bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of ion‐exchange on montmorillonite clays
Authors: Crooks John E. , El‐Daly Hosny , El‐Sheikh Mohammed Y. , Habib Abdul‐Fatah M. , Zaki Ahmed B. 
Published: January 2005

AbstractThe kinetics for the exchange of Li+, K+, Rb+, and Cs+ for Na+ as the exchangeable cation on bentonite and montmorillonite K10 and KSF have been studied using conductimetric stoppedflow. Dilute aqueous suspensions of the clays, of particle sizes of a few micrometers, were used, so that diffusion was fast and the rate‐determining step was the substitution of one cation by another on the lattice surface. The kinetics were treated in terms of relaxation from equilibrium. Relaxation times ranged from 100 to 250 ms, and forward rate constants from 30 to 500 M−1 s−1. The reactions had very low activation enthalpies (7–25 kJ mol−1) and were only slow enough to be studied by the stopped‐flow technique because of the large negative entropies of activation (−120 to −170 J K−1 mol−1). © 1993 John Wiley & Sons, Inc.
Kinetics of the reaction of OH radicals with t‐amyl methyl ether revisited
Authors: Wallington T. J. , Potts A. R. , Andino J. M. , Siegl W. O. , Zhang Z. , Kurylo M. J. , Huie R. E. 
Published: January 2005

AbstractThe kinetics of the reaction of OH radicals with t‐amyl methyl ether (TAME) have been reinvestigated using both absolute (flash photolysis resonance fluorescence) and relative rate techniques. Relative rate experiments were conducted at 295 K in 99 kPa (740 torr) of synthetic air using ethyl t‐butyl ether, cyclohexane, and di‐isopropyl ether as reference compounds. Absolute rate experiments were performed over the temperature range 240–400 K at a total pressure of 4.7 kPa (35 torr) of argon. Rate constant determinations from both techniques are in good agreement and can be represented by k1=(6.32 ± 0.72) × 10−12 exp[(−40 ± 70)/T] cm3 molecule−1 s−1.
equation image
Quoted errors represent 2σ from the least squares analysis and do not include any estimate of systematic errors. We show that results from the previous kinetic study of reaction (1) are in error due to the presence of a reactive impurity. Results are discussed in terms of the atmospheric chemistry of TAME. © 1993 John Wiley & Sons, Inc.
Rate constants and atmospheric lifetimes for the reactions of OH radicals and Cl atoms with haloalkanes
Authors: Donaghy T. , Shanahan I. , Hande M. , Fitzpatrick S. 
Published: January 2005

AbstractRate constants for the reactions of Cl atoms and OH radicals with haloalkanes were measured using the relative rate technique. From these values the atmospheric lifetimes of the organics with respect to Cl atoms and OH radicals were calculated. Cl atoms were produced by the photolysis of chlorine gas, and photolysis of methyl nitrite was the source of OH radicals. The rate constants were measured for a series of brominated and chlorinated alkanes for which measurements have not yet been reported excepting: k(Cl + 1‐chloropropane) and k(OH + 1‐chloropropane, 2‐chloropropane, and bromoethane). The organics studied were 1‐chloropropane, 2‐chloropropane, 1,3 dichloropropane, 2‐chloro 2methylpropane, bromoethane, 1‐bromopropane, 2‐bromopropane, 1‐bromobutane, 1‐bromopentane, and 1‐bromohexane. Cl atom reactions were measured at 298 K, the OH radical reactions were measured at temperatures between 298–308 K. © 1993 John Wiley & Sons, Inc.
Solvent effects on binuclear complex formation between aquopentacyanoferrate(II) and tetraamminepyrazinecarboxylatocobalt(III) in binary aqueous mixtures
Authors: Moyá María Luisa , Burgess John , Sánchez Francisco 
Published: January 2005

AbstractThe substitution reaction between aquopentacyanoferrate(II) and tetraamminepirazynecarboxylatocobalt(III) to form a binuclear species is studied in various binary aqueous mixtures at different temperatures. Values of activation parameters seem to indicate no change in the mechanism of the reaction in the different mixtures. Medium effects have been rationalized by using a multiparameter regression of solvent parameters. Results show that the reaction follows a dissociative mechanism. © 1993 John Wiley & Sons, Inc.
Relative rate constants for reactions of HFC 152a, 143, 143a, 134a, and HCFC 124 with F or Cl atoms and for CF2CH3, CF2HCH2, and CF3CFH radicals with F2, Cl2, and O2
Authors: Kaiser E. W. 
Published: January 2005

