bluuebunny/crossref_metadata_2025_split huggingface dataset:
The heat of formation of the acetonyl radical VLPP studies of acetonyl bromide, isopropenylmethylether, and hexanedione‐2,5 in a search for acetonyl stabilization energy
Authors: Zabel F. , Benson S. W. , Golden D. M. 
Published: January 2005

AbstractThe decomposition of acetonyl bromide, isopropenylmethylether, and hexanedione‐2,5 was studied using the very‐low‐pressure pyrolysis (VLPP) technique. The acetonyl radical is a product of each reaction. Arrhenius parameters determined are or acetonyl bromide ← acetonyl + Br:

and for isopropenylmethylether ← acetonyl + CH3:

These lead to values of acetonyl stabilization energy (SE) of 0.8 and −4.0 kcal/mol, respectively. Comparison of the pyrolyses of hexanedione‐2,5 and 2,5‐dimethylhexane indicate a value of SE ∼ 2 kcal/mol. The total of these results is taken, along with previous work, to indicate that 0 ≲ SE ≲ 2 kcal/mol.
Activation parameters and kinetic isotope effect in the system tropaeolin O‐OH−
Authors: Perlmutter‐Hayman Berta , Shinar Ruth 
Published: January 2005

AbstractThe kinetics of the deprotonation of tropaeolin O by OH− ions was investigated between 9° and 30°C, and by OD− ions at 24.7°C. The pH range was 10.7–12.5, and the ionic strength 0.1M throughout. All results were obtained by the temperature jump method. On the basis of a mechanism suggested earlier, rate constants k31 for the reaction between OL− and the internally bonded weak acid and k32 for the opening of the internal hydrogen bond were evaluated. The activation energies in ordinary water were found to be ΔH≠31 = 3.6 kcal/mol, ΔS≠31 = –19 eu, and ΔH≠32 = 27 kcal/mol, ΔS≠32 = 46 eu. The kinetic isotope effect was k31/k31 ∼ 1.5 and k32/k32 ∼ 0.9. The unusual results for reaction path
equation image
are discussed in terms of solvent participation.
Kinetics of the thermal decomposition of trans‐1,2‐dicyanocyclobutane
Authors: King Keith D. , Goddard Richard D. 
Published: January 2005

AbstractThe kinetics of the thermal decomposition of trans‐1,2‐dicyanocyclobutane, which yields only vinyl cyanide, have been studied in the temperature range of 570°‐660°K using a stirred‐flow reactor. The reaction was found to be first order and homogeneous with rate constants represented by the Arrhenius equation

where θ = 2.303 RT kcal/mol. The Arrhenius parameters are considerably higher than previously reported. On the assumption of a biradical mechanism the results are consistent with a cyano stabilization energy of ∼5 kcal/mol, in good agreement with the results of recent studies of related systems.
The thermal reaction of 2‐pentene around 500°C at low extent of reaction
Authors: Perrin D. , Richard C. , Martin R. 
Published: January 2005

AbstractThe thermal reaction of 2‐pentene (cis or trans) has been performed in a static system over the temperature range of 470°–535°C at low extent of reaction and for initial pressures of 20–100 torr. The main products of decomposition are methane and 1,3‐butadiene. Other minor primary products have been monitored: trans‐2‐pentene, trans‐ and cis‐2‐butenes, ethane, 1,3‐pentadienes, 3‐methyl‐1‐butene, propylene, 1‐butene, hydrogen, ethylene, and 1‐pentene. The initial orders of formation, 0.8–1.1 for most of the products and 1.5–1.8 for 1‐pentene, increase with temperature. The formation of the products and the influence of temperature on their orders can be essentially explained by a free radical chain mechanism. But cis–trans or trans–cis isomerization and hydrogen elimination from cis‐2‐pentene certainly involve both molecular and free radical processes. The formation of 1‐pentene mainly occurs from the abstraction of the hydrogen atom of 2‐pentene by resonance stabilized free radicals (C5H9.).
Very low‐pressure pyrolysis (VLPP) of but‐1‐yne the heat of formation and stabilization energy of the propargyl radical
Authors: King Keith D. 
Published: January 2005

