bluuebunny/crossref_metadata_2025_split huggingface dataset:
Linear correlation of polar substituents in the gas‐phase pyrolyses of ethyl α‐substituted acetates
Authors: Rotinov Alexandra , Chuchani Gabriel 
Published: January 2005

AbstractThe pyrolysis kinetics of several ethyl esters with polar substituents at the acyl carbon have been studied in the temperature range of 319.8–400.0°C and pressure range of 50.5–178.0 torr. These eliminations are homogeneous, unimolecular, and follow a first‐order rate law. The rate coefficients are given by the Arrhenius equations: for ethyl glycolate, log k1 (s−1) = (12.75 ± 0.30) – (201.4 ± 3.8) kJ/mol/2.303RT; for ethyl cyanoacetate, log k1 (s−1) = (12.19 ± 0.18) – (191.8 ± 2.1) kJ/mol/2.303RT; for ethyl dichloroacetate, log k1 (s−1) = (12.62 ± 0.36) – (193.9 ± 4.3) kJ/mol/2.303RT; for ethyl trichloroacetate, log k1 (s−1) = (12.27 ± 0.09) – (185.1 ± 1.0) kJ/mol/2.303RT. The results of the present work together with those reported recently in the literature give an approximate linear correlation when plotting log k/k0 vs. σ* values (ρ* = 0.315 ± 0.004, r = 0.976, and intercept = 0.032 ± 0.006 at 400°C). This linear relationship indicates that the polar substituents affect the rate of elimination by electronic factors. The greater the electronegative nature of the polar substituent, the faster is the pyrolysis rate. The alkyl substituents yield, within experimental error, similar values in rates which makes difficult an adequate assessment of their real influence.
The kinetics of the addition of alkyl radicals to carbonyl groups. II. The addition of methyl radicals to trifluoroacetone in the gas phase. The formation reaction of the trifluoro‐t‐butoxy radical
Authors: Kerr J. Alistair , Wright J. Paul 
Published: January 2005

AbstractBy photolyzing azomethane over the temperature range 331–491 K in the presence of trifluoroacetone the kinetics of the addition reaction (1), ĊH3 + CF3COCH3 → CF3C(Ȯ)(CH3)2 have been studied. Detailed analyses have shown that the principal product of the adduct radical, CF3C(Ȯ)(CH3)2, is CH3COCH3 from reaction (−2), CF3C(Ȯ)(CH3)2 → CH3COCH3 + ĊF3. The rate constant of the addition reaction has been determined to be k1(dm3/mol s) = (4.5 ± 1.4) × 107 exp(‐(3370 ± 120)/T) over the temperature range 331–491 K, based on the value k3 = 2.2 × 1010 dm3/mol s for the reaction (3), 2ĊH3 → C2H6. The results are discussed in relation to existing data for radical additions to magnified image groups.
High temperature collisional energy transfer in highly vibrationally excited molecules: Isotope effects in tert‐butyl chloride systems
Authors: Brown Trevor C. , King Keith D. , Gilbert Robert G. 
Published: January 2005

AbstractThe average downward collisional energy transfer (<ΔEdown>) is obtained for highly vibrationally excited tert‐butyl chloride, both undeuterated and per‐deuterated, with Kr, N2, CO2, and C2H4 bath gases, at ca. 760 K. Data are obtained using the technique of pressure‐dependent very low‐pressure pyrolysis. Reactant internal energies to which the data are sensitive are in the range 200–250 kJ mol−1. For C4H9Cl, the <ΔEdown> values (cm−1) are 255 (Kr), 265 (N2), 440 (CO2), and 585 (C2H4), and for C4D9Cl, 245 (N2), 370 (CO2), and 540 (C2H4). The uncertainties in these values are ca. 20% (40% for Kr); the uncertainties in the deuteration ratios are 10–15%. The value for Kr is in agreement with theoretical predictions of a biased random walk model for internal energy change in monatomic/substrate collisions. The effect of deuteration of <ΔEdown> is also in accord with that predicted by a modification of the theory. Extrapolated highpressure rate coefficients for the thermal decomposition of reactant are 1013.6 exp(‐187 kJ mol−1/RT) s−1 (C4H9Cl) and 1014.2 exp(−196 kJ mol−1/RT) s−1 (C4D9Cl), in accord with other studies and the expected isotope effect.
Reactions of trichloromethyl radicals with organosilicon compounds
Authors: Rice J. A. , Treacy J. J. , Sidebottom H. W. 
Published: January 2005