AbstractRelative rate experiments using UV photolysis of F2 or Cl2 have been used to determine rate constant ratios for several hydrofluorocarbon (HFC) reactions with Cl or F atoms and for HFC alkyl radicals with molecular halogens. For mixtures with F2 present, dark reactions are, also, observed which are attributed to thermal dissociation of the F2 to form F atoms. At 296 K, the rate of reaction (1a) [CF2HCH3 + F → CF2CH3 + HF] relative to (1b) [CF2HCH3 + F → CF2HCH2 + HF] is k1a/k1b = 0.73 (±0.13) and is independent of T (= 262–348 K). At 296 K, the ratio of reaction (2a) [CF2HCH2F + F → products] to that of (k1a + k1b) is (k1a + k1b)/k2a = 2.7 (±0.4), and for reaction (2b) [CF3CH3 + F → products] (k1a + k1b)/k2b = 22 ± 12. The temperature dependence (263–365 K) of the rate constant of reaction (3) [CF3CFH2 + Cl → products] relative to reaction (4) [CF3CFClH + Cl → products] is k3/k4(±10%) = 1.55 exp(−300 K/T). For the alkyl radicals formed from HFC 152a (CF2HCH2 and CF2CH3) and from HFC 134a (CF3CFH), rate constants for the reactions with F2 and Cl2 were measured relative to their reactions with O2. The rate constant of reaction (5cl) [CF2CH3 + Cl2 → CF2ClCH3 + Cl] relative to (5o) [CF2CH3 + O2 → CF2(O2)CH3] is k5cl/k5o(±15%) = 0.3 exp(200 K/T). For reaction (5f) [CF2CH3 + F2 → CF3CH3 + F], k5f/k5o(±35%) = 0.23. The ratio for reaction (6f) [CF2HCH2 + F2 → CF2HCH2F + F] relative to (6o) [CF2HCH2 + O2 → CF2HCH2O2] is k6f/k6o(±40%) = 1.23 exp(−730 K/T). The rate constant ratio for reaction (8cl) [CF3CFH + Cl2 → CF3CFClH + Cl] relative to reaction (8o) [CF3CFH + O2 → CF3CFHO2] is k8cl/k8o(±18%) = 0.16 exp(−940 K/T). For reaction (8f) [CF3CFH + F2 → CF3CF2H + F], k8f/k8o(±35%) = 0.6 exp(−860 K/T). © 1993 John Wiley & Sons, Inc.
The method of asymptotic approximations as applied to analyzing the mechanism of inhibited liquid‐phase oxidation
Authors: Kalyakin L. A. , Maslennikov S. I. , Komissarov W. D. 
Published: January 2005

AbstractA new method for analyzing the problems of chemical kinetics is elaborated involving the technique of mathematical modeling. Namely, the matching method of the asymptotic expansion is applied to analyzing the inhibition mechanism of oxidation. The proposed approach is an extension of the well‐known method of quasi‐stationary concentrations and may be applied to study a series of problems in the field of chemical kinetics. Three different time scales were established for the mechanism of inhibited oxidation under restrictions k7[InH]0/(2k6Wi)1/2 ⩽ 1 and k8 ≫ 2k6 ≫ k7. At the first time scale (that is very fast and is measured in second fractions) the concentration of radicals In only changes while [RO2] ≃ [RO2]0, [In H] ≃ [In H]0 are constants. At the second time scale (s), [RO2] changes while [In] ≃ [In]st, [In H] ≃ [In H]0 are constants. At the third time scale (min), [In H] changes. An asymptotic analysis of the differential equations allows us to find out both the time duration of each step and the variation of the component which changes at this step. After that the rate constants k8, 2k6, k7 are determined from comparison with the experimental measurements of [In], [RO2], and [In H]. Due to the simplicity and efficiency of the asymptotic method, one may be applied to treating the complex multicenter radical chain processes such as conjugated oxidation, radical copolymerization, sulfoxidation, etc. © 1993 John Wiley & Sons, Inc.
A kinetic study of the reaction of chlorine and fluorine atoms with CF3CHO at 295 ± 2 K
Authors: Wallington T. J. , Hurley M. D. 
Published: January 2005

