bluuebunny/crossref_metadata_2025_split huggingface dataset:
Collisional deactivation of O2(1Σg+)
Authors: Chatha J. P. S. , Arora P. K. , Raja Smt. Nalini , Kulkarni P. B. , Vohra K. G. 
Published: January 2005

AbstractRelaxation rates for O2(1Σg+) by nonradiative pathways have been determined using the fast‐flow technique. O2(1Σg+) is formed from O2(1Δg) by an energy pooling process. O2(1Δg) is generated by passing purified oxygen through a microwave discharge. Oxygen atoms are removed by distilling mercury vapor through the discharge zone. It has been observed that the wall loss rate for O2(1Σg+) decreases with increasing pressure of oxygen and thus appears to be diffusion controlled. Quenching rate constants for O2, N2, and He have been determined and found to be (1.5 ± 0.1) × 104, (1.0 ± 0.05) × 106 and (1.2 ± 0.1) × 105 l./mol·sec, respectively.
The photolysis of n‐butyraldehyde in isooctane at 313 nm
Authors: Förgeteg S. , Bérces T. 
Published: January 2005

AbstractThe effects of aldehyde concentration, incident light intensity, and temperature on the quantum yields of reaction products were studied. Mechanisms for primary and secondary photochemical processes were suggested, and primary quantum yields as well as rate constant ratios were derived. Reversibility of intramolecular γ‐hydrogen transfer and disproportionation of the radical pair formed in the reaction of an excited triplet and ground state molecule were shown to provide important pathways for radiationless decay of the triplet state.
Automatic sensitivity analysis of kinetic mechanisms
Authors: Koda Masato , Mcrae Gregory J. , Seinfeld John H. 
Published: January 2005

AbstractAn algorithm for the automatic sensitivity analysis of kinetic mechanisms based on the Fourier amplitude sensitivity test (FAST) method of Shuler and co‐workers is reported. The algorithm computes a measure of the relative sensitivity of each concentration to each parameter of interest, such as rate constants, Arrhenius parameters, stoichiometric coefficients, and initial concentrations. Arbitrary variations in the magnitude of the parameters are allowable. The algorithm is illustrated for the simple example of computing the sensitivity of the concentration of species A to variation of the two Arrhenius parameters for the hypothetical reaction A + A →.
Chlorine atom and ClO wall reaction products
Authors: Martin L. Robbin , Wren Anthony G. , Wun Marilyn 
Published: January 2005

AbstractThe products of the heterogeneous reactions of chlorine atoms and chlorine oxide radicals with acid coated Pyrex walls have been directly determined for the first time. Contrary to the usual assumption that chlorine atoms recombine to form Cl2, we find that the major product is HCl, with small amounts of perchlorate also formed. Similarly, ClO radicals form HCl rather than Cl2. The source of hydrogen for these reactions is probably the water always found in this type of vacuum system. These results may change the interpretation of flow tube experiments with chlorine atoms. Application to the H + HCl reaction is discussed as an example.
Absolute quantum yield of O(1D2) in the photolysis of ozone in the hartley band
Authors: Kajimoto O. , Cvetanovi R. J. 
Published: January 2005

AbstractThe absolute quantum yield of O(1D2) in the photolysis of ozone in the Hartley band, between about 230 and 280 nm, has been determined using the isotopic exchange reaction between C16O2 and 18O(1D2). A value of 1.00 ± 0.05 has been obtained within a 95% confidence limit. A value of unity may therefore be accepted as the average quantum yield of O(1D2) atoms in the 230–280‐nm region within an uncertainty of only several percent.
Homogeneous decomposition of vinyl ethers. The heat of formation of ethanal‐2‐yl
Authors: Rossi M. , Golden D. M. 
Published: January 2005

