bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on the effect of the cation nature on the kinetics of the isotopic exchange reaction between chloride ion and O,O‐diphenylphosphorochloridothionate in acetonitrile
Authors: Reimschüssel W. , Tilk S. , Mikołajczyk M. , Ślebocka‐tilk H. 
Published: January 2005

AbstractRate constants and activation parameters for the isotopic exchange reactions between (PhO)2PSCl and M36Cl (M = Me4N+, Et4N+, n‐Bu4N+, Et3HN+, EtH3N+, Li+) in acetonitrile were measured in order to find the effect of the cation nature onthe kinetics of the reaction. The rate constants measured for a range of concentrations of Et3HN36Cl, EtH3N36Cl, and Li36Cl were analyzed using the Acree equation. The equivalent conductance of LiCl in acetonitrile was determined. The nature of the cation has no effect on the mechanism of the reaction. The cation changes only the experimental rate constant proportionally to the dissociation degree of the salt. Smaller values of the rate constant and smaller activation parameters ΔH‡ and ΔS‡ for the reaction with Li36Cl indicate the existenceof the intermolecular interaction between lithium ions and O,O‐diphenylphosphorochloridothionate.
The thermal decomposition of fluorinated esters
Authors: Blake P. G. , Shraydeh B. F. 
Published: January 2005

AbstractThe kinetics of thermal decomposition of ethyl, isopropyl, and t‐butyl trifluoroacetates have been studied in the gas phase. In each case initial decomposition follows the normal ester route to give an olefin and trifluoroacetic acid, and elimination of hydrogen fluoride does not occur. However, trifluoroacetic acid is thermally unstable at ethyl and isopropyl ester decomposition temperatures, and further products result, including those from the difluorocarbene produced by decomposing trifluoroacetic acid. Placing a CF3 group at an ester's γ carbon increases the polarity of its transition state and decreases its thermal stability. The activation energies of the ethyl and isopropyl esters are lowered by 3.8 and 4.7 kcal/mol compared to the corresponding acetates, and the primary decomposition kinetics, which are homogeneous and of the first order, are expressed by
equation image
α‐Methylation enhances the reactivity of the trifluoroacetates, and the t‐butyl ester, the transition state for which is sufficiently polar for heterogeneous decomposition to occur, shows signs of thermal instability at room temperature. The equilibrium
equation image
was also investigated and gave ΔH° = +13,580 cal/mol and ΔS° = +31.07 gibbs/mol in the forward direction. The results obtained extend and support the known structure–rate correlations in the gas‐phase elimination of esters.
Cl‐atom transfer from CFCl3 to the c‐C6H11 radical. An indirect estimation of the CFCl2Cl bond dissociation energy
Authors: Baruch G. , Rajbenbach L. A. , Horowitz A. 
Published: January 2005

AbstractThe Cl‐transfer reaction between CFCl3 and c‐C6H11 radicals (R) was studied in liquid cyclohexane (RH). The Arrhenius parameters for Cl abstraction were determined in the RH‐CFCl3 system versus the termination reaction between cyclohexyl radicals and competitively versus addition to C2Cl4 in the RH‐CFCl3‐C2Cl4 system. The two sets of results are in very good agreement and give the following Arrhenius expression for the reaction R + CFCL3 → RCl + CFCl2 (2):

where θ = 2.303RT in kcal/mol. Comparison with Cl‐transfer data of other chloromethanes and chloroethanes shows that an increase in the CCl bond dissociation energy is the main cause of the reduced reactivity of CFCl3. Based on a previously developed correlation, D(CFCl2  Cl) is estimated to be equal to 74.4 kcal/mol.
The kinetics of radiation induced hydrogen abstraction by CCl3 radicals in the liquid phase: Cyclanes
Authors: Alfassi Zeev B. , Feldman Liviu 
Published: January 2005

