Yield of Formyl Radical from the Vinyl + O₂ Reaction

Abstract

The yield of formyl (HCO) radical from the reaction of vinyl (C2H3) radical with O2 has been investigated by using a pulsed laser photolysis/cavity ring‐down spectroscopy technique at room temperature. The rate constants for the C2H3 + O2 and HCO + O2 reactions were measured to be (8.60 ± 0.87) × 10−12 and (5.55 ± 1.00) × 10−12 cm3 molecule−1 s−1, respectively, which were consistent with preceding studies. The yield of HCO radical was determined to be ϕ(HCO) = 0.222 ± 0.066, and it was independent of pressure in the pressure range 10–100 Torr with He or N2 buffer. The Rice–Ramsperger–Kassel–Marcus calculation combined with a prior energy distribution model could reproduce the experimental HCO‐radical yield and indicated that a significant portion of HCO radicals formed in the C2H3 + O2 reaction promptly dissociated to H + CO. The first CO‐stretch excited state of HCO radical, HCO(0,0,1), was observed at the total pressure of 1 Torr; the time profiles of which were satisfactory reproduced by a kinetic simulation including the relaxation of hot HCO radicals. These experimental, theoretical, and modeling results provide solid evidence for the prompt dissociation of hot HCO radicals formed in the C2H3 + O2 reaction. The product‐specific rate constants that extrapolated to higher temperature and wider pressure ranges are presented. Implications of the suggested mechanism for combustion modeling are also discussed.

Estimation of rate coefficients and branching ratios for gas-phase reactions of OH with aliphatic organic compounds for use in automated mechanism construction

“…e Based on the average of rate coefficients reported by Bowry et al (1991) for a series of cyclopropyl-alkyl radicals, representing the value per relevant bond. f The values of k dec /k O 2 shown for the secondary and tertiary reagent radical (1) can be adjusted approximately for the effects of a substituent group, X, in cyclo-propyl-ĊH-X and cyclo-propyl-Ċ(R )-X, using the following temperature-independent factors: i F dec/O 2 (-OH) = 0.6, based on rate coefficients reported for reactions of O 2 with the α-hydroxyalkyl radicals, CH 3Ċ HOH (http://iupac.pole-ether.fr/; last access: September 2017), C 2 H 5Ċ HOH (Miyoshi et al, 1990) and CH 3Ċ (OH)CH 3 (Miyoshi et al, 1990); (ii) F dec/O 2 (-C(=O)-) = 7.0, based on rate coefficients reported for reactions of O 2 with the β-oxoalkyl/vinoxy radicals CH 3 C(=O)ĊH 2 (http://iupac.pole-ether.fr/; last access: September 2017) and CH 3Ċ HC(=O)H (Oguchi et al, 2001); (iii) F dec/O 2 (-C(OH)<) = 1.7, based on rate coefficients reported for reactions of O 2 with the β-hydroxyalkyl radicals CH 3Ċ HCH 2 OH and CH 3 CH(OH)ĊH 2 (Miyoshi et al, 1990); (iv) F dec/O 2 (=O) = 4.5, based on rate coefficient reported for reaction of O 2 with CH 3Ċ O (http://iupac.pole-ether.fr/; last access: September 2017); and (v) F dec/O 2 (=C<) = 0.9, based on rate coefficient reported for reaction of O 2 with CH 2 =ĊH (Matsugi and Miyoshi, 2014). For other substituents, F dec/O 2 = 1.0 is assumed, in the absence of data.…”

“…b Product channels reported for the reaction of O 2 with vinyl radicals (e.g. Carpenter, 1995;Eskola and Timonen, 2003;Matsugi and Miyoshi, 2014). Product ratios applied here are based on observations for the reaction of O 2 with the methylvinyl radical (Orlando et al, 1999), formed during the OH-initiated oxidation of methacrolein (see Sect.…”

“…The reactions of O 2 with vinyl radicals, >C=ĊR , form chemically activated [>C=C(R )OO] ‡ adducts, which isomerize and decompose to form a carbonyl product and a chemically activated acyl radical (e.g. Carpenter, 1995;Eskola and Timonen, 2003;Matsugi and Miyoshi, 2014):…”

Dissociation of 1,1,1-Trifluoroethane Is an Intrinsic RRKM Process: Classical Trajectories and Successful Master Equation Modeling

“…The nascent energies can be evaluated from the solutions of the master equations 66 and the results of the trajectory calculations as…”

Experimental and Kinetic Modeling Study of C2H2 Oxidation at High Pressure

“…As discussed above, the reaction was studied recently by Goldsmith et al , based on state‐of‐the‐art calculations of the C 2 H 3 O 2 potential energy surface. Here, their recommendation was preferred to earlier theoretical studies of this reaction . For C 2 H 2 + O, we use the rate constants for the two major channels, HCCO + H (R4) and CH 2 + CO (R5) proposed by Miller and coworkers ; these values represent well available experimental results.…”