bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heat of formation of Benzophenone Oxide
Authors: Hartstock F. W. , Kanabus‐kaminska J. M. , Griller D. 
Published: January 2005

AbstractThe heat of formation of benzophenone oxide, Ph2CO2, was measured using photoacoustic calorimetry. The enthalpy of the reaction Ph2CN2 + O2 → Ph2CO2 + N2 was found to be −48.0 ±0.8 kcal mol−1 and ΔHf(Ph2CN2) was determined by measuring the reaction enthalpy for Ph2CN2 + EtOH → Ph2CHOEt + N2 (−53.6 ±1.0 kcal mol−1). Taking ΔHf(PhCHOEt) = −10.6 kcal mol−1 led to ΔHf(Ph2CN2) = 99.2 ± 1.5 kcal mol−1 and hence to ΔHf(Ph2CO2) = 51.1 ± 2.0 kcal mol−1. The results imply that the self‐reaction of benzophenone oxide i.e., 2Ph2CO2 → 2Ph2CO + O2 is exothermic by −76.0 ±4.0 kcal mol−1.
Kinetic and thermochemical parameters of chlorine atom transfer reactions from CF3Cl, CF3CF2Cl, CF2ClCF2Cl, and CF2ClCFCl2 in gas phase
Authors: Taccone R. A. , Salinovich O. , Staricco E. H. 
Published: January 2005

AbstractThe following reactions:
equation image
were studied over the temperature ranges 533–687 K, 563–663 K, and 503–613 K for the forward reactions respectively and over 683–763 K, for the back reaction. Arrhenius parameters for chlorine atom transfer were determined relative to the combination of the attacking radicals. The ΔHr°(1) = −3.95 ± 0.45 kcal mol−1 was calculated and from this value the ΔH∮(C2F5Cl) = −2.66.3 ± 2.5 kcal mol−1 and D(C2F5‐Cl) = 82.0 ± 1.2 kcal mol−1 were obtained. Besides, the ΔHr°(2) was estimated leading to D(CF2ClCF2Cl) = 79.2 ± 5 Kcal mol−1. The bond dissociation energies and the heat of formation are compared with those of the literature. The effect of the halogen substitutents as well as the importance of the polar effects for halogen transfer processes are discussed.
Rate constants for the gas‐phase reactions of the OH radical with a series of aromatic hydrocarbons at 296 ± 2 K
Authors: Atkinson Roger , Aschmann Sara M. 
Published: January 2005

AbstractUsing a relative rate method, rate constants have been determined at 296 ± 2 K for the gas‐phase reactions of the OH radical with toluene, the xylenes, and the trimethylbenzenes. Using the recommended literature rate constant for the reaction of OH radicals with propene of (2.66 ± 0.40) × 10−11 cm3 molecule−1 s−1, the following rate constants (in units of 10−12 cm3 molecule−1 s−1) were obtained: toluene, 5.48 ± 0.84; o‐xylene, 12.2 ± 1.9; m‐xylene, 23.0 ± 3.5; p‐xylene, 13.0 ± 2.0; 1,2,3‐trimethylbenzene, 32.7 ± 5.3; 1,2,4‐trimethylbenzene, 32.5 ± 5.0; and 1,3,5‐trimethylbenzene, 57.5 ± 9.2. These data are compared with the literature values.
Detailed chemical kinetic modeling of butylbenzene pyrolysis
Authors: Freund H. , Olmstead W. N. 
Published: January 2005

AbstractA chemical kinetic model was constructed for the pyrolysis of butylbenzene. The mechanism was based on free radical reactions. All relevant reactions were considered, and a final selection of 60 reactions involving 29 molecules and free radicals was made. The rate constants and thermodynamic parameters were taken from the literature or estimated using accepted literature methods such as group additivity. The results from the model were compared to experimental rates and product selectivity for butylbenzene pyrolysis over a temperature range of 778 K to 868 K and to an experimental rate at 923 K. The rates agreed within a factor of two and were usually much closer. The experimental and theoretical yields of the major products, styrene, ethane, toluene, and propylene, agreed within two percentage points. The agreement for seven minor products was not quite as good, with the worst case being an overprediction of the yield of allylbenzene by a factor of 2.6.
Pyrolysis of 1,1,1‐Trichloroethane in the absence and the presence of added HCl and/or CCl4
Authors: Huybrechts G. , Hubin Y. , Van Mele B. 
Published: January 2005

