bluuebunny/crossref_metadata_2025_split huggingface dataset:
Etching of GaAs (100) with gaseous H/CH3 mixtures
Authors: Meharg Paul F. A. , Ogryzlo Elmer A. 
Published: January 2005

AbstractGaAs (100) wafers were etched in mixtures of hydrogen atoms and methyl radicals. The atoms were formed in a remote hydrogen plasma, and a fraction of these were converted into methyl radicals by introducing methane into the flow system upstream from the semiconductor surface. The flux of hydrogen atoms into the reaction chamber was determined by isothermal calorimetry. The methyl radical flux passing over the substrate was then calculated using previously determined rate parameters for the reaction between atomic hydrogen and methane, and a simple modeling program. The GaAs etch rates were about an order of magnitude faster when methyl radicals were present in the hydrogen atom stream, and were found to follow a first‐order dependence on the partial pressure of methyl radicals. Absolute rate constants were determined and an Arrhenius activation energy of 1.2 kcal mol−1 was calculated. The values of k and Ea are consistent with a diffusion‐controlled process. SEM photographs of the surface revealed small crystallographic features that made the surface appear very rough. XPS analysis indicated that these surfaces were arsenic deficient. A mechanism is proposed for the etching of GaAs by a combination of methyl radicals and hydrogen atoms. © 1994 John Wiley & Sons, Inc.
Two‐color multiphoton decomposition of 1‐bromo 2‐fluoroethane
Authors: McRae G. A. , Ivanco M. , Goodale J. W. 
Published: January 2005

AbstractMultiphoton decomposition of 1‐bromo 2‐fluoroethane (CH2BrCH2F, BFE) with a two‐color CO2 infrared laser is reported as a function of number of laser pulses. For single color irradiation at a wavelength chosen to excite BFE, the decomposition product, vinyl fluoride, which accumulates during the many‐pulse MPD experiment, is found to deactivate BFE decomposition. When a second laser, tuned to a vinyl fluoride absorption is introduced, coincident with the first, the vinyl fluoride is found to activate further BFE decomposition. These results are accounted for in terms of a pressure‐dependent model. Changes in model parameters, upon addition of the second laser, are shown to be consistent with interpretations in terms of collision‐dependent reaction schemes. © 1994 John Wiley & Sons, Inc.
The rate of methyl radical decomposition at high temperatures and pressures
Authors: Su J. Z. , Teitelbaum H. 
Published: January 2005

AbstractRate constants are calculated for CH3 (+ Ar) ⇄ CH2 + H (+ Ar) at the limiting low‐pressure, the limiting high‐pressure, as well as the intermediate fall‐off ranges. The results show that published experimental rate constants for methyl dissociation correspond to the fall‐off region close to the low‐pressure limit. At the low‐pressure limit the activation energy is less than the bond dissociation energy, in agreement with experimental results. Forward and backward rate coefficients at the high‐pressure limit are compared with other theoretical calculations. More theoretical and experimental work is necessary to understand the reverse reaction and its competing reactions, as well as the decomposition channel leading to CH + H2. © 1994 John Wiley & Sons, Inc.
Thermal decomposition of di‐t‐butyl peroxide in the presence of (CH3)2CCH2: Reactions of CH3, (CH3)2ĊCH2CH3, and (CH3)2ĊCH2C(CH3)2CH2CH3 radicals
Authors: Seres Lászloó , Nacsa Ágnes , Arthur Neville L. 
Published: January 2005