AbstractUsing a relative rate technique the reactions of chlorine and fluorine atoms with CF3CHO have been determined to proceed with rate constants of (1.8 ± 0.4) × 10−12 and (2.7 ± 0.1)×10−11 cm3 molecule−1 s−1, respectively. Experiments were performed at 295 ± 2 K and 700 torr total pressure of nitrogen. The results are discussed with respect to the design and interpretation of laboratory studies of the atmospheric chemistry of CFC replacements. © 1993 John Wiley & Sons, Inc.
Alkaline hydrolysis of cephaloridine: An 1HNMR study. Temperature dependence of the rate constants
Authors: Vilanova B. , Donoso J. , Muñoz F. , Blanco F. García 
Published: January 2005

AbstractA kinetic study on the basic hydrolysis of cephaloridine at pD= 10.5 was carried out by using the 1HNMR technique. Epimerization at H7, a nucleophilic attack of hydroxyl ion on the β‐lactam carbonyl group followed by the release of the pyridine molecule, and isomerization of the double bond at position 3 in the dihydrothiazine ring were the major reactions observed.Based on the results obtained, it should be emphasized that the presence of a pyridine group at 3′ results in a slightly increased formation constant for the exo methylene compound relative to other cephalosporins with different substituents at that position.The activation energy for the epimerization constant and the cleavage of the β‐lactam ring at pD 10.5 was 21.2 kcal/mol. © 1993 John Wiley & Sons, Inc.
The oxidation of cinnamaldehyde with alkaline hydrogen peroxide
Authors: Wright Philip , Abbot John 
Published: January 2005

AbstractThe oxidation of cinnamaldehyde (3‐phenyl‐2‐propenal) by alkaline peroxide results in epoxidation of the double bond to form cinnamaldehyde epoxide (3‐phenyl‐2,3‐epoxy‐propanal) which undergoes further reaction by ring opening and side chain cleavage to yield benzaldehyde and acidic fragments. The reactions are first‐order in the organic substrates and perhydroxyl anion and second‐order overall. In the presence of alkali alone, two further reactions take place in which cinnamaldehyde and cinnamaldehyde epoxide side chains are cleaved by reaction with hydroxide ion to form benzaldehyde and side chain fragments. These reactions are first‐order in the organic substrates and hydroxide ion and second‐order overall. Increasing solvent polarity accelerates the rates of reaction and reaction mechanisms have been proposed to describe the observed kinetic behavior. The stereoselectivity of the epoxidation reaction has been examined in terms of an existing model for epoxidation of α, β‐unsaturated ketones by alkaline peroxide. © 1993 John Wiley & Sons, Inc.
Gas phase reaction of the hydroxyl radical with the unsaturated peroxyacyl nitrate CH2C(CH3)C(O)OONO2
Authors: Grosjean Daniel , Williams Edwin L. , Grosjean Eric 
Published: January 2005

AbstractThe gas phase reaction of the hydroxyl radical with the unsaturated peroxyacyl nitrate CH2  C(CH3)C(O)OONO2 (MPAN) has been studied at 298 ± 2 K and atmospheric pressure. The OH‐MPAN reaction rate constant relative to that of OH + n‐butyl nitrate is 2.08 ± 0.25. This ratio, together with a literature rate constant of 1.74 × 10−12 cm3 molecule−1 s−1 for the OH + n‐butyl nitrate reaction at 298 K, yields a rate constant of (3.6 ± 0.4)× 10−12 cm3 molecule−1 s−1 for the OH‐MPAN reaction at 298 ± 2 K. Hydroxyacetone and formaldehyde are the major carbonyl products. The yield of hydroxyacetone, 0.59 ± 0.12, is consistent with preferential addition of OH at the unsubstituted carbon atom. Atmospheric persistence and removal processes for MPAN are briefly discussed. © 1993 John Wiley & Sons, Inc.
A study of ethane decomposition in a shock tube using laser absorption of CH3
Authors: Davidson D. F. , Di Rosa M. D. , Hanson R. K. , Bowman C. T. 
Published: January 2005

