bluuebunny/crossref_metadata_2025_split huggingface dataset:
The thermal unimolecular decomposition of bromocyclobutane
Authors: King Keith D. , Gilbert Robert G. 
Published: January 2005

AbstractThe thermal unimolecular decomposition of bromocyclobutane has been investigated over the temperature range of 791–1224 K using the technique of very low‐pressure pyrolysis (VLPP). HBr elimination is the sole mode of decomposition under the experimental conditions. No evidence could be found for the ring‐cleavage pathway to ethylene and vinyl bromide. Assuming a four‐center transition state and an Arrhenius A factor the same as that for HCl elimination from chlorocyclobutane, RRKM calculations show that the experimental unimolecular rate constants are consistent with the Arrhenius expression

where θ = 2.303RT kcal/mol. The activation energy is higher than that for the open‐chain analog, 2bromobutane. This finding is consistent with the results for the corresponding chloro and iodo compounds.
Kinetics of radiation‐induced abstraction of hydrogen atoms by CCl3 radicals in the liquid phase: 2,3‐dimethylbutane
Authors: Alfassi Zeev B. , Feldman Liviu 
Published: January 2005

AbstractThe kinetics of the gamma‐radiation induced free radical reactions in carbon tetrachloride solutions of 2,3‐dimethylbutane (DMB) were studied in the temperature range 32–118 °C. The kinetics of the following reactions were measured:

and the following rate constants expression was obtained:

. The activation energy and the A factor obtained are in good agreement with the values obtained at the gaseous phase, considering the activation energy for self‐diffusion of CCl4.
Oxidation of formic acid by bromine in aqueous, strongly acid media
Authors: Herbine Peter , Brummer James G. , Field Richard J. 
Published: January 2005

AbstractSpectrophotometric methods were used to investigate the rate of the reaction of Br2 with HCOOH in aqueous, acidic media. The reaction products are Br− and CO2. The kinetics of this reaction are complicated by both the formation of Br3− as Br− is formed and the dissociation of HCOOH into HCOO− and H+. Previous work on this reaction was carried out at acidities lower than the highest used here and led to the conclusion that only HCOO− reacts with Br2. It is agreed that this is by far the principal reaction. However, at the highest acidity experiments, an added small component of reaction was found, and it is suggested that it results from the direct reaction of Br2 with HCOOH itself. On this assumption, values of the rate constants for both reactions are derived here. The rate constant for the reaction of HCOO− with Br2 agrees with values previously reported, within a factor of 2 on the low side. The reaction involving HCOOH is more than 2000 times slower than the reaction involving HCOO−, but it does contribute to the overall rate as [H+] approaches 1M. These derived rate constants are able to simulate quantitatively the authors' absorbance‐versus‐time data, demonstrating the validity of their data treatment methods, if not mechanistic assignments. Finally, activation parameters were determined for both rate constants. The values obtained are: ΔE‡(HCOOH + Br2) = 13.3 ± 1.1 kcal/mol, ΔS‡ (HCOOH + Br2) = −28 ± 3 cal/deg mol, ΔE‡ (HCOO− + Br2) = 13.1 ± 0.9 kcal/mol, and ΔS‡(HCOO− + Br2) = −12 ± 1 cal/deg mol. That the activation energies of the two reactions turn out to be essentially identical does not support the authors' suggestion that both HCOOH and HCOO− react with Br2.
Mechanism of pyrolysis of C2Cl6
Authors: Weissman Maia , Benson Sidney W. 
Published: January 2005

AbstractUsing published data on the kinetics of pyrolysis of C2Cl6 and estimated rate parameters for all the involved radical reactions, a mechanism is proposed which accounts quantitatively for all the observations:
equation image
The steady‐state rate law valid for after about 0.1% reaction is
equation image
and the reaction is verified to proceed through the two parallel stages suggested earlier whose net reaction is
equation image
A reported induction period obtained from pressure measurements used to follow the rate is shown to be compatible with the endothermicity of reaction A, giving rise to a self‐cooling of the gaseous mixture and thus an overall pressure decrease.From the analysis, the bond dissociation energy DH0(C2Cl5Cl) is found to be 70.3 ± 1 kcal/mol and ΔHf3000(·C2Cl5) = 7.7 ± 1 kcal/mol. The resulting πbond energy in C2Cl4 is 52.5 ± 1 kcal/mol.
Reaction of hydrogen atoms with dimethyldisulfide
Authors: Ekwenchi M. M. , Jodhan A. , Strausz O. P. 
Published: January 2005