AbstractA study of the reaction initiated by the thermal decomposition of di‐t‐butyl peroxide (DTBP) in the presence of (CH3)2CCH2 (B) at 391–444 K has yielded kinetic data on a number of reactions involving CH3 (M·), (CH3)2CCH2CH3 (MB·) and (CH3)2ĊCH2C(CH3)2CH2CH3 (MBB·) radicals.The cross‐combination ratio for M· and MB· radicals, rate constants for the addition to B of M· and MB· radicals relative to those for their recombination reactions, and rate constants for the decomposition of DTBP, have been determined. The values are, respectively,

where θ = RT ln 10 and the units are dm3/2 mol−1/2 s−1/2 for k2/k and k9/k, s−1 for k0, and kJ mol−1 for E.Various disproportionation‐combination ratios involving M·, MB·, and MBB· radicals have been evaluated. The values obtained are: Δ1(M·, MB·) = 0.79 ± 0.35, Δ1(MB·, MB·) = 3.0 ± 1.0, Δ1(MBB·, MB·) = 0.7 ± 0.4, Δ1(M·, MBB·) = 4.1 ± 1.0, Δ1(MB·, MBB·) = 6.2 ± 1.4, and Δ1(MBB·, MBB·) = 3.9 ± 2.3, where Δ1 refers to H‐abstraction from the CH3 group adjacent to the center of the second radical, yielding a 1‐olefin. © 1994 John Wiley & Sons, Inc.
Infrared multiphoton decomposition of highly excited t‐butyl chloride‐d9
Authors: McAlpine Robertd , McRae Glenn A. , Goodale J. W. 
Published: January 2005

AbstractThe infrared multiphoton decomposition (IR MPD) of t‐butyl chloride‐d9 as a function of pressure and fluence is reported. The major decomposition route was molecular elimination of DCl in accord with earlier pyrolysis studies. The effect of added gases (2‐methyl propene‐d8, DCl and 2‐methyl propene‐h8) on the MPD is presented. This study is a further example of the utility of a new method of analysis of MPD experiments. © 1994 John Wiley & Sons, Inc.
Salt effects upon reactions of different charge type reactants: Peroxodisulphate Oxidations of Fe(CN)4(bpy)2−, cis‐Fe(CN)2(bpy)2 and Fe(bpy)32+ and Iron(II) Oxidation by Co(NH3)5Cl2+
Authors: Múñoz Ernestina , Graciani María Del Mar , Jiménez Rafael , Rodríguez Amalia , Moyá María Luisa , Sánchez Francisco 
Published: January 2005

AbstractSalt effects on the oxidation of the iron(II) complexes Fe(CN)4(bpy)2−, cis‐(CN)2(bpy)2 and Fe(bpy)32+ by S2O82− as well as on the reaction Fe2+ + Co(NH3)5Cl2+ have been studied in concentrated electrolyte solutions at 298.2 K. We have gone from anion–anion to cation–cation reaction with the intermediate cases of anion–neutral and cation–anion reactions. Results show that the main cause of the kinetic salt effects observed is the interaction between supporting electrolytes and the solvent. © 1994 John Wiley & Sons, Inc.
Kinetics of solvolysis of 2‐chloroquinoxaline
Authors: Patel R. D. 
Published: January 2005

AbstractPseudo‐first‐order rate constants and activation parameters have been measured for the solvolysis of 2‐chloroquinoxaline in various aquo‐organic mixtures using methanol, ethanol, and isopropanol as the organic solvent. Excellent linear correlations are found between lnk and the mol fraction of cosolvent and ln[H2O]. The medium effect on the rates of solvolysis is assessed by Grunwald–Winstein's mY correlationship. The estimated values of m (0.55–0.72) and the entropy of activation (148–212 J deg−1 mol−1) for the reactions are well in the range for a bimolecular aromatic substitution reactions. © 1994 John Wiley & Sons, Inc.
On the role of transport in the combustion kinetics of a steady‐state premixed laminar CO + H2 + O2 flame
Authors: Mishra Manoj K. , Yetter Richard , Reuven Yakir , Rabitz Herschel , Smooke Mitchell D. 
Published: January 2005