AbstractThe title reaction has been studied in a static quartz reaction vessel between 587 and 658 K at pressures between 40 and 152 torr. The dehydrochlorination is the only significant reaction and is autoaccelerated by the produced HCl. Numerical modelling indicates that the Rice‐Herzfeld mechanism, generally used for describing the pyrolysis of halogenated ethanes, has to be completed in the case of CC13CH3 with additional transfer reactions converting “dead” radicals into chain carriers and vice‐versa. The numerical simulation fits the experimental results, in the absence as well as in the presence of different amounts of added HCl. The dehydrochlorination is also accelerated by the addition of CCl4, which can be explained in terms of additional elementary steps involving · CCl3 radicals.
The UV absorption spectrum of the CCl3 radical and the kinetics of its mutual combination reaction from 253 to 623 K
Authors: Danis F. , Caralp F. , Veyret B. , Loirat H. , Lesclaux R. 
Published: January 2005

AbstractThe UV absorption spectrum and the kinetics of the self combination reaction of the CCl3 radical were studied by flash photolysis in the temperature range 253–623 K. Experiments were performed at the atmospheric pressure, except for a few runs at the highest temperatures, which were performed between 30 and 760 torr. CCl3 radicals were generated by flash photolysis of molecular chlorine in the presence of chloroform. The UV spectrum exhibits a strong unstructured band between 195 and 260 nm with a maximum at 211 ± 2 nm. The absorption cross section, measured relative to σ(HO2), is σ(CCl3) = (1.45 ± 0.35) × 10−17 cm2 molecule−1 at the maximum. This value takes into account the uncertainty in σ(HO2) which was taken equal to (4.9 ± 0.7) × 10−18 cm2 molecule−1. The absolute rate constant for the CCl3 mutual combination was determined by computer simulation of the transient decays. The rate constant, which exhibits a slight negative temperature coefficient, can be expressed as:

The study of the pressure dependence showed that only a slight fall‐off behavior could be observed at the highest temperature (623 K). This result was corroborated by RRKM calculations which showed that the rate constant is at the high pressure limit under most experimental conditions below 600 K.
Lack of kinetic hydrogen isotope effect in acetylene pyrolysis
Authors: Durán R. P. , Amorebieta V. T. , Colussi A. J. 
Published: January 2005

AbstractSecond order rate constants for C2H2 or C2D2 polymerizations into vinylacetylene and higher CnHn products have been measured in a static reactor by dynamic mass spectrometry between 770–980 K. They are nearly identical within experimental error (±50%). It is shown that these results are consistent with the participation of thermally equilibrated vinylidene H2C  C: as a reactive intermediate:
equation image
since this assumption only introduces a modest reverse equilibrium isotope effect (KiH/KiD ca. 0.48 in this range) into overall rate constants. At the same time they seem to discriminate in general against alternative mechanisms in which the required H‐atom transfers take place in rate determining steps. Present evidence, in conjunction with an updated analysis of relevant issues such as experimental and theoretical vs. termochemical estimates of the heat of formation of H2CC:, the nature of the transition states of singlet vinylidene addition reactions and the likelihood of discrete biradical intermediates in C2H2 dimerization, seems to lend further support to the notion that acetylene behaves as a singlet carbene at high temperatures.
The pressure and temperature dependence of methane decomposition
Authors: Stewart P. H. , Smith G. P. , Golden D. M. 
Published: January 2005

