bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluated and estimated kinetic data for phase reactions of the hydroperoxyl radical
Authors: Lloyd Alan C. 
Published: January 2005

AbstractMethods are discussed for the production and detection of the hydroperoxyl radical for use in gas phase kinetic studies. Rate constants for gas phase reactions of the hydroperoxyl radical with itself, H2, H2O, CO, NO, SO2, O3, C2H6, C3H8, i‐and n‐C4H10, C2H4, i‐C4H8, HCHO, C2H5CHO, n‐C3H7CHO, Br, O, OH, and H are critically evaluated. Recommended or estimated rate constant expressions with associated error limits are given applicable over specified temperature ranges (normally 300–1000°K). The reactivity of HO2 compared with OH, O, H, F, Cl, Br, CH3, and CH3O is presented in tabular form and the implications for atmospheric chemistry are discussed.
A kinetic study of the reactions of the hydrogen atom with the cyclohexadiene isomers in the gas phase
Authors: Furukawa Kiyoshi , James D. G. L. , Papic M. M. 
Published: January 2005

AbstractAbsolute values of the rate constants for the reaction of hydrogen atoms with cyclic olefins in the gas phase have been measured in a discharge‐flow system under 3.5, 16, and 22 torr Ar at 23°C. The attenuation of hydrogen atom concentration in the reaction tube in the presence of a large excess of olefin was measured with an ESR spectrometer, and the products were analyzed by gas chromatography. Cyclic C6 hydrocarbons were the only significant products obtained when the hydrogen atom concentration was 2.6 × 10−10 mole/1., the olefin concentration was in the range of 9 to 22 × 10−8 mole/1., and the pressure was 16 torr Ar. The values for the rate constants for reaction with cyclohexadiene‐1,3, cyclohexadiene‐1,4, and cyclohexene are, respectively, (9 ± 2) × 108, (12 ± 1) × 108, and (6 ± 1) × 108 l./mole‐sec, and they are not changed significantly by a sixfold change in total pressure. The fraction of the total interaction that proceeds by addition is 84% in the cyclohexadiene‐1,3 system, but only 18% in the cyclohexadiene‐1,4 system, and the cyclohexadienyl radical is therefore the dominant radical species in the latter system. The pattern of interaction between the hydrogen atom and the cyclohexadienyl radical was determined, and comprises 65% of disproportionation, and 13% and 23% of combination to yield cyclohexadiene‐1,3 and cyclohexadiene‐1,4, respectively. These results are consistent with the general patterns of reactivity emerging from studies of the reactions between free radicals and olefins in related systems.
Thermochemical kinetics of nitrogen compounds. V. The unimolecular thermal decomposition of diallylamine in the gas phase
Authors: Egger Kurt W. , Vitins Peter 
Published: January 2005

AbstractThe kinetics of the thermal decomposition of diallylamine to propylene and prop‐2‐enaldimine have been studied in the gas phase in presence of an excess of methylamine over the temperature range of 532.7 to 615.6°K, using a static reaction system. Methylamine reacted with the unstable primary product prop‐2‐enaldimine, forming the thermally stable N‐methyl prop‐2‐enaldimine.First‐order rate constants, based on the internal standard technique, fit the Arrhenius relationship log k(s−1) = (11.04 ± 0.13) − (37.11 ± 0.33 kcal/mole)/2.303 RT. They were independent on the initial total pressure (46–340 torr), the initial pressure of diallylamine (9.2–65 torr), or methylamine as well as the conversion attained. Despite an apparent surface sensitivity, the reaction is essentially homogeneous in nature as demonstrated by experiments carried out in a packed reaction vessel.The observed activation parameters for the title reaction together with those observed earlier for triallylamine and allylcyclohexylamine are consistent with the proposed concerted reaction mechanism involving a cyclic 6‐center transition state. The observed substituent effects suggest a nonsynchronous mode of bond breaking and bond formation.
Reaction between ozone and allene in the gas phase
Authors: Toby Frina S. , Toby Sidney 
Published: January 2005

