Gas phase reaction of Cl atoms with a series of oxygenated organic species at 295 K

The relative rate technique has been used to determine the rate constants for the reaction of chlorine atoms with a series of oxygenated organic species. Experiments were performed at 295 ± 2 K and atmospheric pressure of synthetic air or nitrogen. The decay rates of the organic species were measured relative to that of ethane or n-butane. Using rate constants of 5.7 × 10^?11 cm³ molecule^?1 s^?1, and 2.25 × 10^?10 cm³ molecule^?1 s^?1 for the reaction of Cl with ethane and n-butane respectively the following rate constants were derived, in units of 10^?11 cm³ molecule^?1 s^?1: propane, (16.0 ± 0.4);i-butane, (15.1 ± 0.9) n-pentane, (31.0 ± 1.6); n-hexane, (34.5 ± 2.3); cyclohexane, (36.1 ± 1.5); methanol, (4.57 ± 0.40); ethanol, (8.45 ± 0.91); n-propanol, (14.4 ± 1.2); t-butylalcohol, (3.26 ± 0.19); acetaldehyde, (8.45 ± 0.79); propionaldehyde, (11.3 ± 0.9); dimethylether, (20.5 ± 0.8); diethylether, (35.6 ± 2.8); and methyl-t-butylether, (16.6 ± 1.2). Quoted errors represent 2σ, and do not include any errors due to uncertainties in the rate constants used to place our relative measurements on an absolute basis. The results are discussed with respect to the mechanisms of these reactions and to previous literature data.     

A relative rate study of the reaction of Cl atoms with a series of alkyl nitrates and nitro alkanes in air at 295 ± 2 K

The relative rate technique has been used to measure rate constants for the reaction of chlorine atoms with nitro methane, nitro ethane, nitro propane, nitro butane, nitro pentane, ethyl nitrate, isopropyl nitrate, n-propyl nitrate, 2-pentyl nitrate, and 2-heptyl nitrate. Decay rates of these organic species were measured relative to one or more of the following reference compounds; n-butane, ethane, chloroethane, and methane. Using rate constants of 2.25 × 10^?10 5.7 × 10^?11, 8.04 × 10^?12, and 1.0 × 10^?13 cm³ molecule^?1 s^?1 for the reaction of Cl atoms with n-butane, ethane, chloroethane, and methane, respectively, the following rate constants were derived, in units of cm³ molecule^?1 s^?1: nitro methane, <7 × 10^?15; nitro ethane, (2.05 ± 0.14) × 10^?13; nitro propane, (1.13 ± 0.05) × 10^?11; nitro butane, (5.13 ± 0.68) × 10^?11; nitro pentane, (1.40 ± 0.14) × 10^?10; ethyl nitrate, (3.70 ± 0.24) × 10^?12; n-propyl nitrate, (2.15 ± 0.13) × 10^?11; i-propyl nitrate, (3.94 ± 0.48) × 10^?12; 2-pentyl nitrate, (1.00 ± 0.06) × 10^?10; and 2-heptyl nitrate, (2.84 ± 0.50) × 10^?10. 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 (?740 torr) of synthetic air. The results are discussed with respect to the previous literature data and to the modeling of these compounds in the atmosphere.     

A kinetic study of the reaction of chlorine and fluorine atoms with CF3CHO at 295 ± 2 K

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.     

Absolute rate constants for the reaction of bromine atoms with ozone from 234 to 360 K

The rate constant for the reaction of Br + O₃ → BrO + O₂ has been measured at four temperatures from 234 to 360 K by the technique of discharge flow coupled with resonance-fluorescence detection of bromine atoms. The measured rate constants obey the Arrhenius expression k = (9.45 ± 2.48) × 10^?12 exp(-659 ± 64/T) cm³/molec·sec (one standard deviation). The results are compared with two previous studies, one of which utilized the flash-photolysis–resonance-fluorescence technique and the other utilized the discharge-flow–mass-spectrometric technique. The result is also discussed from a theoretical point of view.     

