bluuebunny/crossref_metadata_2025 huggingface dataset:
A kinetic study of the air oxidation of pyrogallol and purpurogallin
Authors: Abrash Henry I. , Shih Dorcas , Elias Woodrow , Malekmehr Farshad
Published: January 2005

Pyrogallol (1,2.3‐benzentriol, 1) reacts with dioxygen in weakly alkaline solutions to form purpurogallin (2,3,4,6‐tetrahydroxy‐5H‐benzocycloheptene‐5‐one, 2) which then reacts to form purpurogalloquinone (3) which then decays to a product absorbing at 440 nm. The formation of 3 requires 1.5 mol O2 per mol 1, and 1.0 mol per mol 2. No O2 is consumed during the decay of 3, and this reaction, being insensitive to O2 concentrations and the presence of both superoxide dismutase (SOD) and catalase, does not appear to be an oxidation. The first‐order rate of decay of 3 decreases with increasing pH. 1 and 3 react at pH 9.0 with a second‐order rate constant of ca. 100 M−1 s−1. SOD inhibits the oxidation of 1 and 2. Slight and variable apparent inhibition of the oxidation of 2 and 3 by SOD may be due to trace impurities in 2, but not contamination by 1. The peak concentration of 3 is attained more rapidly during the oxidation of 1 than during the oxidation of 2. A kinetic scheme based on parallel oxidation of 1 by dioxygen and superoxide, and it which the semiquinone of 1 oxidizes 2, is partially successful in simulating the observed kinetic behavior.
Thermal decomposition of propyne and allene in shock waves
Authors: Hidaka Yoshiaki , Nakamura Takuji , Miyauchi Aya , Shiraishi Toshihiko , Kawano Hiroyuki
Published: January 2005

Propyne (p‐C3H4) or allene (a‐C3H4) mixtures, highly diluted with Ar, were heated to the temperature range 1200–1570 K at pressures of 1.7–2.6 atm behind reflected shock waves. The thermal decompositions of propyne and allene were studied by both measuring the profiles of the IR emission at 3.48 μm or 5.18 μm and analyzing the concentrations of reacted gas mixtures. The mechanism and the rate constant expressions were discussed from both the profiles and the concentrations of reactant and products obtained. The rate constant expressions for reactions, (1) p‐C3H4 → a‐C3H4, (−1) a‐C3H4 → p‐C3H4, and (5) p‐C3H4 + H → CH3 + C2H2 were evaluated.
Unusual selectivities of radical reactions. Experimental studies on alkyl versus phenoxyl reaction systems
Authors: Rüegge Daniel , Fischer Hanns
Published: January 2005

Radical reactions involving two or more intermediates and many mutual reaction channels may lead to the specific formation of one cross‐reaction product if one species is rather persistent and if transient and persistent species are produced with equal rates. A previous kinetic analysis of the phenomenon revealed that the concentrations of the intermediates and the selectivities of product formation depend critically on the relative initiation rates. The present experimental ESR studies on systems involving simultaneously generated phenoxyl radicals as persistent and alkyl radicals as transient species confirm the predicted behavior. They also lead to absolute rate constants for reactions of alkyl with phenoxyl radicals and for hydrogen atom transfer from phenols to alkyl radicals.
The production of chlorine atoms from the reaction of OH with chlorinated hydrocarbons
Authors: Kleindienst Tadeusz E. , Shepson Paul B. , Nero Chris M. , Bufalini Joseph J.
Published: January 2005

Measurements from previous studies have shown that when hydroxyl radicals react with various chlorinated hydrocarbons under atmospheric conditions, free chlorine atoms can be produced. In one such study (Edney et al., [3]) from an analysis of the rate equations under a strict set of assumptions, Cl‐atom yields could be inferred. Since the approach was indirect, a more direct method for obtaining these yields has been developed. The technique described in this study involves scavenging Cl atoms produced by the reaction (using ethylene or propylene as the scavenger) and then measuring the yield of the stable chlorinated product generated. Cl‐atom yields were determined for allyl chloride, vinyl chloride, vinylidene chloride, trichloroethylene, and benzyl chloride. The experiments were performed by irradiating mixtures of CH3ONO/NO/chlorinated hydrocarbon/alkene in air in 150‐L Teflon chambers. The yields for the reaction of Cl atoms with the alkenes generating the stable products were determined in seperate experiments. Yields for the formation of Cl atoms upon reaction with hydroxyl radicals are as follows (with 1 σ deviation): allyl chloride: 0.37 ± 0.10, vinyl chloride: 0.04 ± 0.01, vinylidene chloride: 0.23 ± 0.09, trichloroethylene: 0.63 ± 0.34, and benzyl chloride: 0.08 ± 0.03.
Predicting the preexponential temperature dependence of bimolecular metathesis reaction rate coefficients using transition state theory
Authors: Cohen N.
Published: January 2005

