bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoactivated α‐ketocarbenes: Formation and isomerization reactions. RRKM calculations with semi‐empirical parameters (AM1, MNDOC)
Authors: Bachmann Christian , N'Guessan Thomas Yao 
Published: January 2005

AbstractThe dynamical aspects of some α‐diazoketones (DZ) photolysis are investigated within the framework of statistical theories (RRKM formulation). On the whole, the results agree satisfactorily with the gas‐phase experimental observations (quantum yields). In particular, the reactions DZ + hv → α‐ketocarbene (KC) + N2, appear to be mainly governed by statistical behavior. The two channel isomerizations KC → ketene (KE), i.e, the Wolff Rearrangement, and KC → α,β‐unsaturated ketone (ON) are also considered. It is suggested that the trapping of the α‐ketocarbenes and oxirenes (OX) species would be favored under appropriate conditions (among them the irradiation wavelength and the relaxation processes involved in the reactive medium). The parametrization of the model relies on semi‐empirical quantum calculations and is improved by some adjustments with experimental data. © 1994 John Wiley & Sons, Inc.
The IR multiphoton decomposition of CF3I. The effect of inert and reactive gases
Authors: Rinaldi Carlos A. , Lane Silvia I. , Ferrero Juan C. 
Published: January 2005

AbstractThe multiphoton decomposition of CF3I with a pulsed CO2 laser has been studied at incident fluences of 0.6 and 1.2 J/cm2. The effect of pressure on the reaction probability for dissociation of CF3I was measured in the presence of added isobutane, Ar and CO2. In the experiments with isobutane, the CF3 radicals generated by the decomposition of excited CF3I react to yield CF3H in competition with the recombination to C2F6. The laser absorption cross section was also measured as a function of fluence at a pressure of 0.1 torr of CF3I and with 0.5–2.0 torr of added isobutane. The experimental results were modeled with a master equation in order to obtain information on the energy transferred by collisions of excited CF3I with the bath molecules. An energy dependent value of 〈ΔE〉d produces the best fit to the experimental data. Integration of the rate equations to account for the fractional product yield, [CF3I]/[C2F6], allowed for the calculation of the specific rate constant for hydrogen abstraction from isobutane by CF3 radicals. The value obtained is dependent on the total pressure and higher than expected at room temperature. From these results, an effective temperature for the reaction mixture was calculated. © 1994 John Wiley & Sons, Inc.
Pulsed laser powered homogeneous pyrolysis: A computational analysis
Authors: Swihart Mark T. , Carr Robert W. 
Published: January 2005

AbstractThe use of the pulsed laser powered homogeneous pyrolysis technique for measuring unimolecular decomposition rate constants under unambiguously homogeneous conditions is investigated by numerical simulation of the experiment. The coupled partial differential equations which govern the gas dynamics and chemical kinetics are solved numerically and the results analyzed. Conditions under which rate constants can be extracted from the experimental data using a simplified analysis are determined. The effects of five sources of error in the simplified analysis are computed. A correlation is presented which may be used to correct for overestimation of the rate constant which is inherent in the simple analysis. Conditions under which the other four sources of error become negligible are presented. Overall, it is expected that this technique will be capable of routinely measuring rate constants within a factor of 2, and will do much better when a high power laser with a uniform beam profile is used and/or a well characterized thermal monitor molecule is available which decomposes with kinetic parameters close to that of the reactant being investigated. © 1994 John Wiley & Sons, Inc.
Kinetics of the DS‐radical reactions with CINO and NO2
Authors: Fenter Frederick F. , Anderson James G. 
Published: January 2005

AbstractThe rate constants for the reactions of the DS radical with NO2 (reaction 1) and ClNO (reaction 2) have been measured using the discharge‐flow technique at 2 torr total pressure of helium. The DS radical was monitored by laser‐induced fluorescence. The reactions were found to have the following bimolecular rate constants (95% confidence level, in units of cm3 molecule−1 s−1):

This expression for k1 is found to be in excellent agreement with one of several previous studies. The magnitude of k2 is examined within the framework of a well‐established reactivity trend. © 1994 John Wiley & Sons, Inc.
Kinetics of oxidation of heterocyclic secondary alcohols by N‐chloro‐r‐2,c‐6‐diphenyl‐t‐3 methyl piperidin‐4‐one (NCP) in perchloric acid medium
Authors: Selvaraj Kuppusamy , Venkateswaran Vinayagam , Ramarajan Krishnasamy 
Published: January 2005