AbstractThe unimolecular decomposition of but‐1‐yne has been investigated over the temperature range of 1052° – 1152°K using the technique of very low‐pressure pyrolysis (VLPP). The primary process is CC bond fission yielding methyl and propargyl radicals. Application of RRKM theory shows that the experimental rate constants are consistent with the highpressure Arrhenius parameters given by

where θ = 2.303 RT kcal/mol. The parameters are in good agreement with estimates based on shock‐tube studies. The activation energy, combined with thermochemical data, leads to DH°[HCCCH2CH3] = 76.0, ΔH(HCCĊCH2,g) = 81.4, and DH° [HCCCH2H] = 89.2, all in kcal/mol at 300°K. The stabilization energy of the propargyl radical SE° (HCCĊCH2) has been found to be 8.8 kcal/mol. Recent result for the shock‐tube pyrolysis of some alkynes have been analyzed and shown to yield values for the heat of formation and stabilization energy of the propargyl radical in excellent agreement with the present work. From a consideration of all results it is recommended that ΔH(HCCĊCH2,g) = 81.5±1.0, DH[HCCCH2H] = 89.3 ± 1.0, and SE° (HCCĊCH2) = 8.7±1.0 kcal/mol.
The mechanism of the photochemical reactions of SO2 with isobutane excited at 3130 Å
Authors: Su Fu , Calvert Jack G. 
Published: January 2005

AbstractThe mechanism of the reactions of electronically excited SO2 with isobutane has been studied through the measurement of the initial quantum yields of product formation in 3130 Å irradiated gaseous binary mixtures of SO2 and isobutane and ternary mixtures of SO2, isobutane, C6H6 or CO2. Under low‐pressure conditions (P < 10 torr) the kinetic treatment of the present data shows that only one singlet and one triplet state, presumably the 1B1 and 3B1 states, are involved in the photoreaction mechanism. The data give k2a = 8.4 × 109; SO2(1B1) + isobutane → products (2a); k5a ≃ k5 = 8.7 × 108 l./mol·sec; SO2(3B1) + isobutane → products (5a) SO2(3B1) + isobutane → (SO2) + isobutane (5b) k1a/k1 = 0.145 ± 0.037; SO2(1B1) + SO2 → SO2(3B1) + SO2 (1a) SO2(1B1) + SO2 → (2SO2) (1b) k2b/k2 = 0.273 ± 0.018; SO2(1B1) + isobutane → SO2(3B1) + isobutane (2b); SO2(1B1) + isobutane → (SO2) + isobutane (2c) error limits are ± 2 σ. The contribution from the excited SO2(1B1) molecules to the quantum yields of the photolyses of SO2–isobutane mixtures is not negligible. Under high‐pressure conditions (P > 10 torr) the low‐pressure mechanism coupled with the saturation effect on the phosphorescence lifetimes of SO2(3B1) molecules cannot alone rationalize the quantum yields. The evaluation suggests that some nonradiative intermediate state (X) is involved in the formation of “extra” triplet molecules. This ill‐defined state decays largely nonradiatively to SO2 in experiments at low pressures, X → SO2 (12). In the presence of C6H6 the low‐pressure data give k7 = (8.5 ± 1.8) × 1010, and the high‐pressure data give k7 = (8.3 ± 0.6) × 1010 and (9.9 ± 0.9) × 1010l./mol·sec; SO2(3B1) + C6H6 → nonradiative products (7). These estimates are in good agreement with values directly measured from low‐pressure lifetime studies, (8.1 ± 0.7) × 1010 and (8.8 ± 0.8) × 1010l./mol·sec.
Thallation of fluorenes: A kinetic and mechanistic study
Authors: Narasimhan S. , Ramani P. V. , Venkatasubramanian N. 
Published: January 2005

AbstractThe kinetics of thallation of fluorene with thallium triacetate (TTA) in HOAc‐H2SO4 solutions led to the rate expression

The rate of thallation is found to increase with increasing acid concentration, and a sixth‐order dependence on [H2SO4] is observed. Decrease in solvent polarity increases the rate of thallation. The effect of substituents is in accord with the electrophilic substitution at an aromatic system. Thallation occurs at 4‐position. A mechanism similar to aromatic bromination is proposed for the thallation of fluorene.
The recombination of iodine atoms in the presence of nitric oxide
Authors: Basco N. , Hunt J. E. 
Published: January 2005