The thermochemical kinetics formulation of conventional transition state theory for bimolecular reactions allows for a separate contribution from each degree of freedom (translation, rotation, vibration, etc.) in the activated complex to the entropy and heat capacity of activation, and thus to the preexponential terms in the Arrhenius rate expression, k = ATn exp(−B/T). The number of vibrations and (possibly hindred) internal rotations varies depending on the nature of the reaction: atom + diatom, diatom + linear polyatom, etc. The temperature exponent n can be evaluated explicitly for each type of reaction if the harmonic oscillator‐rigid free rotor approximation is valid for the reagents and activated complex and if the contribution from tunneling is small. Various reaction types are examined successively, and n is evaluated for each case. The possible contributions of other factors (vibrational anharmonicity, hindered internal rotation, tunneling, “looseness” of activated complex) to the value of n are also considered.
A relative rate study of the reaction of bromine atoms with a variety of organic compounds at 295 K
Authors: Wallington Timothy J. , Skewes Loretta M. , Siegl Walter O. , Japar Steven M.
Published: January 2005

The relative rate technique has been used to determine rate constants for the reaction of bromine atoms with a variety of organic compounds. Decay rates of the organic species were measured relative to i‐butane or acetaldehyde or both. Using rate constants of 1.74 × 10−15 and 3.5 × 10−12 cm3 molecule−1 s−1 for the reaction of Br with i−butane and acetaldehyde respectively, the following rate constants were derived, in units of cm3 molecule−1 s−1: 2, 3−dimethylbutane, (6.40 ± 0.77) × 10−15; cyclopentane, (1.16 ± 0.18) × 10−15, ethene, (≤2.3 × 10−13); propene, (3.85 ± 0.41) × 10−12; trans‐2‐butene, (9.50 ± 0.76) × 10−12, acetylene, (5.15 ± 0.19) × 10−15; and propionaldehyde, (9.73 ± 0.91) × 10−12. Quoted errors represent 2σ and do not include possible systematic errors due to errors in the reference rate constants. Experiments were performed at 295 ± 2 K and atmospheric pressure of synthetic air or nitrogen. The results are discussed with respect to the mechanisms of these reactions and their utility in serving as a laboratory source of alkyl and alkyl peroxy radicals.
A product study of the gas‐phase reaction of methyl vinyl ketone with the OH radical in the presence of NOx
Authors: Tuazon Ernesto C. , Atkinson Roger
Published: January 2005

The gas‐phase reaction of methyl vinyl ketone with the OH radical, in the presence of NOx, was investigated at 298 ± 2 K and atmospheric pressure of air. Glycolaldehyde and methylglyoxal were observed to be the major products, with a combined yield of 0.89 ± 0.16. The sum of the yields of the two other main products, formaldehyde and peroxyacetyl nitrate, were found to be essentially unity. The product yield data for glycolaldehyde and methylglyoxal indicate that OH radical addition to the terminal carbon atom of the >CC< bond accounts for 72 ± 21% of the overall reaction, with the remaining 28 ± 9% proceeding via addition to the inner carbon atom of the double bond.
Incubation in cyclohexene decomposition at high temperatures
Authors: Shi Jichun , Barker John R.
Published: January 2005

