bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oxidation of benzyl alcohols by nitrous and nitric acids in strong sulfuric acid media
Authors: Ross David S. , Gu Chee‐Liang , Hum Georgina P. , Malhotra Ripudaman 
Published: January 2005

AbstractWe have studied the oxidation of benzyl alcohols by nitrous and nitric acid in sulfuric acid media. The oxidation by nitrous acid is rapid and has an activation energy of 10.6 ± 0.8 kcal mol−1. A Hammett plot of logk2 vs. σ+ is linear with a ρ value of −1.4. The oxidation by nitric acid in sulfuric acid media is autocatalytic. From the kinetic and product analyses, it is concluded that a common oxidant, the nitrosonium ion is involved when either nitrous or nitric acid is used. A mechanism is proposed which involves the abstraction of hydride from the alcohols as the rate determining step. It is demonstrated that the autoxidation of the alcohols is catalyzed by nitrous acid or nitric oxide.
Kinetics of the oxidation of nitric oxide by chlorine and oxygen in nonaqueous media
Authors: Nottingham Winston C. , Sutter John R. 
Published: January 2005

AbstractThe kinetics of the reaction between nitric oxide and chlorine have been investigated in both carbon tetrachloride and glacial acetic acid. The nitric oxide‐oxygen reaction has been investigated in carbon tetrachloride.The appearance of product, NOCl or NO2, was monitored spectrophotometrically at a wavelength of 475 nm for NOCl and 343 nm for NO2. These measurements were performed using an Amino‐Morrow stopped‐flow apparatus equipped with a Beckman D U monochromator.The data for both the NOCl2 and NOO2 systems could be fitted to the third‐order integrated equation and the calculated rate constants were 2.75 × 103 M−2 s−1 and 2.79 × 106 M2 s−1, respectively, at 25.1°C.There was a noted increase in rate constants on changing the solvent from carbon tetrachloride to acetic acid.The likelihood of a termolecular encounter is inherent in the mechanism, however, no real evidence to substantiate either a direct termolecular or a series of two bimolecular steps has been obtained, although a −7 kcal for ΔH0 would support the latter.
Rate constant of OH + OCS reaction over the temperature range 255–483 K
Authors: Cheng Bing‐Ming , Lee Yuan‐Pern 
Published: January 2005

AbstractThe rate constant of the reaction between OH and OCS in helium over the temperature range 255–483 K has been determined using the discharge flow‐resonance fluorescence technique. The OCS has been carefully purified to avoid interference from H2S and CO impurities. An FTIR with a multireflection cell was used to determine the impurity concentrations and the purified sample was found to contain less than 0.005% of H2S. At 300 K, the rate constant was determined to be (2.0 ±0.40.8) × 10−15 cm3 molecule−1 s−1. Although the rate constants showed slight positive deviation at lower temperatures, thev can be satisfactorily fitted by the Arrhenius equation, k = 1.13 × 10−13 exp(−1200/T) cm3 molecule−1 s−1. No pressure dependence was observed at all temperatures, nor was O2 enhancement observed under our experimental conditions.
Rates and mechanisms of oxidation of ZnTPP by CCI3O2 radicals in various solvents
Authors: Alfassi Z. B. , Harriman A. , Mosseri S. , Neta P. 
Published: January 2005

AbstractTrichloromethylperoxyl radicals were produced by pulse radiolysis of air saturated solutions containing CCl4. The rate constants for the reaction of CCl3O2 radicals with zinc tetraphenylporphyrin (ZnTPP) were determined in various solvents. They were found to vary between 3 × 107 and 3 × 109 M−1 s−1. The changes in rate constants result from complexation of ZnTPP with the different solvents, but did not correspond to changes in redox potential of ZnTPP. The rate constants were found to depend on the strength of the axial complexation, indicating an inner sphere mechanism whereby the radical binds to the metal prior to electron transfer.
The reaction of acetylperoxy radicals with NO2
Authors: Basco Norman , Parmar Sucha S. 
Published: January 2005

AbstractAcetylperoxy radicals were produced by the flash photolysis of chlorine in the presence of acetaldehyde and oxygen. By adding various concentrations of nitrogen dioxide, the rate constant for the reaction producing PAN
equation image
was measured to be k4 (153 Torr) = (2.29 ± 0.05) × 109 L/mol s.The effect of pressure has been studied over the range 76–612 Torr and the data fitted to a fall‐off curve with k = 1.85 × 1013 L2/mol2 s. and k = 3.67 × 109 L/mol s. With a calculated value of the dissociation constant, k = 268 L/mol s and of the equilibrium constant, K4 = 1.04 × 1012 L/mol, the expected strong collision value for k is 2.79 × 1014 L2/mol2 s.The ultraviolet absorption spectrum of PAN has been characterized in the range 205–260 nm.
A study of the reaction NO3 + NO2 + M → N2O5 + M(M = N2, O2)
Authors: Wallington Timothy J. , Atkinson Roger , Winer Arthur M. , Pitts James N. 
Published: January 2005

