bluuebunny/crossref_metadata_2025_split huggingface dataset:
The √t law in solid‐phase reactions. Analysis of the hypothesis on rate constant distribution
Authors: Zaskul'nikov V. M. , Vyazovkin V. L. , Bol'shakov B. V. , Tolkatchev V. A. 
Published: January 2005

AbstractThe reaction C2H5 + O2 → C2H5O2 in glassy methanol‐d4 and the H‐atom abstraction by CH3, C2H5, and n‐C4H9 radicals in C2H5OH + C2D5OH and CD3CH2OH + C2D5OH glassy mixtures have been studied by electron spin resonance. The analysis of the dependence of the reaction rates on the concentration of O2 (oxidation) and C2H5OH, CD3CH2OH (H‐atom abstraction) has shown that the √t law is not conditioned by the existence of regions characterized by different rate constants.
The kinetics of radiation‐induced hydrogen abstraction by CCl3 radicals in the liquid phase: Cyclohexene
Authors: Alfassi Zeev B. , Feldman Liviu 
Published: January 2005

AbstractThe kinetics of hydrogen abstraction from cyclohexene by CCl3 radicals were studied in CCl4 solution as a function of cyclohexene concentration and temperature in the range of 26–140°C. The CCl3 radicals were produced both by radiolysis of CCl4 and by photolysis of CCl3Br. The rate constant for the reaction
equation image
was found to be given by the equation

where θ = 2.303 RT kcal/mol. This activation energy leads to CH bond strength for the allylic hydrogen of 85 ± 1 kcal/mol, which means a resonance stabilization energy of 11 ± 1.5 kcal/mol for the C‐C6H11 radical.
Temperature dependence of rate constants for the reaction of atomic oxygen with hydrogen chloride
Authors: Singleton Donald L. , Cvetanovi R. J. 
Published: January 2005

AbstractA phase‐shift method has been used to determine the rate constant for the reaction of ground state oxygen atoms with HCl over the temperature range of 330–600 K. Oxygen atoms were generated by modulated mercury photosensitized decomposition of N2O, and monitored by the chemiluminescence from their reaction with NO. After correction for diffusion of oxygen atoms from the viewing zone, the rate constants can be represented by the Arrhenius equation k1 = (3.06 ± 1.43) × 1012 exp[(−3160 ± 184)/T] cm3/mol·s. The indicated uncertainties are 95% confidence limits for 15 degrees of freedom. Also, the third‐body efficiency of HCl relative to N2O in the reaction O + NO + M ← NO2 + M was determined to be 1.9 ± 0.2 over the temperature range of 298–360 K.
Mechanistic details of the Belousov–Zhabotinsky oscillations IV. Sensitivity analysis
Authors: Edelson David 
Published: January 2005

AbstractThe sensitivity of the period of the Belousov–Zhabotinsky oscillations to the rate constants and initial conditions of our previously proposed mechanism is computed by the technique recently developed for this purpose and shown to be valid in our analysis of the Oregonator. The principal rate‐controlling steps for the determination of the period are found to be the enolization and bromination of malonic acid. Dependence of the period on initial conditions qualitatively agrees with available experimental data, except for the hydrogen ion, where a large discrepancy exists. It is suggested that this may be due to deficiencies in the organic reactions in the mechanism, or to a hydrogen‐ion catalyzed bromination mechanism for malonic acid. Other components of the mechanism, which participate in characterizing the period and amplitude of the oscillations, are discussed.
Estimation of rate constants from growth and decay data
Authors: Carrington Tucker 
Published: January 2005