A detailed master equation simulation has been carried out for the thermal unimolecular decomposition of C6H10 in a shock tube. At the highest temperatures studied experimentally [J. H. Kiefer and J. N. Shah, J. Phys. Chem., 91, 3024 (1987)], the average thermal vibrational energy is greater than the reaction threshold and therefore 〈ΔE〉 (up and down steps) is positive for molecules at that energy, rather than negative; the converse is true at lower temperatures. The calculated incubation time, in which the decomposition rate constant rises to 1/e of its steady state value, is found to be only weakly dependent on temperature (at constant pressure) between 1500 K and 2000 K and to depend almost exclusively on 〈ΔE〉d (down steps, only), and not on collision probability model. Simulations of the experimental data show the magnitude of 〈ΔE〉d depends weakly on assumed collision probability model, but is nearly independent of temperature. The second moment 〈ΔE〉½ is found to be independent of both temperature and transition probability model. The experimental data are not very sensitive to the possible energy‐dependence of 〈ΔE〉d for a wide range of assumptions. It is concluded that the observed experimental “delay times” probably can be identified with the incubation time; further experiments are desirable to test this possibility and obtain more direct measures of the incubation time.
Influence of N‐hexadecyl‐N, N,N‐trimethylammonium nitrate on the dehydrobromination reaction of 2‐phenylethyl derivatives
Authors: Wilk Kazimiera A.
Published: January 2005

The basis dehydrobromination of p‐substituted 2‐phenylethyl bromides promoted by hydroxide ion has been studied in micelles of N‐hexadecyl‐N,N,N‐trimethylammonium nitrate (CTANO3). The pseudophase ion exchange model can be adapted to explain the kinetic results at low hydroxide ion concentration, i.e., less than 0.075 M of NaOH. At high hydroxide ion concentration in solution the applied model does not describe the kinetic results unless the empirical variations are applied for the mol ratio of reactive ion to micellar head group (β) and the binding constant of the organic reagent to the micelle (Ks).
The rate coefficient for the reaction of O(3P) with CH3OOH at 297 K
Authors: Vaghjiani Ghanshyam L. , Ravishankara A. R.
Published: January 2005

The absolute second‐order rate coefficient for the reaction, O(3P) + CH3OOH → products, was measured to be 𝓀1 = (1.06 ± 0.26) × 10−14 cm3 molec−1 s−1 at 297 K, where the quoted error is 2σ including precision and estimated systematic errors. The possible presence of (CH3CH2)2O in our sample of CH3OOH leads to a large error in 𝓀1 which reflects the relatively large uncertainty indicated. O(3P) was generated in excess CH3OOH by photolyzing a small amount of O3 at 532 nm, where CH3OOH does not photolyze. The rate of removal of O(3P) in the experiments was monitored by resonance fluorescence detection. The increased reactivity of O(3P) with CH3OOH relative to H2O2 is interpreted as due to H abstraction from the CH3 group.
Time‐resolved mass spectrometric study of the reaction H + Trans‐2‐Butene
Authors: Herman Kazimiera , Forst Wendell
Published: January 2005

The title reaction was studied in a discharge flow system using mass flow and modulated molecular beam sampling with phase‐sensitive detection in order to obtain time‐resolved mass spectrometric analysis. At total conversion exceeding 30%, the major products are methane and ethane when initially hydrogen atoms are in excess; when butene is in excess, the major products are ethane and propylene. No hydrocarbons with more than 4 carbon atoms were detected in the products. The reaction is a complicated one since the simplest reaction scheme that successfully simulates the experimental results comprises 20 elementary reactions. The simulation, coupled with sensitivity analysis, shows that with hydrogen atoms in excess, significant amounts of propylene formed in the initial decomposition of the butyl radical react further with hydrogen atoms to form methane and ethane. When butene is in excess, approximately [C3H6] ≈ [CH4] + ½[C2H6] which means that this propylene does not react further and almost all methyl radicals end up as CH4 or C2H6. At small conversion, simulation shows that the major product by far is propylene regardless of the [H]/[butene] ratio. The absence of higher hydrocarbons in the products is at variance with earlier results of Rabinovitch and coworkers; however the present work leads to a comparable value for the average rate constant 𝓀a = ωD/S where D and S is the amount of products arising from the decomposition and stabilization, respectively, of the butyl radical and ω is the collision frequency.
Kinetics of alkaline hydrolysis of organic esters and amides in neutrally‐buffered solution
Authors: Robinson Bruce A. , Tester Jefferson W.
Published: January 2005