AbstractThe gas‐phase reaction of the NO3 radical with NO2 was investigated, using a flash photolysis‐visible absorption technique, over the total pressure range 25–400 Torr of nitrogen or oxygen diluent at 298 ± 2 K. The absolute rate constants determined (in units of 10−13 cm3 molecule−1 s−1) at 25, 100, and 400 Torr total pressure were, respectively, (4.0 ± 0.5), (7.0 ± 0.7), and (10 ± 2) for M = N2 and (4.5 ± 0.5), (8.0 ± 0.4), and (8.8 ± 2.0) for M = O2. These data show that the third‐body efficiencies of N2 and O2 are identical, within the error limits, and that previous evaluations for M = N2 are applicable to the atmosphere. In addition, upper limits were determined for the rate constants of the reactions of the NO3 radical with methanol, ethanol, and propan‐2‐ol of ⩽6 × 10−16, ⩽9 × 10−16, and ⩽2.3 × 10−15 cm3 molecule−1 s−1, respectively, at 298 ± 2 K.
Absolute rate constants for hydrogen abstraction from hydrocarbons by the trichloromethylperoxyl radical
Authors: Mosseri S. , Alfassi Z. B. , Neta P. 
Published: January 2005

AbstractAbsolute rate constants have been measured for the reactions of trichloromethylperoxyl radicals with cyclohexane, cyclohexene, and hexamethylbenzene. The CCl3O2 radicals were produced by pulse radiolysis of air‐saturated CCl4 solutions containing various amounts of the hydrocarbons. The rate constants were determined by competition with the one‐electron oxidation of metalloporphyrins, using the rate of formation of the metalloporphyrin radical cation absorption to monitor the reaction by kinetic spectrophotometry. The rate constants for hydrogen abstraction from cyclohexane, cyclohexene, and hexamethylbenzene were found to be 1 × 103, 1.0 × 105, and 7.5 × 104 M−1 s−1, respectively.
Collisional energy transfer in highly vibrationally excited molecules: A very low‐pressure pyrolysis study of acetyl chloride
Authors: Lim Kieran F. , Gilbert Robert G. , Brown Trevor C. , King Keith D. 
Published: January 2005

AbstractThe average downward energy transfer (〈Δ Edown〉) is obtained for highly vibrationally excited acetyl chloride with Ne and C2H4 bath gases at ca. 870 K. Data are obtained by the technique of very low‐pressure pyrolysis (VLPP). Fitting these data by solution of the appropriate reaction‐diffusion integrodifferential master equation yields the gas/gas collisional energy transfer parameters: 〈Δ Edown〉 values are 220 ± 10 cm−1 (Ne bath gas) and 330 ± 20 cm−1 (C2H4).These energy transfer quantities are much less than those predicted by statistical theories, or those observed for similar sized molecules such as CH3CH2Cl. These results are explained by the qualitative predictions of the biased random walk model wherein the fundamental mechanism of energy transfer is the multiple interactions between the bath gas and the individual atoms of the reactant molecule, during the course of the collision event. The charge distribution of acetyl chloride decreases the number of such interactions, thereby reducing the amount of energy transferred per collision.
A modeling study of the oxidation of propionaldehyde in the negative temperature coefficient regime
Authors: Kaiser E. W. 
Published: January 2005

AbstractA chemical kinetic reaction mechanism has been developed which describes the oxidation of propanal within the temperature range 400–700 K. This mechanism has been tested against data obtained by four experimental groups over a wide range of initial conditions. The induction period and the absolute rate of propanal consumption are predicted to within a factor of 2 for initial densities of oxygen and propanal ranging over factors of 400. The existence and location of the negative temperature coefficient in the consumption of propanal are also simulated properly. The yields of all major and most minor products are predicted to within a factor of 2 for the wide variety of initial conditions tested. Sensitivity analyses were carried out at 553 and 713 K to identify the reactions primarily responsible for controlling the rate of propanal consumption and the distribution of products.
Kinetic study of the reaction of IO with CH3SCH3
Authors: Martin D. , Jourdain J. L. , Laverdet G. , Le Bras G. 
Published: January 2005