AbstractThe kinetics of the reaction between ozone and allene (A) were studied in the range of 226 to 325°K in the gas phase. Initial O3 pressures varied from 0.01 to 0.7 torr and allene pressures varied from 0.05 to 6 torr. At the higher initial O3 pressures the most important product was O2 followed by CO, H2O, CO2, and C2H4. Oxygen balances averaging about 110% were obtained, which implies that no important oxygenated products were missed. However, carbon balances were only about 50% and hydrogen balances were even less, so that unidentified hydrocarbons were presumably formed. The rate law found was − d[O3]/dt = k1[O3][A] + k2a[O3]2[A]/[O3]0 where log k1(M−1sec−1) = 6.0 ± 0.7 − (5500±1000)/2.30RT and log k2a(M−1sec−1) = 6.9 ± 0.7 − (6200 ± 800/2.30RT). A mechanism is proposed which accounts for the rate law and the observed stoichiometry of O2 formed–O3 used. This involves a heterogeneous catalyzed decomposition of O3. The rate constant k1 is identified with the primary addition reaction A + O3 → AO3, and this rate constant is compared with those from other O3 addition reactions.
The kinetics of nucleophilic substitution processes in the alkyl halides. Part B—analysis of experimental data
Authors: German E. D. , Dogonadze R. R. 
Published: January 2005

AbstractNucleophilic substitution reactions in the alkyl halides, RX + Y− → RY + X−, proceeding in polar media are considered on the basis of the theory presented in Part A. It is shown that the solvent reorganization energy is the main part of the activation energy for this processes. According to calculations performed, the values of the solvent reorganization energy equal ∼2.5–3 eV for H2O and ∼ 1.8–2.3 eV for acetone. From experimental data on the kinetic isotope effect, an estimate for the splitting of nonadiabatic terms and for the slope of the potential curve v′ of the intermolecular interaction between halide ion and methyl halide near transition configuration is made. Further, the parameter v′ is used for calculating the activation entropy of substitution reactions in the methyl halides. Theoretical activation energies and activation entropies agree with experimental values. In the framework of theory presented an interpretation of change of Ea and the preexponential factor with the type of alkyl halide is given.
The reaction of cyclohexyl radicals with carbon tetrachloride
Authors: Currie Jim , Sidebottom Howard , Tedder John 
Published: January 2005

AbstractThe photolysis of azocyclohexane, carbon tetrachloride, and cyclohexane at 360 nm has been investigated over a wide temperature range. At moderate temperatures a chain reaction ensues from which the following approximate rate constants could be determined assuming 2CCl3. → C2Cl6, k5 = 109.7 (303–673K):

equation image

The really striking feature of the results is that they show that termination in bicyclohexyl [reaction (7)] is extremely slow:

equation image

The root‐mean‐square rule for estimating the cross‐combination rate

equation image

is also followed.The photolysis of carbon tetrachloride and cyclohexane at 250 nm has also been investigated. The reaction is complicated by the occurrence of two concurrent photolytic processes, the main one yielding trichloromethyl radicals and chlorine atoms, and the subsidiary one yielding dichlorocarbene and molecular chlorine. Nonetheless the results from this reaction can be interpreted in the medium temperature range 360–430K, where long chains are present, in terms of the rate constants derived from the azocyclohexane system.
The decomposition of acetylenedicarboxylic acid in acetophenone
Authors: Hsu A. M. , Huang Thomas T.‐S. 
Published: January 2005

AbstractThe decomposition of acetylenedicarboxylic acid in acetophenone was studied in the temperature range of 100–130°C. The rate constants and activation parameters for the consecutive pair of first‐order steps (each yielding carbon dioxide) were calculated. Hydrogen kinetic isotope effects were also studied. Comparisons were made with the decompositions of oxalic acid and malonic acid. An intramolecular HC transfer is believed to be the main part of the reaction coordinate in addition to the CC bond breaking.
The unimolecular decomposition of vibrationally excited 1‐deuterio‐1,1,2‐trifluoroethane
Authors: Follmer D. W. , Pritchard G. O. 
Published: January 2005