Reaction rate constants for the hydrolysis of organic esters and amides were determined at temperatures of 100–240°C in aqueous solutions buffered at pH values between 5.5 and 7.3. Experiments are modeled assuming alkaline hydrolysis with a thermodynamic solution model included to account for the temperature dependence of hydroxide ion concentration. In most cases, the ester hydrolysis second order rate constants agree well with published values from experiments in strongly basic solutions at pH values from 11 to 14 and temperatures from 25–80°C, despite the large extrapolations required to compare the data sets. The amide hydrolysis rate constants are about one order of magnitude higher than the extrapolated results from other investigators, but the reaction rate increased proportionally with hydroxide ion concentration, suggesting that an alkaline hydrolysis mechanism is also appropriate. These data establish the validity of the alkaline hydrolysis mechanism and can be used to predict hydrolysis reaction rates in neutrally‐buffered solutions such as many groundwater and geothermal fluids.
A shock tube study of the CH2O + NO2 reaction at high temperatures
Authors: Lin Chin‐Yu , Wang Hung‐Tai , Lin M. C. , Melius C. F.
Published: January 2005

The reaction of CH2O with NO2 has been studied with a shock tube equipped with two stabilized ew CO lasers. The production of CO, NO, and H2O has been monitored with the CO lasers in the temperature range of 1140–1650 K using three different Ar‐diluted CH2O‐NO2 mixtures. Kinetic modeling and sensitivity analysis of the observed CO, NO, and H2O production profiles over the entire range of reaction conditions employed indicate that the bimolecular metathetical reaction, NO2 + CH2O → HONO + CHO (1) affects most strongly the yields of these products. Combination of the kinetically modeled values of 𝓀1 with those obtained recently from a low temperature pyrolytic study, ref. [8], leads to

for the broad temperature range of 300–2000 K.
Background reactivity in smog chambers
Authors: Killus James P. , Whitten Gary Z.
Published: January 2005

Data from several smog chamber reaction vessels have been analyzed in an attempt to elucidate the chemical species which are responsible for chamber specific background phenomena, and the nature of the processes which determine the heterogeneous interactions of those species. There is good evidence for the emission of a compound which yields both NOx, and free radicals (probably HONO) and emissions of reactive organics (e.g. HCHO) may also be deduced. Total integrated chamber emission of these compounds may be as high as 20 to 60 ppb during a typical smog chamber experiment. In addition to the direct emission of these contaminants, the surface reaction of NO2 and H2O to HONO is examined. In some cases this reaction may have as great an effect on a smog chamber experiment as the emission of trace contaminants. Overall chamber perturbations to gas phase chemistry have been estimated for several experiments and were found to be less than 20 percent in the majority of cases, although higher perturbations were found in experiments involving compounds of low reactivity such as butane.
Kinetics and mechanism for the oxidation of 1,1,1‐trichloroethane
Authors: Nelson Linda , Shanahan Imelda , Sidebottom Howard W. , Treacy Jack , Nielsen Ole J.
Published: January 2005

The reaction mechanisms for oxidation of CH3CCl2 and CCl3CH2 radicals, formed in the atmospheric degradation of CH3CCl3 have been elucidated. The primary oxidation products from these radicals are CH3CClO and CCl3CHO, respectively. Absolute rate constants for the reaction of hydroxyl radicals with CH3CCl3 have been measured in 1 atm of Argon at 359, 376, and 402 K using pulse radiolysis combined with UV kinetic spectroscopy giving 𝓀(OH + CH3CCl3) = (5.4 ± 3) 10−12 exp(−3570 ± 890/RT) cm3 molecule−1 s−1. A value of this rate constant of 1.3 × 10−14 cm3 molecule−1 s−1 at 298 K was calculated using this Arrhenius expression. A relative rate technique was utilized to provide rate data for the OH + CH3 CCl3 reaction as well as the reaction of OH with the primary oxidation products. Values of the relative rate constants at 298 K are: 𝓀(OH + CH3CCl3) = (1.09 ± 0.35) × 10−14, 𝓀(OH + CH3CClO) = (0.91 ± 0.32) × 10−14, 𝓀(OH + CCl3CHO) = (178 ± 31) × 10−14, 𝓀(OH + CCl2O) < 0.1 × 10−14; all in units of cm3 molecule−1 s−1. The effect of chlorine substitution on the reactivity of organic compounds towards OH radicals is discussed.
Reaction rate constant of SO3 + CH3OH in the gas phase
Authors: Shen Guanlin , Suto Masako , Lee L. C.
Published: January 2005

