bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the gas‐phase free radical displacement reaction CH3 + CD3COCD3 → CD3 + CH3COCD3
Authors: Knoll H. , Richter Gislind , Schliebs R. 
Published: January 2005

AbstractThe gas‐phase free radical displacement reaction
equation image
has been studied in the temperature range of 240–290°C and at 140°C with the thermal decomposition of azomethane (AM) and di‐tert‐butylperoxide (DTBP), respectively, as methyl radical sources. The reaction products of the CD3 radicals were analyzed by mass spectrometry. Assuming negligible isotope effects, Arrhenius parameters for the elementary radical addition reaction
equation image
were derived:

The data are discussed with respect to the back reaction and general features of elementary addition reactions.
On the reaction between ethylene and cyclopentene, a radical mechanism
Authors: Benson Sidney W. 
Published: January 2005

AbstractThe bimolecular reaction
equation image
is shown to proceed via a simple, nonchain, radical mechanism:
equation image
with the net reaction the same as (1). Rate constants are estimated for each step and for each possible competing reaction and shown to yield minor or negligible side reactions in agreement with the observations of Lalonde and Back. Estimated and observed rate constants (1) and (1′) are in excellent agreement with the assumption that k'‐1 is a typical radical disproportionation with zero activation energy.From the reported data a best value for k′1 is

where θ = 2.303RT kcal/mol.
Peroxy radical reactivities in the cooxidation of ethylbenzene and substituted 3‐phenylindans
Authors: Rafikova V. S. , Maizus Z. K. , Skibida I. P. , Volkov R. N. 
Published: January 2005

AbstractThe rate constants of peroxy radical recombination in the oxidation of 1‐methyl‐3‐phenylindan, 1,3‐dimethyl‐3‐phenylindan, and 1,1‐dimethyl‐3‐phenylindan were measured using the nonstationary‐state technique. A cooxidation method was applied to obtain the reactivities of these compounds with respect to α‐phenylethyl peroxy radicals.
The rate constant for H + i‐C4H8 → t‐C4H9 in the range of 298–563 K
Authors: Canosa Carlos E. , Marshall Roger M. , Sheppard Adrian 
Published: January 2005

AbstractThe overall rate constant for hydrogen‐atom addition to isobutene has been measured in the temperature range of 298–563 K in a flow discharge system coupled to a quadrupole mass spectrometer. Previously published results allow the determination of

where the error limits are 95% confidence limits.
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The pyrolysis kinetics of 4‐chloro‐2‐butanone in the gas phase
Authors: Dominguez Rosa M. , Chuchani Gabriel 
Published: January 2005

AbstractThe rates of pyrolysis of 4‐chloro‐2‐butanone in the gas phase have been determined in a static system seasoned with the products of decomposition of allyl bromide. The reaction is catalyzed by hydrogen chloride. Under maximum catalysis of HCl, the kinetics were found to be of order 1.5 in the substrate suggesting that a complex elimination is involved. The reaction, when maximally inhibited with propene, appears to undergo a unimolecular elimination and follows a first‐order law kinetics. The products are methylvinyl ketone and hydrogen chloride. The kinetics have been measured over the temperature range of 402.0–424.4°C.The rate coefficients are given by the Arrhenius equation \documentclass{article}\pagestyle{empty}\begin{document}$ \log k_1 (\sec ^{ - 1}) = (13.67 \pm 0.69) - (225.2 \pm 8.6)\,{\rm kj}/{\rm mol}/2.303RT\angle $\end{document}. Thepyrolysis of 4‐chloro‐2‐butanone is 31 times greater in rate than that of ethyl chloride at 440°C. This large difference in rate may be attributed to the ‐M effect of the acetyl substituent in the pyrolysis of the former halo compound.
Kinetics and mechanism of the thermal decomposition of cyclopentyl cyanide
Authors: King Keith D. , Goddard Richard D. 
Published: January 2005