AbstractThe thermal unimolecular decomposition of three vinylethers has been studied in a VLPP apparatus. The high‐pressure rate constant for the retro‐ene reaction of ethylvinylether was fit by log k (sec−1) = (11.47 + 0.25) ‐ (43.4 ± 1.0)/2.303 RT at <T> = 900 K and that of t ‐ butylvinylether by log k (sec−1) = (12.00 ± 0.27) ‐ (38.4 ± 1.0)/2.303 RT at <T> = 800 K. No evidence for the competition of the higher energy homolytic bond‐fission process could be obtained from the experimental data. The rate constant compatible with the CO bond scission reaction in the case of benzylvinylether was log k (sec−1) = (16.63 ± 0.30) ‐ (53.74 ± 1.0)/2.303 RT at <T> = 750 K. Together with ΔHf,3000(benzyl·) = 47.0 kcal/mol, the activation energy for this reaction results in ΔHf,3000(CH2CHO) = +3.0 ± 2.0 kcal/mol and a corresponding resonance stabilization energy of 3.2 ± 2.0 kcal/mol for 2‐ethanalyl radical.
Redox kinetics of metal complexes in nonaqueous solutions. V. Kinetics and mechanism of the iron (II) reduction of the acetylacetonates of manganese (III) and cobalt (III) in acetonitrile
Authors: Schmid Roland , Sapunov Valentin N. 
Published: January 2005

AbstractThe electron transfer step of the reduction of Mn(acac)3 and Co(acac)3 by Fe(II) in acetonitrile is preceded by the one‐ended dissociation of an acac ligand and the formation of a binuclear bridged complex. After the electron transfer has taken place through the bridging ligand, the complex dissociates into the products M(acac)2 (M = Mn, Co) and Fe(acac)2+. These primary reaction products could not be identified, since the transfer of acac from M(acac)2 to Fe(acac)2+ is too rapid, producing ultimately Fe(acac)3 and M2+. The M(III)‐oxygen cleavage is accelerated by M(acac)2. Furthermore, the dissociation of the binuclear intermediate is catalyzed by the M(acac)3 reactant. Mn(acac)3 is reduced more than a thousand times faster than Co(acac)3.
Rate of decomposition of hexafluoroazomethane and the absolute rate of recombination of trifluoromethyl radical at higher temperatures
Authors: Rossi M. , Golden D. M. 
Published: January 2005

AbstractThe unimolecular homogeneous decomposition of hexafluoroazomethane was studied in a VLPP apparatus in the temperature range 720–1050 K and is consistent with the following Arrhenius parameters:

at 900 K, where the A factor was assumed to be the same as for 2,2′‐azoisobutane. The homogeneous rate of recombination of ·CF3 radicals at temperatures around 1000 K was also studied under VLPP conditions and was found to be in the fall‐off region, corresponding to k/k∞ = 8.5 × 10−3 when a rotational transition‐state model was used. This model predicts an essentially constant value of kr∞ of 109.7 over the temperature range 300–1000 K.
Thermal decomposition of hexamethylethane in a flow system
Authors: Walker James A. , Tsang Wing 
Published: January 2005

AbstractHexamethylethane has been decomposed in a flow system in the temperature range of 700–900 K. The mechanism involves carbon–carbon bond cleavage at the most highly substituted position and rapid formation of isobutene from the t‐butyl radical. The rate expression is

and is completely consistent with deductions from radical buffer, shock‐tube, and direct recombination studies. Of special importance is experimental evidence for large decreases of the A factor with increasing temperature and a high heat of formation for the t‐butyl radical, ΔHf(tC4H9·)300 = 52.7 ± 6 kJ.
Sampling effects on observed cyclopropane isomerization in a single pulse shock tube
Authors: Jeffers Peter M. , Northing Jeffrey 
Published: January 2005