AbstractThe photolysis of carbon tetrachloride in the presence of a number of organosilicon compounds has been investigated in the gas phase. The products obtained from the photolysis experiments were those expected from a chain reaction in which trichloromethyl radicals abstract hydrogen atoms from the organosilane. Arrhenius parameters for hydrogen atom transfer were determined relative to those for trichloromethyl radical combination.
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The activation energies for the reaction of methyl, trifluoromethyl, and trichloromethyl radicals with organosilicon compounds are compared and the results rationalized in terms of polar effects.
Single pulse shock tube study on the thermal stability of ketones
Authors: Tsang Wing 
Published: January 2005

Abstract5‐Methyl‐hexanone‐2, 3‐methyl‐pentanone‐2, and hexanone‐2 have been decomposed in comparative rate single pulse shock tube experiments. The mechanism of decomposition involves the breaking of carbon‐carbon bonds as well as molecular processes involving 6‐center complexes. The following rate expressions at 1100 K have been obtained:

These results lead to ΔHf(CH3ĊO) = − 13.8 kJ and ΔHf(CH3COCH2·) = − 12.6 kJ at 300 K. They are compared with existing literature values and some generalizations are made with regard to the stability of carbonyl compounds.
The effect of temperature on formaldehyde photooxidation in oxygen‐lean atmospheres
Authors: Carmely Yaakov , Horowitz Abraham 
Published: January 2005

AbstractThe photooxidation of formaldehyde in CH2OO2, oxygen‐lean mixtures was studied in the temperature range 298–378 K. H2 and CO formation and the loss of O2 proceed by a chain mechanism, which between 328 and 378 K follows the previously suggested kinetics [1] with one modification. The reaction HO2 + CH2O ⇄ HO2CH2O (5) is now assumed to be reversible and ΔH is estimated to be between 14 and 19 kcal/mol. The relative yields of the chain formed H2 and CO and of the consumed O2 remained constant over the entire temperature range indicating that the relative efficiencies of the HO reactions: HO + CH2O → H2O HCO† (7), HO + CH2O → H2O + HCO (8) and HO + CH2O → HOCH2O (9) are temperature independent.
Iodine catalyzed pyrolysis of dimethyl sulfide. Heats of formation of CH3SCH2I, the CH3SCH2 radical, and the pibond energy in CH2S
Authors: Shum Lilian G. S. , Benson Sidney W. 
Published: January 2005

AbstractA kinetic study has been made of the gas phase, I2‐catalyzed decomposition of (CH3)2S at 630–650 K. Some I2 is consumed initially, reaching a steady‐state concentration. The initial major products are CH4 and CH2S together with small amounts of CH3SCH2I, CH3I, HI, and CS2. The initial reaction corresponds to a pseudo‐equilibrium:

accompanied by:

and

which brings (I2) into steady state and a final complex reaction:
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From the initial rate of I2 loss it is possible to obtain Arrhenius parameters for the iodination:
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We measure k1, (644 K) = 150 L/mol s and from both the Arrhenius plot and independent estimates A1 (644 K) = 1011.2 ± 0.3 L/mol s. Thus, E1 = 26.7 ± 1 kcal/mol. From the steady‐state I2 concentration, an assumed mechanism and the known rate parameters for the CH3I/HI system. It is possible to deduce KA (644) = 3.8 × 10−2 with an uncertainty of a factor of 2. Using an estimated ΔS (644) = 4.2 ± 1.0 e.u. we find ΔHA (644) = 7.0 ± 1.1 kcal. With 〈ΔCPA〉644 = 1.2 this becomes: ΔHA(298) = 6.6 ± 1.1 kcal/mol. Then ΔH (CH3SCH2I) = 6.3 ± 1 kcal/mol. Making the assumption that E−1 = 1.0 ± 0.5 kcal/mol we find ΔH (644) = 25.7 ± 0.7 kcal/mol and with 〈ΔCPI〉 = 1.2; ΔH = 25.3 ± 0.8 kcal/mol. This gives ΔH (CH3SĊH2) = 35.6 ± 1.0 kcal/mol and DH (CH3SCH2H) = 96.6 ± 1.0 kcal/mol. This then yields Eπ(CH2S) = 52 ± 3 kcal. From the observed rate of pressure increase in the system and the preceding data k3, is calculated for the step CH3SCH2 → CH3 + CH2S. From an estimated A‐factor E3 is deduced and from the overall thermochemistry values for k−3 and E−3. A detailed mechanism is proposed for the I‐atom catalyzed conversion of CH2S to CS2 + CH4.
The flash photolysis—shock tube technique using atomic resonance absorption for kinetic studies at high temperatures
Authors: Michael J. V. , Sutherland J. W. , Klemm R. B. 
Published: January 2005