AbstractThe thermal decomposition of cyclopentyl cyanide has been investigated in the temperature range of 905–1143 K using both conventional stirred‐flow reactor and very low‐pressure pyrolysis (VLPP) techniques. The results from both techniques are consistent. The main primary processes are HCN elimination to form cyclopentene:
equation image
and ring fragmentation to form vinyl cyanide plus propylene and ethylene plus cyanopropenes:
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Under the experimental conditions cyclopentene undergoes further decomposition to cyclopentadiene plus hydrogen. There is evidence for conversion of some of the reactant to a solid residue, presumably polymer. From the stirred‐flow reactor results the following Arrhenius expressions were obtained: log k1(s−1) = (12.8 ± 0.3) − (65.6 ± 1.3)/θ and log k2(s−1) = (16.0 ± 0.3) − (80.0 ± 1.1)/θ, where θ = 2.303RT kcal/mol. Application of RRKM theory shows that the VLPP experimental rate constants are consistent with high‐pressure Arrhenius parameters given by log k1(s−1) = (12.8 ± 0.3) − (67.8 ± 2.5)/θ for HCN elimination, and log k4(s−1) = (16.3 ± 0.3) − (80.1 ± 2.0)/θ for the sum of the ring fragmentation pathways. The rate parameters for HCN elimination are in good agreement with previous VLPP studies of alkyl cyanides and with theoretical predictions. The difference in activation energies for the ring opening of cyclopentane and cyclopentyl cyanide is reasonably close to the established value for the cyano stabilization energy. This supports the assumption of a biradical mechanism.
Kinetics of the formation of primary products of cumeme cracking over a partially exchanged LaY‐Zeolite
Authors: Corma A. , Farag H. , Wojciechowski B. W. 
Published: January 2005

AbstractThe kinetics of formation of primary products from cumene cracking over a partially exchanged LaNaY catalyst have been studied at 400, 450, and 500°C. It has been found that in both the fully and the partially exchanged LaNaY zeolite catalysts the nature of active sites is the same. The higher activity of the fully exchanged catalyst is attributed to a higher concentration of the active sites. It has also been found that an increase in exchange level leads to an increase in the number of both Bronsted and Lewis active sites, but in somewhat different proportions. A comparatively slight increase in the decay rate constant is observed over the same increase in the level of exchange.
High‐energy kinetic study of chemically activated 1,1‐dichlorocyclopropane
Authors: Eichler K. , Heydtmann H. 
Published: January 2005

Abstract1,1‐Dichlorocyclopropane has been produced by addition of CH2(1A1) to 1,1‐dichloroethylene. CH2(1A1) was generated by the photolysis of ketene at 277–334 nm. The 1,1‐dichlorocyclopropane was formed in a chemically activated state, had an energy content between 386 and 400 kJ/mol, and reacted in two parallel channels to 2,3‐dichloropropene and 1,1‐dichloropropene. 1,1‐Dichloropropene was also formed directly by insertion of CH2(1A1) into the CH bond of 1,1‐dichloroethylene. As secondary reactions elimination of HCl from chemically activated 2,3‐dichloropropene occurred with 3‐chloropropyne and chloroallene as products. In some of the experiments perfluoropropane was added as an inert gas. The apparent rate constants for the isomerization and elimination reactions are reported. The results of RRKM calculations including distribution functions for the activated 1,1‐dichlorocyclopropane and a step‐ladder model for the deactivation verify the proposed reaction scheme.
Kinetics of free‐radical decay reactions in polymeric solids
Authors: Basheer Rafil , Dole Malcolm 
Published: January 2005