AbstractThe role of mechanistic steps, diffusion, and their interrelation is explored in a steady‐state premixed laminar CO + H2 + O2 flame using a numerical model. Sensitivity coefficients and Green's functions calculated for this system offer systematic characterization of the role of diffusion and exothermicity in carbon monoxide oxidation kinetics. The results reveal that the uncertainties in transport parameters are as important to the model predictions as those in the kinetic steps. The rate controlling steps of the CO + H2 + O2 reaction are found to be different for adiabatic and nonadiabatic premixed flames, and also for systems with and without transport. In particular, the reactions of the hydroperoxyl radical with hydrogen, oxygen, and hydroxyl radicals are found to be important at all temperatures in the fuel lean (40 torr) adiabatic flame studied here. The diffusive mixing of chemical species from the low and the high temperature portions of the flame and the larger heats of reaction associated with the hydroperoxyl radicals are found to be responsible for the increased importance of these reactions. © 1994 John Wiley & Sons, Inc.
Kinetics of the acid and alkaline hydrolysis of Monofluorophosphite
Authors: Dishman Karla , Karnell Leigh Ann , Larson John W. 
Published: January 2005

AbstractThe kinetics of the acid and alkaline hydrolysis of monoflorophosphorous acid has been studied by P‐31 NMR and static pH titration over a wide temperature range. The acid catalyzed hydrolysis has a rate constant at 25°C equal to 0.35 dm3 mol−1 s−1 and an activation energy of 53 kJ while the alkaline hydrolysis has a rate constant of 4.6 dm3 mol−1 s−1 and an activation energy of 42 kJ. When the hydrogen in this compound is replaced by either fluorine or a hydroxyl group, the rates of reaction decrease by two orders of magnitude. © 1994 John Wiley & Sons, Inc.
Gas‐phase thermolysis of allyl propargyl amine, allyl cyanomethyl propargyl amine, allyl propargyl 2‐thiapropyl amine, and allyl methanesulfonyl propargyl amine
Authors: Martin Gonzalo , Ascanio Julian , Rodriguez Jesus 
Published: January 2005

AbstractThe title amines have been pyrolyzed in a stirred‐flow reactor, at temperatures of 360–500°C, pressures of 7–16 torr, and residence times of 0.5–2.9 s, using toluene as carrier gas. The reaction products were allene, propene, and the corresponding imines. The ratio allene:propene varied in the range 6.7–1.6. The amines with CH2CN and SO2CH3 substituents also formed HCN and SO2. These appear to arise from complex free radical decomposition of the imine product. The first‐order rate coefficients for the production of allene plus propene followed the Arrhenius equations: Allyl propargl amine:

Allyl cyanomethyl propargyl amine:

Allyl propargyl 2‐thiapropyl amine:

Allyl methanesulfonyl propargyl amine:

Nonconcerted mechanisms, involving polar six center cyclic transition states, are suggested for the elimination of allene and propene. © 1994 John Wiley & Sons, Inc.
Kinetics and mechanism of the thermal decomposition reaction of acetone cyclic diperoxide in the gas phase
Authors: Cafferata Lázaro F. R. , Lombardo José D. 
Published: January 2005

AbstractThe kinetics of the thermal decomposition reaction of gaseous 3,3,6,6‐tetramethyl‐1,2,4,5‐tetroxane (ACDP) in the presence of n‐octane was studied in the 403.2–523.2 K temperature range. This reaction yields acetone as the organic product. Under optimum conditions, first‐order kinetics were observed, included when the S/V ratio of the Pyrex reaction vessel was increased by a nearly six‐fold factor. In the range 443.2–488.2 K the temperature dependence of the rate constants for the unimolecular reaction in conditioned vessels is given by In k1/(s−1) = (31.8 ± 2.5) − [(39.0 ± 2.5)/RT]. The value of the energy of activation in kcal/mol correspond to one OO bond homolysis of the ACDP molecule in a stepwise biradical initiated decomposition mechanism. At the lower reaction temperatures as well in preliminary experiments participation of a surface catalyzed ACDP decomposition process could be detected. © 1994 John Wiley & Sons, Inc.
Error analysis for complex kinetics systems methyl‐vinyl cross‐radical reactions
Authors: Fahr A. , Braun W. 
Published: January 2005