The reaction rates of SO3 with CH3OH in He were measured at total pressures of 0.7–1.6 torr in flow tubes. The concentration of SO3 was monitored by the SO2* fluorescence from excitation of SO3 at 147 nm. The reaction rate constant of SO3 + CH3OH in the gas phase is determined to be (1.17 ± 0.16) × 10−13 cm3 molec−1 s−1 at room temperature.
FTIR study of the Cl‐atom initiated oxidation of methylglyoxal
Authors: Green M. , Yarwood G. , Niki H.
Published: January 2005

The kinetics and mechanism of Cl‐atom initiated reactions of CH3C(O)CHO were studied using the FTIR detection method in the photolysis (λ < 300 nm) of Cl2CH3C(O)CHO mixtures in 700 torr of N2O2 diluent at 298 ± 2 K. The observed product distribution over the O2 pressure range from 0–700 torr, combined with relative rate measurements, provided evidence that: (1) the primary step is Cl + CH3C(O)CHO → HCl + CH3C(O)CO with a rate constant of (4.8 ± 1.1) × 10−11 cm3 molecule−1 s−1; and (2) the predominant fate of the primary radical CH3C(O)CO under atmospheric conditions is unimolecular dissociation to CH3C(O) radicals and CO, rather than O2‐addition to yield the corresponding carbonylperoxy radical CH3C(O)C(O)OO.
Rate constants for the gas‐phase reactions of O3 with a series of monoterpenes and related compounds at 296 ± 2 K
Authors: Atkinson Roger , Hasegawa David , Aschmann Sara M.
Published: January 2005

Rate constants for the gas‐phase reactions of O3 with a series of monoterpenes and related compounds have been determined at 296 ± 2 K and 740 torr total pressure of air or O2 using a combination of absolute and relative rate techniques. Good agreement between the absolute and relative rate data was observed, and the rate constants obtained (in units of 10−17 cm3 molecule−1 s−1) were: α‐pinene, 8.7; β‐pinene, 1.5; Δ3‐carene, 3.8; 2‐carene, 24; sabinene, 8.8; d‐limonene, 21; γ‐terpinene, 14; terpinolene, 140; α‐phellandrene, 190; α‐terpinene, 870; myrcene, 49; trans‐ocimene, 56; p‐cymene, <0.005; and 1,8‐cineole, <0.015. While these rate constants for α‐ and β‐pinene and sabinene are in good agreement with recent absolute and relative rate determinations, those for the other monoterpenes are generally lower than the literature data by factors of ca. 2–10. The measured rate constants for the monoterpenes are reasonably consistent with predictions based upon the number and positions of the substituent groups around the 〉CC〈 bond(s).
Reactions of naphthalene in N2O5NO3NO2 air mixtures
Authors: Atkinson Roger , Tuazon Ernesto C. , Arey Janet
Published: January 2005

The reactions of naphthalene in N2O5NO3NO2N2O2 reactant mixtures have been investigated over the temperature range 272–297 K at ca. 745 torr total pressure and at 272 K and ca. 65 torr total pressure using long pathlength Fourier transform infrared absorption spectroscopy. 2,3‐Dimethyl‐2‐butene was added to the reactant mixtures at 272 K to rapidly scavenge the NO3 radicals both initially present in the added N2O5 and formed from the thermal decomposition of N2O5 during the reactions. The data obtained in the presence and absence of added 2,3‐dimethyl‐2‐butene showed that napthalene undergoes initial reaction with the NO3 radical to form an NO3‐naphthalene adduct, which either rapidly decomposes back to the reactants (at a rate of ca. 5 × 105 s−1 at 298 K) or reacts exclusively with NO2 to form products. When NO3 radicals, N2O5 and NO2 are in equilibrium, this overall process is kinetically equivalent to reaction of naphthalene with N2O5, and previous kinetic and product studies have indeed assumed the reactions of naphthalene and alkyl‐substituted naphthalenes in N2O5NO3NO2air mixtures to be with N2O5, and not with NO3 radicals.
Kinetics of electron transfer reactions of manganese (III) complexes of trans‐cyclohexane‐1,2‐diamine,‐NNN′N′‐tetraacetic acid and 2,2′‐bipyridyl with ascorbic acid in aqueous acid media
Authors: Gangopadhyay Sumana , Saha Swapan K. , Ali Mahammad , Banerjee Pradyot
Published: January 2005