AbstractCyclopropane in argon mixtures was heated in a single‐pulse shock tube, and syringes were used to withdraw samples from both the central gas slug and the gas adjacent to the tube walls. Differences were observed in the measured conversion, with larger conversion found in the center location. The discrepancy increased with increasing conversion, and the results indicate that boundary‐layer effects can seriously affect the results of absolute single‐pulse shock‐tube studies when percent conversion is large.
The absolute rate constant for the metathesis t‐C4H9• + DI → C4H9D + I• and the heat of formation of the t‐butyl radical
Authors: Rossi Michel , Golden David M. 
Published: January 2005

AbstractThe Arrhenius parameters for the title reaction have been measured in a very‐low‐pressure pyrolysis apparatus in the temperature range 644–722 K and are given by log k2 (M−1 · sec−1) = 9.68 ‐ 2.12/θ, where θ = 2.303RT in kcal/mol. Together with the published Arrhenius parameters for the reverse reaction from iodination studies, they result in a standard heat of formation of the t‐butyl radical of 8.4 kcal/mol, accepting S0(C4H9·) = 72.2 e.u. at 300 K from other kinetic data, and thus confirm the accepted value for ΔHf0(t‐C4H9·), at variance with recent investigations which yielded significantly higher values. This value for ΔHf0(t‐C4H9·) results in a bond‐dissociation energy (BDE) for isobutane of 92.7 kcal/mol.
Reaction of methoxy radicals with oxygen. I. Using dimethyl peroxide as a thermal source of methoxy radicals
Authors: Batt L. , Robinson G. N. 
Published: January 2005

AbstractUsing dimethyl peroxide as a thermal source of methoxy radicals overthe temperature range of 110–160°C, and the combination of methoxy radicals and nitrogen dioxide as a reference reaction:
equation image
a value was determined of the rate constant for the reaction of methoxy radicals with oxygen:
equation image
is independent of nitrogen dioxide or oxygen concentration and added inert gas (carbon tetrafluoride). No heterogeneous effects were detected. The value of k4 is given by the expression

In terms of atmospheric chemistry, this corresponds to a value of 105.6 M−1·sec−1 at 298 K. Extrapolation to temperatures where the combustion of organic compounds has been studied (813 K) produces a value of 107.7 M−1·sec−1 for k4. Under these conditions, reaction (4) competes with hydrogen abstraction or disproportionation reactions of the methoxy radical and its decomposition (3):
equation image
In particular k3 is in the falloff region under these conditions. It is concluded that reaction (4) takes place as the result of a bimolecular collision process rather than via the formation of a cyclic complex.
Reduction of hexachloroiridate (IV) by benzene‐1,2‐diol in aqueous perchloric acid
Authors: Morris D. F. C. , Ritter T. J. 
Published: January 2005

AbstractThe kinetics of the reaction between benzene‐1,2‐diol(catechol) and hexachloroiridate (IV) have been measured in aqueous acidic perchlorate solutions by the stopped‐flow method. The reaction is second order overall, and first order in each reactant. A reverse reaction also occurs, but it is much slower than the forward process. Observed rate constants are dependent on acidity, but the variation can be attributed to activity rather than mechanistic effects. The reaction appears to proceed predominantly by an outer sphere electron transfer mechanism, yielding o‐benzoquinone and hexachloroiridate (III), although monoaquopentachloroiridate (III) is formed also at the higher [catechol]/[IrCl62−]ratios.
A Program package using stiff, sparse integration methods for the automatic solution of mass action kinetics equations
Authors: Carver M. B. , Boyd A. W. 
Published: January 2005

AbstractA portable program package, MACKSIM, for mass action chemical kinetics simulation, is discussed. As these kinetics are readily expressed in explicit mathematical terms, such a package contains two major and distinct modules, the numerical analysis and the user interface. For the first, MACKSIM uses the latest proven developments incorporating sparse matrix techniques in the backward difference predictor corrector methods originated by Gear for the integration of stiff ordinary differential equations, and thus requires minimal computing time to solve large systems of equations. For the second, the program provides a flexible interface which permits simple specification and variation of reactions, requires no special character input, and has no limit on the number of reactions or species involved other than that imposed by the size of the computer. The technology of these components is discussed briefly, the use of the package for standard reactions is illustrated, and current applications are mentioned.
The kinetics of the interaction of peroxy radicals. I. The Tertiary Peroxy Radicals
Authors: Nangia Prakash S. , Benson Sidney W. 
Published: January 2005