AbstractThe reaction IO + CH3SCH3 → products (3) was studied at room temperature and near 1 Torr pressure of He, using the discharge flow mass spectrometric technique. The rate constant was found to be k3 = (1.5 ± 0.5) × 10−11 cm3 molecule−1 s−1. CH3S(O)CH3 was detected as a product suggesting the following channel: IO + CH3SCH3 → CH3S(O)CH3 + I. The rate constant of the reaction IO + IO → products (1) was also measured: k1 = (3 ± 0.5) × 10−11 at 298 K and 1 Torr pressure. The atmospheric implication of reaction (3) is discussed. The results indicate that this reaction could be a potential important sink of CH3SCH3 in marine atmosphere.
Self‐inhibition or the lack of it in the pyrolyses of neopentane and n‐hexane
Authors: Marshall Roger M. 
Published: January 2005

AbstractPublished data show that in its early stages (up to 3% decomposition), the pyrolysis of n‐hexane in the ranges 723–823 K and 10–100 Torr is not inhibited by the olefin products, in contrast with neopentane pyrolysis which is very strongly inhibited in similar conditions. Detailed consideration of the chain mechanisms for the two pyrolyses shows that the reactivity of the chain terminating radical towards hydrogen abstraction from an allylic CH bond in product olefin is the factor which determines whether or not observable self‐inhibition occurs. Thus, n‐hexane pyrolysis, whose chain decomposition is terminated by recombination and disproportionation of ethyl, is not significantly self‐inhibited, whereas that of neopentane which is terminated by recombination of methyl is very strongly inhibited because methyl is 14× more reactive than ethyl. The implications for other alkanes are briefly discussed.
Kinetics and mechanism of the thermal reactions of endo‐ and exo‐5‐cyanobicyclo[2.2.2]oct‐2‐ene and methyl‐substituted derivatives in the gas phase
Authors: Van Mele B. , Huybrechts G. 
Published: January 2005

AbstractThe thermal reactions of endo‐ and exo‐5‐cyanobicyclo‐[2.2.2]oct‐2‐ene and their trans‐ and cis‐6‐methyl‐substituted derivatives have been investigated in the gas phase between 518 and 630 K. Each product decomposes by two parallel first‐order retro‐Diels‐Alder reactions, a main one with formation of cyclohexa‐1,3‐diene and a minor one with elimination of ethene. Slight isomerizations are also observed. The kinetic results can be explained in terms of a biradical mechanism. The rate‐determining step is shown to depend on the amount of resonance energy in the biradical. Heats of formation and entropies of the bicyclo[2.2.2]oct‐2‐enes studied are estimated.
Large inefficiencies of unweighted least‐squares treatment of logarithmically transformed A exp(–kt) data
Authors: Kalantar A. H. 
Published: January 2005

AbstractThe standard deviations (σ) of the parameters of a single exponential function can vary strongly with the range of the data, the character of the underlying error structure and also with the inclusion or omission of the appropriate relative weights. These effects are studied quantitatively, for least squares analysis of uniformly spaced, ln‐linearized simulated data. The parameters, k and A, extracted are less precise when weighting is omitted, increasingly so as the range of the data increases, particularly for the case of equal amplitude errors for each A exp(–kti) datum. The results, expressed as efficiencies (σ2[using weights]/σ2[omitting weights]), show < 1% efficiency in some cases. This is tantamount to ignoring > 99% of the data and treating the remainder with proper relative weighting.
Disproportionation reactions between alkyl and fluoroalkyl radicals. IV. Pentafluoroethyl and ethyl radicals
Authors: Pritchard G. O. , Kennedy V. H. , Heldoorn G. M. , Piasecki M. L. , Johnson K. A. , Golan D. R. 
Published: January 2005

AbstractA new determination of the disproportionation/combination ratio for C2F5 and C2H5 radicals gives a value of Δ(C2F5, C2H5) = 0.24 ± 0.02, independent of temperature. The cross‐combination ratio for the two radicals was found to increase with temperature and the significance of this is discussed in evaluating Δ.
The photochemistry of methyl cyclobutyl ketone. Part 2. Temperature dependence and the acetyl radical decomposition
Authors: Baldwin Philip J. , Canosa‐Mas Carlos E. , Frey H. Monty , Walsh Robin 
Published: January 2005

AbstractFollowing earlier room‐temperature studies, gaseous mixtures of methyl cyclobutyl ketone (MCK) diluted in argon have been photolyzed at temperatures up to 205°C. Experiments have been carried out at a variety of pressures (up to ca. 2 atm) at wavelengths of 313 nm (steady state conditions) and 308 nm (pulsed photolysis). The results are consistent with a mechanism dominated by radical‐radical reactions involving acetyl, methyl, and cyclobutyl radicals. Acetyl radical processes predominate at lower temperatures while methyl radical reactions are more important at high temperatures.The results are interpreted via kinetic modelling of a mechanism in which a key role is played by the acetyl radical decomposition reaction