AbstractHydrogen atoms, generated by the mercury (3P1) sensitization of H2, were allowed to react with dimethyldisulfide in the temperature range of 25–155°C. The only retrievable product is methanethiol, formed in the primary metathetical reaction \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm H} + {\rm CH}_3 {\rm SSCH}_3 {\rm CH}_3 {\rm SH} + {\rm CH}_3 {\rm S} $\end{document}. The intermediacy of thiyl radicals was clearly demonstrated in experiments carried out in the presence of ethylene where one of the major products detected was ethyl methyl sulfide, formed via CH3S + C2H5 → CH3SC2H5. The major fate of the CH3S radical is recombination and disproportionation, and the yield of methanethiol formed via disproportionation contributes less than 5% to the total thiol yield. The rate coefficient of step 1, from competition with the reaction \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm H} + {\rm C}_{\rm 2} {\rm H}_{\rm 4} {\rm C}_{\rm 2} {\rm H}_5 $\end{document}, is k1 = (5.7 ± 1.2) × 1012 exp[(100 ± 100)/RT] cm3/mol sec.
Experimental measurement of the rate of the reaction o(3P) + H2(v = 0) → OH(v = 0) + H at T = 298 K
Authors: Light Glenn C. , Matsumoto James H. 
Published: January 2005

AbstractMeasurement of the rate of the reaction
equation image
is reported. The measurements were made in a flow tube apparatus. The result is based on data for the absolute density of OH(v = 0) obtained from laser‐induced fluorescence measurements in the (0–0) band of the OH(A2Σ+ → X2II) system. The density of oxygen atoms was varied by changing the flow rate of NO which is consumed in the reaction N + NO → O + N2. We find that k1 (298 K) = (5.5 ± 3.0) × 106 cm3/mol sec. This result was obtained with consideration and control of the effect of reaction (2):
equation image
for which vibrationally excited hydrogen is created by energy transfer in the presence of active nitrogen. It was found that the addition of N2 or CO2 effectively suppressed the excitation of H2(v = 1). Measurements of the density of H2(v = 1) were made by VUV absorption in the Lyman band system of H2. All of the reports of low‐temperature measurements and some recent theoretical calculations for k1 are discussed. The present result confirms and extends the growingevidence for significant curvature in the low‐temperature end of a modified Arrhenius plot of k1 (T).
Reaction of carbon monoxide with ozone: Kinetics and chemiluminescence
Authors: Toby Sidney , Ullrich Elizabeth 
Published: January 2005

AbstractThe reaction of carbon monoxide with ozone was studied in the range of 75–160°C in the presence of varying amounts of CO2and, for a few experiments, of O2. At room temperature the reaction was immeasurably slow, but in a flow system it showed chemiluminescence with undamped oscillations. In a static system above 75°C the emission showed damped oscillations when O2was present. In the absence ofadded O2the emission showed a slow decay with a half‐life of 1 hr. The luminescence consisted of partially resolved bands in the range of 325–600 nm, and the source was identified as CO2(1B2) → CO2(1Σg+) +hv. The kinetics were complex, and the observed rate law could be accounted for bya mechanism involving the chain sequence\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm O(}^{\rm 3} P{\rm ) + CO( + M)}\mathop {{\rm rightarrow}}\limits^{\rm 3} {\rm CO}_{\rm 2} {\rm (}^{\rm 3} B_{\rm 2} {\rm ) ( + M), CO}_{\rm 2} {\rm (}^{\rm 3} B_{\rm 2} {\rm ) + O}_{\rm 3} {\rm }\mathop {{\rm rightarrow}}\limits^{\rm 7} {\rm CO}_{\rm 2} {\rm (}^{\rm 1} \sum\nolimits_{\rm g}^{\rm + } {} {\rm ) + O}_{\rm 2} {\rm + O} $\end{document}. From measurements of ‐d[O3]/dtand relative emission, rate constant ratios were obtained and estimates ofk3were made.
The hydrogen peroxide–iodic acid–manganese (ii)–acetone oscillating system: Further observations
Authors: Cooke David O. 
Published: January 2005