The kinetics of the reactions of manganese(III) complexes of trans‐cyclohexane‐1,2‐diamine‐NNN′N′‐tetraacetic acid (H4cydta) and 2,2′‐bipyridyl (bpy) have been investigated in the acid ranges [H+] = 1.00 ×10−5 − 3.16 × 10−3 M and [H+] = 0.10 − 1.00 M, respectively, at different temperatures and at a constant ionic strength. Both the molecular and mono‐anionic forms of ascorbic acid have been found to be reactive in the experimental acid ranges. The monoanionic species has been found to be more reactive than the molecular form. Attempts have been made to correlate the kinetic results in terms of the Marcus relationship for outer‐sphere electron transfer reaction. Differences between the calculated rates (k0.8) and experimental rates (k) by approximately four and seven orders of magnitude (k0.8≪ k) suggest an innersphere pathway for the reaction of Mn(cydta)(H2O)−. Inner‐sphere reaction is also believed to be operative for the other reaction. The activation parameters have been evaluated and compared with other reported systems.
Kinetics of CN reactions with N2O and CO2
Authors: Wang N. S. , Yang D. L. , Lin M. C. , Melius C. F.
Published: January 2005

The rate constants for the reaction of CN with N2O and CO2 have been measured by the laser dissociation/laser‐induced fluorescence (two‐laser pump‐probe) technique at temperatures between 300 and 740 K. The rate of CN + N2O was measurable above 500 K, with a least‐squares averaged rate constant, k = 10−11.8±0.4 exp(−3560 ± 181/T) cm3/s. The rate of CN + CO2, however, was not measurable even at the highest temperature reached in the present work, 743 K, with [CO2] ⩽ 1.9 × 1018 molecules/cm3.

In order to rationalize the observed kinetics, quantum mechanical calculations based on the BAC‐MP4 method were performed. The results of these calculations reveal that the CN + N2O reaction takes place via a stable adduct NCNNO with a small barrier of 1.1 kcal/mol. The adduct, which is more stable than the reactants by 13 kcal/mol, decomposes into the NCN + NO products with an activation energy of 20.0 kcal/mol. This latter process is thus the rate‐controlling step in the CN + N2O reaction. The CN + CO2 reaction, on the other hand, occurs with a large barrier of 27.4 kcal/mol, producing an unstable adduct NCOCO which fragments into NCO + CO with a small barrier of 4.5 kcal/mol. The large overall activation energy for this process explains the negligibly low reactivity of the CN radical toward CO2 below 1000 K.

Least‐squares analyses of the computed rate constants for these two CN reactions, which fit well with experimental data, give rise to

for the temperature range 300–3000 K.
Kinetic studies of the reactions of IO, BrO, and ClO with dimethylsulfide
Authors: Barnes I. , Bastian V. , Becker K. H. , Overath R. D.
Published: January 2005

The kinetics of the reactions of IO, BrO, and ClO with DMS have been investigated at 298 K and total pressures of 0.5–6.8 mbar He using the discharge flow‐mass spectrometry technique to monitor the halogen oxide radicals. Rate coefficients of (8.8 ± 2.1) × 10−15, (2.7 − 0.5) × 10−13 and (9.5 ± 2.0) × 10−15 cm3 molecule−1 s−1 have been obtained for the reactions of IO, BrO, and ClO with DMS, respectively. The result for IO with DMS is in good agreement with two other recent studies on this reaction but is nearly three orders of magnitude slower than two earlier studies, one of which was from this laboratory. The earlier studies are now thought to be in error because of heterogeneous and secondary chemistry occurring in the systems investigated. The rate coefficient for BrO with DMS is in excellent agreement with a previously reported preliminary value from this laboratory. However, the rate coefficient for ClO with DMS is a factor of 4 lower than our previously determined value. The new data are considered more reliable in view of the much improved experimental technique in the present study. DMSO was detected as a product in all of these reactions. A semi‐quantitative determination of the DMSO yield was only possible in the case of the reaction of IO with DMS where a yield of 84 ± 40% was found.
Kinetics of the reaction between H atoms and allyl radicals
Authors: Hanning‐Lee Mark A. , Pilling Michael J.
Published: January 2005