AbstractKinetic equations for the decay of the free radicals in polymeric solids are given for the following assumptions on which they are based: (1) two simultaneous first‐order but physically separated decay reactions; (2) two simultaneous noninteracting second‐order decay reactions; (3) combined simultaneous but intermingled first‐ and second‐order decay reactions; (4) the same but for independent, i.e., not intermingled, first‐ and second‐order decay reactions; (5) a second‐order decay reaction in the presence of some free radicals that do not decay; and (6) a first‐order decay reaction in the presence of some free radicals that do not decay. In all of the above physical systems the total concentration only can be measured. Hence the above kinetic equations refer to the change of the total concentration with time. It is found that the data for the decay of the free radicals in irradiated isotactic polypropylene and 61% styrene‐39% butadiene block copolymer agree best with the equations for the second‐order decay in the presence of a fraction of nondecaying free radicals.
Flash photolysis of biacetyl in gas phase. Rate constants of reactions between methyl and acetyl radicals
Authors: Timonen Raimo , Kalliorinne Kaarlo , Blomqvist Kurt , Koskikallio Jouko 
Published: January 2005

AbstractThe flash photolysis of biacetyl produces CO, C2H6, and CH3COCH3 as main products, and in small amounts CO2, C2H4, and CH3CHO. The rate constants of reactions (2) and (3)

of thermally equilibrated radicals were calculated from the amounts of products:

.
Disproportionation reactions between CF2H and C2H5radicals in the gas phase
Authors: Nilsson William B. , Pritchard Glyn O. 
Published: January 2005

AbstractThe disproportionation and combination reactions between CF2H and C2H5radicals have been studied in the gas phase from room temperature to 70°C. For the pathway which yields CF2H2+ C2H4, relative to CF2HC2H5, Δ = 0.072 ± 0.019. The competing reaction channel that produces CF2+ C2H6is approximately four times as efficient, with Δ = 0.265 ± 0.038. With CF2D radicals an isotope effect for the CF2+ C2H5D reaction pathway was observed with Δ ≅ 0.2.
Kinetics and mechanism of Rh(III) catalyzed oxidation of styrene, stilbene and phenylacetylene by acid periodate
Authors: Radhakrishnamurti P. S. , Misra S. A. 
Published: January 2005

AbstractThe kinetics of Rh(III) catalyzed oxidative cleavage of styrene, stilbene, and phenylacetylene by periodate have been investigated in the presence of HClO4 in aqueous acetic acid medium. The kinetic orders are completely dependent on the nature of unsaturation. In the cases of styrene and stilbene the reactions are first order in the oxidant and Rh(III), zero order with respect to the substrate, and independent of [H+], whereas in the case of phenyl acetylene the reaction is zero order with respect to the oxidant and first order with respect to the substrate and Rh(III). The reaction is independent of [H+] in the range of 0.01−0.05M studied. A mechanism involving higher Rh(V) species has been postulated in the case of styrene as well as stilbene, and metal ion catalyzed hydration has been postulated in case of phenylacetylene. The influence of the solvent has been investigated, and a comparative analysis of the kinetic orders of styrene and stilbene is made with those of phenylacetylene.
Rate constants for the gas‐phase reaction of OH radicals with a series of ketones at 299 ± 2 K
Authors: Atkinson Roger , Aschmann Sara M. , Carter William P. L. , Pitts James N. 
Published: January 2005

AbstractRelative rate constants for the reaction of OH radicals with a series of ketones have been determined at 299 ± 2 K, using methyl nitrite photolysis in air as a source of hydroxyl radicals. Using a rate constant for the reaction of OH radicals with cyclohexane of 7.57 × 10−12 cm3 molecule−1 s−1, the rate constants obtained are (× 1012 cm3 molecule−1 s−1): 2‐pentanone, 4.74 ± 0.14; 3‐pentanone, 1.85 ± 0.34; 2‐hexanone, 9.16 ± 0.61; 3‐hexanone, 6.96 ± 0.29; 2,4‐dimethyl‐3‐pentanone, 5.43 ± 0.41; 4‐methyl‐2‐pentanone, 14.5 ± 0.7; and 2,6‐dimethyl‐4‐heptanone, 27.7 ± 1.5. These rate constants indicate that while the carbonyl group decreases the reactivity of CH bonds in the α position toward reaction with the OH radical, it enhances the reactivity in the β position.
Kinetic and mechanistic studies of oxidation of arginine, histidine, and threonine in alkaline medium by N‐chloro‐N‐sodio‐p‐toluenesulfonamide
Authors: Mahadevappa D. S. , Rangappa K. S. , Gowda N. M. M. , Gowda B. Thimme 
Published: January 2005