AbstractThe redox potential and iodine concentration behavior of the title reaction and component reactions have been examined. The effect of hydrogen peroxide, potassium iodate, manganese (II) sulfate, sulfuric acid, and acetone concentration on the time period and redox potential behavior is reported. Iodine production and consumption rates for the component reactions are given, and some mechanistic suggestions, involving iodine dioxide as the one electron oxidant, are made.
Azide mechanisms for the production of NCl metastables
Authors: Pritt A. T. , Coombe R. D. 
Published: January 2005

AbstractThe production of both the b1Σ+ and a1Δ states of NCl has been observed from the reaction of HN3 with flowing streams of Cl and F atoms. The results suggest that a two‐step reaction sequence is responsible for the production of excited NCl, as follows:
equation image

The rate contant (all products) for the first step is k(F + HN3) > 1 × 10−11 cm3/molecule sec. Comparison of this value to results obtained in a previous study of the F + HN3 system yields a value k(F + N3) = 2 × 10−12 cm3/molecule sec. The rate constant for the reaction of chlorine atoms with HN3 was determined to be k(Cl + HN3) 1 × 10−12 cm3/molecule sec. The difference between the Cl + HN3 and F + HN3 rates is interpreted in terms of an addition–elimination mechanism.
Reaction of di‐tert‐butylnitroxide radicals
Authors: Lissi E. A. , Rubio M. A. , Araya D. , Zanocco G. 
Published: January 2005

AbstractDi‐tert‐butylnitroxide (DTBN) is the simplest of the stable nitroxide radicals and is only consumed at temperatures higher than 90°C or in the presence of very reactive substrates. The pyrolysis of DTBN in solution gives, at least at low conversion, 2‐methyl‐2‐nitrosopropane and di‐tert‐butylnitroxide‐tert‐butyl ether. The reaction involves, as the rate‐limiting step, the cleavage of the CN bond. This reaction takes place with an activation energy of 33 kcal/mol. DTBN is stable in the presence of styrene, aldehydes, hydrogen peroxide, α‐methyl‐N‐ethyl nitrone, phenol, and triphenylmethane. On the other hand, it reacts readily with diethylhydroxylamine, ascorbid acid, ethanethiol, and hexanethiol. For the two former compounds the reaction involves a hydrogen transfer as the rate‐determining step, and the reaction proceeds, a low conversion, with simple second‐order kinetics. The reaction with the thiols is complex and shows a clear inductiontime.
Kinetics and mechanism of the addition of trichloromethyl radicals to chloroethylenes. The addition to CIS‐C2Cl2H2, trans‐C2Cl2H2, and C2Cl3H
Authors: Horowitz A. , Baruch G. 
Published: January 2005

AbstractThe addition reactions of CCl3 radicals with cis‐C2Cl2H2, trans‐C2Cl2H2, and C2Cl3H in liquid cyclohexane–CCl4 mixtures were studied between 323 and 448 K. The Arrhenius parameters of these reactions were competitively determined versus H‐atom transfer from cyclohexane and addition to C2Cl4. The present data and the data obtained in previous liquid and gas phase studies show that the reactivities displayed in addition reactions of different radicals with chloroethylenes reflect primarily variations in activation energies rather than in A factors. The activation energies for the addition of CCl3, CF3, and CH3 radicals to chloroethylenes appear, to a large extent, to be determinedby the stability of the adduct radicals. Comparison of the reactivity trends in the addition reactions of chloro‐ and fluoro‐substitutedethylenes indicates that these two electron‐withdrawing substituentshave a converse effect on the reactivity of electrophilic radicals. This behavior is ascribed to the strong mesomeric effect of vinylic chlorosubstituents.
The kinetics of the chlorine isotopic exchange between chloride ion at O,O‐diarylphosphorochloridates or O,O‐diarylphosphorochloridothionates
Authors: ReimschüSsel W. , Mikołajczyk M. , Ślebocka‐tilk H. , Gajl M. 
Published: January 2005