AbstractA flash photolysis‐shock tube technique is described for making kinetic measurements at high temperature. Coupled with sensitive atomic resonance absorption detection, this method allows bimolecular rate constants for atom‐molecule reactions to be measured directly under conditions free from kinetic complications. Experiments were performed in the reflected shock regime, and the temperature and density were calculated using ideal shock wave theory in this initial work. Results for the reaction of atomic hydrogen with ammonia are presented to illustrate the potential of the technique. The values of the Arrhenius rate parameters found in these experiments, 900 K ≤ T ≤ 1850 K, were A = (1.14 ± 0.12) × 10−10 cm3 molecule−1 s−1 and Ea = 13,216 ± 242 cal mol−1. This result gives rate constants that are about five times larger than those from previous studies. Although corrections for nonidealities in the reflected shock region are anticipated and under investigation, the expected changes will be relatively small and thus the large discrepancy noted here will remain.
The rate constants for the reaction of the hydroxyl radical with methyl, n‐propyl, and n‐butyl nitrites
Authors: Baulch Donald L. , Campbell Ian M. , Saunders Sandra M. 
Published: January 2005

AbstractThe kinetics of the reaction of OH radicals with methyl, n‐propyl, and n‐butyl nitrite

have been studied in a discharge flow system under pseudo first‐order conditions. The OH radicals were generated by the reaction of H atoms with NO2 and the concentration of OH; monitored by resonance fluorescence, was followed as a function of time in an excess of each nitrite. Values of k(CH3ONO) = (0.6 ± 0.09) × 109 dm3 mol−1 s−1 k(n – C3H7ONO) = (1.39 ± 0.20) × 109 dm3 mol−1 s−1, and k(n – C4H9ONO) = (2.89 ± 0.43) × 109 dm3 mol−1 s−1 at 295 K were obtained. These results agree with previous relative rate measurements from this laboratory but the value for k (CH3ONO) is a factor of 7 greater than the value obtained by relative rate measurements elsewhere using a different OH source.
Reactivities of cis‐ and trans‐buten‐2‐yl free radicals in presence of D2S. II. Absolute values of rate constants and isotopic effects
Authors: Richard C. , Martin R. 
Published: January 2005

AbstractCis‐ and trans‐buten‐2‐yl free radicals are shown to react with butene‐2 cis (Bc) and D2S in the following metathetical steps: magnified image giving rise to butenes‐1 (B1). The initial formations of butene‐1,3 d1 and total butene‐1 in D2SBc mixtures have been studied in the initial pressure range 20–200 torr for Bc, 0–41 torr for D2S and at 717–817 K. The main initiation and termination steps are shown to be: magnified image Assuming a rapid equilibrium between cis‐ and trans‐C4H7⋅, ki ≃ 1015.5 exp(−85.5/RT) s−1 (RT in kcal mol−1) and kt ≃ 1013 mol−1 cm3 s−1, we get: k2c′ = 1.1 k2t′ = 1012.0 exp[(−9.25 ± 2)/RT] mol−1 cm3 s−1 and k2 + 1.5 k2′ ≃ 1012.1 exp[(−15.2 ± 2)/RT] mol−1 cm3 s−1. Isotopic effects relating to processes (2c′) + (2t′) and to (i′) have been evaluated.
Kinetics of interaction of vibrationally excited OH(X2πi)v=9 with simple hydrocarbons at room temperature
Authors: Finlayson‐Pitts B. J. , Toohey D. W. , Ezell M. J. 
Published: January 2005