AbstractThe kinetics of oxidation of arginine, histidine, and threonine by chloramine‐T (CAT) have been investigated in alkaline medium at 35°C. The rates are first order in both [CAT] and [amino acid] and inverse fractional order in [OH−] for arginine and histidine. The rate is independent of [OH−] for threonine. Variation of ionic strength and addition of the reaction product, p‐toluenesulfonamide, or Cl− ions had no effect on the rate. A decrease of the dielectric constant of the medium by adding methanol decreased the rate with arginine, while the rates increased with histidine and threonine. The solvent isotope effect was studied using D2O. (kobs)/(kobs) was found to be 0.55 and 0.79 for arginine and histidine, respectively. The reactions were studied at different temperatures, and activation parameters have been computed. The oxidation process in alkaline medium, under conditions employed in the present investigations, has been shown to proceed via two paths, one involving the interaction of RNHCl (formed rapidly from RNCl−), with the amino acid in a slow step to form monochloroamino acid, which subsequently interacts with another molecule of RNHCl in a fast step to give the products, p‐toluenesulfonamide (RNH2), and the corresponding nitrile of the amino acid (R'CN). The other path involves the interaction of RNCl− with the amino acid in a similar way to give RNH2 and R'CN. Mechanisms proposed and the derived rate laws are consistent with the observed kinetics. The rate constants predicted using the derived rate laws, as [OH−] varies, are in excellent agreement with the observed rate constants, thus justifying these rate laws and hence the proposed mechanistic schemes.
Kinetics of oxidative coupling of phenols: Oxidation of naphthols by alkaline hexacyanoferrate (III)
Authors: Bhattacharjee Mitra , Mahanti M. K. 
Published: January 2005

AbstractThe oxidation of naphthols by alkaline hexacyanoferrate(III), at constant ionic strength, gave coupled products. The rate of the reaction was dependent on the first powers of the concentrations of substrate, oxidant, and alkali. The activation energies were 31.8 and 34.5 kJ/mol for α naphthol and β naphthol, respectively. The reaction pathway was via the formation of a radical intermediate, which was detected by electron spin resonance spectroscopy.
The oxidation of HI at low temperatures and the heat of formation of HO2
Authors: Shum Lilian G. S. , Benson Sidney W. 
Published: January 2005

AbstractThe kinetics of the oxidation of hydrogen iodide (HI + O2) at low temperature (414–499 K) in the gas phase by the method of iodination kinetics is complicated by a heterogeneous reaction between hydrogen iodide and oxygen. Present work leads to an upper limit for the bimolecular rate constant k1 for the first and rate‐determining step
equation image
These data are combined with an estimated A factor A1 = 109.3±0.2 L/mol·s (assuming a tight linear I···H···O— transition state), to calculate the lower limit of the activation energy for the forward reaction E1. This leads to a minimum value for the heat of formation of the HO2 radical, ΔHf298°(HO2) < 3.0 kcal/mol.
Studies in nickel(IV) chemistry. Kinetics of the Cu(II) ion‐mediated acid decomposition of tris(dimethylglyoximato) nickelate(IV) in aqueous acidic medium
Authors: Neogi G. , Acharya S. , Panda R. K. , Ramaswamy D. 
Published: January 2005