AbstractMany rate constants, particularly for radical‐radical reactions, are determined in systems exhibiting complex kinetics. Parameters often comprise several species concentrations, absorption cross sections, and rate constants. They cannot be obtained from an exact analytic expression, and therefore, must be solved iteratively through an efficient numerical differential equation solver. We examine here the reaction kinetics of the CH3 and the C2H3 mixed‐radical system, generated by excimer laser photolysis of methyl vinyl ketone (MVK) at 193.3 nm. As a model, a detailed error analysis for determination of the cross‐radical reaction rate constant, the initial CH3 and C2H3 radical concentrations are performed using a least‐squares modeling program (Acufit). The least‐squares program, an assumed mechanism, a detailed set of signal‐averaged data, are viewed as the measuring “instrument.” The output of the “instrument” consists of a “signal” that is fit to the data using the least‐squares criterion. This gives estimated parameters that are examined with respect to random as well as systematic errors. The biases due to uncertainties of each known parameter and combined uncertainties on the measured parameters are assessed. © 1994 John Wiley & Sons, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America.
Concerted mechanism of the aminolysis of 2,4,6‐trinitrophenyl o‐ethyl dithiocarbonate in aqueous ethanol
Authors: Castro Enrique A. , Cubillos María , Muñoz Gabriel , Santos José G. 
Published: January 2005

AbstractThe reactions of the title substrate with a series of secondary alicyclic amines are subjected to a kinetic study in 44 wt% aqueous ethanol, 25.0°C, and ionic strength 0.2 M (KCl). The Brönsted‐type plot (log kN vs. pKa of the amine, where kN is the second‐order rate coefficient) obtained is linear with slope β = 0.53, which indicates a concerted mechanism. The predicted Brönsted break for a hypothetical stepwise mechanism is pK = 8.7, which was not observed (pKa range of amines: 6–11). The same reaction in water is stepwise, which shows that the tetrahedral intermediate found in water is much destabilized by the change of solvent from water to aqueous ethanol. © 1994 John Wiley & Sons, Inc.
The heterogeneous propagation of the chains in the reaction of aliphatic aldehydes oxidation
Authors: Bakhchadjyan R. H. , Vardanyan I. A. 
Published: January 2005

AbstractThe low temperature gas‐phase oxidation of CH3CHO and C2H5CHO have been investigated as an example of heterogeneous‐homogeneous reaction. It has been shown that with the increase of S/V (surface/volume) ratio of the reaction vessel the maximum rate of the process increases and the heterogeneous consumption of aldehyde prevails over the homogeneous one. Peroxy radicals have been discovered by EPR method in vessels with different S/V ratios. The concentration of peroxy radicals and the accumulation rate of peracid in the gas phase did not change with the increase of S/V ratio in the same interval. Under the conditions of these experiments excluding the homogeneous propagation of chains the aldehydes oxidized heterogeneously. The peroxy radicals initiate this heterogeneous process which indicate the existence of short chains on the surface. The reaction between the peroxy radicals and aldehyde on the solid surface (SiO2, KCl/SiO2) has been shown by EPR, IR‐spectroscopy, and mass‐spectrometry methods. A conclusion has been drawn that the solid surface takes part in the chain propagation stage of aldehydes oxidation. © 1994 John Wiley & Sons, Inc.
Kinetics of the thermal decomposition of ferrocenyl azide: Character of ferrocenyl nitrene
Authors: Steel C. , Rosenblum M. , Geyh A. S. 
Published: January 2005