AbstractRelative rate constants for the removal of vibrationally excited OH in the ninth vibrational level of its ground electronic state [designated hereafter by OH† (9)] by interaction with a series of simple hydrocarbons at room temperature are reported. The reaction of hydrogen atoms with ozone was used to generate OH†(9) in a fast flow discharge system at 1.1 ± 0.1 torr total pressure. The decrease in the (9 → 3 band) Meinel band chemiluminescent emission intensity at 626 nm was followed as a function of the concentration of added organic or of a reference deactivator (O2), respectively, at a fixed reaction time; these data gave relative rate constants, k/k, for the removal of OH†(9) by the organic. The relative rate constants determined in this study are as follows: C2H6, 2.7 ± 0.2; C3H8, 4.4 ± 0.4; n–C4H10, 7.5 ± 0.6; iso–C4H10, 7.3 ± 0.8; n–C5H12, 10.4 ± 0.7; C2H4, 22.9 ± 1.8; C3H6, 43.4 ± 1.4; cis–2–C4H8, 47.7 ± 3.1; C6H6, 29 ± 7. (Errors are two standard deviations of the weighted mean of experiments in two flow tubes with different wall coatings and carrier gases.) The implications of the trends in these rate constants for the relative contributions of energy transfer and reaction to the net removal of OH† (9) are discussed.
The pyrolysis of dimethyl sulfide, kinetics and mechanism
Authors: Shum Lilian G. S. , Benson Sidney W. 
Published: January 2005

AbstractThe kinetics of the gas phase pyrolysis of dimethyl sulfide (DMS) was studied in a static system at 681–723 K by monitoring total pressure‐time behavior. Analysis showed the pressure increase to follow DMS loss. The reaction follows two concurrent paths:
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with a slow, minor, secondary reaction:
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In a seasoned reactor the reaction follows a 3/2 order rate law with rate coefficient given by

with θ = 2.303 RT in kcal/mol. A free radical mechanism is proposed to account for the data and a theoretical rate coefficient is derived from independent data:

which agrees well with the experimental one over the range studied. The reaction is initiated by Me2S → Me + MeS⋅ and propagated by metathetical radical attack on Me2S. C2H4 is formed by an isomerization reaction which may in part be due to a hot radical:
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Thermochemical data are listed, many from estimations, for both molecular and radical species of interest in the present system.
Kinetics of oxidation of some α‐amino acids L(−) arginine, L(−) histidine, L(+) ornithine, L(−) tryptophan, L(−) threonine by sodium N‐chloro‐4 methyl benzene sulphonamide (chloramine‐T) in alkaline medium
Authors: Gupta K. C. , Gupta Kumkum 
Published: January 2005

AbstractKinetic studies of oxidation of L(−) arginine, L(+) ornithine, L(−) histidine, L(−) tryptophan, L(−) threonine have been carried out in alkaline medium. The reaction showed an inverse fractional order in OH− and first‐order dependence on both amino acid and chloroamine‐T concentration. The effect of varying ionic strength (KCl) on the rate of oxidation is negligible. A general mechanism for the oxidation has been suggested by considering interaction between anionic species of amino acid and p‐toluene‐sulphochloramide. The effect of solvent and temperature have been also discussed. The fractional order obtained in OH− is due to the fact that a fraction of overall reaction proceeds via an alternative OH− independent path. The combined rate law in accordance to observed kinetics is derived as

The rate constants predicted by the derived rate law as the concentration of OH− ions change, are in excellent agreement with the observed rate constants, thus further justifying these rate laws and hence the proposed mechanistic schemes.
Kinetic study for the reactions of OH radicals with dimethylsulfide, diethylsulfide, tetrahydrothiophene, and thiophene
Authors: Martin D. , Jourdain J. L. , LeBras G. 
Published: January 2005