AbstractThe recombination of iodine atoms following the flash photolysis of iodine in the presence of nitric oxide is interpreted through the mechanism
equation image
with k1 = 3.5 × 109 l.2/mol2·sec; k2 ≈ 1 × 1011 l./mol·sec; k3 = 2.1 × 107 l./mol·sec at 298°K; E3 = 11 kJ/ mol; and ΔH°1 = 76 ± 6 kJ/mol. Lower and upper limits for the equilibrium constant are also established. The absorption spectrum of INO has been extended down to 223 nm and extinction coefficients for the region of 223–310 nm and 360–460 nm have been measured.
Chemical lasers produced from O(3P) atom reactions. V. CO laser emissions and vibrational population distribution in the flash‐initiated SO2‐CFBr3 system
Authors: Hsu David S. Y. , Lin M. C. 
Published: January 2005

AbstractCO laser emission at 5 μm was detected when SO2 and CFBr3 were flash photolyzed in the vacuum ultraviolet above 165 nm. Over 40 vibrational–rotational transitions ranging from Δv = 2 → 1 to 14 → 13, with the exception of those between 8 → 7 and 11 → 10, were identified. The CO emission is believed to result from the O + CF reaction:
equation image
The vibrational population of the CO has been measured by means of a CO laser resonance absorption method. The CO was found to be vibrationally excited to v = 24 with a vibrational temperature of about 1.4 × 104°K. The “surprisal analysis” of the observed CO distribution showed the possible occurrence of a minor process (presumably O + CFBr) that generated vibrationally colder CO. The effects of various additives on the CO emission were also examined. The addition of CO2 to a D2‐SO2‐CFBr3‐He mixture resulted in a simultaneous osciallation at 3.6, 5, and 10.6 μm due to DF, CO, and CO2, respectively. Additionally, the utilization of the O + CFn (n = 1, 2, 3) reactions as F‐atom sources for HF‐laser operation in flash‐initiated systems were demonstrated.
The mechanism of methanol formation and other reactions following formaldehyde adsorption on Ni(110)
Authors: Dickinson J. Thomas , Madix Robert J. 
Published: January 2005

AbstractThe adsorption/desorption and reactive behavior of formaldehyde was studied on clean single‐crystal Ni(110) at adsorption temperatures down to 200 °K. For low exposures of the surface to formaldehyde, hydrogen and CO binding states were populated due to decomposition of the molecule upon adsorption. Higher exposures gave rise to a decomposition‐limited hydrogen peak exhibiting an activation energy of 20 kcal/gmol and an apparent frequency factor of 1014 sec−1. At initial coverages of H2CO exceeding about 0.5, monolayer methanol was observed to form. The formation of methanol involved a hydrogen atom transfer between two adsorbed H2CO molecules and did not occur totally via surface hydrogen. Self‐oxidation to form CO2 was also observed. The surface exhibited reaction heterogeneity, and the surface reactivity was observed to depend on the temperature of adsorption of reactants, suggesting strong adsorbate‐induced surface “reconstruction.”
Permanganate ion oxidations X. Kinetics and mechanisms of the initial stage in the oxidation of 4‐hydroxy‐2‐pyrimidinethiols
Authors: Freeman Fillmore , Bond Dorrece Lynn , Chernow Steven Martin , Davidson Pamela Ann , Karchefski Elaine Marie 
Published: January 2005

AbstractPermanganate ion rapidly oxidizes the thiol group in 2‐thiouracils (2,3‐dihydro‐2‐thioxo‐4(1H)‐pyrimidinones, 4‐hydroxy‐2‐pyrimidinethiols) to the corresponding uracil‐2‐sulfonates in phosphate‐buffered solutions. The oxidations, which are first order in oxidant and first order in reductants, are characterized by relatively small energies of activation (Ea ≅ 4.3–6.7kcal/mol) and relatively large negative entropies of activation (ΔS‡ = −24.9–−34.4 eu). The relative rates of oxidation of 2‐thiouracil (2), 6‐methyl‐ (4), 6‐n‐propyl‐ (6), 1,6‐dimethyl‐(8), and 3,6‐dimethyl‐2‐thiouracil (9) are 1.00:1.23:0.98:7.32:2.54. The rate of oxidation of 1,3,6‐trimethyl‐2‐thiouracil (12) is several orders of magnitude slower than that of the other thiouracils. Although the thiol group or thiolate anion is probably involved in the rate‐determining step, several other possible mechanisms are also considered.
The participation of aromatic neighboring groups in gas‐phase elimination reactions
Authors: Hernandez A. Jose A. , Chuchani Gabriel 
Published: January 2005