AbstractAn investigation of the kinetics of oxidation of epimeric piperidin‐4‐ols, oxan‐4‐ols, and cyclohexanol by N‐chloro‐r‐2, c‐6‐diphenyl‐t‐3‐methylpiperidin‐4‐one (NCP) in aqueous acetic acid in the presence of perchloric acid shows that the reaction is first‐order each in substrate and oxidant. Both H3O+ and Cl− which catalyze the reaction, exhibit a fractional order kinetics. While increase in ionic strength increases the rate slightly, an inverse dependence is observed between rate and solvent polarity. Addition of r‐2‐c‐6‐diphenyl‐t‐3‐methylpiperidin‐4‐one, one of the reaction products, did not influence the rate. Also, no kinetic isotope effect has been observed. A plausible mechanism consistent with these observations is proposed and the relative reactivities of the substrates are explained on conformational grounds. © 1994 John Wiley & Sons, Inc.
Products of the gas‐phase reactions of aromatic hydrocarbons: Effect of NO2 concentration
Authors: Atkinson Roger , Aschmann Sara M. 
Published: January 2005

AbstractThe formation yields of selected products of the OH radical‐initiated reactions of toluene, o‐xylene, and 1,2,3,‐trimethylbenzene have been measured in the absence of NOx and in the presence of varying concentrations of NO and NO2. The formation yield of o‐cresol from toluene increased from 0.123 ± 0.022 in the absence of NOx to 0.160 ± 0.008 for an average NO2 concentration of 1.7 × 1014 molecule cm3. The formation yield of 2,3‐butanedione from o‐xylene was 0.092 ± 0.013 in the absence of NOx, and in the presence of NOx decreased from 0.16 at an average NO2 concentration of (7–8) × 1012 molecule cm−3 to 0.09 at an average NO2 concentration of ca. 7 × 1013 molecule cm−3. The formation yield of 2,3‐butanedione from 1,2,3‐trimethylbenzene increased from 0.18 in the absence of NOx to 0.444 ± 0.053 in the presence of ca. (0.16–3.6) × 1013 molecule cm−3 of NO2. These product data are consistent with literature kinetic data showing that the hydroxycyclohexadienyl radicals formed by OH radical addition to the aromatic ring react with both O2 and NO2 and with the NO2 reaction rate constants being ca. 105 higher than the O2 reaction rate constants at room temperature. Under typical tropospheric conditions the reactions of the hydroxycyclohexadienyl radicals with O2 will dominate over their reactions with NO2. © 1994 John Wiley & Sons, Inc.
Formation yields of epoxides and O(3P) atoms from the gas‐phase reactions of O3 with a series of alkenes
Authors: Atkinson Roger , Aschmann Sara M. , Arey Janet , Tuazon Ernesto C. 
Published: January 2005

AbstractReactions of ozone with propene, 1‐butene, cis‐2‐butene, trans‐2‐butene, 2,3‐dimethyl‐2‐butene, and 1,3‐butadiene were carried out in N2 and air diluent at atmospheric pressure and room temperature and, by monitoring the formation of the epoxides and/or a carbonyl compound formed from the reactions of O(3P) atoms with these alkenes, the formation yields of O(3P) atoms from the O3 reactions were investigated. No evidence for O(3P) atom formation was obtained, and upper limits to O(3P) atom formation yields of <4% for propene, <5% for 1.3‐butadiene, and <2% for the other four alkenes were derived. The reaction of O3 with 1,3‐butadiene led to the direct formation of 3,4‐epoxy‐1‐butene in (2.3 ± 0.4)% yield. These data are in agreement with the majority of the literature data and show that O(3P) atom formation is not a significant pathway in O3—alkene reactions, and that epoxide formation only occurs to any significant extent from conjugated dienes. © 1994 John Wiley & Sons, Inc.
Kinetics and mechanism of H2O2 decomposition by Cu(II)‐, Co(II)‐, and Fe(III)‐Amine complexes on the surface of Silica‐Alumina (25% Al2O3)
Authors: Salem Mohamed A. , Salem Ibrahim A. , Gemeay Ali H. 
Published: January 2005

AbstractThe kinetics of the H2O2 decomposition by Cu(II)‐, Co(II)‐, and Fe(III)‐amine complexes supported on the surface of silica‐alumina (25% Al2O3) catalyst have been investigated. The decomposition process proceeded with first‐order kinetics for the substrate concentration. With copper complexes, in particular, the rate of reaction decreased in the sequence: ethylenediamine (en) > monoethanolamine (mea) > triethanolamine (tea). With ethylenediamine as aligand, the rate has also decreased in the order: Cu(II) > Co(II) > Fe(III). Both of the energy and entropy of activation were found to decrease as: en > mea > tea and for one ligand (en) and different metal ions the sequence was Cu(II) > Co(II) > Fe(III). The decomposition reaction involved the formation of an intermediate active species, which converts into a peroxo‐metal‐complex of brown or faint red color. The rate of reaction was directly proportional to the [complex], [H2O2], and [H]−1. A mechanism describing the decomposition process is proposed. © 1994 John Wiley & Sons, Inc.
The oscillating reaction of Hydrogen Peroxide and Iodate with Butanone as substrate
Authors: Love Ian 
Published: January 2005