AbstractThe kinetics of gamma‐radiation induced free radicals reactions in carbon tetrachloride solutions of cyclohexane, cyclooctane and cyclododecane were studied in the range of 27–190°C. The activation energies found were in the order cC6H12 > cC12H24 > cC8H16, which was explained as due to their ring strain which has the same order. The following log k1 was obtained using the known Arrhenius parameters for CCl3 radical recombination:
equation image
The correlation of rate coefficients for H‐atom abstraction by HO radicals with CH bond dissociation enthalpies
Authors: Heicklen Julian 
Published: January 2005

AbstractFor H‐atom abstraction reactions by HO radicals it has been shown that
equation image
If Di is taken as the CH bond dissociation enthalpy at 298 K, then a = 0.323 and D0is obtained from the empirical formula

where D0 is in kcal/mol and T is in K. Thisrelationship is valid for T between 200 and 400 K. Finally empiricalrelationships are given to help estimate Di.
The thermal decomposition of 4‐methyl‐3,6‐dihydro‐2H‐pyran
Authors: Frey Henry M. , Watts Hugo P. 
Published: January 2005

AbstractThe thermal decomposition of the title compound has been studied in the gas phase in the temperature range of 584–634 K. The decomposition was found to be a first‐order homogeneous process yielding 2‐methylbuta‐1,3‐diene and formaldehyde. The rate constants obtained at 11 temperatures within the quoted range fitted the Arrhenius equation

The decomposition is probably unimolecular and concerted.
Evidence for chamber‐dependent radical sources: Impact on kinetic computer models for air pollution
Authors: Carter W. P. L. , Atkinson R. , Winer A. M. , Pitts J. N. 
Published: January 2005

AbstractA series of NOx–air irradiations, with trace amounts of propane and propene present to monitor OH radical concentrations, have been carried out in a 5800‐L evacuable environmental chamber to investigate radical levels and sources during such irradiations. The data obtained show conclusively that unknown radical sources are present, and that photolysis of initial nitrous acid can be, at best, only a minor source of radicals after ∼30–60 min of irradiation.
Thermal reactions of ethane‐d6–acetylene and D2–acetylene mixtures behind shock waves
Authors: Rogers David , Skinner Gordon B. 
Published: January 2005

AbstractA study of the thermal decomposition of an acetylene–ethane‐d6 mixture indicates that the rate constant for hydrogen abstraction from acetylene by methyl is more than 20 times less than for abstraction from ethane. Isotopic exchange is initiated by a rapid reaction between product D atoms and C2H2. A series of experiments involving the reactions of a D2–acetylene mixture indicated that a molecular exchange process was also occurring, and it was shown that d[C2HD]/dt = k[D2]0.7[C2H2]0.3, effective activation energy = 15.8 kcal/mol. This mechanism made an insignificant contribution to isotope exchange in C2H2–C2D6 mixtures.
Kinetics of the bimolecular initiation process in the thermal reactions of ethylene
Authors: Ayranci G. , Back M. H. 
Published: January 2005

AbstractThe initial rates of formation of the major products in the thermal reactions of ethylene at temperatures in the neighborhood of 750 K have been measured in the presence and absence of the additive butene‐1. It has been shown that this ratio of rates is related to the ratio of rate constants for the two initiation processes:
equation image
The ratio k′1/k1 has been measured over the temperature range of 700–773 K and may be expressed as (R = 1.987 cal/mol deg) log k′1k1(mol/L) = 2.8 − 4400/2.3RT. Assuming a value for k′1 of log k′1 (s−1) = 16 − 71,500/2.3RT, the value of k1 may be expressed as log k1(L/mol) = 13.2 − 67,000/2.3RT. The values for the frequency factor and activation energy for reaction (1) are discussed in relation to the heat of formation of the vinyl radical, and it is concluded that reaction (1) is the main initiation process in the thermal decomposition of ethylene under the present conditions.
The dynamics of formation of vibrationally excited HF in reactions of O (21D2) atoms with partially fluorinated alkanes
Authors: Burks T. L. , Lin M. C. 
Published: January 2005