AbstractA study has been made of the unimolecular decomposition of the vibrationally excited molecule CF2DCFH2*, formed from the combination of CF2D and CFH2 radicals. The α,β‐elimination channels lead to the products cis‐ and trans‐CFDCFH and CF2CH2 and H(D)F. The α,α‐elimination channel produces cis and trans‐CFHCFH and DF. The pressure dependencies of the various isomer ratios have been examined. For the α,α elimination the energy partitioning pattern is such that subsequent isomerization of the olefin product can occur. This, and previous work on CDCl2CH2Cl*, clearly show that the energy partitioning in α,α and α,β eliminations is very different. It is tentatively concluded that HF (from the CFH2 group) and HD eliminations also take place.
Photochemically induced reaction between perfluoroacetone and ethane
Authors: Gordon Alvin S. , Norris William P. , Knipe R. H. , Johnson Joseph H. 
Published: January 2005

AbstractThe gas‐phase photolysis of perfluoroacetone in the presence of ethane has been shown to result in the production of significant amounts of 1, 1‐bis(trifluoromethyl)propanol‐1, (CF3)2(C2H5)COH, and 1, 1, 4, 4‐tetrakis(trifluoromethyl)butane‐1, 4‐diol, (CF3)2C(OH)‐CH2CH2C(OH)(CF3)2. A mechanism is presented which accounts for the relative rates of formation of these products at room temperature.
Kinetics and mechanisms of substitution reactions with sulfur‐containing nucleophiles in aqueous acid solutions. I—rates of reactions of some tetrahalopalladate (II) anions with thiourea and selenourea
Authors: Van Z. Bekker P. , Robb W. 
Published: January 2005

AbstractThe activation energy parameters for the reaction of PdX (X=Cl−, Br−) in aqueous halide acid solution with thiourea (tu) and selenourea (seu) have been determined. High rates of reaction parallel low enthalpies and appreciable negative entropy of activation. The rate law in each case simplifies to kobs=k[L] where L=tu or seu, and only ligand‐dependent rate constants are observed at 25°C. The ligand‐dependent rate constants for the first identifiable step in the PdCl + X system is (9.1±0.1) × 103 M−1 sec−1 and (4.5±0.1) × 104 M−1 sec−1 for X=tu and seu, respectively, while for the PdBr + X system it is (2.0±0.1) × 104 M−1 sec−1 and (9.0±0.1) × 104 M−1 sec−1 for X=tu and seu, respectively.
Excited state kinetics and stern‐Volmer quenching plots in the photolysis of azoisopropane at 366 nm
Authors: Pritchard G. O. , Servedio F. M. 
Published: January 2005

AbstractThe photochemistry of azoisopropane is reinvestigated at 366 nm over an extended pressure range by using n‐butane as an added bath gas, and over a range of temperature from 277° to 180°C. The Stern‐Volmer type plot of the N2 product quantum yield is interpreted in terms of the decomposition of the vibrationally excited upper singlet and triplet states, with the onset of the dissociation of the vibrationally equilibrated triplet state as the temperature is increased. The energy barrier for the dissociation of the vibrationally equilibrated first triplet state is found to be 8.8 kcal/mole. Triplet sensitization experiments with biacetyl correlate with our observations, and it is suggested that the proposed mechanism is generally applicable to the photodissociation of acyclic azoalkanes at 366 nm, based on a comparison of our data with those of Wu and Rice on hexafluoroazomethane.
Abstraction of chlorine atoms from chloromethanes by the cyclohexyl radical
Authors: Katz M. G. , Horowitz A. , Rajbenbach L. A. 
Published: January 2005