AbstractThe Arrhenius parameters for the thermal decomposition of ferrocenyl azide in isooctane are A = (5.1 ± 1.4) × 1012 s−1 and Eact = 113.1 ± 0.9 (kJ mol−1) and the rate is relatively insensitive to solvent (isooctane, benzene, acetonitrile: 1:1.7:2.4). The results indicate a relatively nonpolar transition state which is considerably “tighter” than for a normal bond fission reaction. The Arrhenius parameters are comparable to those for aromatic azides and do not offer any support for anchimeric assistance by the iron atom. A kinetic scheme is presented which accounts for the observed products: Nitrogen, ferrocene, aminoferrocene, azoferrocene, and insoluble material. Rates of hydrogen abstraction by the intermediate ferrocenyl nitrene from cyclohexane, benzene, and acetonitrile are used to show that the nitrene is nucleophilic. © 1994 John Wiley & Sons, Inc.
Liquid‐phase autoxidation of organic compounds at elevated temperatures. Absolute rate constant for intermolecular hydrogen abstraction in hexadecane autoxidation at 120–190°C
Authors: Jensen R. K. , Korcek S. , Zinbo M. 
Published: January 2005

AbstractThe absolute rate constants for the intermolecular hydrogen abstraction reactions of secondary hydrogens by secondary alkylperoxy radicals in hexadecane autoxidation, k3, have been determined in the temperature range of 120–190°C using the stirred flow reactor technique. Absolute rate constants determined in this study for hexadecane are in good agreement with those determined for other hydrocarbons in liquid phase, on a per hydrogen basis, at lower temperatures. Arrhenius parameters for k3/H derived from this study are A = 108.6 M−1 s−1 and Ea = 16.0 kcal/mol. The values of these parameters provide experimental confirmation for previous estimates made from both lower temperature reactions in the liquid phase and higher temperature reactions in the gas phase. © 1994 John Wiley & Sons, Inc.
Flowtube reactor study of the association reactions of CHCl2 and CCl3 with O2 at low pressure
Authors: Nottingham Winston C. , Rudolph R. Neil , Andrews Kevin P. , Moore John H. , Tossell John A. 
Published: January 2005

AbstractThe new flowtube reactor employing dissociative electron attachment to produce radicals and high‐pressure photoionization in the mass spectrometric detection of radicals is described. The system has been applied to a study of the association reactions of CHCl2 and CCl3 with O2 in a great excess of helium at total densities below 1017 cm−3 over the temperature range 286 to 332 K. Both reactions display a strong negative temperature coefficient. The results can be parameterized in the form k0(CHCl2 + O2) = (4.3 ± 0.2) × 10−31(T/300)−6.7±0.7 cm6 s−1, k0(CCl3 + O2) = (2.7 ± 0.2) × 10−31(T/300)−8.7±1.0 cm6 s−1. © 1994 John Wiley & Sons, Inc.
Branching ratio of the C2H2 + O reaction at 290 K from kinetic modelling of relative methylene concentration versus time profiles in C2H2/O/H systems
Authors: Peeters Jozef , Boullart Werner , Langhans Ivan 
Published: January 2005

AbstractIn earlier work on the room temperature oxidation of C2H2 by O atoms, two distinct sources of methylene radicals have been identified: (i) direct, primary production via channel 1b of the C2H2 + O reaction, and (ii) delayed formation via the secondary reaction 3 involving the products HCCO and H of the other primary channel 1a: magnified image Presently, it was confirmed by a detailed sensitivity analysis that the precise shapes of the resulting total methylene concentration‐versus‐time profiles in C2H2/O systems depend strongly on the k1a/k1b branching ratio. Along that line, the important parameter k1a/k1b was determined from relative CH2 concentration‐versus‐time profiles measured in a variety of C2H2/O/H systems using Discharge Flow‐Molecular Beam sampling Mass Spectrometry techniques (DF‐MBMS). The data analysis was carried out by deductive kinetic modelling; the method, as applied to profile shapes, is discussed at length. Via this novel, independent approach, the CH2(3B1) yield of the two‐channel C2H2 + O reaction was determined to be k1b/k1 = 0.17 ± 0.08. The indicated 2σ error includes possible systematic errors due to uncertainties in the rate constants of other reactions that influence the shapes of the CH2 profiles. The present result, which translates to an HCCO yield k1a/k1 = 0.83 ± 0.08, is in excellent agreement with other recent determinations. The above mechanism, with the subsequent reactions that it initiates, also reproduces the measured absolute [C2H2], [O], and [H] profiles with an average accuracy of 5%, thus validating the consistency of the C2H2/O/H reaction model put forward here. © 1994 John Wiley & Sons, Inc.
Micellar catalyzed redox reactions of bilirubin in CTAB medium. A pulse radiolysis study
Authors: Adhikari Soumya K. , Guha Shambhu N. , Gopinathan C. 
Published: January 2005