AbstractThe reactions of OH radicals with dimethylsulfide (DMS) diethylsulfide (DES), tetrahydrothiophene (THT), and thiophene have been studied at room temperature for DES and THT, at 273, 293, and 318 K for DMS, and at 293 and 318 K for thiophene by the discharge flow EPR technique in a halocarbon wax coated reactor. The following rate constants were obtained at room temperature.
equation image
For the reaction OH + DMS (1), a very low temperature dependence was noticed.Some additional results concerning the mass spectrometric analysis of the products are also reported.
Kinetic study of the reaction of OH with HCl from 240–1055 K
Authors: Ravishankara A. R. , Wine P. H. , Wells J. R. , Thompson R. L. 
Published: January 2005

AbstractAbsolute rate coefficients for the reaction of OH with HCl (k1) have been measured as a function of temperature over the range 240–1055 K. OH was produced by flash photolysis of H2O at λ > 165 nm, 266 nm laser photolysis of O3/H2O mixtures, or 266 nm laser photolysis of H2O2. OH was monitored by time‐resolved resonance fluorescenceor pulsed laser–induced fluorescence. In many experiments the HCl concentration was measured in situ in the slow flow reactor by UV photometry. Over the temperature range 240–363 K the following Arrhenius expression is an adequate representation of the data: k1 = (2.4 ± 0.2) × 10−12 exp[−(327 ± 28)/T]cm3 molecule−1 s−1. Over the wider temperature range 240–1055 K, the temperature dependence of k1 deviates from the Arrhenius form, but is adequately described by the expression k1 = 4.5 × 10−17 T1.65 exp(112/T) cm3 molecule−1 s−1. The error in a calculated rate coefficient at any temperature is 20%.
The accuracy of equation approximating the integral of the Arrhenius equation to perform the kinetic analysis of solid state reactions
Authors: Criado J. M. , Ortega A. 
Published: January 2005

AbstractThe accuracies of the approximation of the temperature integral of the Arrhenius law proposed by Coats and Redfern(CR), Doyle(D), Gyulai and Greenhow(GG), and MacCallum and Tanner(McT) have been tested. It has been demonstrated that these methods (only with the exception of the MacCallum and Tanner procedure) generally lead to accurate enough values of the activation energy of solid state reactions.The accuracy of these methods increases in the sequence: CC > D ≃ GG ≫ McT.
Hydrogen abstraction by hydrocarbon radicals. I. Interactions between 1‐phenyl ethyl radicals and 1‐phenyl ethanol as well as benzyl alcohol
Authors: Gedra Á. , Lukács J. , Vidóczy T. , Sümegi L. , Gál D. 
Published: January 2005

AbstractHydrogen abstraction by 1‐phenylethyl radicals (ṘH) from phenylmethyl‐carbinol (HROH) and benzyl alcohol (H2R′OH) has been studied in the liquid phase at 120°C. 1‐Phenylethyl radicals have been generated by thermal decomposition of azo‐bis‐1‐phenyl ethane and the formation of ethylbenzene (RH2), acetophenone (RO), and 2,3‐di‐phenyl butane (R2H2) has been monitored during the reaction.In order to optimize the experimental conditions, a mechanism has been assumed for the various pathways of the disappearance of ṘH and by using estimated rate parameters a presimulation was performed.The relative rate constants obtained are:

and

where kH refers to the hydrogen abstraction while kt is the combination rate coefficient of the radicals ṘH.
Gas phase reaction of heptafluoroisopropyl radicals with carbon tetrachloride
Authors: de Vöhringer Cecilia M. , Staricco Eduardo H. 
Published: January 2005

AbstractThe reaction
magnified image
was investigated in the gas phase over the range 80–225°C using the photolysis of heptafluoroisopropyl iodide as the source of radicals. The rate constant, based on the value of 1013.36 cm3 mol−1 s−1 for the recombination of i‐C3F7 radicals, is given by

where θ = 2.303 RT/cal mol−1. Arrhenius parameters for chlorine abstraction from CCl4 by CF3, C2F5, n‐C3F7, and some hydrogenated radicals are compared.
Kinetics and mechanism of oxidation of aliphatic aldehydes by peroxomonosulphate
Authors: Renganathan Rajalingam , Maruthamuthu Pichai 
Published: January 2005