AbstractThe system iodate‐peroxide‐manganese(II)‐butanone is a member of the Briggs–Rauscher set of oscillators. The stoichiometry and variation of the oscillation period with concentration for each component is studied under batch conditions. The system is simulated using the skeleton mechanism of earlier workers and reproduces the observed variation in oscillation period. Examination of the roles of the reaction steps shows that there are significant differences from those found using malonic acid. Iodine is stored during the low iodide regime and utilized during the high iodide regime, and different overall reactions occur during the two regimes. © 1994 John Wiley & Sons, Inc.
Kinetics of solvolysis of trans‐dichlorotetra (t‐butylpyridine)‐cobalt(III) ions in mixtures of water with ethane‐1,2‐diol and with 2‐methoxyethanol. A contrast with the effect of hydrophobic co‐solvents
Authors: Halawani Kamal H. , Wells Cecil F. 
Published: January 2005

AbstractThe kinetics of the solvolysis of the hydrophobic ion, Co(4‐t‐Bupy)4Cl2+, have been followed in mixtures of water with co‐solvents having a hydrophilic tendency, ethane‐1,2‐diol and 2‐methoxyethanol. The variation of In(rate constant) with the reciprocal of the dielectric constant is nonlinear for both co‐solvents. The enthalpy and the entropy of activation are rather insensitive to changes in the solvent composition in both mixtures, but low maxima may exist at mol fractions of co‐solvent Ca. 0.10–0.20. The application of a Gibbs energy cycle to the process of the initial state going to the transition state suggest that, in water‐rich conditions, the increase in the stability of the emergent solvated CoIII ion in the transition state relative to the increase in the stability of Co(4‐t‐Bupy)4Cl2+ in the initial state as the co‐solvent content rises is greater for 2‐methoxyethanol than for ethane‐1,2‐diol. © 1995 John Wiley & Sons, Inc.
Kinetics and mechanism of the aminolysis of O‐ethyl S‐phenyl dithiocarbonate in aqueous ethanol
Authors: Castro Enrique A. , Cabrera Mauricio , Santos Jose G. 
Published: January 2005

AbstractThe reactions of secondary alicyclic amines with the title substrate (PDTC) are subjected to a kinetic study in 44 wt.% aqueous ethanol, 25.0°C, ionic strength 0.2 M (KCl). Pseudo‐first‐order rate coefficients (kobs) are found under amine excess. Linear plots of [N]/kobs against 1/[N], where N is the free amine, are obtained for the reactions with piperidine, piperazine, 1‐(2‐hydroxyethyl)piperazine, and morpholine. The reaction with 1‐formylpiperazine exhibits a linear plot of kobs against [N]2. These results are interpreted through a mechanism consisting of two tetrahedral intermediates: a zwitterionic (T±) and an anionic (T−), where the amine catalyzed proton transfer from T± to T− is partially rate determining for the four former reactions and is fully rate determining for the reaction of 1‐formylpiperazine. The rate microcoefficients involved in the reaction scheme are either determined experimentally or estimated. Comparison with the corresponding microcoefficients reported for the same reactions in water reveals that the rate coefficient for formation of T± from reactants (k1) is smaller and that for the reversal of this (k−1) is larger in aqueous ethanol compared to water, in agreement with the expected structure of the corresponding transition state.Bronsted‐type plots are obtained for k1, k−1, and K1 (=k1/k−1) with slopes ca. 0.4, −0.6, and 1.0, respectively. Comparison of the present stepwise reactions with the concerted ones found in the same aminolysis of O‐ethyl 2,4,6,‐(trinitrophenyl) dithiocarbonate indicates that T± is so destabilized by the change of PhS by the 2,4,6‐trinitrobenzenethio group that T± no longer exists and becomes a transition state. © 1995 John Wiley & Sons, Inc.
Oxidation of S and SO by O2 in high‐temperature pyrolysis and photolysis reaction systems
Authors: Woiki D. , Roth P. 
Published: January 2005

