Kinetics of the reactions of vinyl radicals with molecular oxygen and chlorine at temperatures 200–362 K

Eskola, Arkke J.; Timonen, Raimo S.

doi:10.1039/b302894a

Cited by 67 publications

(83 citation statements)

References 31 publications

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“…On the other hand, the activation energy they have obtained for this reaction, E a (C 2 H 5 + Cl 2 ) 5 = −1.3 ± 0.5 kJ/ mol −1 , is less negative than obtained in this work, E a = −3.70 ± 0.19 kJ mol −1 . Similar differences were also observed in the context of C 2 H 3 + Cl 2 reaction measurements 11. We are unable to propose any probable reason for these differences.…”

Section: Resultssupporting

confidence: 80%

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Kinetics of the reactions of C₂H₅, n‐C₃H₇, and n‐C₄H₉ radicals with Cl₂ at the temperature range 190–360 K

Eskola

Lozovsky

Timonen

2007

Int J of Chemical Kinetics

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The kinetics of the C 2 H 5 + Cl 2 , n-C 3 H 7 + Cl 2 , and n-C 4 H 9 + Cl 2 reactions has been studied at temperatures between 190 and 360 K using laser photolysis/photoionization mass spectrometry. Decays of radical concentrations have been monitored in time-resolved measurements to obtain reaction rate coefficients under pseudo-first-order conditions. The bimolecular rate coefficients of all three reactions are independent of the helium bath gas pressure within the experimental range (0.5-5 Torr) and are found to depend on the temperature as follows (ranges are given in parenthesis): k(C 2 H 5 + Cl 2 ) = (1.45 ± 0.04) × 10 −11 (T /300 K) −1.73 ± 0.09 cm 3 molecule −1 s −1 (190-359 K), k(n-C 3 H 7 + Cl 2 ) = (1.88 ± 0.06) × 10 −11 (T /300 K) −1.57 ± 0.14 cm 3 molecule −1 s −1 (204-363 K), and k(n-C 4 H 9 + Cl 2 ) = (2.21 ± 0.07) × 10 −11 (T /300 K) −2.38 ± 0.14 cm 3 molecule −1 s −1 (202-359 K), with the uncertainties given as one-standard deviations. Estimated overall uncertainties in the measured bimolecular reaction rate coefficients are ±20%. Current results are generally in good agreement with previous experiments. However, one former measurement for the bimolecular rate coefficient of C 2 H 5 + Cl 2 reaction, derived at 298 K using the very low pressure reactor method, is significantly lower than obtained in this work

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Section: Resultssupporting

confidence: 80%

“…Details of the experimental apparatus used have been described previously 11, and so only a brief overview is given here. The radical R(R = C 2 H 5 , n ‐C 3 H 7 , or n ‐C 4 H 9 ) was generated from an appropriate precursor along the flow reactor by pulsed unfocused exciplex laser (ELI‐76E) photolysis at 193 nm.…”

Section: Methodsmentioning

confidence: 99%

Kinetics of the reactions of C₂H₅, n‐C₃H₇, and n‐C₄H₉ radicals with Cl₂ at the temperature range 190–360 K

Eskola

Lozovsky

Timonen

2007

Int J of Chemical Kinetics

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“…The flow reactor with laser photolysis coupled to the resonance gas lamp photoionization mass spectrometer (LP-RPIMS) used in this work has been described previously, 15,16 and only a brief 10 The main photolysis channel leads to C3−C4 bond fission, but in addition other products are formed:…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Gas Phase Kinetics and Equilibrium of Allyl Radical Reactions with NO and NO₂