AbstractSingle‐channel hindered Gorin model RRKM calculations were performed on reaction (1).
equation image
Good agreement between theory and experiment was obtained for the temperature and pressure dependence of reaction (1). Isotopic data for the reverse association reaction, (−1), reported previously, are consistent with the model. Rate constants were cast in the form of an analytical expression and appropriate parameters were tabulated.
Thermal reaction of CH2O with NO2 in the temperature range of 393–476 K: FTIR product measurement and kinetic modeling
Authors: He Yisheng , Kolby Elizabeth , Shumaker Peter , Lin M. C. 
Published: January 2005

AbstractThe thermal reaction of CH2O with NO2 has been investigated in the temperature range of 393–476 K by means of FTIR product analysis. Kinetic modeling of the measured CH2O, NO, CO, and CO2 concentration time profiles under varying reaction conditions gave rise to the rate constants for the following key reactions:
equation image
and
equation image
The error limits shown represent only the scatter (±1 σ) of the modeled values. In the modeling, the total rate constant for the CHO + NO2 reaction, k2 + k3, was not varied and the value reported by Gutman and co‐workers (ref. [8]) was used for the whole temperature range investigated here. The proposed reaction mechanism, employing these newly established rate constants, can quantitively account for nearly all measured product yields, including the [CO]/([CO] + [CO2]) ratios reported by earlier workers.
Energy transfer from optoacoustic measurements and fourier transform deconvolution
Authors: Braun W. , Price I. , Cadoff B. C. , Peterson N. C. 
Published: January 2005

AbstractThe rate of V → R, T energy relaxation following pulsed ir laser excitation is measured by employing an optoacoustic single pulse method. Under present experimental conditions the operation of convolution applies. The experimental optoacoustic waveform can be viewed as the convolution of the kinetic relaxation waveform with an optoacoustic waveform obtained under very fast energy relaxation conditions. A discrete Fourier transform deconvolution method is applied to optoacoustic measurements on SF6 in argon to obtain the time constant, τ, for energy transfer. The present method gives τP = 182 ± 15 μs torr, in good agreement with other methods. These results were obtained without requiring either a theoretical description of the pressure waveform or an assumed laser irradiation geometry. For convolution to apply, the differential equation describing the pressure pulse must be linear under the conditions of the experiment. The linearity of the system can usually be tested experimentally.
Reaction kinetics of NH in the shock tube pyrolysis of HNCO
Authors: Mertens John D. , Chang Albert Y. , Hanson Ronald K. , Bowman Craig T. 
Published: January 2005

AbstractThe high temperature kinetics of NH in the pyrolysis of isocyanic acid (HNCO) have been studied in reflected shock wave experiments. Time histories of the NH(X3Σ−) radical were measured using a cw, narrow‐linewidth laser absorption diagnostic at 336 nm. The second‐order rate coefficients of the reactions:
equation image
were determined to be:

cm3−mol−1−s−1, where f and F define the lower and upper uncertainty limits, respectively. The data for k1a are somewhat better fit by:
Kinetics and mechanism of tris (p‐bromophenyl) aminium hexachloroantimonate induced decomposition of 9‐diazofluorene
Authors: Ahmad Iftikhar 
Published: January 2005

AbstractThe kinetics and products of the decomposition of 9‐diazofluorene by tris (p‐bromophenyl) aminium hexachloroantimonate in acetonitrile solvent has been investigated. The reaction is first order with respect to the concentration of both 9‐diazofluorene and tris (p‐bromophenyl) aminium hexachloroantimonate. A reaction mechanism has also been proposed.
The kinetics of complexation of nickel(II) and cobalt(II) with cinchomeronate in aqueous solution
Authors: Yun Sock Sung , Choi Ki Young 
Published: January 2005