AbstractThe reaction of S atoms with O2 was studied behind reflected shock waves applying atomic resonance absorption spectroscopy (ARAS) for concentration measurements of S and O atoms. S atoms were generated either by laser‐flash photolysis (LFP) of CS2 or by the high‐temperature pyrolysis of COS, respectively. The concentrations of O2 in the mixtures ranged between 50 ppm and 400 ppm, and those of the S precursors, CS2 and COS, between 5 and 25 ppm. The rate coefficient of the reaction
equation image
was determined from the observed decay of the S absorption signals for temperatures 1220 K ⩽ T ⩽ 3460 K. The measured O‐atom concentration profiles in COS/O2/Ar reaction systems were evaluated, using simplified kinetic mechanism, to verify the given rate coefficient k5. In experiments with the highest value of the [O2]/[COS] ratio the measured O‐atom concentrations were found to be sensitive to the reaction:
equation image
The fitting of the calculated O‐atom profiles to the measured ones results in mean value of:

which is to be valid for the temperature range 2570 K ⩽ T ⩽ 2980 K.A first‐order analysis of the observed S absorption decay in LFP shock wave experiments on CS2/Ar gas mixtures resulted in a rate coefficient of the background reaction (R4):
equation image
for temperatures 1260 K ⩽ T ⩽ 1820 K. © 1995 John Wiley & Sons, Inc.
The elimination kinetics of 2‐bromo‐3‐methylbutyric acid in the gas phase
Authors: Chuchani Gabriel , Dominguez Rosa M. 
Published: January 2005

AbstractThe kinetics of 2‐bromo‐3‐methylbutyric acid in the gas phase was studied over the temperature range of 309.3–357.0°C and pressure range of 15.5–100.0 torr. This process, in seasoned static reaction vessels and in the presence of the free radical inhibitor cyclohexene, is homogeneous, unimolecular, and follows first‐order rate law. The observed rate coefficients are represented by the following Arrhenius equations: log k1(s−1) = (12.72 ± 0.25) − (181.8 ± 2.9) kJ mol−1 (2.303RT)−1. The primary products are isobutyraldehyde, CO, and HBr. The polar five‐membered cyclic transition state type of mechanism appears to be preferred in the dehydrohalogenation process of α‐haloacids in the gas phase. © 1995 John Wiley & Sons, Inc.
Kinetics of the solvolysis of trans‐dichlorotetra(4‐t‐butylpyridine)‐cobalt(III) ions in mixtures of water with methanol and with ethanol
Authors: Halawani Kamal H. , Wells Cecil F. 
Published: January 2005

AbstractFor the solvolysis of Co(4‐t‐Bupy)4Cl2− ions in water + methanol and water + ethanol, log (rate constant) does not vary linearly with the reciprocal of the dielectric constant. The Gibbs free energy, the enthalpy, and the entropy of activation are insensitive to changes in the solvent composition in these mixtures, although a slight broad maximum in ΔH* and ΔS* probably exists at mole fractions of about 0.2 in water + ethanol. This contrasts with the extrema in ΔH* and ΔS* found with more hydrophobic alcohols used as cosolvents. However, the application of a Gibbs energy cycle to the solvolysis in water and in the mixtures shows that there is a differential effect of changes in solvent structure on the emergent solvated CoIII cation in the transition state and on Co(4‐t‐Bupy)4Cl2+ in the initial state. The stability of the former increases relative to that of the latter as the cosolvent content of the mixture rises. © 1995 John Wiley & Sons, Inc.
Gas phase thermolysis of allyl cyanomethyl amine, diallyl cyanomethyl amine, diethyl cyanomethyl amine, and diethyl propargyl amine
Authors: Martin Gonzalo , Ascanio Julian , Rodriguez Jesus 
Published: January 2005

AbstractThe title amines were pyrolyzed in a stirred‐flow reactor at 380–510°C, pressures of 8–15 torr and residence times of 0.3–2.4 s, using toluene as carrier gas. The substrates with an allyl group yielded propene and iminonitriles as reaction products. HCN is formed by decomposition of the iminonitriles. The first‐order rate coefficients for propene formation fit the Arrhenius equations

Allyl cyanomethyl amine:

Diallyl cyanomethyl amine:

Diethyl cyanomethyl amine gave a 20:1 gas mixture of ehylene and ethane, plus HCN. The liquid product fraction contained mainly N‐ethyl methanaldimine. The first‐order rate coefficients for ethylene formation followed the Arrhenius equation

Diethyl propargyl amine decomposed cleanly into allene and N‐ethyl ethanaldimine. The first‐order rate coefficients for allene formation fit the Arrhenius equation