AbstractKinetics of the Cu(II) ion‐mediated acid decomposition of tris (dimethylglyoximato)nickelate(IV), Ni(dmg)32− (dmg2− = dimethylglyoximate dianion), are reported in aqueous medium in the range of 3.6 ⩽ pH ⩽ 6.6 at 35°C and μ = 0.57 M. The pseudo‐first‐order rate constants of the disappearance of Ni(IV) kobs(M) satisfy the equation

where kad refers to the pseudo‐first‐order rate constants for the proton‐assisted decomposition of the Ni(IV) complex determined independently and is a function of [H+], and kdec(M) to that for the Cu(II) ion‐mediated route and is a function of [H+] and [Cu2+]. Both kobs(M) and kdec(M) are found to increase with increasing [Cu(II)]0, tending to attain limiting values at higher relative [Cu(II)]0. At low [Cu(II)]0 the kdec(M) is found to register a decrease with increasing pH in the pH range of 3.6–4.4, then an increase in the range of 4.4–5.76, and again a decrease in the range of 5.76–6.6. Results on the Cu(II) ion‐mediated acid decomposition are interpreted in terms of a probable mechanism involving pH‐dependent adduct formation equilibria involving the one‐protonated and the two‐protonated species of Ni(IV) and the various species of Cu(II) ion in the media, followed by rate‐determining acid decomposition of the adduct(s) to give Ni(II) aq. and Cu(dmgH)2. While the two‐protonated Ni(IV) complex apparently reacts about five orders of magnitude faster than the one‐protonated species, the aquacopper(II) reacts about two orders of magnitude slower than the hydroxoaquacopper(II).
TI(III) oxidation of alkenes and alkynes and Ru(III) catalysis in the oxidation of alkenes: A kinetic and mechanistic study
Authors: Radhakrishnamurti P. S. , Panda H. P. 
Published: January 2005

AbstractThe oxidation of trans‐stilbene, phenylacetylene, and diphenylacetylene by Tl(OAc)3 in aqueous acetic acid medium in the presence of HClO4 follows the rate law

in [H+] of 0.1–1.0M, the [H+] dependence below 0.1M being marginal. The reactions are strongly dielectric dependent. The order of reactivity among the substrates is styrene > phenylacetylene and trans‐stilbene > diphenylacetylene. A mechanism involving the oxythallation adduct by the Tl+(OAc)2 species has been discussed. The use of Ru(III) as a homogeneous catalyst brings a change in the kinetic orders for trans‐stilbene, the rate law being

The formation constants K for the Ru(III)–alkene π complex at 40, 50, and 60°C are 90.14M−1, 105.2M−1, and 127.7M−1, respectively. Interestingly the oxidation of phenylacetylene and diphenylacetylene does not undergo catalysis by Ru(III). The mechanism involving the metal–arene π complex is discussed.
Kinetics and mechanism of the cerium (IV) oxidation of α‐Hydroxycycloalkanecarboxylic acids and cyclic alcohols in acidic perchlorate media
Authors: Hanna Samir B. , Fenton Jeff Taylor 
Published: January 2005

AbstractThe Ce(IV) oxidation of the five‐, six‐, and seven‐membered ring α‐hydroxycycloalkanecarboxylic (C5, C6, and C7) acids to the corresponding cyclic ketones has been studied in acidic perchlorate media. The data may be interpreted in terms of a mechanism which involves fast preequilibrium complexation steps between Ce(IV) and the hydroxy acids, yielding two complexes which differ only by a proton. Complexation is followed by rate‐determining decarboxylation to an intermediate (free radical?), which reacts quickly with another Ce(IV) to give products. Of the two proposed complexes, the protonated one is virtually unreactive. The C7 ring acid is oxidized more rapidly than the C6 acid, which, in turn, is oxidized faster than the C5 acid.For comparison, the oxidation of the five‐, six‐, and seven‐membered ring cyclic alcohols to the corresponding cyclic ketones by Ce(IV) in acidic perchlorate was also studied. The order of reactivity is cyclopentanol > cycloheptanol > cyclohexanol. The differences in observed reactivities between the hydroxy acids and the cyclic alcohols are explained in terms of differences in transition state structure.The stepwise hydrolysis constants of Ce(IV) leading to Ce(OH)3Plus; and Ce(OH)22+ were determined. In the case of the hydroxy acids, evidence is in favor of Ce(OH)3+ as the reactive ceric species in aqueous acidic perchlorate media.
Sensitivity analysis in chemical kinetics by the method of polynomial approximations
Authors: Hwang Jenn‐Tai 
Published: January 2005