AbstractThe pressure‐jump method has been used to determine the rate constants for the formation and dissociation of nickel(II) and cobalt(II) complexes with cinchomeronate in aqueous solution at zero ionic strength. The forward and reverse rate constants obtained are kf = 2.27 × 106 M−1 s−1 and kr = 3.81 × 101 s−1 for the nickel(II) complex and kf = 1.23 × 107 M−1 s−1 and kr = 2.66 × 102 s−1 for the cobalt(II) complex at 25°C. The activation parameters of the reactions have also been obtained from the temperature variation study. The results indicate that the rate determining step of the reaction is a loss of a water molecule from the inner coordination sphere of the cation for the nickel(II) complex and the chelate ring closure for the cobalt(II) complex. The influence of the pyridine ring nitrogen atom of the cinchomeronate ligand on the complexation of cobalt(II) ion is also discussed.
Kinetics of the reactions Br + NO2 + M and I + NO2+ M
Authors: Mellouki A. , Laverdet G. , Jourdain J. L. , Poulet G. 
Published: January 2005

AbstractThe reactions Br + NO2 + M → BrNO2 + M (1) and I + NO2 + M → INO2 + M (2) have been studied at low pressure (0.6‐2.2 torr) at room temperature and with helium as the third body by the discharge‐flow technique with EPR and mass spectrometric analysis of the species. The following third order rate constants were found k1(0) = (3.7 ± 0.7) × 10−31 and k2(0) = (0.95 ± 0.35) × 10−31 (units are cm6 molecule−2 s−1). The secondary reactions X + XNO2 → X2 + NO2 (X = Br, I) have been studied by mass spectrometry and their rate constants have been estimated from product analysis and computer modeling.
Linear free energy relationships for peroxy radical‐phenol reactions. Influence of the para‐substituent, the ortho‐di‐tert‐butyl groups and the peroxy radical
Authors: Héberger Károly , Lopata Antal , Müller József 
Published: January 2005

AbstractCalculations were carried out on several data sets to study the mechanism of hydrogen abstraction from phenols by peroxy radicals:
equation image
Rate constants, k values, were collected for the reactions of cumyl‐, 1‐phenylethyl‐ and tert‐butyl‐peroxy radicals with ortho‐para‐substituted phenol inhibitors. The rate constants were recalculated for the same temperature. Solvent effects were neglected because the solvents used were similar in nature. The phenol ortho substituents were characterized by an indicator variable ItBu accounting for the presence or absence of di‐tert‐butyl groups. The phenol para substituents were characterized by Charton's σI, σR, and σ substituent constants.The dependence of log k values on Itbu, σI, σR, σ was investigated using stepwise linear regression analysis. The combined data set of 32 reactions gives:

and

The results suggest that hydrogen abstraction from phenols by peroxy radicals proceeds by an electrophilic mechanism, and that neither the peroxy‐radical nor the ortho‐di‐tert‐butyl groups have considerable effect on the rate of reaction (1).
The pressure‐dependence of fluorescence intensity and photolysis rate of the vapors of carbon bisulfide, nitrogen dioxide, and sulfur dioxide
Authors: Makarov V. I. 
Published: January 2005

AbstractThis article is concerned with the Stern–Volmer dependence on the NO2, SO2, and CS2fluorescence self‐quenching within a wide range of pressure variations of these gases. Besides, the pressure‐dependences of the photolysis rate of these substances have been investigated. The deviations from linearity in the Stern–Volmer dependences and photolysis rate of NO2, SO2, and CS2in the highpressure region have been revealed. These deviations correspond to increasing effective rate constant of the collision quenching ofexcited molecules NO2, SO2, and CS2.A model to describe the deviations observed has been proposed. The model assumes the formation of excimer particles which may dissociate in a monomolecular way and may be quenched at collisions. The estimates of the lifetimes of excimer particles yield the values of the order of several nanoseconds.
Rate constants for the gas‐phase reactions of the OH radical with the cresols and dimethylphenols at 296 ± 2K
Authors: Atkinson Roger , Aschmann Sara M. 
Published: January 2005

