The gas‐phase reaction of ozone with unsaturated alcohols in air has been investigated at atmospheric pressure and ambient temperature (288–291 K). Cyclohexane was added to scavenge the hydroxyl radical which forms as a product of the ozone–unsaturated alcohol reaction. The reaction rate constants, in units of 10−18 cm3 molecule−1 s−1, are 16.2 ± 0.7 for (±) 3‐buten‐2‐ol, 17.9 ± 1.8 for 1‐penten‐3‐ol, 10.0 ± 0.3 for 2‐methyl‐3‐buten‐2‐ol, 169 ± 25 for cis‐2 penten‐1‐ol, and 251 ± 41 for 2‐buten‐1‐ol (mixture of isomers). Substituent effects on reactivity are discussed. The reactivity of unsaturated alcohols towards ozone is similar to that of their alkene structural homologues. Implications of these results with respect to the atmospheric persistence of unsaturated alcohols are briefly discussed. © 1994 John Wiley & Sons, Inc.