AbstractA new approach, the method of polynomial approximations (PAM), to the sensitivity analysis in chemical kinetics is presented. The method is based on first dividing the time domain of interest into subintervals, and then, within each subinterval, using low‐degree interpolation polynomials to mimic the system temporal behavior. This procedure forces all parametric dependences of the system to reside in the expansion coefficients and transforms the differential sensitivity equations into a set of algebraic ones. The major computational effort of PAM is proportional to the number of components in the system, not to the number of parameters. In addition, higher order sensitivity coefficients in PAM can be generated quite readily once first‐order ones are known. The information required to divide the time domain comes from a preliminary simulation study of the system temporal behavior, which is always available in any kind of modeling studies. Typically, for an interpolation polynomial of degree 3–4, only 10–20 subintervals are needed to attain satisfactory accuracy. The application of PAM is well suited to large‐scale kinetic models, especially when an inexpensive scanning of the system sensitivity behavior is desired. The extremely high computational speed of PAM in securing sensitivity informations was demonstrated by two illustrative kinetic examples. Furthermore the problem of utilizing sensitivity information to unravel the functional dependence of a species concentration upon rate coefficients, to simplify a complex reaction model, and to elucidate mechanistic details of a reaction process was examined in detail.
Kinetics and mechanism of the reactions of the superoxide ion in solutions. III. Kinetics and mechanism of the reaction of the superoxide ion with ethyl acetate in dimethylformamide, acetonitrile, and their mixtures
Authors: Afanas′ev I. B. , Kuprianova N. S. 
Published: January 2005

AbstractThe kinetics of the reaction of the superoxide ion with ethyl acetate have been studied in DMF, AN, and their mixtures. It was shown that the rate constants depend on the ethyl acetate concentration, which indicates the formation of an intermediate in this process. Equilibrium constants for the process of the intermediate formation and the rate constants for its decay have been determined. It is concluded that aprotic solvents affect mainly the stage of the intermediate decay in this reaction.
Kinetic study of the reactions of CL and BR with H2O2
Authors: Heneghan Shawn P. , Benson Sidney W. 
Published: January 2005

AbstractThe reactions of Cl and Br atoms with H2O2 have been studied in the range of 300–350 K using the very‐low‐pressure‐reactor technique. It was found that metathesis to produce HX and HO2 is the only significant process (≤99%). For the reaction of Br

k2 (300 K) = 1.3 ± 0.45 × 10−14 and k2 (350 K) = 3.75 ± 1.1 × 10−14 cm3/molecules·s, with an activation energy of 4.6 ± 0.7 kcal/mol. Using an estimated A factor for A2, we find

suggesting that a best choice is E2 = 3.9 ± 0.4 kcal/mol. The relation of these values to ΔH (HO2) is discussed.
Rate constants for quenching of O2(1Δg) with sulfur compounds
Authors: Raja Nalini , Chatha J. P. S. , Arora P. K. , Vohra K. G. 
Published: January 2005

AbstractThe rate constants for the quenching of O2(1Δg) with carbon disulfide, dimethyl sulfide, dimethyl disulfide, diallyl disulfide, ethyl mercaptan, and thiophene have been determined in a discharge flow system in the absence of oxygen atoms. The rate constants are found to be (6.5 ± 0.6) × 104, (1.8 ± 0.2) × 104, and (3.5 ± 0.6) × 103 L/mol · s for dimethyl sulfide, ethyl mercaptan, and thiophene, respectively. The other compounds have rate constants <9.9 × 102 L/mol · s. In the case of dimethyl sulfide, even when NO2 concentration is more than what is required to remove oxygen atoms completely, the rate constants are found to vary with different amounts of NO2. No correlation is found to exist between the logarithm of the rate constants and the ionization potentials of the compounds.