AbstractUsing a relative rate technique, rate constants for the gas‐phase reactions of the OH radical with the three cresols and the six dimethylphenols have been determined at 296 ± 2 K and atmospheric pressure. The rate constants for the cresols, which range from 4.3 × 10−11 cm3molecule−1 s−1to 6.8 × 10−11 cm3molecule−1 s−1, are in good agreement with previous literature data. The rate constants for 2,3‐, 2,4‐, 2,5‐, 2,6‐, and 3,4‐dimethylphenol are all in the range (6.6–8.1) × 10−11 cm3 molecule−1 s−1, with the rate constant for 3,5‐dimethylphenol being somewhat higher at 1.13 × 10−10 cm3 molecule−1 s−1. Rate constants estimated from the number, identity, and positions of the substituent groups around the aromatic ring agree to within a factor of approximately 2 with these experimentally determined rate constants.
Kinetics and mechanism of the oxidation of some cyclic and acyclic ketones by dodecatungstocobaltate(III)—A comparative study
Authors: Gupta Mala , Saha Swapan K. , Banerjee Pradyot 
Published: January 2005

AbstractThe kinetics of oxidation of cyclohexanone(chxn), 2‐butanone(but), and 1,3‐dihydroxy‐2‐propanone (dhp) have been investigated in aqueous acidic media. A first‐order dependence in complex is obtained at high acid and low oxidant concentration for these ketones. However, a zero‐order rate prevails at high oxidant and low acid concentration, and this rate has been shown to be the acid catalyzed enolization rate of the ketone. A general rate expression has been derived to explain these behaviors and plausible mechanism has been offered by assuming the enol as the reactive species.
Reactive and non‐reactive counterion surfactants in water and aqueous acetonitrile
Authors: Berndt D. C. , Rossman C. A. , Hach C. L. , Fillar D. J. 
Published: January 2005

AbstractRates of hydrolysis of hydroxamic acids with perfluorooctanoic acid as a reactive counterion surfactant and also with sodium sulfonate surfactants plus HCl have been determined in both water and aqueous acetonitrile solvents. The pseudophase ion exchange model satisfactorily explains the micellar effects for both the reactive and non‐reactive counterion surfactants in both solvent systems.
A relative rate study of the reaction of Cl atoms with a series of alkyl nitrates and nitro alkanes in air at 295 ± 2 K
Authors: Wallington T. J. , Hinman M. M. , Andino J. M. , Siegl W. O. , Japar S. M. 
Published: January 2005

AbstractThe relative rate technique has been used to measure rate constants for the reaction of chlorine atoms with nitro methane, nitro ethane, nitro propane, nitro butane, nitro pentane, ethyl nitrate, isopropyl nitrate, n‐propyl nitrate, 2‐pentyl nitrate, and 2‐heptyl nitrate. Decay rates of these organic species were measured relative to one or more of the following reference compounds; n‐butane, ethane, chloroethane, and methane. Using rate constants of 2.25 × 10−10 5.7 × 10−11, 8.04 × 10−12, and 1.0 × 10−13 cm3 molecule−1 s−1 for the reaction of Cl atoms with n‐butane, ethane, chloroethane, and methane, respectively, the following rate constants were derived, in units of cm3 molecule−1 s−1: nitro methane, <7 × 10−15; nitro ethane, (2.05 ± 0.14) × 10−13; nitro propane, (1.13 ± 0.05) × 10−11; nitro butane, (5.13 ± 0.68) × 10−11; nitro pentane, (1.40 ± 0.14) × 10−10; ethyl nitrate, (3.70 ± 0.24) × 10−12; n‐propyl nitrate, (2.15 ± 0.13) × 10−11; i‐propyl nitrate, (3.94 ± 0.48) × 10−12; 2‐pentyl nitrate, (1.00 ± 0.06) × 10−10; and 2‐heptyl nitrate, (2.84 ± 0.50) × 10−10. Quoted errors represent 2σ and do not include possible systematic errors due to errors in the reference rate constants. Experiments were performed at 295 ± 2 K and atmospheric pressure (≃740 torr) of synthetic air. The results are discussed with respect to the previous literature data and to the modeling of these compounds in the atmosphere.
Room temperature rate coefficient for the reaction between CH3O2 and NO3
Authors: Crowley J. N. , Burrows J. P. , Moortgat G. K. , Poulet G. , LeBras G. 
Published: January 2005