AbstractThe kinetics of chlorine atom abstraction from the chloromethanes (CM)CCl4, CHCl3, and CH2Cl2 by radiolytically generated cyclohexyl radicals has been studied in the liquid phase by a competitive method. The halogen abstraction data have been put on an absolute basis by comparing the rates of the metathetical reactions with the known rate of addition of cyclohexyl radicals to C2Cl4.The following Arrhenius parameters were obtained:

CM
log A(CM)/A(C2Cl4)
E(CM)E(C2Cl4)(kcal/mole)
log A(CM)(1./mole·sec)
E(CM) (kcal/mole)
Temperaure Range(°K)

CCl4
0.72±0.02
−1.42±0.05
9.40±0.08
5.88±0.15
333–453

CHCl3
0.77±0.06
2.86±0.01
9.45±0.12
10.16±0.11
392–492

CH2Cl2
0.56±0.12
6.37±0.27
9.42±0.18
13.67 ± 0.37
463–543

The error limits are the standard deviations from least mean square Arrhenius plots.The possible application of the Evans–Polanyi relationship to chlorine atom abstraction reaction from CM is considered.
Excited state kinetics of the π*←n photochemistry of hexafluoroacetone
Authors: Servedio Frank M. , Pritchard G. O. 
Published: January 2005

AbstractThe π*←n excited state kinetics of hexafluoroacetone are reinvestigated in the presence of a vibrational relaxer and sufficient triplet state quencher so that only the reactions of the electronically excited upper singlet state are examined. From a Stern–Volmer type analysis it is concluded that vibrational relaxation of the initially formed vibrationally and electronically excited upper singlet state is via a multistage collisional mechanism. An activation energy of about 6 kcal/mole is reported for the unimolecular decomposition of the upper singlet state.
Kinetic demonstration of the intramolecular nature of the rearrangement of aromaticN‐nitroso‐amines (Fischer‐Hepp)
Authors: Williams D. L. H. 
Published: January 2005

AbstractRate equations have been deduced for two possible mechanisms for the reactions ofN‐methyl‐N‐nitrosoaniline in acid solution, namely, (1) for the generally acceptedintermolecularmechanism which involves denitrosation followed byC‐nitrosation and (2) a mechanism involvingintramolecularrearrangement which takes place concurrently with denitrosation. The observed rate constants obtained under various experimental conditions are consistent only with mechanism (2). In particular the question of halide ion catalysis differentiates clearly between the two mechanisms. Mechanism (1) predicts a first‐order dependence upon chloride (or other halide) ion under all conditions, whereas (2) allows a first‐order chloride ion dependence only in the presence of a large excess of a “nitrite trap” such as sulphamic acid, urea, hydrazoic acid, hydroxylamine, etc., whereas at the other limit of high concentration of addedN‐methylaniline, the rate constants should be independent of the halide ion concentration. The predictions based on mechanism (2) are all borne out by experiment.
Decarbonylation of complex iridium carbonyls in solution: A problem in chemical dynamics
Authors: D'Agostino Riccardo , Gerardi Sergio , Molinari Ettore 
Published: January 2005

AbstractThe kinetics of decarbonylation of [Ir(CO)(dp)2]Cl and [IrCl(CO)2(Ph3P)2] has been studied in different solvents, at temperatures between −25° and +70°C, by means of reactors of defined fluid dynamics which allow a separation to be made between “physical” and “chemical” rate constants. Chemical rate constants have been found to depend markedly on the diffusion coefficients of carbon monoxide in the various solvents. The process of decarbonylation has been described, for both reactions, by the sequence: structural isomerization, characterized by a very low preexponential factor, decomposition of the less stable isomer against the solvent's barrier, and diffusion of carbon monoxide to the gas–liquid interface. The kinetic problems involved in the determination of rate constants and their implications have been emphasized.
Thermal hydrocracking of indan. Effects of the hydrogen pressure on thekinetics and Arrhenius parameters
Authors: Van Boven M. , Roskam G. J. , Penninger J. M. L. 
Published: January 2005