The reaction between H and C3H5 has been studied at 291 K. Exciplex laser flash photolysis at 193.3 nm of hexa‐1,5‐diene‐He mixtures generated both H and C3H5 ([H] ≪ [C3H5]), which were detected in time‐resolved mode by resonance fluorescence and absorption spectroscopy, respectively. Rate coefficients are presented at four pressures in the range 98 ⩽ P/torr ⩽ 400; no clear pressure‐dependence is found in this range of pressures and the mean rate coefficient is (2.8 ± 1.0) × 10−10 cm3 molecule−1 s−1. Calculations based on the Troe factorization method confirm that this reaction is near its high‐pressure limit under the experimental conditions.
Kinetics and mechanism of decarboxylation of aspartic acid with ninhydrin
Authors: Zhan Zaheer , Gupta Dileep , Khan A. Aziz
Published: January 2005

The kinetic study of the decarboxylation of aspartic acid has been carried out at various [ninhydrin], [H+] and at different temperature ranging from 60–95°C. The reaction follows an irreversible first‐order reaction path under pseudo first‐order kinetic conditions. The variation of pseudo first‐order rate constant (kobs) with ninhydrin concentration was found to be in agreement with equation 1/kobs = B1 + B2/[Ninhydrin]. One mol of carbondioxide evolved from decarboxylation of α‐COOH and second mol of carbondioxide comes from the decarboxylation of β‐keto acid which is an intermediate and formed during the course of ninhydrin and aspartic acid reaction. On the basis of the observed data, a possible mechanism has been proposed.
Rate constants for the gas‐phase reactions of O3 with a series of alkenes at 296 ± 2 K
Authors: Greene Chipper R. , Atkinson Roger
Published: January 2005

The kinetics of the gas‐phase reactions of O3 with a series of alkenes have been investigated at atmospheric pressure (ca. 740 torr) of air and 296 ± 2 K, using a relative rate method in the presence of sufficient n‐octane to scavenge any OH radicals generated in these reactions. Relative to k(O3 + propene) = 1.00, the rate constants obtained were: 1‐butene, 0.975 ± 0.030; 2‐methylpropene, 1.14 ± 0.04; 2‐methyl‐1,3‐butadiene (isoprene), 1.21 ± 0.02; 1,4‐cyclohexadiene, 4.75 ± 0.23; cyclohexene, 7.38 ± 0.48; cis‐2‐butene, 12.8 ± 0.8; trans‐2‐butene, 21.5 ± 1.5; 2‐methyl‐2‐butene, 42.1 ± 2.8; cyclopentene, 64.9 ± 4.3; and 2,3‐dimethyl‐2‐butene, 123 ± 11. These relative rate constants have been placed on an absolute basis using a rate constant for the reaction of O3 with propene of 1.01 × 10−17 cm3 molecule−1 s−1 at 296 K derived from an analysis of the available literature data. The resulting rate constants then lead to a self‐consistent set of room temperature data for the reactions of O3 with these alkenes. © John Wiley & Sons, Inc.
Kinetics of the reaction of H(2S) with HBr
Authors: Talukdar Ranajit K. , Warren Rachel F. , Vaghijiani Ghanshyam L. , Ravishankara A. R.
Published: January 2005

The rate constants for the reaction H + HBr → H2 + Br were measured between 217 and 383 K using pulsed laser photolysis of HBr and cw resonance fluorescence detection of H(2S). The temporal profiles of the product Br atoms were also monitored to obtain the rate constant at 298 K. The yield of Br from the reaction was determined to be unity. The rate coefficient as a function of temperature is given by the Arrhenius expression, k
1 = (2.96 ± 0.44) × 10−11 exp(−(460 ± 40)/T) cm3 molecule−1 s−1. The quoted errors are at the 95% confidence level and include estimated systematic errors. Our results are compared with those from previous direct measurements. © John Wiley & Sons, Inc.
UV absorption spectra, kinetics, and mechanisms of the self reaction of CF3O2 radicals in the gas phase at 295 K
Authors: Nielsen Ole J. , Ellermann Thomas , Sehested Jens , Bartkiewicz Elzbieta , Wallington Timothy J. , Hurley Michael D.
Published: January 2005