AbstractMany experiments in chemical kinetics are initiated by a fast pulse, such as electric discharge, shock wave, flash lamp, or laser. After this pulse one observes the production and subsequent decay of a reactive intermediate. One then postulates a mechanism and adjusts the associated rate constants so as to minimize the difference between the results of the experiment and the prediction of the mechanism. The parameters to be estimated are usually strongly correlated, so that it is not possible to determine them separately. These estimated parameters are of little value unless we can also estimate statistically valid confidence limits for them. The difficulties are discussed which frequently arise in estimating parameters and confidence limits for a kinetic mechanism which is widely used in interpreting laser excitation and fluorescence measurements, that is, first‐order production and decay. These difficulties, and methods for dealing with them, are illustrated with realistic data. The estimation problem is particularly ill conditioned when the production and loss rates are nearly equal. In some experimental systems this can be avoided, but in others it is inevitable.
A completely inorganic oscillating system of the Belousov–Zhabotinskii type
Authors: Adamčíková Ľubica , Ševčíak Peter 
Published: January 2005

AbstractAn inorganic compound, NaH2PO2, has been found to generate temporal chemical oscillations in Belousov–Zhabotinskii type reactions when it is substituted for the organic reducing material. Gaseous products were removed by a constant flow of nitrogen carrier gas. Periodic Br2 evolution was measured polarographically.
Kinetics of the reactions of OH radicals with n‐alkanes at 299 ± 2 K
Authors: Atkinson R. , Aschmann S. M. , Carter W. P. L. , Winer A. M. , Pitts J. N. 
Published: January 2005

AbstractRelative rate constants for the reaction of OH radicals with a series of n‐alkanes 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 n‐butane of 2.58 × 10−12 cm3 molecule−1s−1, the rate constants obtained are (X1012 cm3 molecule−1 s−1): propane 1.22 ± 0.05, n‐pentane 4.13 ± 0.08, n‐heptane 7.30 ± 0.17, n‐octane 9.01 ± 0.19, n‐nonane 10.7 ± 0.4, and n‐decane 11.4 ± 0.6. The data for propane, n‐pentane, and n‐octane are in good agreement with literature values, while those for n‐heptane, n‐nonane, and n‐decane are reported for the first time. These data show that the rate constant per secondary C—H bond is ∽40% higher for —CH2— groups bonded to two other —CH2— groups than for those bonded to a —CH2— group and a —CH3 group.
Basic hydrolysis of glyceryl nitrate esters. I. 1‐glyceryl and 2‐glyceryl nitrate esters
Authors: Capellos C. , Fisco W. J. , Ribaudo C. , Hogan V. D. , Campisi J. , Murphy F. X. , Castorina T. C. , Rosenblatt D. H. 
Published: January 2005

AbstractKinetics of the basic hydrolysis of 1‐glyceryl mononitrate (1‐MNG) and 2‐glyceryl mononitrate (2‐MNG) were investigated in CO2‐free aqueous calcium hydroxide solutions. The hydrolysis reactions were carried out in a temperature‐controlled reactor vessel with provision for continuous N2 sparging of the reaction mixture. Both glyceryl nitrate esters hydrolyzed via second‐order reaction at 25°C. 2‐MNG in calcium hydroxide solution isomerized to 1‐MNG, which subsequently hydrolyzed to form NO. In strongly basic aqueous solutions of NaOH (30%), 2‐MNG is converted to glycidol and NO.
Quantitative treatment of the effect of counterions on ctab‐catalyzed reactions of stabilized carbonium ions with cyanide ion
Authors: Srivastava S. K. , Katiyar Sarvagya S. 
Published: January 2005

AbstractThe reactions of stabilized carbonium ions of setoglaucin, methyl violet, and ethyl violet with cyanide ions are largely catalyzed by the cationic micelles of cetyltrimethylammonium bromide (CTAB) in aqueous media. Added counterions (anions in this case) have strong inhibitory effects on the CTAB‐catalyzed reactions in the following order: N > NO > Br− > Cl− > F− > no salt. The inhibitory effects of the counterions have been attributed to the exchange between added anions and reagent (CN−) in the micellar media. The data have been analyzed by the model schemes, and mathematical formulations were developed. Various parameters associated with the exchange process, such as equilibrium exchange constant, number of surfactant molecules per substrate molecule, number of added anions, and a factor related to the binding of additives to the catalytic micellar aggregates, have been evaluated.
Studies in nickel(IV) chemistry. Part 6. Kinetics of electron transfer from phenylhydrazine to tris‐(dimethylglyoximato) nickelate(IV) in aqueous medium
Authors: Acharya S. , Neogi G. , Panda R. K. , Ramaswamy D. 
Published: January 2005