AbstractThe rate coefficient for the unimolecular reaction, C2H6 → CH3 + CH3, was measured in reflected shock wave experiments using narrow‐linewidth laser absorption of methyl radicals at 216.6 nm. The experiments were conducted in the falloff regime at the conditions 1350 to 2110 K, 0.58 to 4.4 atm, in 50 to 500 ppm C2H6/Ar and 190 ppm C2H6/N2 mixtures. At temperatures below 1500 K, the measured rate coefficients are in good agreement with the expression of Wagner and Wardlaw (1989). Above 1500 K, the measurements fall increasingly below their predictions. © 1993 John Wiley & Sons, Inc.
The lifetimes of gas phase CO2˙− and N2O˙− calculated from the transition probability of the autodetachment process A− → A + e−
Authors: Rauk Arvi , Armstrong David A. , Yu Dake 
Published: January 2005

AbstractA procedure to calculate the quantum mechanical transition probability of a unimolecular primary chemical process, A− → A + e− is investigated for the circumstance where A− and A have different numbers of vibrational and rotational degrees of freedom (one is linear, the other not). A procedure is introduced to deal with the coupling between the vibrational and rotational motions. The proposed method was applied to calculating the lifetimes of CO2˙− and N2O˙− in the gas phase. The geometry optimizations and frequency calculations for CO2, CO2˙−, N2O, and N2O˙− are performed at HF, MP2, and QCISD(T) levels with 6‐31G* or 6–31+G* basis sets, in order to obtain reliable geometric and spectroscopic information on these systems. Lifetimes are calculated for several of the lower vibrational–rotational states of the anions, as well as for the Boltzmann distribution of states at 298 K. The lifetime of the lowest vibrational–rotational state of CO2˙−, is 1.03 × 10−4 s, and of the lowest vibrational state with rotational levels weighted by Boltzmann distribution at 298 K, 1.50 × 10−4 s. These values are in good agreement with the experimental number, 9.0 ± 2.0 × 10−5 s, and support the experimental evidence that CO2˙− was formed in its ground vibrational level by the techniques used. The lifetime of CO2˙− calculated with Boltzmann distribution over its vibrational and rotational levels at 298 K, is 1.51 × 10−5 s. There are no direct measurements of the lifetime of N2O˙−, but it was estimated to be greater than 10−4 s from experimental evidence. The predicted lifetimes of N2O˙−, at its lowest vibrational–rotational state (0 K) and lowest vibrational state with rotational levels weighted by the Boltzmann distribution at 298 K, are 238 and 19.1 s, respectively. The lifetime of N2O˙− at thermal equilibrium at 298 K is 6.66 × 10−2 s, indicating that electron loss from the excited vibrational states of N2O˙− is significant. This study represents the first theoretical investigation of CO2˙− and N2O˙− lifetimes. © 1994 John Wiley & Sons, Inc.
Reactions of the copper dimer, Cu2, in the gas phase
Authors: Lian Li , Akhtar Farah , Hackett Peter A. , Rayner David M. 
Published: January 2005

AbstractReactions of Cu2 with several small molecules have been studied in the gas phase, under thermalized conditions at room temperature, in a fast‐flow reactor. They fall into one of two categories. Cu2 does not react with O2, N2O, N2, H2, and CH4 at pressures up to 6 torr. This implies bimolecular rate constants of less than 5 × 10−15 cm3 s−1 at 6 torr He. Cu2 reacts with CO, NH3, C2H4, and C3H6 in a manner characteristic of association reactions. Second‐order rate constants for all four of these reagents are dependent on total pressure. The reactions with CO, NH3, and C2H4 are in their low pressure limit at up to 6 torr He buffer gas pressure. The reaction with C3H6 begins to show fall‐off behavior at pressures above 3 torr. Limiting low‐pressure, third‐order rate constants are 0.66 ± 0.10, 8.8 ± 1.2, 9.3 ± 1.4, and 85 ± 15 × 10−30 cm6 s−1 in He for CO, NH3, C2H4, and C3H6, respectively. Modeling studies of these rate constants imply that the association complexes are bound by at least 20 kcal mol−1 in the case of C2H4 and C3H6 and at least 25 kcal mol−1 in the other cases. The implications of these results for Cu‐ligand bonding are developed in comparison with existing work on the interactions of these ligands with Cu atoms, larger clusters, and surfaces. © 1994 John Wiley & Sons, Inc.
A kinetic analysis of the photolysis of mixtures of acetone and propylene
Authors: Kinsman Aaron C. , Roscoe John M. 
Published: January 2005