The ultraviolet absorption spectrum and the self reaction kinetics of CF3O2 radicals have been studied in the gas phase at 298 K using the pulse radiolysis technique. Long pathlength Fourier transform infrared (FTIR) spectroscopy was used to identify and quantify reaction products. Absorption cross sections were quantified over the wavelength range 215–270 nm. The measured cross section at 230 nm was;

Errors represent statistical (2σ) together with our estimate of potential systematic errors. The absorption cross section data were then used to derive the observed self reaction rate constant for reaction (1), defined as −d[CF3O2]/dt = 2k obs[CF3O2]2

equation image

klobs = (3.6 ± 0.9) × 10−12 cm3 molecule−1 s−1. The only carbon containing product observed by FTIR spectroscopy was CF3OOOCF3. Consideration of the loss of CF3O2 radicals to form the trioxide CF3OOOCF3 allows derivation of the true bimolecular rate constant for reaction (1); k1 = (1.8 ± 0.5) × 10−12 cm3 molecule−1 s−1. These results are discussed with respect to previous studies of the absorption spectra of peroxy radicals, the kinetics, and mechanisms of their self reaction. © John Wiley & Sons, Inc.
Kinetics of the N‐chlorination of 2‐aminobutyric, 3‐aminobutyric, 3‐aminoisobutyric and 4‐aminobutyric acids in aqueous solution
Authors: Antelo J. M. , Arce F. , Pérez‐moure J. C.
Published: January 2005

We studied the kinetics of the N‐chlorination of 2‐aminobutyric, 3‐aminoisobutyric, and 4‐aminobutyric acids by sodium hypoclorite in strongly alkaline aqueous solution. As in the case of other amines, the rate of formation of the four N‐chloroamino acids was proportional to the concentrations of hypochlorite and amino acid, and inversely proportional to the concentration of hydroxyl ions. A reaction mechanism compatible with these results is proposed and discussed. © John Wiley & Sons, Inc.
Kinetics and mechanism of dimerization of arylmercurials
Authors: Wang Yulan
Published: January 2005

The kinetics of dimerization of arylmercurials XC6H4HgCl (X  H, p‐CH3, m‐CH3, p‐Cl, m‐OCH3, m‐CO2C2H5, and o‐OCH3) in the presence of [ClRh(CO)2]2 was studied in hexamethylphosphoramide (HMPA). The experimental rate law obtained is −d[ArHgCl]/dt=k[ArHgCl]2. The kinetic parameters of these reactions have been reported, and the variation, therein, has been explained on the basis of steric effect of substituents. The apparent activation energy E is linearly proportional to pre‐exponential factor lnA. A most plausible mechanism has been proposed on the basis of experimental results. © 1993 John Wiley & Sons, Inc.
Kinetics of base hydrolysis of tris‐(1,10‐phenanthroline)iron(II) and of solvolysis of cis‐dichlorobis(1,2‐ethanediamine)cobalt(III) in water + diol mixtures
Authors: Alshehri S. , Burgess J.
Published: January 2005

Rate constants for base hydrolysis of the tris‐(1,10‐phenanthroline)iron(II) cation and for solvolysis of the cis‐dichlorobis(1,2‐ethanediamine)cobalt(III) cation have been measured in binary aqueous mixtures containing 1,2‐ethanediol, 1,2‐ or 1,4‐butanediol, 1,2‐ or 1,6‐hexanediol, 1‐propanol, or t‐butyl alcohol, at 298.2 K. Kinetics of base hydrolysis of the cobalt(III) complex have also been monitored in methanol‐water and ethanol‐water mixtures, again at 298.2 K. The observed reactivity trends are discussed in terms of the hydrophilic and hydrophobic properties of the respective diols. The dominant factor determining reactivity is hydration of the attacking hydroxide or leaving chloride, as is evidenced by the close correspondence between rate constants and transfer chemical potentials for these anions. The role of hydration has also been probed through the determination of activation volumes for these two reactions in 60% 1,4‐butanediol. © 1993 John Wiley & Sons, Inc.
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

The 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

The 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

Rate 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

The 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

Relative 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

A 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

Using 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

A 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

The 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

The 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

The 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

A 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.
The nitrogen pentoxide dissociation equilibrium
Authors: Pritchard Huw O.
Published: January 2005

The third‐law method is used to assess the authenticity of available equilibrium constants for the thermal dissociation of N2O5 ⇌ NO2 + NO3. © 1994 John Wiley & Sons, Inc.