AbstractThe kinetics of electron transfer from phenylhydrazine(S) to tris‐(dimethylglyoximato) nickelate(IV), Ni(dmg) (dmg2− = dimethylglyoximate dianion), have been studied in aqueous medium in the range of 6.21 ⩽ pH ⩽ 12.2. The kinetics exhibit a pseudo‐first‐order disappearance of Ni(dmg) when excess S is present. The pseudo‐first‐order rate constants kobs are almost linearly dependent on [S]0 for varying concentrations of the reductant. At constant [S]0, the kobs−pH profile is U shaped. The kobs values register a decrease as the [H+] is increased in the pH range of ∽12.2–9.5, remain almost constant (minimum) in the range of ∽9–8, and then again linearly increase as [H+] is increased in the pH range of ∽7–6.21. Results are interpreted in terms of a probable mechanism involving outer‐sphere electron transfer from the phenylhydrazine and phenylhydrazinium cation species to the unprotonated and one‐protonated species of the Ni(IV) complex. The reduction rate appears to be dependent on the nature of the species (unprotonated and one‐protonated) of the oxidant Ni(IV) complex. The phenylhydrazinium cation reduces the Ni(IV) complex at least one order of magnitude faster than does the neutral reductant species. The major product of the oxidation of phenylhydrazine by the Ni(IV) complex is 4‐hydroxyazobenzene with a small amount of phenol.
Induced heterogeneity, a novel technique for the study of gas‐phase reactions. Part I. Determination of the arrhenius parameters for CC bond scission in propane
Authors: Kanan Khalid , Purnell Howard , Smith Eileen 
Published: January 2005

AbstractIt is shown that, by deliberate activation of the reaction vessel, heterogeneous reaction at the wall can be made to dominate chain termination in a complex gas‐phase reaction. For a homogeneous process, characterized, as is often the case, by multiple terminations, this has the effect of simplifying the mechanism and allowing explicit solution of the relevant steady‐state equations so that the rate constants of some individual steps can be evaluated without assumption as to the values of those of others.The pyrolysis of propane, in the vicinity of 500°C, has been used as an example of this approach. Enhancement of the wall activity leads to the reaction
equation image
providing, almost exclusively, chain termination. As a result, rate constants for the initiation step
equation image
can be directly determined. The results of this study provide the Arrhenius equation

In combination with current thermochemical values this result gives k−1 = 1013.40 cm3/mol·s which, in turn, implies, via the geometric mean rule, kEt‐Et = 1012.9 cm3/mol·s for ethyl–ethyl recombination, in good accord with the most recent determinations and compatible with the newly proposed value of the enthalpy of formation of ethyl.The first‐order wall constant k8 has been evaluated as k8<104.2 s−1. This appears to be the first occasion on which a wall constant has been evaluated from data for a high‐temperature complex gas reaction.
Kinetics of the gas‐phase reactions of OH radicals with a series of α,β‐unsaturated carbonyls at 299 ± 2 K
Authors: Atkinson Roger , Aschmann Sara M. , Pitts James N. 
Published: January 2005