AbstractThe kinetics of the chlorine isotopic exchange reaction between tetraethylammonium chloride‐36Cl and O,O‐diarylphosphorochloridates (p‐RC6H4O)2POCl or O,O‐diarylphosphorochloridothionates (p‐RC6H4O)2PSCl has been studied in acetonitrile solution. Good Hammett's correlations of the rate constants with Taft's σ0 constants were obtained. The values of the reaction constants ρ were found identical for phosphoryl and thiophosphoryl compounds. In comparison with oxygen in the phosphoryl group, the sulfur atom exhibits an electron‐donating effect (Δσ0 ∼ 0.80). No correlation has been found for the enthalpy and entropy of activation. The effect of the substituents aryloxy groups, oxygen, or sulfur atoms in the phosphoryl group on the kinetics of the SN2‐P reaction is discussed. The reactivity of the investigated compounds is determined by the extent of the positive charge localized on the phosphorus atom. The positive charge is formed by the direct interactions of the substituents with the reaction center and the indirect–intramolecular interactions revealed in the structure of the compound.
Ion pair catalysis of the autooxidative cleavage of benzoin in emulsion systems
Authors: Franklin Thomas C. , Ogiya Naoyuki 
Published: January 2005

AbstractA study was made of the autooxidation of benzoin in organic‐aqueous sodium hydroxide emulsions in the presence of several quaternary ammonium salts. The rate of the reaction was found to be accelerated by these salts, probably by ion pair extraction. In pyridine and acetonitrile systems the reaction was almost exclusively the formation of benzoate. Neither benzil nor benzaldehyde were intermediates in the oxidation process. The rate law for the reaction was found to be

which led to the conclusion that the rate‐determining step in the catalyzed pathway was the reaction of oxygen with the ion pair: magnified image
Use of two‐parameter correlations for studying the radical reactivity of aromatic compounds
Authors: Afanas'ev I. B. 
Published: January 2005

AbstractTwo‐parameter equation correlations are reported for radical reactions of aromatic compounds. In these correlations polar and resonance substituent constants identical with the substituent constants of aliphatic compounds were used. The equations correlate the rate constants for H abstraction reactions and for the addition of a variety of free radicals to the ortho‐, meta‐, and para‐substituted aromatic compounds. Besides, they correlate parameters of the spectra for substituted aromatic radicals. The correlations show that the effects of para substituents on the reactions studied are nearly entirely resonance effects, whereas for the meta‐ and ortho‐substituted compounds polar (inductive) effects become essential. Application of the two‐parameter correlations permits also to determine the structure of transition states (σ or π‐complex) in free‐radical reactions.
Rate constants for ozone–alkene reactions under atmospheric conditions
Authors: Adeniji S. A. , Kerr J. A. , Williams M. R. 
Published: January 2005

AbstractBy measuring the rates of decay of ozone in a large excess of reactant, second‐order rate constants have been obtained for the reactions of ozone with ethene, propene, but‐1‐ene, trans‐but‐2‐ene, isobutene, hex‐1‐ene, cyclopentene, cyclohexene, isoprene, vinyl fluoride, 1,1‐difluoroethene, cis‐1,2‐difluoroethene, trans‐1,2‐difluoroethene, trifluoroethene, tetrafluoroethene, and 2,5dihydrofuran. The reactions have been studied in synthetic air at atmospheric pressure and at temperatures of 294 and 260 K. The rate constants and Arrhenius parameters are discussed in relation to existing kinetic data on ozone–alkene reactions.
Kinetics of competitive pathways in the thermal unimolecular decomposition of hex‐1‐yne
Authors: King Keith D. 
Published: January 2005