AbstractThe photolysis of mixtures of acetone and propylene at 308 nm has been studied kinetically from approximately 300 K to 580 K. Rate constants were calculated for the reactions
equation image
at total pressures ranging from 110 torr to 750 torr and for [C3H6]/[(CH3)2CO] ratios in the range 0.03 to 3.3. No dependence of the rate constants on total pressure or on this concentration ratio could be detected within this range of conditions. The temperature dependence of the rate constants is given by

© 1994 John Wiley & Sons, Inc.
A spectrokinetic study of CH2I and CH2IO2 radicals
Authors: Sehested Jens , Ellermann Thomas , Nielsen Ole John 
Published: January 2005

AbstractThe UV absorption spectrum and kinetics of CH2I and CH2IO2 radicals have been studied in the gasphase at 295 K using a pulse radiolysis UV absorption spectroscopic technique. UV absorption spectra of CH2I and CH2IO2 radicals were quantified in the range 220–400 nm. The spectrum of CH2I has absorption maxima at 280 nm and 337.5 nm. The absorption cross‐section for the CH2I radicals at 337.5 nm was (4.1 ± 0.9) × 10−18 cm2 molecule−1. The UV spectrum of CH2IO2 radicals is broad. The absorption cross‐section at 370 nm was (2.1 ± 0.5) × 10−18 cm2 molecule−1. The rate constant for the self reaction of CH2I radicals, k = 4 × 10−11 cm3 molecule−1 s−1 at 1000 mbar total pressure of SF6, was derived by kinetic modelling of experimental absorbance transients. The observed self‐reaction rate constant for CH2IO2 radicals was estimated also by modelling to k = 9 × 10−11 cm3 molecule−1 s−1. As part of this work a rate constant of (2.0 ± 0.3) × 10−10 cm3 molecule−1 s−1 was measured for the reaction of F atoms with CH3I. The branching ratios of this reaction for abstraction of an I atom and a H atom were determined to (64 ± 6)% and (36 ± 6)%, respectively. © 1994 John Wiley & Sons, Inc.
Reactions of NO3‐naphthalene adducts with O2 and NO2
Authors: Atkinson Roger , Tuazon Ernesto C. , Bridier Isabelle , Arey Janet 
Published: January 2005

AbstractThe kinetics of the gas‐phase reaction of the NO3 radical with naphthalene have been investigated at 150 torr O2 + 590 torr N2 and 600 torr O2 + 140 torr N2 at 298 ± 2 K. Relative rate measurements were carried out in reacting NO3N2O5‐naphthalene‐propene‐O2N2 mixtures by longpath Fourier transform infrared absorption spectroscopy. A rate constant ratio for the reactions of O2 and NO2 with the NO3‐naphthalene adduct of k/k < 4 × 10−7 was obtained from the competition between O2 and NO2 for reaction with the NO3‐naphthalene adduct and thermal decomposition of the adduct back to reactants. Atmospheric pressure ionization MS/MS measurements of the nitronaphthalene products of the NO3 radical‐initiated reaction of naphthalene are consistent with the proposed reaction mechanism, and the atmospheric implications of the data are discussed. © 1994 John Wiley & Sons, Inc.
High‐temperature ignition of propane with MTBE as an additive: Shock tube experiments and modeling
Authors: Gray Jeffrey A. , Westbrook Charles K. 
Published: January 2005

AbstractIgnition of propane has been studied in a shock tube and by computational modeling to determine the effect of methyl tert‐butyl ether (MTBE) as a fuel additive. MTBE and isobutene were added in amounts up to 25% of the fuel to propane‐oxygen‐argon mixtures in shock tube experiments covering a range of temperatures between 1450 and 1800 K. Ignition delays were measured from chemiluminescence at 432 nm due to excited CH radicals. The temperature dependence of the ignition rates was analyzed to yield Arrhenius parameters of Ea ca. 40 kcal/mol and A ca. 109 s−1 for the overall propane reaction and Ea ca. 34 kcal/mol and A ca. 108.3 s−1 for the overall propane/MTBE reaction. Reactions involving MTBE and its decomposition products were combined with an established propane mechanism in a numerical model to describe the kinetic interaction of this additive with a typical hydrocarbon fuel. The experiments and the kinetic model both show that MTBE and isobutene retard propane ignition with nearly equal efficiency. The kinetic model demonstrates that isobutene kinetics are responsible for inhibition by both MTBE and isobutene, and the specific elementary reactions that produce this behavior are identified. © 1994 John Wiley & Sons, Inc.
The role of water in promoting the oxidative dehydrogenation of ethane
Authors: Lunsford Jack H. , Morales Edrick , Dissanayake Dhammike , Shi Chunlei 
Published: January 2005