A kinetic study of the reaction of chlorine and fluorine atoms with HC(O)F at 295±2 K

Using relative rate techniques the reactions of chlorine and fluorine atoms with HC(O)F have been determined to proceed with rate constants of k₁ = (1.9 ± 0.2) × 10⁻¹⁵ and k₂ = (8.3 ± 1.7) × 10⁻¹³ cm³ molecule⁻¹ s⁻¹, respectively. Stated errors reflect statistical uncertainty; possible systematic uncertainties could add additional 10% and 20% ranges to the values of k₁ and k₂, respectively. Experiments were performed at 295 ± 2 K and 700 torr total pressure of air. The results are discussed with respect to the design and interpretation of laboratory studies of the atmospheric chemistry of CFC replacements. © 1997 John Wiley & Sons, Inc.     

Absolute rate constants for the gas-phase reaction of OH radicals with cyclohexane and ethane at 295 K

The absolute rate constants for the gas-phase H-atom abstraction by hydroxyl radicals from cyclohexane and ethane have been determined at room temperature. OH radicals were produced by pulse radiolysis of an H₂O-Ar mixture, and the decay of OH was followed by monitoring the transient light absorption around 309 nm. The rate constants were found to be k = (5.24±0.36) × 10⁻¹² and (2.98±0.21) × 10⁻¹³ cm³ molecule⁻¹ s⁻¹ for cyclohexane and ethane, res- pectively. These results are compared with literature data.     

A study of the reaction of sulfur with organic compounds

The reaction of sulfur with isomeric exo-polychloro derivatives of iso- and n-propylbenzenes containing from 4 to 6 chlorine atoms in the side chain at 200°–300° C has been studied. The reaction of sulfur with α, β, β, β′-tetrachloro- and α, β, β, β′, β′-pentachlorocumenes leads to the formation of the previously unknown thianaphtheno-[2, 3-d]-1, 2-dithiole-3-thione (yield 48%) and thionaphtheno[2,3-d]-3-chloro-1, 2-dithiolium chloride (yield 65%), respectively. The sulfuration reaction of the isomeric exo-tetrachloro-and exo-pentachloro-n-propylbenzenes leads to the formation of 4-chloro-5-phenyl-1, 2-dithiole-3-thione (yield 5–35%). The exo-hexachloro derivatives of iso- and n-bromobenzenes, on being heated with sulfur, form only resinous sulfuration products.     

A study of the reaction of sulfur with organic compounds

The reaction of sulfur with isomeric exo-polychloro derivatives of iso- and n-propylbenzenes containing from 4 to 6 chlorine atoms in the side chain at 200°–300° C has been studied. The reaction of sulfur with , , , -tetrachloro- and , , , , -pentachlorocumenes leads to the formation of the previously unknown thianaphtheno-[2, 3-d]-1, 2-dithiole-3-thione (yield 48%) and thionaphtheno[2,3-d]-3-chloro-1, 2-dithiolium chloride (yield 65%), respectively. The sulfuration reaction of the isomeric exo-tetrachloro-and exo-pentachloro-n-propylbenzenes leads to the formation of 4-chloro-5-phenyl-1, 2-dithiole-3-thione (yield 5–35%). The exo-hexachloro derivatives of iso- and n-bromobenzenes, on being heated with sulfur, form only resinous sulfuration products.For part XVI, see [1].     

A study of the reaction of sulfur with organic compounds

The reactions of sulfur with alip-halogen derivatives of 1,2-diphenylethane, 1,2-diphenylethylene, and tetraphenylethane have been studied. A new method for the production of tetraphenylthiophene (from C₆H₅CHClCHClC₆H₅), benzothieno[3,2-b]benzothiophene (from C₆H₅CHClCCl₂C₆H₅), and of 2-phenylbenzo[b] thiophene (from C₆H₅CHBrCHBrC₆H₅) has been developed. On being treated with sulfur, tetraphenyl-1,2-dichloroethane is converted into tetraphenylethylene. 1,2-Diphenylethylene reacts with sulfur in the presence of hydrogen bromide forming 2-phenylbenzo[b]thiophene and tetraphenylthiophene.For part XVII, see [1].     