AbstractExisting data on the self‐reactions of tertiary peroxy radicals RO2 has been reanalyzed and corrected to deduce Arrhenius parameters for both termination and nontermination paths. For R = t‐Butyl, these are logkt(M−1sec−1) = 7.1 ‐ (7.0/θ) and logknt(M−1sec−1) = 9.4 ‐ (9.0/θ), respectively, different from those recommended by other authors. The higher magnitudes observed for termination processes of tertiary peroxy radicals like those of cumyl and 1,1‐diphenylethyl have been discussed in terms of a much greater cage recombination of cumyloxy radicals as contrasted with t‐butoxy radicals. It is shown that for benzyl peroxy radicals, the R—O bond dissociation energy is sufficiently low (18–20 kcal) that reversible dissociation into R˙ + O2 opens a competing second‐order path to fast recombination R˙ + RO → ROOR. This path is probably not important for cumyl peroxy radicals under usual experimental conditions but can become important for 1,1‐diphenyl ethyl peroxy radicals at (O2) < 10−3M. At very low RO concentrations (<10−5M), in the absence of added O2, an apparent first‐order disappearance of RO can occur reflecting the rate determining breaking of the cumyl—O bond followed by the second step above. The thermochemistry of RO is used to show that the reaction of R2O4 → 2RO + O2 must be concerted and cannot proceed via RO which is too unstable and cannot form even from RO˙ + O2.
Kinetic studies of free radical reactions by mass spectrometry. I. The reactions SO + NO2 and ClO + NO
Authors: Clyne Michael A. A. , Macrobert Alexander J. 
Published: January 2005

AbstractA novel technique is described for forming ground‐state SO X3Σ radicals free of reactive impurities in a discharge‐flow system. Mass spectrometric detection of SO and ClO free radicals has been used to study the kinetics of the following reactions at 295 K:
equation image
The √t law in solid‐phase reactions verification of the √t law stability in h‐atom abstraction reactions
Authors: Bol'shakov B. V. , Stepanov A. A. , Tolkatchev V. A. 
Published: January 2005

AbstractThe law c = c0 exp(K √t) in the alkyl radical abstraction reaction is affected by neither the matrix annealing nor the way of the radical generation. If the reaction runs at varying temperature, a dimensionless time τ which does determine unambiguously the degree of conversion can be introduced.
A concerted hydrogen‐transfer reaction in the gas phase
Authors: Lalonde P. J. , Back M. H. 
Published: January 2005

AbstractThe kinetics of the thermal reaction of mixtures of ethylene and cyclopentene has been examined for the occurrence of a concerted hydrogen‐transfer reaction,

. The main products of the reaction were ethane and cyclopentadiene, and the rate of formation of ethane was first order in each reactant over a 2500‐fold change in the ratio of concentrations of the reactants. An increased surface‐to‐volume ratio of the reaction vessel or additions of oxygen and nitric oxide had little effect on the rate of formation of ethane, and it was concluded that the dominant reaction in the system was the concerted hydrogen‐transfer process. The rate constant for the reaction, measured over the temperature range of 325–505°C, was represented as
Micellar effects upon electron transfer from ferrocenes
Authors: Bunton Clifford A. , Cerichelli Giorgio 
Published: January 2005