et al. 2013

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Allyl radical reactions with NO and NO 2 were studied in direct, time-resolved experiments in a temperature controlled tubular flow reactor connected to a laser photolysis/photoionization mass spectrometer (LP-PIMS). In the C 3 H 5 + NO reaction 1, a dependence on the bath gas density was observed in the determined rate coefficients and pressure falloff parametrizations were performed. The obtained rate coefficients vary between 0.30− 14.2 × 10 −12 cm 3 s −1 (T = 188−363 K, p = 0.39−23.78 Torr He) and possess a negative temperature dependence. The rate coefficients of the C 3 H 5 + NO 2 reaction 2 did not show a dependence on the bath gas density in the range used (p = 0.47−3.38 Torr, T = 201−363 K), and they can be expressed as a function of temperature with k(C 3 H 5 + NO 2 ) = (3.97 ± 0.84) × 10 −11 × (T/300 K) −1.55±0.05 cm 3 s −1 . In the C 3 H 5 + NO reaction, above 410 K the observed C 3 H 5 radical signal did not decay to the signal background, indicating equilibrium between C 3 H 5 + NO and C 3 H 5 NO. This allowed the C 3 H 5 + NO ⇄ C 3 H 5 NO equilibrium to be studied and the equilibrium constants of the reaction between 414 and 500 K to be determined. With the standard second-and third-law analysis, the enthalpy and entropy of the C 3 H 5 + NO ⇄ C 3 H 5 NO reaction were obtained. Combined with the calculated standard entropy of reaction (ΔS°2 98 = 137.2 J mol −1 K −1 ), the third-law analysis resulted in ΔH°2 98 = 102.4 ± 3.2 kJ mol −1 for the C 3 H 5 −NO bond dissociation enthalpy. ■ INTRODUCTIONReactive hydrocarbon free radicals and nitrogen oxides (NO x = NO + NO 2 ) are produced in several common environments. Energy released by burning of hydrocarbons creates a variety of reactive intermediates, including unsaturated alkenyl radicals, and combustion under atmospheric conditions leads to the formation of nitrogen oxides. 1,2 Oxides of nitrogen are primary anthropogenic pollutants but also have natural sources in the atmosphere. 3,4 The principles governing mutual reactions of alkenyl radicals and NO x are important for the understanding of hydrocarbon oxidation mechanisms and optimization of combustion processes.Allyl radical (C 3 H 5 ) is the simplest conjugated, resonancestabilized alkenyl radical. Alkenyl radicals are formed in hydrogen abstraction reactions by reactive species (e.g., OH or other radicals) from carbon atoms at the β-position to the double bond in alkenes and by pyrolysis of larger hydrocarbons at elevated temperatures. 5−7 Small unsaturated hydrocarbon radicals with resonance-stabilized structures are thermodynamically more stable than similar saturated radicals lacking resonance stabilization. Consequently, they reach higher concentrations under combustion conditions and play a role in the molecular weight growth chemistry. They are identified as precursors for polycyclic aromatic hydrocarbons (PAHs) and, subsequently, for soot formation. 8−10 In the present work, two reactions of allyl radical with nitrogen oxides were investigated:(1)Both reactions have been stu...

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“…It has a well-characterized absorption band in the 400 -530 nm range (the A 2 A″ ← X 2 A′ transition) with an extensive vibrational progression and a moderate absorption cross-section (~ 3•10 -19 cm 2 at 404 nm) [15][16][17]. In the presence of O 2 the main decay pathways of the vinyl radical are shown below [14,18] …”

Section: Studies Of Vinyl Radical Oxidationmentioning

confidence: 99%

Time-resolved broadband cavity-enhanced absorption spectroscopy for chemical kinetics.

Sheps¹,

Chandler²

2013

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Experimental measurements of elementary reaction rate coefficients and product branching ratios are essential to our understanding of many fundamentally important processes in Combustion Chemistry. However, such measurements are often impossible because of a lack of adequate detection techniques. Some of the largest gaps in our knowledge concern some of the most important radical species, because their short lifetimes and low steady-state concentrations make them particularly difficult to detect. To address this challenge, we propose a novel general detection method for gas-phase chemical kinetics: time-resolved broadband cavity-enhanced absorption spectroscopy (TR-BB-CEAS). This all-optical, non-intrusive, multiplexed method enables sensitive direct probing of transient reaction intermediates in a simple, inexpensive, and robust experimental package. 4 ACKNOWLEDGMENTSWe thank Dr. David Osborn (8353) and Dr. Steven S. Brown (NOAA, Boulder, CO) for helpful discussions regarding cavity-enhanced optical methods and experimental design. We also thank Dr. Craig Taatjes (8353) for the use of lab space and for the loan of a YAG laser and optics. 5

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Kinetics of the reactions of vinyl radicals with molecular oxygen and chlorine at temperatures 200–362 K

Cited by 67 publications

References 31 publications

Kinetics of the reactions of C₂H₅, n‐C₃H₇, and n‐C₄H₉ radicals with Cl₂ at the temperature range 190–360 K

Kinetics of the reactions of C₂H₅, n‐C₃H₇, and n‐C₄H₉ radicals with Cl₂ at the temperature range 190–360 K

Gas Phase Kinetics and Equilibrium of Allyl Radical Reactions with NO and NO₂

Time-resolved broadband cavity-enhanced absorption spectroscopy for chemical kinetics.

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Kinetics of the reactions of vinyl radicals with molecular oxygen and chlorine at temperatures 200–362 K

Cited by 67 publications

References 31 publications

Kinetics of the reactions of C2H5, n‐C3H7, and n‐C4H9 radicals with Cl2 at the temperature range 190–360 K

Kinetics of the reactions of C2H5, n‐C3H7, and n‐C4H9 radicals with Cl2 at the temperature range 190–360 K

Gas Phase Kinetics and Equilibrium of Allyl Radical Reactions with NO and NO2

Time-resolved broadband cavity-enhanced absorption spectroscopy for chemical kinetics.

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Kinetics of the reactions of C₂H₅, n‐C₃H₇, and n‐C₄H₉ radicals with Cl₂ at the temperature range 190–360 K

Kinetics of the reactions of C₂H₅, n‐C₃H₇, and n‐C₄H₉ radicals with Cl₂ at the temperature range 190–360 K

Gas Phase Kinetics and Equilibrium of Allyl Radical Reactions with NO and NO₂