Temperature‐dependent rate coefficient measurements for the reaction of bromine atoms with a series of aldehydes

Relative rate coefficient data have been obtained for the reactions Br + RCHO → RCO + HBr for a series of aldehydes: HCHO, reaction (1); CH₃CHO, reaction (2); CH₃CH₂CHO, reaction (3); CH₃CH₂CH₂CHO, reaction (4). Measurements were made over the temperature range 240–300 K in an environmental chamber/FTIR spectrometer system, using standard relative rate techniques. All measured rate coefficient ratios were found to be independent of temperature over the range studied (k₂/k₁ = 3.60 ± 0.29, k₃/k₁ = 6.65 ± 0.53, k₄/k₁ = 8.62 ± 0.69, and k₃/k₂ = 1.80 ± 0.14), implying that the activation barriers for all four reactions are essentially identical with the A‐factors increasing with the size of the aldehyde. Relative rate coefficients for k₁ and k₂ agree well with currently recommended data at room temperature, but inconsistencies on the order of 20% arise at lower temperatures. The entire set of relative rate coefficient measurements is put on an absolute scale using a combination of currently recommended values for k₁ and k₂. The following expressions (all in units of cm³ molecule⁻¹ s⁻¹) are obtained: k₁ = (0.79 ± 0.10) × 10⁻¹¹ exp(−580 ± 200/T), k₂ = (2.7 ± 0.4) × 10⁻¹¹ exp(−567 ± 200/T), k₃ = (5.75 ± 0.75) × 10⁻¹¹ exp(−610 ± 200/T), k₄ = (5.75 ± 0.75) × 10⁻¹¹ exp(−540 ± 200/T), where uncertainties quoted for the A‐factor reflect the uncertainty in the room temperature value. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 460–465, 2000     

A relative rate study of the reaction of chlorine atoms (Cl) and hydroxyl radicals (OH) with a series of ethers

Rate constants for the gas phase reactions of hydroxyl radicals and chlorine atoms with a number of ethers have been determined at 300 ± 3 K and at a total pressure of 1 atmosphere. Both OH radical and chlorine atom rate constants were determined using a relative rate technique. Values for the rate constants obtained are as follows.

Titrimetric determination of some organic compounds with bromine chloride

Bromine chloride is used in hydrochloric acid medium as a standard reagent for the rapid and precise determination of organic compounds by direct or indirect titrimetric methods. Hydrazine and its aryl derivative undergo a 4-electron change. Carbonyl compounds are determined by reaction with excess of 2,4-dinitrophenylhydrazine and estimation of the surplus. Sulphanilamide undergoes a substitution reaction in 1:3 molar ratio to bromine chloride. Thiobarbituric acid and thiourea or its alkyl derivatives show an 8-electron change but aryl thioureas also undergo nuclear bromination. Thiosemicarbazide and semicarbazide give a 10- and a 2-electron change respectively. In the direct titration, methionine is oxidized to its sulphoxide whereas cystine and cysteine form cysteic acid. In presence of bromide, glutathione forms the sulphonic acid but in the presence of iodide the product is the disulphide. The analytical results obtained by bromine chloride method are compared favourably with those afforded by established procedures.     

FTIR study of the reaction of ethyl radicals with O2 and Cl2 in air at 295 K

Using Fourier transform infrared spectroscopy, the ethene yield from the reaction of C₂H₅ radicals with O₂ has been determined to be 1.50 ± 0.09%, 0.85 ± 0.11%, and <0.1% at total pressures of 25, 50, and 700 torr, respectively. Additionally, the rate constant of the reaction of C₂H₅ radicals with molecular chlorine was measured relative to that with molecular oxygen. (1) A ratio k₆/k₇ = 1.99 ± 0.14 was measured at 700 torr total pressure which, together with the literature value of k₇ = 4.4 × 10^?12 cm³ molecule^?1s^?1, yields k₆ = (8.8 ± 0.6) × 10^?12 cm³ molecule^?1s^?1. Quoted errors represent 2σ. These results are discussed with respect to previous kinetic and mechanistic studies of C₂H₅ radicals.     

Effective rate constants for the surface reaction between solid methanol and deuterium atoms at 10 K

The surface reactions of CH3OH, CH2DOH, and CHD2OH with cold D atoms at 10 K were investigated using an atomic beam source and FTIR. Methyl-deuterated isotopologues CH2DOH, CHD2OH, and CD3OH were produced by exposure of amorphous solid CH3OH to D atoms at 10 K, and the pseudo-first-order rates for the reactions CH3OH + D --> CH2OH + HD, CH2DOH + D --> CHDOH + HD, and CHD2OH + D --> CD2OH + HD were estimated. The ratios of the reaction rates of the second and third reactions to the first reaction were 0.69 +/- 0.11 and 0.52 +/- 0.14, respectively. The difference in reaction rates is thought to be due to a secondary kinetic isotope effect on the H-abstraction reaction from the methyl side by D atoms.     