AbstractThe gas‐phase pyrolysis of 2‐chloroethylbenzene and p‐methoxy‐2‐chloroethylbenzene was studied in a static system over the temperature range of 411°–471°C and a pressure range of 39–202 mm Hg. The reactions in seasoned vessels, with the propene inhibitor always present, were homogeneous, first‐order, and unimolecular. The rate constants are given by the Arrhenius equation for 2‐chloroethylbenzene:

and for p‐methoxy‐2‐chloroethylbenzene:

The presence of phenyl substituents in the β position of ethyl chloride has been found to provide anchimeric assistance in these elimination reactions.
The gas‐phase pyrolysis of alkyl nitrites VI. t‐Amyl nitrite
Authors: Batt L. , Islam T. S. A. , Rattray G. N. 
Published: January 2005

AbstractThe rate of decomposition of tert‐amyl nitrite (t‐AmONO) has been studied in the absence (120°–155°C) and presence (160°–190°C) of nitric oxide. In the absence of nitric oxide for low concentrations of tert‐amyl nitrite (∼10−4M) and small extents of reaction (∼1%), the first‐order homogeneous rates of acetone formation are a direct measure of reaction (1) since k3a ≫ k2(NO):
equation image
The rate of acetone formation is unaffected by the addition of large amounts of carbon tetrafluoride or isobutane (∼1 atm) but is completely suppressed by large amounts of nitric oxide (1 atm 120°–155°C).The rate of reaction (1) is given by k1 = 1016.3±0.1 10−40.3±0.1/θ sec−1. Since (E1 + RT) and ΔH°1 are identical, both may be equated with D(t‐AmO – NO) = 40.9 ± 0.1 kcal/mol and E2 = 0 ± 0.1 kcal/mol. The thermochemistry leads to the result that ΔH°f (t‐AmO) = −26.6 ± 1 kcal/mol. From ΔS°1 and A1, k2 is calculated to be 1010.5±0.2 M−1·sec−1.Although the addition of nitric oxide completely suppresses acetone formation at lower temperatures, it reappears at higher temperatures. This is a result of reaction (3a) now competing with reaction (2), thus allowing k3a to be determined. The rate constant for reaction (3a) is given by k3a = 1014.7 ± 0.2 10−14.3 ± 1/θ sec−1. There are two possible routes for the decomposition of the tert‐amyloxyl radical:
equation image
The dominating process is (3a). From the result at 160°C that k3a/k3b = 80, we arrive at the result k3b = 1015.0–18.7/θ sec−1.In addition to the products accounted for by the radical split (1), methyl‐2‐but‐1‐ene and methyl‐2‐but‐2‐ene are produced as a result of the six‐centre elimination of nitrous acid (5):
equation image
The ratio k5a/k5b was 0.35. Unlike tert‐butyl where the rates of the two paths were comparable [(l) and (5)], here the total rate of the elimination process was only 0.5% that of the radical split (1). The reason for this is not clear.
Stopped‐flow studies of the mechanisms of ozone–alkene reactions in the gas phase propene and isobutene
Authors: Herron John T. , Huie Robert E. 
Published: January 2005

AbstractThe reactions of ozone with propene and isobutene have been studied in the gas phase at 298°K and 530 Pa (4 torr) using a stopped‐flow reactor coupled to a photoionization mass spectrometer. Reactant and product concentrations were followed as a function of reaction time. The major reaction products monitored were CH2O, CH3CHO, CO2, and H2O from the propene reaction, and CH2O, (CH3)2CO, CO2, and H2O from the isobutene reaction. The observations were interpreted on the basis of the Criegee mechanism for ozonolysis in solution: magnified image for which we find kA≈kB.In the gas phase the carbene peroxy radical is postulated to isomerize and decompose into molecular and free‐radical products.
The reaction of hydrogen atoms with 1‐butanethiol and thiolane the role of chemically activated 1‐butanethiol
Authors: Horie Osamu , Nishino Junya , Amano Akira 
Published: January 2005