AbstractThe addition of water vapor has a strong positive effect on the rate of ethane oxidation at 575°C. This effect is attributed to the role of H2O as a third body in the decomposition of H2O2 to OH radicals. Carbon tetrafluoride likewise enhances the rate of ethane conversion, although not to the extent realized with H2O. A kinetic model, based on known elementary reactions, adequately accounts for the conversions and selectivities observed as a function of H2O pressure, temperature, contact time, and O2 pressure. © 1994 John Wiley & Sons, Inc.
Gas‐phase kinetics of N‐substituted diacetamide
Authors: Al‐Awadi Nouria A. , Al‐Omran Fatima A. 
Published: January 2005

AbstractGas‐phase elimination reactions of number of N‐substituted diacetamides have been studied. The rates of N‐phenyl, 4‐methoxyphenyl, 4‐nitrophenyl, and benzyl diacetamide have been measured between 643–683, 642–693, 673–725, and 555–610 K, respectively. They undergo unimolecular first‐order elimination reactions, for which log A = 12.8, 12.9, 12.8, and 11.0 s−1 and Ea = 185.7, 191.4, 193.4, and 143.6 kJ mol−1, respectively. The reactivity of these compounds has been compared with the unsubstituted diacetamide at 600 K. The kinetic data reveals that each of the N‐aryldiacetamides is less reactive than the parent molecule. We attribute this observation to the resonance of the lone pair of electrons on the nitrogen with either the two carbonyl oxygen atoms or with the 6π electrons in the aromatic ring which will result in the stabilization of the N‐aryldiacetamides related to the parent molecules. © 1994 John Wiley & Sons, Inc.
Ozonolysis of trans‐ and cis‐2‐butenes in low parts‐per‐million concentration ranges
Authors: Horie Osamu , Neeb Peter , Moortgat Geert K. 
Published: January 2005

AbstractOzonolysis of 1–5 ppm concentrations of trans‐ and cis‐2‐C4H8 was carried out in a 580 l spherical glass reaction vessel at 730 ± 5 torr and 296 ± 2 K. The yields of CH3CHO, HCHO, CO, CO2, CH4, and CH3OH were determined by long‐path FTIR spectroscopy. About 60% of C4H8 that reacted with O3 decomposed via the formation of the excited CH3CHO2* intermediates into the following pathways: (4a) CO2 + CH4, (4b) CO2 + H + CH3, (4c) CO + OH + CH3, and (4d) CO + CH3OH. The branching ratios for each channel, expressed as the percent of the total pathways, were determined for trans isomer: 20, 30, 40, and 10, and for cis isomer: 29, 35, 24, and 12, respectively. The conversion of C4H8 relative to the reacted O3 was about 1.6 and 1.4 for trans and cis isomers, respectively. These results were explained by the reactions of OH radicals formed in (4c) with C4H8, in which secondary OH radicals were generated: C4H8 + OH + O2 → CH3CH(OH)CH(CH3)OO, followed by CH3‐CH(OH)‐CH(CH3)OO → 2 CH3CHO + OH. About 40% of C4H8 that reacted with O3 yielded a mixture of a carbonyl and a noncarbonyl product, assigned as hydroxyethyl formate, CH3CH(OH)OCHO, and secondary butene ozonide, respectively. The addition of HCHO increased the formation of the former while the latter was unaffected. These results were consistent with the mechanism proposed by Cremer et al. [Chem. Phys. Lett., 187, 491 (1991)], where the primary ozonide rearranges, before dissociation, to the carbonyl oxide‐aldehyde complex (the dipole complex) which is the precursor of the secondary ozonide. © 1994 John Wiley & Sons, Inc.