AbstractThe kinetics of the thermal hydrocracking of indan were investigatedin a high‐pressure flow reactor at temperatures from 470 to 530°C, total pressures of up to 300 atm, and molar ratios from 3 to 40. The effect of the hydrogen pressure was reflected especially in a change of the experimental rate equations for the formation of toluene from rT=k [indan]0.5 [hydrogen] to rT=k′ [indan] 0.75[hydrogen]0.75 with hydrogen partial pressureincreasing from 73 to 230 atm. The rate equation of n‐propylbenzene remained constant at rPr=k″ [indan] [hydrogen]1.5. Simultaneously the Arrheniusparameters of toluene changed significantly, while those of n‐propylbenzene remained unchanged.The observed effect of the hydrogen pressure is explained as a change inthe rates of the intermediate reactions; it provides an excellent agreementbetween the theoretical and experimental data. It was found that the steady‐state concentration of the hydrogen atoms, which act as chain carriers in the thermal hydrocracking, was much smaller than the thermodynamic equilibrium concentrations
Mechanistic details of the Belousov–Zhabotinskii oscillations
Authors: Edelson D. , Field R. J. , Noyes R. M. 
Published: January 2005

AbstractA detailed chemical mechanism for the cerium catalyzed bromination and oxidation of malonic acid by bromate has been developed, and complete numerical solutions have been obtained for the temporal behavior of the concentrations of the intermediate species. The many points of similarity with the experimentally observed initial decay, long quiescence, and abrupt transition to sustained oscillation establish confidence in the essential validity of the proposed mechanism. Close examination of the time dependence of these species concentrations as well as the magnitude of the several reaction channels permits the clarification of the switching mechanism causing theoscillatory behavior of this system. The results appear to exhibit limit cycle behavior, in accordance with theoretical predictions.
Reaction rates for nucleophiles with cyanogen chloride: Comparison with two other digonal carbon compounds
Authors: Edwards John O. , Erstfeld Thomas E. , Ibne‐Rasa Khairat M. , Levey Gerrit , Moyer Maria 
Published: January 2005

AbstractThe hydrolysis kinetics of CICN have been reinvestigated from pH 0.0–10.5 and from 18–40°C. In the pH range from 1–5, the hydrolysis rate is invariant and the activation parameters (ΔH‡ = 84 kJ mol−1 and ΔS‡ = −84 J mol−1 K−1) are consistent with water attack. In basic solution the rate is first order each in CICN and OH− concentrations with parameters ΔH‡ and ΔS‡ equal to 82 kJ mol−1 and + 54 J mol−1 K−1, respectively. The rate constants with 20 other donors have been measured. Nitrogen nucleophiles are more reactive than oxygen donors, and an alpha‐effect is seen. The constants follow a pattern indicative of attack at carbon. Cyanate in its acid form reacts with nucleophiles. Further points on the cyanate rate–pH profile have been obtained. A chromate‐catalyzed hydrolysis can contribute between pH 5–10. Some studies were made of the reaction of cyanate with hydrogen peroxide. Free energy correlations are presented.
Effects of olefins on the thermal decomposition of propane part III. Some remarks on the kinetics of decomposition
Authors: Dombi A. , Horváth I. , Huhn P. 
Published: January 2005

AbstractConditions of applicability of quasi‐steady‐state kinetic treatment have been investigated with respect to the explanation of the decomposition of propane and the influence of ethylene on this.From the measured rate of accumulation of ethane and from the relations between the kinetic equations describing product formation, the rate parameters of the initiation reactions
equation image
were determined, for which the temperature‐dependences

and

were found.In the decomposition of propane under the examined conditions, the chain length exceeds 500. In response to ethylene the chain length significantly decreases, but even in this case the decomposition chains are long enough for it to be assumed that the ratios of radical concentrations are governed by the propagation steps.Calculations demonstrated that the actual radical concentration during a sufficiently short induction period approximates to the stationary concentration, so that it does not seriously affect the accuracy of the kinetic treatment.
Rate constants for the gas‐phase reactions of the OH radical with a series of monoterpenes at 294 ± 1 K
Authors: Atkinson Roger , Aschmann Sara M. , Pitts James N. 
Published: January 2005