AbstractRelative rate constants for the reaction of OH radicals with a series of α,β‐unsaturated carbonyls 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 propene of 2.52 × 10−11 cm3/molec·s, the rate constants obtained are (× 1011 cm3/molec·s: acrolein, 1.83 ± 0.13; crotonaldehyde, 3.50 ± 0.40; methacrolein, 2.85 ± 0.23; and methylvinylketone, 1.88 ± 0.14). These data, which are necessary input to chemical computer models of the NOx–air photooxidations of conjugated dialkenes, are discussed and compared with literature values.
Kinetics of the reaction: 2C2H4 → C2H5 + C2H3· heat of formation of the vinyl radical
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 800 K have been measured in the presence and absence of the additives neopentane and ethane. It has been shown that in the absence of the additive the main initiation process is
equation image
while in the presence of neopentane and ethane the following additional initiation processes occur:
equation image
From the ratios of the rates of formation of the major products in the presence and absence of the additive the ratios kN/k1 and kE/k1 were measured over the temperature range of 750–820 K. Taking values from the literature for kN and kE, the following value was obtained for k1:

Previous results using butene‐1 as additive were rexamined and shown to be consistent with this measurement. From this measurement the following values were derived: ΔHf(C2H3) = 63.4 ± 2 kcal/mol and D(C2H3H) = 103 kcal/mol.
Investigation of the thermal isomerization of 1α,25‐dihydroxycholecalciferol by nuclear magnetic resonance spectroscopy
Authors: Grant Anne , Bhattacharyya Pranab K. 
Published: January 2005

AbstractThis investigation of the kinetics and thermodynamics of the thermal isomerization reaction of 1α,25‐dihydroxycholecalciferol, the physiologically active metabolite of vitamin D3, is based on the simultaneous determinations of 1α,25‐(OH)2D3 and its previtamin analog by nuclear magnetic resonance spectroscopy which distinguishes these compounds from possible impurities. The kinetics at different temperatures are used to obtain the activation parameters for the sigmatropic [1,7] thermal interconversion process which is shown to be compatible with a reaction that is unimolecular and concerted. The nature of the transition state of the activated complex, the reaction energetics, and the relative stabilities of 1α,25‐(OH)2D3 and vitamin D3 are discussed.
The kinetics and mechanisms of elementary NF2reactions with O and N atoms
Authors: Gershenzon Yu. M. , Il'in S. D. , Kishkovitch O. P. , Malkhasyan R. T. , Rozenshtein V. B. , Umanskii S. Ya. 
Published: January 2005

AbstractA combined EPR–LMR spectrometer with a fast‐flow system has been used to investigate the kinetics and mechanisms of NF2reactions with O and N atoms at 298 K. The overall rate constants of these reactions are:k0= (2.8 ± 0.4) × 10−11cm3/s andkN= (5.7 ± 0.8) × 10−11cm3/s. The stoichiometry of the reactions with respect to O, N, NF2, F, and NO has been determined. The statistical theory of bimolecular reactions has been used for interpretation of the results obtained.
Kinetics of gas‐phase decomposition of oxetan and oxetan‐2,2‐d2
Authors: Zalotai L. , Hunyadi‐zoltán Zs. , Bérces T. , Márta F. 
Published: January 2005

AbstractThe pressure dependence of the first‐order rate coefficient of oxetan and oxetan‐2,2‐d2 decomposition has been studied in the pressure range from about 7 kPa down to 0.01 kPa at various temperatures between 673 and 758 K. Experimental data were analyzed using RRKM theory. Interpretation of the fall‐off curves lends support to the high‐pressure Arrhenius parameters A = 1015.42s−1 and EA = 259.5 kJ/mol derived from measurements made in the pressure‐independent range. Decomposition of oxetan is found to occur via biradical intermediates. Data for the kinetic isotope effect were used to derive kinetic parameters for the ring‐opening elementary steps in oxetan and oxetan‐d2 decomposition.
Kinetics of the thermal gas‐phase dimerization of hexafluoropropene
Authors: Robinson Peter J. , Skelhorne Graham G. 
Published: January 2005