Values for k3 have been obtained and its temperature and pressure dependence are fitted by RRKM theory and a weak‐collisional activation model to yield

This high‐pressure limiting Arrhenius equation is consistent with other studies in the same temperature range, but is difficult to reconcile with higher temperature investigations.
The gas phase reactions of hydroxyl radicals with a series of aliphatic alcohols over the temperature range 240–440 K
Authors: Wallington Timothy J. , Kurylo Michael J. 
Published: January 2005

AbstractAbsolute rate constants were determined for the gas phase reactions of OH radicals with a series of aliphatic alcohols using the flash photolysis resonance fluorescence technique. Experiments were performed over the temperature range 240–440 K at total pressures (using Ar diluent gas) between 25–50 Torr. The kinetic data for methanol (k1), ethanol (k2), and 2‐propanol (k3) were used to derive the Arrhenius expressions

and

At 296 K, the measured rate constants (in units of 10−13 cm3 molecule−1 s−1) were: k1 = (8.61 ± 0.47), k2 = (33.3 ± 2.3), and k3 = (58.1 ± 3.4). Room temperature rate constants for the OH reactions with several other aliphatic alcohols were also measured. These were (in the above units): 1‐propanol, (53.4 ± 2.9); 1‐butanol, (83.1 ± 6.3) and 1‐pentanol, (108 ± 11). The results are discussed in terms of the mechanisms for these reactions and are compared to previous literature data.
Measurement of absolute rate data for the reaction of ground state atomic silicon, Si(33PJ), with halogenated olefinic and aromatic compounds by time‐resolved atomic resonance absorption spectroscopy
Authors: Basu Subhash C. , Husain David 
Published: January 2005

AbstractWe present a kinetic study of the reaction of ground state silicon atoms with halogenated unsaturated organic compounds (R). Si(33PJ) was generated by the repetitive pulsed irradiation of SiCl4 in the presence of excess helium buffer gas and the reactant R in a slow flow system, kinetically equivalent to a static system. The ground state atom was monitored by time‐resolved atomic resonance absorption spectroscopy at λ = 252 nm [Si(43PJ) ← Si(33PJ)] on time scales by which the optically metastable tates,Si(31D2) and Si(31S0) had relaxed to the 3P state, using signal averaging methods. Computerized fitting of the resulting atomic decay traces in the presence of the various reactants, R, yielded the following new body of absolute second‐order rate constants (kR, T = 300 K, errors = 2sigma;):

R
kR/cm3 molecule−1 s−1

C2F4
1.6 ± 0.2 × 10−10

C2Cl4
9.9 ± 1.7 × 10−10

CH2CF2
4.0 ± 0.6 × 10−10

CHClCCl2
7.0 ± 1.1 × 10−10

CF3CHCH2
4.6 ± 0.5 × 10−10

C6H6
4.4 ± 1.0 times; 10−10

C6F6
4.4 ± 0.6 × 10−10

C6HF5
4.6 ± 1.3 × 10−10

C6H2F4
3.9 ± 0.8 × 10−10

C6F5—CF3
5.1 ± 0.6 × 10−10

These data are compared, where appropriate, with analogous data for unsaturated hydrocarbon organic compounds. They are also discussed within the general context of nuclear recoil measurements involving 31Si.
A study of product ratios in the direct (313 nm) and Hg‐sensitized (254 nm) photodecomposition of 2‐methylcyclohexanone in the gas phase
Authors: Pritchard G. O. , Badcock C. C. , Follmer D. W. 
Published: January 2005

AbstractThe photolysis of 2‐methylcyclohexanone has been studied in the gas phase at 313 nm, mainly at 100°C, over a range of pressures. The Hg(63P1) photosensitized decomposition has also been investigated at 100°C. Under conditions of high excitation and/or little collisional quenching the major products are carbon monoxide and the hydrocarbons: 1‐hexene, trans‐and cis‐2‐hexene and methylcyclopentane, with minor aldehyde formation. The various product ratios are presented in tabular form. At lower excitation energies, and with increased collisional deactivation, trans‐ and cis‐5‐heptenal become important products, and the trans/cis aldehyde ratio is seen to be slightly pressure dependent when all the systems are compared. Similarly, there is a small pressure dependence for the Σ hexenes/methylcyclopentane ratio. From experiments at 250°C the temperature dependence of this ratio was established, and for thermalized hexane‐1,5‐diyl an activation energy difference (Ed − Ec) = −1.3 kcal mol−1 has been determined for the disproportionation and combination of the biradical. The mechanism for the photolysis is discussed in terms of triplet state photochemistry and biradical intermediates as developed, in particular, by Frey and coworkers, this Journal, 16, 1337 (1984).
The kinetics and mechanism of the decomposition of N‐chloroleucine
Authors: Antelo Juan M. , Arce Florencio , Franco Julia , Rodriguez Pilar , Varela Angel 
Published: January 2005