AbstractUsing a relative rate technique, rate constants for the gas‐phase reactions of the OH radical with a series of monoterpenes have been determined in one atmosphere of air at 294 ± 1 K. Relative to a rate constant for the reaction of OH radicals with 2,3‐dimethyl‐2‐butene of 1.12 × 10−10 cm3 molecule−1 sec−1, the rate constants obtained were (in units of 10−11 cm3 molecule−1 sec−1): α‐Pinene, 5.45 ± 0.32; β‐pinene, 7.95 ± 0.52; Δ3‐carene, 8.70 ± 0.43; d‐limonene, 16.9 ± 0.5; α‐terpinene, 36.0 ± 4.0; γ‐terpinene, 17.6 ± 1.8; α‐phellandrene, 31.0 ± 7.1; myrcene, 21.3 ± 1.6; and ocimene (acis‐, trans‐mixture), 25.0 ± 1.9. These are the first quantitative kinetic data reported for many of these monoterpenes. The rate constants obtained are compared with the available literature data and with a priori estimates based on the number and configuration of substituents around the double bond(s). The tropospheric lifetimes of these monoterpenes with OH radicals, NO3 radicals and O3 are estimated and compared. Atmospheric lifetimes with respect to reaction with the OH radical are calculated to range from ∼0.75 hr for α‐terpinene to ∼5 hr for α‐pinene.
Effects of Olefins on the Thermal Decomposition of Propane Part IV. Influence of Propylene
Authors: Dombi A. , Huhn P. 
Published: January 2005

AbstractOn the basis of the thermal decomposition of mixtures of propylene and propane with molar ratios of 0.0–0.33 in the temperature range 779–812K, the influencing functions describing the inhibition by propylene of the decomposition of propane were determined. The rate‐reducing effect is explained mainly by the reactions

(in which .R = .H, .CH3 and 2‐Ċ3H7) and also by the addition reactions

It was established that the bulk of the allyl radicals formed

participate in the chain step, but, due to their lower reactivity, they restore the decomposition chain more slowly than the original radicals do.From the characteristic change in the ratio υ/υ, the rate ratios of hydrogenabstraction reaction by radicals from propylene and propane could be determined. In these reactions there was no significant difference between the selectivities of the radicals. For an interpretation of the changes, the decomposition mechanism must be completed with the reaction

Evaluation of the influencing curves revealed that the initiation reactions

must be taken into account.By parameter estimation we have determined the rate ratios characterizing the above initiation reactions, the unimolecular decomposition of propane, hydrogen abstraction by radicals from propane and propylene, intermolecular isomerization of the 2‐propyl radical via propane and propylene, and abstraction of propane hydrogens by the ethyl and methyl radicals; these are given in Tables II.
Gas phase decomposition and isomerization reactions of 2‐pentoxy radicals
Authors: Dóbé S. , Bérces T. , Márta F. 
Published: January 2005

AbstractThe rate of decomposition of 2‐pentoxy radical to acetaldehyde and n‐propyl radical has been studied in the presence of NO in competition with nitrite formation at and above 200 kPa pressure over the temperature range of 363‐413 K. The rate coefficient for the decomposition is given as log(kla/s−1) = (14.2 ± 0.4) ‐ (13.8 ± 0.8) kcal mol−1/RT ln 10. Isomerization of 2‐pentoxy radical by 1,5‐hydrogen shift has been investigated in the range 279–385 K in competition with the decomposition in a static system, with methyl radicals present in high concentration to ensure trapping of the isomerized free radicals. The rate coefficient for isomerization is given as log(k3/s−1) = (11.1 ± 0.7) ‐ (9.5 ± 1.1) kcal mol−1/RT ln 10. The implications of the results for atmospheric chemistry are discussed.