AbstractThe nascent vibrational energy distributions of the HF† formed in the reactions of a series of partially fluorinated alkanes (RFH; RF = CH2F, CHF2, CF3, C2F5, C3F7, and C7F15) with electronically excited oxygen atoms O(21D2) have been determined by measuring the appearance times of stimulated emissions from various vibration–rotation transitions in a grating‐tuned optical cavity. The vibrational energy contents of the HF formed in these reactions were found to be considerably greater than statistically expected. These reactions are believed to occur via vibrationally excited short‐lived α;‐fluorinated alcohols (RFOH†), formed by insertion of the O(21D2) atoms into CH bonds. The observation of nonstatistical energy partitioning in the above reactions is in clear contrast to the result obtained from the O(21D2) + CF3CH3 reaction that produces the β‐fluorinated alcohol CF3CH2OH, from which the HF product carries a near statistical vibrational energy distribution. A mechanism for HF† formation in these very exothermic reactions is presented.
Kinetic studies of the reaction of C2H5 with O2 at 295 K
Authors: Plumb I. C. , Ryan K. R. 
Published: January 2005

AbstractThe reaction between C2H5 and O2 at 295 K has been studied with a flow reactor sampled by a mass spectrometer. With helium as the carrier gas the rate coefficient was found to increase from (1.2 ± 0.3) × 10−12 to (3.6 ± 0.9) × 10−12 cm3/s as [He] was increased from 2 × 1016 to 3.4 × 1017 cm−3. The importance of
equation image
has been determined from a knowledge of the initial C2H5 concentration together with a measurement of the C2H4 produced in reaction (5). F, the fraction of the C2H5 radicals removed by path (5), was found to decrease from 0.15 to 0.06 as [He] increased from 2 × 1016 to 3.4 × 1017 cm−3. The rate coefficient for reaction (5) was found to be independent of [He] and to have a value of (2.1 ± 0.5) × 10−13 cm3/s. The variation in F reflects the fact that k1b increases as [He] increases. These observations are taken as evidence for a direct mechanism for C2H4 production and a collision‐stabilized route for C2H5O2 formation. Calculations indicate that the high‐pressure limit for reaction (1b) is ∼4.4 × 10−12 cm3/s and that in the polluted troposphere the branching ratio for reactions (1b) and (5) will be ∼l20.
On the kinetics of the transition metal catalyzed decomposition of secondary hydroperoxides
Authors: Hajdu I. P. , Nemes I. , Sümegi L. , Vidóczy T. , Gál D. 
Published: January 2005

AbstractA general mechanism was proposed for the title reactions which describes the kinetics of hydroperoxide decomposition as well as product accumulation throughout the whole reaction period in an analytical form. The following catalytic steps were included: magnified image where the deactivation takes place as a result of radical–catalyst interaction inside the cage. The resulting equations give satisfactory description of the literature data in the case of various catalysts and hydroperoxides.
The kinetics of propylene oxide reaction with certain alkylamino alcohols in the presence of basic catalysts
Authors: Ślipko Kazimiera , Chlebicki Jan 
Published: January 2005

AbstractRate constants for direct reactions of propylene oxide with certain aminoisopropanols in the presence of basic catalysts were studied at a temperature of 363–383 K. This reaction was found to be of the first order in propylene oxide, amino alcohol and catalyst. The observed kinetics are consistent with a termolecular mechanism.
The acetyl radicals CH3CO· and CD3CO· studied by flash photolysis and kinetic spectroscopy
Authors: Adachi Hiroyuki , Basco N. , James D. G. L. 
Published: January 2005