AbstractThe thermal unimolecular decomposition of hex‐1‐yne has been investigated over the temperature range of 903–1153 K using the technique of very low‐pressure pyrolysis (VLPP). The reaction proceeds via the competitive pathways of C3C4 fission and molecular retro‐ene decomposition, with the latter being the major pathway under the experimental conditions. RRKM calculations, generalized to take into account two competing pathways, show that the experimental unimolecular rate constants are consistent with the high‐pressure Arrhenius parameters at 1100 K given by

and

where θ = 2.303 RT kcal/mol and the A factors were assigned from the results of recent shock‐tube studies of hex‐1‐yne and related alkynes. The results for CC fission are consistent with previous VLPP and shock‐tube determinations of the propargyl resonance energy, and the parameters for the molecular pathway are consistent with systematic trends for the retro–ene decomposition of unsaturated hydrocarbons.
The infrared chemiluminescent reaction of Cl atoms with H2CO
Authors: Fasano D. M. , Nogar N. S. 
Published: January 2005

AbstractThe reaction Cl + H2CO → HCl + HCO has been studied at 295 K. Chlorine atoms were produced via the infrared laser induced dissociation of CCl3F, using a pulsed CO2 TEA laser. Using HCl infrared chemiluminescence as the diagnostic, we find the rate constant to be 7.4 ± 0.7 × 10−11 cm3/molecule sec, in good agreement with several recent studies. An evaluation of TEA laser photolysis as a technique for the generation of chlorine atoms is made, and the relationship of this experiment to recent theories of infrared laser induced chemistry is discussed.
The determination of the arrhenius parameters for the reaction Cl + C2F5I → ICl + C2F5 using a competitive method
Authors: Ahonkhai Samuel I. , Whittle Eric 
Published: January 2005

AbstractThe reactions
equation image

equation image
have been studied competitively over the range of 28–182°C by photolysis of mixtures of Cl2 + C2F5I+ CH4. We obtain

where θ = 2.303RT J/mol. The use of published data on reaction (2) leads to log (k1cm3/mol sec) = (13.96 ± 0.2) − (11,500 ± 2000)/θ.
Very‐low‐pressure pyrolysis of ethylbenzene, isopropylbenzene, and tert‐butylbenzene
Authors: Robaugh David A. , Stein Stephen E. 
Published: January 2005

AbstractThe thermal unimolecular decomposition of ethylbenzene, isopropylbenzene, and tert‐butylbenzene was studied using the very‐low‐pressure pyrolysis (VLPP) technique. Each reactant decomposed by way of β CC bond homolysis, producing methyl radicals and benzyl or benzylic‐type radicals. RRKM calculations show that the observed rate constants, when combined with thermochemical estimates, are consistent with the following high‐pressure rate expressions: \documentclass{article}\pagestyle{empty}\begin{document}$ \log k(\sec ^{ - 1}) = 15.3 - (72.7/{\rm \theta)} $\end{document} for ethylbenzene between 1053 and 1234 K, \documentclass{article}\pagestyle{empty}\begin{document}$ \log k(\sec ^{ - 1}) = 15.8 - (71.3/{\rm \theta)} $\end{document} for isopropylbenzene between 971 and 1151 K, and \documentclass{article}\pagestyle{empty}\begin{document}$ \log k(\sec ^{ - 1}) = 15.9 - (69.1/{\rm \theta)} $\end{document} for tert‐butylbenzene between 929 and 1157 K, where θ (kcal/mol) = 2.303RT. Resulting activation energies combined with heat capacity and heat of formation data led to the following dissociation enthalpies and enthalpies of formation at 298 K: DH° (øCH(CH3)CH3) = 73.8 kcal/mol, ΔHf° (øÇCH(CH3)) = 39.6 kcal/mol, DH° (øC(CH3)2CH3) = 72.9 kcal/mol, and ΔHf° (øÇ(CH3)2) = 32.4 kcal/mol. Derived high‐pressure rate constants are in good accord with results of lower temperature toluene‐ and aniline‐carrier experiments.
Rate constants for the reaction of tert‐butyl radicals with chloroform in solution
Authors: Dütsch H.‐R. , Fischer H. 
Published: January 2005