AbstractThe reaction of 1‐butanethiol with hydrogen atoms has been studied at temperatures of 295° and 576° K under the pressure of 660 Pa, using a conventional discharge‐flow apparatus. The reaction products (besides hydrogen sulfide and methane) under the low conversion range (∼10%) consisted mainly ofn‐butane, 1‐butene, and propylene‐propane, with the relative yields of 70, 25, and 5% at 295° K and 25, 50, and 10% at 576°K. Analysis of kinetic equations by numerical integration indicates that the following initial steps are consistent with the experimental results:equation imagewhere the following expressions have been derived fork1andk2:The subsequent reaction of the butylthio radical with hydrogen atoms leads to the chemically activated 1‐butanethiol which either stabilizes to 1‐butanethiol or decomposes to 1‐butene and hydrogen sulfide, depending on the experimental conditions. A similar analysis of the data on the thiolane‐H system has yielded the following rate parameters for the initial step to form the 4‐mercapto‐1‐butyl radical:equation image.
Kinetics of the reaction O(3P) + SO2 + M → SO3 + M over the temperature range of 299°–440°K
Authors: Atkinson R. , Pitts J. N. 
Published: January 2005

AbstractRate constants for the reaction O(3P) + SO2 + M have been determined over the temperature range of 299°–440°K, using a flash photolysis–NO2 chemiluminescence technique. For MAr, the Arrhenius expression

was obtained. At room temperature k2Ar = (1.05 ± 0.21) × 10−33 cm6/molec2·sec. In addition, the rate constants k2 = (1.37 + 0.27) × 10−33 cm6/molec2·sec, k2 = (9.5 ± 3.0) ± 10−33 cm6/molec2·sec, k3 = (1.1 ± 0.2) ± 10−31 cm6/molec2·sec, and k3 = (2.6 − 0.9) ± 10−31 cm6/molec2·sec were obtained at room temperature where k3M is the rate constant for the reaction O + NO + M → NO2 + M. The rate data are compared and discussed with literature values.
Studies by the electron cyclotron resonance (ECR) technique. XII. Interactions of thermal‐energy electrons with the molecules CHF3, CHClF2, and CHCl2F
Authors: Christodoulides A. A. , Schumacher R. , Schindler R. N. 
Published: January 2005

AbstractUsing the ECR technique the electron scavenging properties of the halomethanes CHF3, CHClF2, and CHCl2F were investigated. A brief discussion is given on the evaluation of experimental data for inefficient polar scavengers. Absolute attachment rate constants were obtained from the decrease of the cyclotron resonance signal upon addition of the above scavengers. For the molecules CHF3 and CHCl2F the activation energies for the capture processes are given. Possible capture mechanisms are discussed.
Quenching of biacetyl (3Au) molecules by near‐resonant and off‐resonant collisional partners
Authors: Wampler F. B. , Oldenborg R. C. 
Published: January 2005

AbstractLaser‐induced time‐resolved phosphorescence has been used to evaluate the quenching of gaseous biacetyl (3Au) molecules by various molecules at 25°C. The quenching of biacetyl (3Au) molecules by biacetyl itself was not detectable under our experimental conditions, and a pressure‐independent lifetime of 1.70 ± 0.08 msec was found. The bimolecular rate constants (units of l/mol·sec) for quenching of the 3Au molecules by cis‐2‐pentene, trans‐2‐pentene, cis‐1,3‐pentadiene, trans‐1,3‐pentadiene, and oxygen were found to be (3.3 ± 1.9) × 103, (4.0 ± 0.2) × 104, (3.9 ± 0.1) × 108, (1.3 ± 0.1) × 108, and (5.2 ± 0.4) × 108, respectively.
The kinetics of ClO formation in the flash photolysis of chlorine–oxygen mixtures
Authors: Ashford R. D. , Basco N. , Hunt J. E. 
Published: January 2005