AbstractAt 298 K the rate constant for the decomposition of N‐chloroleucine has the constant value 3.20 × 10−4 s−1 over the range pH 5–12, increases with increasing acidity at pH < 5, and increases with pH at pH > 12. A mechanism is put forward which explains these results.
The thermochemistry of polyoxides and polyoxy radicals
Authors: Francisco J. S. , Williams I. H. 
Published: January 2005

AbstractA new estimate is derived for the group additivity contribution ΔH[O—(O)2] = 55 ± 6 kJ mol−1, based upon recent experimental data, which enables heats of formation and bond dissociation energies to be estimated for species ROnR and RO(R = H, CH3, and CF3). Semi‐empirical MNDO calculated heats of formation, for these species, provide independent support for the new thermochemical estimates. The results are also consistent with other theoretical and experimental evidence.
Thermal decomposition of 1,2 butadiene
Authors: Kern R. D. , Singh H. J. , Wu C. H. 
Published: January 2005

AbstractThe thermal decomposition of 1,2 butadiene has been studied behind reflected shock waves over the temperature and total pressure ranges of 1300–2000 K and 0.20–0.55 atm using mixtures of 3% and 4.3% 1,2 butadiene in Ne. The major products of the pyrolysis are C2H2, C4H2, C2H4, CH4 and C6H6. Toluene was observed as a minor product in a narrow temperature range of 1500–1700 K. In order to model successfully the product profiles which were obtained by time‐of‐flight mass spectrometry, it was necessary to include the isomerization reaction of 1,2 to 1,3 butadiene. A reaction mechanism consisting of 74 reaction steps and 28 species was formulated to model the time and temperature dependence of major products obtained during the course of decomposition. The importance of C3H3 in the formation of benzene is demonstrated.
The high temperature pyrolysis of 1,3‐butadiene II: Pulsed laser flash absorption rate constants, and consideration of possible molecular dissociation pathways
Authors: Kiefer J. H. , Mitchell K. I. , Wei H. C. 
Published: January 2005

AbstractRate constants for the unimolecular dissociation of 1,3‐butadiene have been measured with the pulsed laser flash absorption technique, following butadiene disappearance at 222 nm. The results are in excellent agreement with previous laser‐schlieren measurements interpreted with a ΔH°298 = 100 kcal/mol heat of dissociation. A new RRKM calculation agreeing with both sets of rate constants gives log k∞(s−1) = 17.03 ± 0.3 – 94(kcal/mol)/RT. These data and product measurements using ARAS, single‐pulse product analysis, and time‐of‐flight mass spectrometry, in shock tubes, all provide independent evidence against any major participation by molecular reactions in the dissociation. The only dissociation channel, or combination of channels, consistent with all the measurements is C‐C scission to two vinyl radicals. However, the extremely slow rate of H‐atom formation seen in ARAS experiments then requires an unacceptably low rate of vinyl dissociation.
The UV absorption spectra and kinetics of the self reactions of CH2ClO2 and CH2FO2 radicals in the gas phase
Authors: Dagaut Philippe , Wallington Timothy J. , Kurylo Michael J. 
Published: January 2005

AbstractThe ultraviolet absorption spectra of chloromethylperoxy and fluoromethylperoxy radicals, CH2ClO2 and CH2FO2, and the kinetics of their respective self reactions have been studied in the gas phase using a flash photolysis technique. The absorption spectra for both radicals were quantified over the wavelength range 210 and 290 nm. The measured absorption cross‐sections

were used to derive the observed self‐reaction rate constants (for reactions 1 and 2) over the temperature range 228–380 K, defined as –d[CH2XO2]/dt = 2k[CH2XO2]2, where X represents Cl or F.
magnified image
The rate constants at 298 K were found to be independent of pressure over the range 25–400 torr N2 with values of k1(298 K) = (3.78 ± 0.45) × 10−12 and k2(298 K) = (3.07 ± 0.65) × 10−12 in units of cm3 molecule−1 s−1. The kinetic data over the complete temperature range are represented by the Arrhenius expressions:

where the error limits represent 2σ from linear least squares analysis. These results are discussed with respect to previous measurements of the absorption spectra and reactions of alkylperoxy radicals.