AbstractThe oxidations of ferrocene (FcH) and n‐butylferrocene (FcBu) by ferric salts (nitrate or bromide) are strongly inhibited by aqueous cetyltrimethylammonium bromide and nitrate (CTABr and CTANO3, respectively). The kinetics of inhibition fit a model in which the substrates are distributed between water, and the micelles and binding constants Ks to the micelle can be estimated. The oxidations are strongly catalyzed by micelles of sodium lauryl sulfate (NaLS), and the kinetics can be fitted to a model in which the reaction rate depends upon the concentration of both reactants in the micellar pseudophase and the rate constants in that pseudophase, which for both substrates are very similar to those in water. Some added salts reduce the micellar catalysis by excluding ferric ions from the micelle. The oxidations of FcH and FcBu by ferricyanide ions are too fast to be followed in water, but they are inhibited by anionic micelles of NaLS. By analyzing the rate surfactant profiles using independently measured values of Ks the second‐order rate constants in water have been estimated.
On the effect of copper (II) and chloride ions on the iodate‐hydrogen peroxide reaction in the presence and absence of manganese (II)
Authors: Cooke David O. 
Published: January 2005

AbstractThe effect of copper (II) and chloride ions on the manganese (II) catalyzed iodate‐peroxide reaction has been examined with reference to the hydrogen peroxide‐iodic acid‐manganese (II)‐organic species oscillatory reaction. The observations are considered to provide evidence for iodine dioxide as the key intermediate in the manganese (II) catalyzed reaction. Kinetic data for the copper (II) catalyzed reaction are reported.
The kinetic isotope effect for carbon and oxygen in the reaction CO + OH
Authors: Stevens C. M. , Kaplan Louis , Gorse Robert , Durkee Susan , Compton Michael , Cohen Sidney , Bielling Karen 
Published: January 2005

AbstractThe kinetic isotope effect (KIE) for carbon and oxygen in the reaction CO + OH has been measured over a range of pressures of air and at 0.2 and 1.0 atm of oxygen, argon, and helium. The reaction was carried out with 21–86% conversion under static conditions, utilizing the photolysis of H2O2 as a source of OH radicals. The value of the KIE for carbon varies with pressure and the kind of ambient gas; for air the ratio of the reaction rates 12k/13k has the value 1.007 at 1.00 atm and decreases to 0.997 at 0.2 atm; for oxygen and argon over the same pressure range the values are 1.002–0.994 and 1.000–0.991, respectively. The value of the KIE for the CO oxygen atom is 16k/18k = 0.990 over the pressure range 0.2–1.0 atm and is independent of the kind of ambient gas. No exchange of the oxygen atoms in the activated complex, followed by decomposition to the starting molecules, was observed. From the mechanistic standpoint the normal KIE observed for carbon at the high pressure is attributed to the initial formation of the activated HOCO radical, whereas the inverse KIE observed at low pressures is a result of the KIE for the reverse reaction HOCO† → CO + OH being greater than that for the forward reaction HOCO† → CO2 + H. The derived isotopic equilibrium constant for HOCO ⇄CO favors the enrichment of 13C in the more strongly bound HOCO.
An FTIR study of the Cl atom‐initiated oxidation of CH2Cl2 and CH3Cl
Authors: Niki H. , Maker P. D. , Savage C. M. , Breitenbach L. P. 
Published: January 2005

AbstractThe Cl atom‐initiated oxidation of CH2Cl2 and CH3Cl was studied using the FTIR method in the photolysis of mixtures typically containing Cl2 and the chlorinated methanes at 1 torr each in 700 torr air. The results obtained from product analysis were in general agreement with those reported by Sanhueza and Heicklen. The relative rate constant for the Cl atom reactions of CH2Cl2 and CH3Cl was determined to be k(Cl +CH3Cl)/k(Cl + CH2Cl2) = 1.31 ± 0.14 (2σ) at 298 ± 2 K.
Ion pair catalysis of the autooxidation of pyridine and benzil in emulsion systems
Authors: Franklin Thomas C. , Ogiya Naoyuki 
Published: January 2005

AbstractIt was found that the rates of absorption of oxygen by pyridine–aqueous sodium hydroxide emulsions and the same emulsions containing benzil were catalyzed by the addition of quaternary salts and followed the same rate law:

. It was concluded that the autooxidation of benzil in pyridine‐aqeuous sodium hydroxide emulsions has as its rate‐determining step a step in the autooxidation of pyridine. Possibly the superoxide formed in the autooxidation of pyridine is the oxidizing agent in the oxidation of benzil.
An overall and detailed kinetic study of the pyrolysis of propane
Authors: Hautman D. J. , Santoro R. J. , Dryer F. L. , Glassman I. 
Published: January 2005

AbstractOverall and detailed kinetic descriptions of the pyrolysis of C3H8 have been proposed as a result of a turbulent flow reactor investigation in the temperature range of 1110–1235 K and at atmospheric pressure. The overall reaction was described by a first‐order rate expression with an activation energy of 58.65 kcal/mol and a preexponential factor of 3.2 × 1012 sec−1. This expression agrees with previously reported rate data. In addition, a kinetic mechanism involving 13 chemical species and 32 elementary reactions has been postulated to describe the kinetics. Experimental data from the present flow reactor experiments and from static vessel and shock tube experiments reported in the literature were used to verify the mechanism. Agreement over the temperature range of 800–1400 K and over the pressure range of 0.1–8.5 atm was obtained by adjusting three rate constants. Previously reported values for these rate constants appear to require reexamination. The reactions in question are the following:
equation image
The sum of the rate constants for reactions (2a) and (2b) and the rate constant for reaction (23) are best represented by

and

which differ with the expressions in the literature.
The rate constant for t‐C4H9 → H + i‐C4H8 and the thermodynamic parameters of t‐C4H9
Authors: Canosa Carlos E. , Marshall Roger M. 
Published: January 2005

AbstractThe rate of the reverse reaction of the system
equation image
has been measured in the range of 584–604 K from a study of the azomethane sensitized pyrolysis of isobutane. Assuming the published value for the rate constant of recombination of t‐butyl we obtain

Combination with our published data for k1 permits the evaluation

We have modified a previously published structural model of t‐butyl by the inclusion of a barrier to free rotation of the methyl groups in order to calculate values of the entropy and enthalpy of t‐butyl as a function of temperature. Using standard data for H and for i‐C4H8 we obtain

We have obtained other, independent values of this quantity by a reworking of published data using our new calculations of the entropy and enthalpy of t‐butyl. There is substantial agreement between the different values with one exception, namely, that derived from published data on the equilibrium

which is significantly lower than the other values.We conclude that the value

obtained from the present work and a reworking of published data which involves the use of experimental data on t‐butyl recombination is incompatible with the result based on iodination data.
The hydrolysis of phosphoranes in aqueous dioxane
Authors: Queen A. , Lemire A. E. , Janzen A. F. 
Published: January 2005

AbstractThe entropy of activation for the hydrolysis of pentaphenoxyphosphorane in 25% aqueous dioxane is −188 J/mol deg. The enthalpy of activation is 22.5 kJ/mol, which is small for the relatively slow reaction. This suggests that the reaction is a multistep process having a preliminary equilibrium with a negative heat of reaction. This conclusion is supported by the results obtained for the hydrolysis of C6H5
equation image
[OCH(CF3)2]2. A kinetic isotope effect kH2O/kD2O of 3.46 was found for the latter reaction. Orders in water were obtained, and a mechanism of hydrolysis is proposed.
Persulfate and perphosphate oxidation of 2‐propanol: A relative rate study
Authors: Levey Gerrit , Bida Gerald , Edwards John O. 
Published: January 2005

AbstractA competitive reaction study for two isoelectronic peroxides (peroxodisulfate S2O and peroxodiphosphate P2O) interacting with the free radical ·Clpar;CH3)2OH is described. The radical formation is initiated by photolysis, the amounts of peroxide remaining analyzed volumetrically. It is found that persulfate reacts with the organic radical over 100 times more rapidly than does perphosphate. Mechanistic consequences in relation to previous work are briefly discussed.