AbstractThe production of ClOO and ClO radicals following the flash photolysis of chlorine + oxygen mixtures has been studied. For the mechanism
equation image
the following kinetic parameters were measured: k3K = 1.3 × 1010 l2/mol2·sec; k2/k3 = 17; and k3/ϵ(ClOO; 250 nm) = 9.7 × 105 cm/sec. Then k3 = 5.9 × 109 l/mol·sec, k2 = 1.0 × 1011 l/mol·sec, and ϵ(ClOO; 250 nm) = 6.1 × 103 l/mol·cm. From limits established for the equilibrium constant K, ΔH°f (ClOO) = 94 ± 2 kJ/mol.
Thermal decomposition of ethane
Authors: Olson D. B. , Tanzawa T. , Gardiner W. C. 
Published: January 2005

AbstractThe decomposition of C2H6in Ar was studied by laser‐absorption and laser‐schlieren measurements of the reaction rate behind incident shock waves with 1300 <T< 2500°K and 1.1 < ρ < 4.4 × 10−6mol/cm3. The experimental profiles were parameterized by suitable measures of reaction progress. Computer simulations using a 14‐reaction mechanism were used to compare assumptions about rate constant expressions with the experimental parameters and to investigate the sensitivity of computed parameters to these assumptions. A rate constant expressionk(cm3/mol˙sec) = 2 × 10111T−25.26exp(−80 320/T) was found for the primary dissociation step C2H6+ M  CH3+ CH3+ M under the conditions studied; no difference in rate was discernable between M  Ar and M  C2H6. Rate constant expressions found to be suitable for the remaining reactions of the mechanism, to some of which the computed parameters were sensitive, were in accord with previous proposals. Our results and results from earlier investigations of the primary decomposition reaction, in both forward and reverse directions, were extrapolated, using RRK methods, to obtain low‐pressure limiting rate constants and found to be concordant.
Competitive chlorination–dehydrochlorination of 1,1,1,2‐C2H2Cl4
Authors: Olbregts J. 
Published: January 2005

AbstractThe competitive photochlorination and chlorine photosensitized dehydrochlorination of 1,1,1,2‐C2H2Cl4 have been studied over the temperature range of 349.4–404.5 K after less than 1% conversion. The results are discussed and a value of

is proposed for the reaction

This result, combined with existing thermochemical data, indicates that there is no evidence of an activation energy for the addition of a Cl atom on the most chlorinated carbon in trichloroethylene: in that case the selectivity of the addition of Cl on the less chlorinated carbon should not depend on temperature.
Kinetics and mechanism for the iodination of methylmalonic acid
Authors: Furrow Stanley D. 
Published: January 2005

AbstractThe reaction\documentclass{article}\pagestyle{empty}\begin{document}$ CH\left({CH_3 } \right)\left({COOH} \right)_2 + I_2 \rightleftharpoons CI(CH_3)\left({COOH} \right)_2 + H^ + + I^ - $\end{document} was followed spectrophotometrically at 353 nm and 470 nm at 25°C under various conditions of pH and methylmalonic acid concentration. The equilibrium constant for the reaction is 0.11 ± 0.02. An iterative technique was used to integrate postulated rate equations. Agreement between experimental and calculated absorbance versus time curves was generally better than 0.005 A (approximately 5% of maximum) at both wavelengths for a mechanism where the rate‐determining step is formation of an enolate (k = 1.63 Θ 10−4 ± 0.03 Θ 10−4 sec−1). The enolate may be rapidly transformed to the enol or enol carboxylate anion depending on the pH. All three forms are rapidly iodinated. The mechanism of general base catalysis is supported by rate increases proportional to base concentration in buffer solutions. The bases, acetate ion, chloracetate ion, sulfate ion, dichloracetate ion, and water, follow a Brønsted relationship with β = 0.7.
The very‐low‐pressure study of the kinetics and equilibrium: Cl + CH4 ⇄ CH3 + HCl at 298 K. The heat of formation of the CH3 radical
Authors: Baghal‐Vayjooee Mohammad H. , Colussi Agustin J. , Benson Sidney W. 
Published: January 2005

AbstractThe bimolecular rate constant for the direct reaction of chlorine atoms with methane was measured at 25°C by using the very‐low‐pressure‐pyrolysis technique. The rate constant was found to be

In addition, the ratio k1/k−1 was observed with about 25% accuracy: K1(298) = 1.3 ± 0.3. This gives a heat of formation of the methyl radical ΔH° f 298(CH3) = 35.1 ± 0.15 kcal/mol. A bond dissociation energy BDE (CH3  H) = 105.1 ± 0.15 kcal/mol in good agreement with literature values was obtained.