AbstractUltraviolet absorption spectra have been characterized for the acetyl‐h3 and acetyl‐d3 radicals, which were generated by the flash photolysis of the corresponding acetones. The spectra are broad and intense, with values of the extinction coefficient at the respective maxima estimated as: ϵCH3CO(215) = (1.0 ± 0.1) × 104 L/mol·cm and ϵCD3CO(207.5) = (1.0 ± 0.05) × 104 L/mol·cm. Rate constants for the reactions of mutual interaction
equation image
were estimated as: k = 3.5 × 1010 L/mol·s and k = 3.4 × 1010 L/mol·s. Rate constants for the reactions of cross interaction
equation image
were estimated as: k = 8.6 × 1010 L/mol·s and k = 5.2 × 1010 L/mol·s. The related values of the cross interaction ratios k/(kk)1/2 = 2.6 and k/(kk)1/2 = 1.6 do not differ significantly from the statistical value of 2. The participation of the radical displacement reactions
equation image
was estimated in terms of the fractions k/k = 0.38 and k/k = 0.47.Corroborative spectra were obtained from the flash photolysis of methyl ethyl ketone and biacetyl, and the relative rates of the competing primary processes were estimated from the relative peak heights of the acetyl and methyl radicals in each system.
Chain reactions in stirred‐flow reactors–a tool for exploring initiation and termination steps independently
Authors: Benson Sidney W. , Weissman Maia 
Published: January 2005

AbstractIt is shown that chain reactions may be studied in stirred‐flow reactors under conditions in which the escape of radicals from the reactor competes significantly with the chemical termination reaction. The appropriate rate law permits the independent evaluation of the rate constants of the initiation and termination steps. Such information is of special interest in the study of surface effects on chain reactions.
Kinetics and mechanism of the addition of 1,3‐butadiene to cyclohexa‐1,3‐diene in the gas phase
Authors: Huybrechts G. , Hubin Y. , Narmon M. , Van Mele B. 
Published: January 2005

AbstractThe thermal reactions of 1,3‐butadiene (BD) with cyclohexa‐1,3‐diene (CHD) have been studied in a static system between 437 and 526 K. The pressures of BD and CHD were varied from 61 to 397 torr and from 50 to 93 torr, respectively. The percentages of consumed BD and CHD were always kept lower than 14%. The reactions—in the order of importance—are
magnified image
All the reactions are homogeneous and of the first order with respect to the reagents. Their rate constants (in L/mol·s) are given by

A thermochemical analysis of a biradical mechanism is in agreement with these results.
Heterogeneous reactions of sulfur dioxide with carbonaceous particles
Authors: Baldwin Alan C. 
Published: January 2005

AbstractThe rate of adsorption of SO2 on a prototype carbonaceous surface was measured at low pressure in a flow reactor. The measured rate indicates a maximum atmospheric loss of SO2 by heterogeneous reaction of 1%/h for a particle density of 100 μg/m3. The capacity of carbon particles to adsorb SO2 is limited at ∼1 mg SO2 g−1 C. NO2 has no effect on the rate of SO2 adsorption or the saturation behavior.
The thermal decomposition of fluorinated esters. II. The effect of γ‐substitution
Authors: Blake P. G. , Shraydeh B. F. 
Published: January 2005

AbstractThe gas‐phase kinetics of thermal decomposition of ethyl difluoroacetate, pentafluoropropionate, and hepatfluorobutyrate have been studied. The normal ester decomposition route to ethylene plus carboxylic acid is taken in each case, but the fluorinated acids decompose rapidly at the temperatures used. The primary decompositions are homogeneous and unimolecular, and the three Arrhenius equations are

The postulate of a slightly electron‐rich γ carbon in six‐center ester transition states is supported by the higher rates and lowered activation energies observed when increasingly electron‐withdrawing fluorinated groups are linked to this center. The stabilization is reflected in a ρ constant of +0.30. The results are compared with previous work on α substitution in fluorinated esters.
Effects of buffer gases on the infrared multiphoton dissociation of C2H4DCl: A chemical clock to explore highly excited molecules
Authors: Papagiannakopoulos P. J. , Kosnik Ken , Benson S. W. 
Published: January 2005