Kinetics of the reaction of OH radicals with a series of esters under simulated conditions at 295 K

The rate constants of the isopropyl acetate, n-propyl acetate, isopropenyl acetate, n-propenyl acetate, n-butyl acetate, and ethyl butyrate reactions with OH radicals were determined in purified air under atmospheric conditions, at 750 torr and (295 ± 2) K. A relative rate experimental method was used; n-heptane, n-octane, and n-nonane were the reference compounds, with, respectively, rate constants for the reaction with OH of 7.12 × 10⁻¹², 8.42 × 10⁻¹², and 9.70 × 10⁻¹² molecule⁻¹ cm³s⁻¹. The following rate constants were obtained in units of 10⁻¹² molecule⁻¹ cm³s⁻¹; isopropyl acetate, (3.12 ± 0.29); n-propyl acetate, (1.97 ± 0.24); isopropenyl acetate, (62.53 ± 1.24); n-propenyl acetate, (24.57 ± 0.24); n-butyl acetate, (3.29 ± 0.35); and ethyl butyrate, (4.37 ± 0.42). Tertiary butyl acetate has a low reactivity with OH radicals (<1 × 10⁻¹² molecule⁻¹ cm³s⁻¹). © 1996 John Wiley & Sons, Inc.     

Absolute rate constant for the disproportionation reaction of formyl radicals from 295 to 475 K

The rate constant for the reaction HCO + HCO → CH₂O + CO was measured at temperatures between 298 and 475 K. The formyl radicals were produced by flash photolysis of formaldehyde and were detected by resonance absorption at 614.5 nm. At low pressure and room temperature, k₁ = (3.35 ± 0.85) × 10^?11 cm³ molecule^?1 s^?1. There is no discernable variation of k₁ with temperature up to 475 K.     

Kinetic studies of the reaction of C2H5 with O2 at 295 K

The reaction between C₂H₅ and O₂ at 295 K has been studied with a flow reactor sampled by a mass spectrometer. With helium as the carrier gas the rate coefficient was found to increase from (1.2 ± 0.3) × 10^?12 to (3.6 ± 0.9) × 10^?12 cm³/s as [He] was increased from 2 × 10¹⁶ to 3.4 × 10¹⁷ cm^?3. The importance of has been determined from a knowledge of the initial C₂H₅ concentration together with a measurement of the C₂H₄ produced in reaction (5). F, the fraction of the C₂H₅ radicals removed by path (5), was found to decrease from 0.15 to 0.06 as [He] increased from 2 × 10¹⁶ to 3.4 × 10¹⁷ cm^?3. The rate coefficient for reaction (5) was found to be independent of [He] and to have a value of (2.1 ± 0.5) × 10^?13 cm³/s. The variation in F reflects the fact that k_1b increases as [He] increases. These observations are taken as evidence for a direct mechanism for C₂H₄ production and a collision-stabilized route for C₂H₅O₂ formation. Calculations indicate that the high-pressure limit for reaction (1b) is ～4.4 × 10^?12 cm³/s and that in the polluted troposphere the branching ratio for reactions (1b) and (5) will be ～l20.     

Kinetics of the reaction of C2H5O2 with NO at 295 K

The reaction of C₂H₅O₂ with NO in helium carrier gas at 295 K with [He] = 1.6 × 10¹⁷ cm^?3 has been studied using a gas flow reactor sampled by a mass spectrometer. Because no parent molecular ion or suitable fragment ion produced by C₂H₅O₂ could be detected, the reaction was followed by measuring the formation of NO₂. In so doing, account had to be taken of the small amount of HO₂ known to be present in the reaction mixture, which also leads to NO₂ on reaction with NO. The rate coefficient for the total reaction of C₂H₅O₂ with NO was found to be (8.9 ± 3.0) × 10^?12 cm³/s, and the path which produces NO₂ was found to account for at least 80% of all C₂H₅O₂.