The results suggest that the above allyl and propargyl amines decompose unimolecularly by mechanisms involving six‐center cyclic transition states. For diethyl cyanomethyl amine, a nonchain free radical mechanism is proposed. © 1995 John Wiley & Sons, Inc.
Rate constants for reactions of iodine atoms in solution
Authors: Alfassi Z. B. , Huie R. E. , Marguet S. , Natarajan E. , Neta P. 
Published: January 2005

AbstractLaser flash photolysis (at 248 or 308 nm) or aryl iodides in water or water/methanol solutions produces iodine atoms and phenyl radicals. Iodine atoms react rapidly with added I− to form I2− but do not react rapidly with O2 (k ⩽ 107 L mol−1 s−1). Iodine atoms oxidize phenols to phenoxyl radicals, with rate constants that vary from 1.6 × 107 L mol−1 s−1 for phenol to about 6 × 109 L mol−1 s−1 for 4‐methoxyphenol and hydroquinone. Ascorbate and a Vitamin E analogue are also oxidized very rapidly. N‐Methylindole is oxidized by I atoms to its radical cation with a diffusion‐controlled rate constant, 1.9 × 1010 L mol−1 s−1. Iodine atoms also oxidize sulfite and ferrocyanide ions rapidly but do not add to double bonds. The phenyl radicals, produced along with the I atoms, react with O2 to give phenylperoxyl radicals, which react with phenols much more slowly than I atoms. © 1995 John Wiley & Sons, Inc.
Revised values for the rate coefficients of ethane and methane decomposition
Authors: Davidson D. F. , Hanson R. K. , Bowman C. T. 
Published: January 2005

AbstractRevised values are given for the rate coefficients of ethane and methane decomposition derived from the laser absorption shock tube measurements performed by Davidson et al. (1992, 1993). This revision results from a reassessment of the methyl absorption coefficient used in the original studies. © 1995 John Wiley & Sons, Inc.
The heterogeneous interaction of Br(2P3/2) and Br(2P1/2) with surfaces of Teflon™ and polycrystalline nickel
Authors: Müller‐Markgraf Wolfgang , Rossi Michel J. 
Published: January 2005

AbstractPulses of Br(2P3/2) and Br(2P1/2) (=Brast;) have been exposed to Teflon (PTFE) and to polycrystalline Ni surfaces in a Knudsen cell. The Br and Br* atom densities have been measured as a function of time using [3 + 2] Resonance Enhanced Multiphoton Ionization (REMPI) at 461.9 and 459.1 nm, respectively, and an absolute calibration of the sum of the density of Br and Br* on Teflon at ambient temperature has been measured to result in identical values within experimental error for both Br and Br*, namely γ(Br) = (5.6 ± 1.5) · 10−5, if an appropriate correction for the radiative lifetime of Br* of 0.77 s−1 is applied. The uptake coefficients for Br and Br* on polycrystalline Ni seem to be identical: γ(Br) = γ(Br*) = (5.6 ± 1.8) · 10−3 and independent of temperature in the range 295 to 500 K. A possible exception is the value for γ(Br*) of 2.3 · 10−3 at T = 295 K which seems to be significantly lower than the remainder of the uptake data. In the temperature range 500 to 700 K the uptake coefficients for both Br and Br* can be expressed as

. The system has a small positive activation energy in the range 3.3 to 4.5 kcal/mol. Br* seems to be less reactive than Cl* with respect to surface deactivation on poly Ni by a factor of six. In analogy to Cl the present system is characterized by kinetic complications in conjunction with the reversible surface poisoning of bromine, both atomic and molecular, on surfaces of Teflon (PTFE) and poly Ni that leads to the decrease of Br and Br* uptake with increasing exposure. © 1995 John Wiley & Sons, Inc.
Studies in mixed solvents: Comparison between solvated electron reactions and quenching of excited states
Authors: Kapoor Sudhir Kumar , Gopinathan C. 
Published: January 2005

AbstractThe rate constants for the reaction of electron pulse produced solvated electrons and a number of solutes in water‐isopropanol mixtures have been measured. The quenching of the singlet excited state of naphthalene has also been studied in the same mixtures, using triethylamine and acrylamide as quenchers. The variation of the bimolecular solvated electron reaction rate constants with the composition of the solvent has been compared with the variation in the quenching constants with the composition of the solvent. Both these variations are surprisingly similar, with acrylamide behaving in a reverse manner (to the other solutes) in both the cases. It has been possible to quantitatively correlate both sets of data using dielectric constant (ϵ) as a measure of polarity and the viscosity (η) as an index of the microstructure. The curves obtained provide insights with respect to the nature of charge transfer processes involved. © 1995 John Wiley & Sons, Inc.