AbstractObservations are reported of the effect of the buffer gases He, Ne, and CF4, in the pressure range of 0–30 torr, on the branching ratio [HCl]/[DCl] of the unimolecular decomposition magnified imageThe ratio R = kH/kD has been measured in high‐pressure thermal decomposition (670–1100 K) and was shown to give a unique measure of the internal energy of the decomposing molecules and hence, with RRKM theory and pressure fall‐off data, a time scale for their decomposition.Applying the thermal data to the photolysis leads to the conclusion that excitation and decomposition are produced by the laser spike (high intensity, 70 ns FWHM) and also at a slower rate by the larger, less intense tail (1.6 μs). Added buffer gases quench the latter, leaving the former which, from measurements of R, is shown to correspond to excitations of 115 ± 15 kcal/mol and lifetimes of ∼30 ps. No bond breaking is seen despite the high energies, in accord with theoretical expectations. The results require an enhanced rate of photon absorption by the highly excited molecules, which are about hundredfold greater than that observed for 300 K molecules. Data are also reported for C2H2F2 and the secondary multiphoton photolysis of the ethylenes produced. Effects of beam geometry and wavelength are explored.
Temperature and third‐body dependence of the rate constant for the reaction O + O2+ M → O3+ M
Authors: Lin C. L. , Leu M. T. 
Published: January 2005

AbstractThe flash photolysis resonance fluorescence technique was used to measure the rate constants of the reaction O + O2+ M → O3+ M (M = N2, O2, Ar, and He) as a function of temperature. The results for the rate constants are given byequation imageThe activation energies with N2, O2, and Ar as third bodies are equal within the experimental error, (−1370 → 340 cal/mol), and the relative third‐body efficiencies at 298 K for N2, O2, Ar, and He are 1.00, 0.99, 0.69, and 0.60, respectively.
Laser‐induced chemical kinetics: Absolute rate constants for the reactions Ċ2F2 + Br2 → C2F5Br + Ḃr and n‐Ċ3F7 + Br2 → n‐C3F7Br + Ḃr
Authors: Rossi M. J. , Barker J. R. , Golden D. M. 
Published: January 2005

AbstractAbsolute rate constants at room temperature for the metathesis reaction have been measured under VLPP conditions: k1 = (2.0 ± 0.5) × 108M−1·s−1, k2 = (3.0 ± 0.7) × 108M−1·s−1. The radicals were generated through collisionless infrared‐multiphoton decomposition of the corresponding iodides by irradiation from a high‐power CO2‐TEA laser. The reaction of Ċ2F5 and Ċ3F7 with \documentclass{article}\pagestyle{empty}\begin{document}$$\mathop {\rm N}\limits^{\rm .} {\rm O}_{\rm 2} $$\end{document} are briefly discussed in relation to the reaction of Ċ3 with \documentclass{article}\pagestyle{empty}\begin{document}$$\mathop {\rm N}\limits^{\rm .} {\rm O}_{\rm 2} $$\end{document}, which had been measured previously.
F‐to‐HF reactions. VIII. Nonthermal complications for the CHF3/C3F6/C2F6 moderated nuclear recoil system
Authors: Mathis Chester A. , Gurvis Rafael , Knickelbein Mark , Knierim Kathleen D. , Mo Siu‐Hong , Root John W. 
Published: January 2005

AbstractResults are reported from moderated nuclear recoil 18F experiments with the 273 K CHF3/C3F6/C2F6 system. Although the measurement sensitivity is only about ±12%, there is no evidence to support the occurrence of nonthermal F‐to‐HF reactions at 95 mol % C2F6 moderator concentration.
Chemiluminescence simulation method for the evaluation of the termination rate constant for 2‐cyanopropyl peroxy and α‐phenyl‐ethyl peroxy radicals
Authors: Lampert R. , Phillips D. , Vidoczy T. , Lukacs J. , Vasvari G. , Gal D. 
Published: January 2005

AbstractAn iterative method has been devised for the simulation of chemiluminescence data during the oxidative decomposition of αα′ azobisisobutyronitrile in the presence of ethylbenzene. From this simulation the cross termination rate constant of the two types of peroxy radicals present has been estimated.
Kinetics of the gas‐phase reactions of OH radicals with alkyl nitrates at 299 ± 2 K
Authors: Atkinson Roger , Aschmann Sara M. , Carter William P. L. , Winer Arthur M. 
Published: January 2005