AbstractThe molecular modulation spectroscopic technique was employed to study the kinetics of NO3 radicals produced in the 253.7 nm photolysis of flowing gas mixtures of HNO3/CH4/O2 at room temperature. By computer fitting of the NO3 temporal behavior, a rate coefficient of (2.3 ± 0.7) × 10−12 cm3 molecule−1 s−1 was obtained for the reaction between NO3 and CH3O2 at 298 K.
Kinetics of reactions between methyl and acetyl radicals in gas phase produced by flash photolysis of acetic anhydride
Authors: Hassinen Eero , Kalliorinne Kaarlo , Koskikallio Jouko 
Published: January 2005

AbstractThe reaction products of photolysis of acetic anhydride in gas phase at 25°C, where He or CO2 was present as buffer gas, were analyzed by gas chromatography. The extent of photodissociation was 52% ± 5% and the extent of intramolecular hydrogen transfer reaction producing acetic acid and ketene was 48% ± 5%. The rate constants of the hydrogen exchange and radical combination reactions between methyl and acetyl radicals were calculated from the amounts of products. The value of the ratio of the rate constants of hydrogen exchange and radical combination reactions between methyl and acetyl radicals, 𝓀7/𝓀6 = 0.15, indicates that acetyl radical is a relatively poor hydrogen donor. The corresponding ratio of rate constants for the reactions between two acetyl radicals, 𝓀9/𝓀s = 0.42, indicates that acetyl radical is a better hydrogen acceptor than methyl radical.
Ionic atmosphere effects on the energetics of thermal and optical electron‐exchange reactions: Application to ferrocenium‐ferrocene self exchange
Authors: Kuznetsov A. M. , Phelps D. K. , Weaver M. J. 
Published: January 2005

AbstractA treatment of ionic‐atmosphere effects upon symmetrical electron‐transfer reactions resulting from added electrolyte is outlined. Relationships are derived on the basis of the extended Debye‐Huckel model for the increase in the activation free energy, ΔGia*, associated with reorganization of the ionic atmosphere for homogeneous‐phase reactions involving a pair of spherical reactants with varying internuclear distance R. Similar relationships apply to the energetics of symmetrical optical electron transfer, since the increase in the optical transition energy, ΔE, should equal the corresponding ionic atmosphere reorganization energy, E; under the anticipated linear response conditions, E = 4ΔGia*. The predicted ΔGia* (and hence ΔE) values increase sharply with increasing R, as a consequence of the diminished “sharing” of the ionic cloud surrounding the donor and acceptor sites under these conditions. Outer‐sphere electrochemical reactions, featuring a single “near‐isolated” reactant, are predicted to feature substantially larger ΔGia* values than for homogeneous processes proceeding with the reaction partners in contact. The influence of more specific “ionic atmosphere” effects upon ΔGia*, especially involving reactant‐electrolyte ion pairing, is also discussed. Unlike that of the nonspecific ionic atmosphere, the nuclear reorganization process associated with counterion transport between donor and acceptor sites coupled with electron transfer is nonlinear in nature, so that E ≠ 4ΔGia*. Some recent experimental data for electrolyte effects upon the rate constants for ferrocenium‐ferrocene self exchange and related systems are examined in the light of these considerations.
Influence of the side chain on the stability of Schiff‐bases formed between pyridoxal 5′‐phosphate and amino acids
Authors: Vazquez M. A. , Muñoz F. , Donoso J. , Blanco F. García 
Published: January 2005

AbstractThe stability of some Schiff‐bases formed between PLP and different amino acids has been investigated in a wide range of pH. The kinetic constants of formation of these compounds and their hydrolysis rate constants have been determined. Results show that the α‐position of the carboxyl group of amino acid plays an important role on the mechanism of water attack upon the CNbond. The absence of ionic groups in the surroundings of that bond must be an important factor of stability. Bulky hydrophobic substituents in the amino acid, near the amine part, protect the imine bond against hydrolysis.