AbstractThe kinetics of the oxidation of aliphatic aldehydes, formaldehyde, acetaldehyde, propionaldehyde, n‐butyraldehyde, and trichloroacetaldehyde by Peroxomonosulphate (PMS) was carried out in aqueous perchloric acid medium (0.1–1 M H+) at constant ionic strength of 1.2 M in the temperature range 10°–60°C. The reactions of all the aldehydes were found to obey a total second‐order kinetics, first order each with respect to [Peroxomonosulphate] and [aldehyde]. Acetaldehyde, propionaldehyde, and n‐butyraldehyde exhibited acid catalysis with the concurrent occurrence of acid‐independent reaction path conforming to the rate law

Formaldehyde was found to undergo oxidation only by acid‐dependent path (kb = 0) and trichloroacetaldehyde exhibited only the acid‐independent reaction path (ka = 0). The products of oxidation were found to be the respective carboxylic acids in each case. The stoichiometry of the reaction, [Peroxomonosulphate]:[Aldehyde] = 1:1, indicated the absence of carbonyl‐assisted decomposition and self‐decomposition of peroxomonosulphate. The kinetic and thermodynamic parameters evaluated pointed to the mechanism of a fast nucleophilic attack of the oxidant on the aldehyde followed by slow acid catalyzed and/or uncatalyzed decomposition of the intermediate to product. A sharp comparison is made with the corresponding reactions of the similar peroxides, S2O and H2PO.
Opacity analysis of the H3 system: Modified rotating‐rod versus Frozen‐Orientation models
Authors: Agmon Noam 
Published: January 2005

AbstractThe Rotating‐Rod Model is modified to make the adjustable α parameter which appears in the treatment energy dependent. Its predictions for opacity and excitation functions compare well with quasi‐classical H3 trajectory results, for translational and vibrationalenergy variations and isotopic mass effects. The Frozen‐Orientation Model in its present form is incapable of such an agreement for mass combinations other than H + D2. It is suggested that the decreaseof α with energy can be interpreted as a transition from adiabatic tosudden behavior, where alignment is only on the average, and much energy isdeposited in the bending modes. This is supported by a correlation between α and the average final rotation.
Isotope effect on the location of variational transition states: The hydrogen exchange reaction
Authors: Morcillo Luis Bañares , Ureña Angel Gonzalez , Menzinger Michael 
Published: January 2005

AbstractThe microcanonical variational transition states of the isotopic reactions H + T2 and T + H2 are shown to migrate with increasing energy in opposite directions away from the classical barrier, i.e., into the reactant and product valleys, respectively. The energy dependence of this isotopic shift is examined and excitation functions are reported, both for collinear and near‐collinear reactions.
A comparative study of the PK(II) and LSTH potential energy surfaces for the H3 system
Authors: Pollak Eli 
Published: January 2005

AbstractRecent dynamical computations on the LSTH and PK(II) potential energy surfaces are analyzed in terms of different properties of the surfaces. Differences in the bend level structure of resonances are found tobe due to the weaker vibrational force constant at the saddle point of the LSTH surface. The importance of including van der Waals wells in the potential energy surface is demonstrated by analysis of quantal resonances in thecollinear Mu + D2 reaction.
Rate constants for one‐electron oxidation by methylperoxyl radicals in aqueous solutions
Authors: HUIE Robert E. , NETA P. 
Published: January 2005

AbstractRate constants for one‐electron oxidation by the methylperoxyl radicals (CH3O2, HOCH2O2, −O2CCH2O2, and CCI3O2) in aqueous solutions have been measured by pulse radiolysis and found to be in the range of 3 × 105 to 6 × 108 M−1 s−1 for compounds with redox potentials between 0.6 and 0.1 V. Substitution on the methylperoxyl radical with OH or CO2− has only a minor effect on the rate of oxidation but substitution with three chlorines increases the rate constants by two orders of magnitude. The redox potential of the CH3O2 radical is estimated to be 0.6–0.7 V.