AbstractThe decay of photochemically generated tert‐butyl radicals in methylcyclopentane solutions containing chloroform is studied by time‐resolved ESR spectroscopy. In the pure solvent it perfectly follows the second‐order rate law for radical self‐termination. Increasing chloroform concentrations cause increasing admixture of a pseudo‐first‐order decay from which the rate constant of the title reaction is obtained. For 273 K ≦ T ≦ 323 K,

where θ = 2.303RT kcal/mol. CIDNP studies of the reaction mechanism and NMR product yields show H and Cl abstractions to occur with the temperature‐independent ratio kH/kCl = 1.4 ± 0.1. The results point to polar effects in the transfer reactions of tert‐butyl. The potential of time‐resolved ESR spectroscopy in studies of first‐ and pseudo‐first‐order reaction rates is discussed.
Kinetics and mechanism of the oxidation of N‐methylformamide and N,N‐dimethylformamide by silver (II) in aqueous perchlorate media and comparison with oxidation by CoIII and MnIII
Authors: Ahmad Firoz , Baswani Vikram S. 
Published: January 2005

AbstractDetailed measurements on the kinetics and stoichiometry of the oxidation of N‐methylformamide and N,N‐dimethylformamide by aquosilver (II) ions are reported. Four Ag ions are consumed for each amide, and the reaction is first order in [Ag] and first order in [amide]. The reaction is inversely dependent on acidity in the range of 1.5–5.0M HClO4. The oxidation rate is independent of [AgI] and ionic strength. The proposed reaction mechanism and activation parameters are compared with those found for the oxidation of amides by other oxidants such as cobalt(III) and manganese(III).
Steric factors in the kinetically controlled direction of elimination of secondary and tertiary esters in the gas phase. The pyrolysis of 4,4‐dimethylpent‐2‐yl acetate
Authors: Chuchani Gabriel , Dominguez Rosa Maria 
Published: January 2005

AbstractThe pyrolysis kinetics of 4,4‐dimethylpent‐2‐yl acetate, in a static system and in a vessel seasoned with allyl bromide, have been studied in the temperature range of 300–350°C and the pressure range of 48–211 torr. The olefin products were 4,4‐dimethylpent‐1‐ene, cis‐4,4‐dimethylpent‐2‐ene, and trans‐4,4‐dimethylpent‐2‐ene. The rate coefficient for the homogeneous unimolecular elimination of this ester is given by the following Arrhenius equation: log k(sec−1) = (12.87 ± 0.31) − (181.2 ± 3.4)kJ/mol/2.303RT. The direction of elimination of this acetate has been found to proceed to the formation of the corresponding olefin by kinetic control. The present data, together with other pyrolysis work subject to kinetic control, imply that the direction of elimination of bulky alkyl esters is determined by steric hindrance in the eclipsed cis conformation. However, further analyses reveal that if a series of esters are compared, in the case of a gradual increase of alkyl branching when adjacent to a hydrogen atom (alkyl–H interactions), the rate was determined by steric acceleration, owing to the crowding effect at the highly substituted carbon atom. Otherwise if this gradual alkyl increase in size happened to be adjacent to another alkyl substituent (alkyl–alkyl interactions), the rate was affected by steric hindrance of the eclipsed cis conformation.
Study of ionic catalytic systems by the electrodialysis method
Authors: Dyachkovskii F. S. , Grigoryan E. H. , Babkina O. N. 
Published: January 2005

AbstractA special method of electrodialysis has been developed for investigation of the kinetics and mechanism of polymerization reactions involving ions. The ionic composition of homogeneous systems such as Cp2TiRClAlRCl2, RTiCl3 + AlRCl2, Ti(OR)4 + AlR3, and (RLi)n has been studied. The composition of catalytically active ions has been determined. Using the regularities of “open” systems, the methods of determining the carbocation reactivity under electrodialysis conditions havebeen worked out. The impulse electrodialysis method has been suggested for studying ionic polymerization kinetics and evaluating the rate constants ofion reactions with the monomer and gegenion.