AbstractRelative rate constants for the gas‐phase reactions of OH radicals with a series of alkyl nitrates have been determined at 299 ± 2 K, using methyl nitrite photolysis in air as a source of OH radicals. Using a rate constant for the reaction of OH radicals with cyclohexane of 7.57 × 10−12 cm3/molec·s, the rate constants obtained are (× 1012 cm3/molec·s): 2‐propyl nitrate, 0.18 ± 0.05; 1‐butyl nitrate, 1.42 ± 0.11; 2‐butyl nitrate, 0.69 ± 0.10; 2‐pentyl nitrate, 1.87 ± 0.12; 3‐pentyl nitrate, 1.13 ± 0.20; 2‐hexyl nitrate, 3.19 ± 0.16; 3‐hexyl nitrate, 2.72 ± 0.22; 3‐heptyl nitrate, 3.72 ± 0.43; and 3‐octyl nitrate, 3.91 ± 0.80. These rate constants, which are the first reported for the alkyl nitrates, are significantly lower than those for the parent alkanes, and a formula, based on the numbers of the various types of CH bonds in the alkyl nitrates, is derived for rate constant estimation purposes.
Pyridiniumchlorochromate oxidations: Studies on the kinetics and substituent effect in the oxidation of aniline in nonaqueous systems
Authors: Panigrahi G. P. , Mahapatro D. D. 
Published: January 2005

AbstractPyridiniumchlorochromate (PCC) oxidizes aniline and substituted anilines except nitro anilines smoothly in chlorobenzene–nitrobenzene mixtures in the presence of dichloroacetic acid. The reaction has unit dependence on each of the aniline, PCC, and dichloroacetic acid concentrations. Electron‐releasing substituents accelerate the reaction, whereas electronwithdrawing groups retard the reaction, and the rate data obey Hammett's relationship. The reaction constant ρ is ‐3.75. Azobenzene and p‐benzoquinone have been obtained as products. The observed experimental data have been rationalized in terms of the formation of an intermediate complex involving PCC–amine undergoing a rapid decomposition to products.
Reaction of hot H atoms with CDCl3
Authors: Gould Philip L. , Oldershaw Geoffrey A. 
Published: January 2005

AbstractEnergetic hydrogen atoms generated by photolysis of HBr or HI react with CDCl3 by abstracting either a deuterium atom (1) or a chlorine atom (2):
equation image
The integral probability of reaction (2) has been measured for several defined initial translational energies of H*, and the phenomenological threshold energy is 31 ± 14 kJ/mol. For initial translational energies in the range of 66–121 kJ/mol, the ratio of the integral probabilities of Cl abstraction and of D abstraction, when normalized to equal numbers of Cl and D atoms, is 2.4 ± 0.3. The interpretation of the integral reaction probabilities in terms of the excitation functions of reactions (1) and (2) is discussed. Measurements of the moderating effect of CO2 on reactions (1) and (2) show that CDCl3 is slightly more effective than CO2 as a moderator of H atoms in the energy range of 90–30 kJ/mol.
Mechanism of oxidation of diphenyl sulfide by peroxyanions
Authors: Srinivasan C. , Kuthalingam P. , Arumugam N. 
Published: January 2005

AbstractReactions of diphenyl sulfide with the two oxidants peroxydisulfate and peroxydiphosphate are described. With each oxidant, the reaction is first order in the oxidant and zero order in the substrate. The rate of the reaction is also independent of the effect of the substituent. Hydrogen ion catalyzes the reactions. The lack of inhibition of the reaction rate by added acrylamide rules out the possibility of a radical reaction initiated by the homolysis of the peroxyanions. From the effect of [H+] on the oxidation rates, the active species involved in the reactions have been determined. The redox reaction is essentially proceeding via hydrolysis of the protonated peroxy anions in a rate‐determining step, followed by a fast step involving the oxidation of diphenyl sulfide to diphenyl sulfoxide. This has been confirmed by estimating the hydrolyzed products in each case and also by the product analyses.