AbstractThe reaction of CO with bilirubin which is not detectable in homogeneous aqueous medium proceeds almost with diffusion controlled rate in CTAB micellar system. This could be explained on the basis of catalysis caused by the possible electrostatic surface potential of cationic CTAB Micelles. The rate constant for the oxidation of bilirubin by haloperoxyl radicals have been shown to increase with increasing solvent polarity. Although the polarity effect was small, it followed a trend in the expected direction. Micellar effect was not observed in the oxidation reactions when alcohol was present in high concentration. But a small increase in the rate constant was observed when alcohol concentration was lower. © 1994 John Wiley & Sons, Inc.
Iron(II)‐bis (salicyladimine) Schiff‐base complexes catalyzed decomposition of hydrogen peroxide
Authors: Salem I. A. , El‐Sheikh M. Y. , Zaki A. B. , Nickel Ulrich 
Published: January 2005

AbstractThe tetradentate Schiff‐base ligands, N,N′‐bis(salicylidene)‐ethylenediamine (Salen), N,N′‐bis(salicylidene) butylenediamine (Salbut), and N,N′‐bis(salicylidene)‐o–phenylenediamine, (sal‐o‐phen) are very strongly sorbed by cation exchange resin (Dowex‐50W) with Fe2+ ions as a counter ion, forming stable complexes. The kinetics of the catalytic decomposition of H2O2 using these complexes was studied in ethanolic medium. The reaction was first‐order with salen and sal‐o‐phen and second‐order with salbut with respect to [H2O2]. The rate of the H2O2 decomposition increased either from salen to salbut or from salen to sal‐o‐phen. Also, the k (per g dry resin) values decreased with increasing both the particle size and the degree of resin cross‐linkage. The active species formed at the beginning of the reaction, had an inhibiting effect on the reaction rate. The corresponding activation parameters were calculated from a least‐squares fit of the temperature dependence of the rate constant. A reaction mechanism is proposed. © 1994 John Wiley & Sons, Inc.
Kinetics and thermochemistry of the reaction of acetylene and nitric oxide
Authors: Benson Sidney W. 
Published: January 2005

AbstractThe shock tube data of Ogura [5] on the pyrolysis of C2H2/NO mixtures (1100–1500 K) is shown to be consistent with a simple mechanism whereby radicals are both initiated and terminated by NO (Scheme I). The scheme accounts for the rate of formation of the main product, vinylacetylene (VA), the lesser products CO and HCN and a very minor product, propionitrile. It is also shown to be consistent with other studies below 900 K and observation at 300 K on the reactions of vinyl radicals with NO. The substantial inhibition of vinyl acetylene formation by 5% NO makes untenable any substantial role of vinylidene in the C2H2 pyrolysis above 1000°K.The reaction of NO with acetylene is an efficient source of HCN. It appears to be a general reaction of NO with substituted acetylenes and below 900 K a mechanism is presented to account for the production of acrylonitrile (AN) from the reaction of NO with VA.Thermochemical data are estimated on ΔfH°298 and S°298 for some alkyl‐NO, vinyl NO, and acetylene NO compounds and radicals and some new and some revised group values are estimated for estimating ΔfH°298 of derivatives of hydroxyl amines, imines, and isoxazolines. © 1994 John Wiley & Sons, Inc.