AbstractThe reversible thermal gas‐phase dimerization of hexafluoropropene to the four isomeric cyclobutanes has been studied by pressure change and by gas‐liquid chromatographic analysis in the temperature range of 645–708 K with initial pressures of olefin from 802 to 4820 mm Hg. The reaction was accurately second order at low conversions of olefin to dimers, and at higher conversions it gave a very good fit to the rate equation for opposing second‐ and first‐order reactions. The rate constants for the dimerization, calculated from initial rates of reaction, yielded the least‐mean‐squares Arrhenius equation (95% confidence limits):

where k2 is defined by

Studies carried out in a packed vessel showed no evidence of heterogeneity. The rate constants found in this work are in excellent agreement with those found at lower pressures by Atkinson and Tsiamis, and the combined results give the Arrhenius equation
Kinetics of the gas‐phase reaction between iodine and monogermane and the bond dissociation energy D(H3GeH)
Authors: Noble Paul N. , Walsh Robin 
Published: January 2005

AbstractThe title reaction has been investigated in the temperature range of 403–446 K. Monoiodogermane and di‐iodogermane together with hydrogen iodide were the main products, although at high conversions at least one other product was formed. GeH3I is clearly the primary product. Initial rates were found to obey the rate law

over a wide range of initial iodine and monogermane pressures. Secondary reactions (of GeH3I with I2) affect the subsequent kinetics, although at sufficiently high initial reactant ratios ([GeH4]0/[I2]0 ≥ 100) an integrated rate equation fits the data with the same rate constants as the initial rate expression.The observed kinetics are consistent with an iodine atom abstraction chain mechanism, and for the step

log k1 (dm3/mol·s) = (11.03 ± 0.13) – (52.3 ± 1.0 kJ/mol)/RT ln 10 has been deduced. From this the bond dissociation energy D(GeH3H) = 346 ± 10 kJ/mol (82.5 kcal/mol) is obtained. The significance of this value, together with derived values for Ge–Ge and Ge–C bond strengths, is discussed.
Rate constants of the reaction of ozone with trans‐1,2‐dichloroethene and vinyl chloride in air
Authors: Zhang Jian , Hatakeyama Shiro , Akimoto Hajime 
Published: January 2005

AbstractKinetic studies on reactions of ozone with trans‐1,2‐dichloroethene (DCE) and vinyl chloride (VC) were performed in air. In the presence of scavengers of radicals, such as CH3CHO, the rates for both reactions are second order (first order in each reactant). Observed rate constants are (1.80 ± 0.29) X 10−19 cm3/molecule·s for DCE and (2.45 ± 0.45) × 10−19 cm3/molecule·s for VC. In the presence of CH3CHO, propene ozonide
\documentclass{article}\pagestyle{empty}\begin{document}$ ({\rm CH}_3 \overline {{\rm CHOOCH}_2 {\rm O}}) $\end{document} was observed as a product in the case of VC. Peroxyformic acid (HC)O(OOH) was detected in both reactions. The Criegee mechanism was proposed to play a major role in the reaction of ozone with chloroolefins. The branching ratio of O3 + CH2=CHCl → CH2OO + HCOCl (6a), CHClOO + HCHO (6b) was obtained as 76:24, and the fraction of the stabilized CH2OO was estimated to be 0.25 of that produced in reaction (6a).
Effects of ring strain on gas‐phase rate constants. I. Ozone reactions with cycloalkenes
Authors: Atkinson Roger , Aschmann Sara M. , Carter William P. L. , Pitts James N. 
Published: January 2005

AbstractRate constants for the gas‐phase reactions of O3 with a series of cycloalkenes and with cis‐2‐butene have been determined at 297 ± 1 K. The rate constants obtained were (in units of 10−16 cm3/molecule·s): cis‐2‐butene, 1.38 ± 0.16; cyclopentene, 2.75 ± 0.33; cyclohexene, 1.04 ± 0.14; cycloheptene, 3.19 ± 0.36; 1,3‐cyclohexadiene, 19.7 ± 2.8; 1,4‐cyclohexadiene, 0.639 ± 0.074; bicyclo[2.2.1]‐2‐heptene, 21.4 ± 3.5; bicyclo[2.2.1]‐2,5‐heptadiene, 46.8 ± 12.9; and bicyclo[2.2.2]‐2‐octene, 0.728 ± 0.090. These data for cis‐2‐butene, cyclopentene, and cyclohexene are compared with previous literature data, and the effects of ring strain on the rate constants are discussed.
Couloamperometry. A fast kinetic technique for halogenations. I. Bromination rate constants of highly reactive enol ethers
Authors: Ruasse M. F. , Poupard D. , Dubois J. E. 
Published: January 2005

AbstractA new couloamperometric apparatus has been designed to extend the range of this kinetic technique to the measurement of very high rate constants, 108M−1s−1, by using TFCR‐EXSEL conditions (TFCR—very low reactant concentration; EXSEL—salt excess), which give half‐lives of a few seconds for very fast second‐order reactions. Very low faradaic currents, in the nanoampere range for halogens, corresponding to very low reactant concentrations of 10−8–10−9M, are measured selectively by compensating the eddy currents, principally the residual and the induced currents. When the electroactive species is bromine, the concentration is demonstrated to be linearly related to the limiting reduction current in the very low concentration range. The upper limit of this technique for bromination is at present 3 × 108M−1s−1. The method is applied to the kinetic study of highly reactive enol ethers EtO‐C(R) = CH‐R′, where R and R′ are H or Me. A value of 2.2 × 108M−1s−1 is obtained for k, the rate constant for free bromine addition to EtO‐CH = CH2, by extrapolating the kinetic bromide ion effects to [Br−] = 0. An α‐methyl effect (kα‐Me/kH)EtO of 15 is found; this is a small decrease in the methyl effect compared to the marked increase in the double bond reactivity. For the enol acetate MeCOO‐CH = CH2, whose rate constant is 6 × 102M−1s−1, (kα‐Me/kH)OCOMe is 21. The dependence of substituent effects on reactivity is discussed in terms of the Hammond effect on the transition state position and of charge delocalization by group G of olefins G‐CH = CH2.
Electron transfer to trans‐dihydroxotetraoxoosmate(VIII). II. Kinetics of the oxidation of dimethylsulfoxide in aqueous alkaline media
Authors: Neogi G. , Acharya S. , Panda R. K. , Ramaswamy D. 
Published: January 2005

AbstractThe kinetics of the oxidation of dimethylsulfoxide by oxohydroxoosmate(VIII) complex ions in alkaline media follow pseudo‐first‐order disappearance in Os(VIII). The values of the observed pseudo‐first‐order rate constant are linearly dependent on initial dimethylsulfoxide concentrations in a fortyfold range, and increase with increasing [OH−], leveling off at higher relative [OH−]. The results are interpreted in terms of outer sphere interactions involving dimethylsulfoxide and various species of the Os(VIII) complex. The more nucleophilic dihydroxotetraoxoosmate(VIII) ion reacts about 50 times faster than the trihydroxotrioxoosmate(VIII) species.
Kinetics of the reaction F + 1,2‐dibromo‐1,1,2‐trifluoroethane
Authors: Forst Wendell , Pavaday Harold 
Published: January 2005

AbstractThe title reaction was studied in a standard flow system with F atoms produced by RF discharge in F2‐He mixture. Analysis was by gas chromatography using electron capture detection. There were two major products, identified as CF2BrCF2H and CF2BrCF2Br, plus presumably HF which was not detectable. The overall rate of disappearance of reactant was found to be of mixed one and one‐half order, indicating a complex reaction. A mechanism is proposed comprising six steps and involving two radical species CF2BrċFBr (R1) and CF2BrċF2. The 300 K rate constant for the initial step F + reactant → HF + R1 is evaluated to be 2.2 × 10−13 cm3/molec·s, which fits in with rates of other saturated hydrocarbon reactants containing one hydrogen atom, thus supporting the view that in this class of reactants the rates of reactions of the type F + saturated hydrocarbon depend mainly on the number of hydrogen atoms in the reactant.