Kinetics of reactions between methyl and acetyl radicals in gas phase produced by flash photolysis of acetic anhydride

Hassinen, E.; Kalliorinne, Kaarlo; Koskikallio, Jouko

doi:10.1002/kin.550220709

Cited by 19 publications

(6 citation statements)

References 14 publications

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“…a Rate constants (in the units of 10 -12 cm 3 molecule -1 s -1 ) were taken from the NIST kinetic database 16 10 -12 cm 3 molecule -1 s -1 . 18 For reaction 11, a value of k 11 ) 4 × 10 -11 cm 3 molecule -1 s -1 was adopted using analogy with CH 3 O 2 + C 2 H 5 reaction. 16 At the same time, reaction 8, being more than one order of magnitude slower than reaction 7, k 8 ) 1.6 × 10 -13 cm 3 molecule -1 s -1 , 19 does not noticeably affect the vinoxy radicals concentration during the initial period of ∼3 ms even at higher O 2 concentration.…”

Section: Resultsmentioning

confidence: 99%

Branching Fractions for H₂O Forming Channels of the Reaction of OH Radicals with Acetaldehyde

2004

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Branching fractions for two hydrogen abstraction channels of the OH + CH3CHO reaction producing H2O + CH3CO (a) and H2O + CH2CHO (b) were determined using chemical ionization mass spectrometry. Reaction took place in a high-pressure turbulent flow reactor at 200 Torr of carrier gas N2. The branching fraction for the abstraction from the methyl group, (5.1+2.4/- 1.7) %, was determined at room temperature by direct detection of the vinoxy radicals (CH2CHO) using proton-transfer ionization. The total H2O yield of (97.7 ± 4.7) % was obtained at T = 298 and 248 K by comparison with OH + C6H12 reaction, confirming that in this temperature range reaction proceeds by H-atom abstraction. Secondary reactions of the acetyl and vinoxy radicals in the presence of O2 and NO2 were studied by monitoring the stable products CH2O, (HCO)2, and CH3OH using proton-transfer ionization. It was found that formaldehyde is the major coproduct of OH in the CH3CO + O2 reaction.

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Section: Resultsmentioning

confidence: 99%

Branching Fractions for H₂O Forming Channels of the Reaction of OH Radicals with Acetaldehyde

2004

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“…for which the rate coefficients at 298 K are k 3 ¼ 2 Â 10 À11 cm 3 mol À1 s À1 and k 4 ¼ 7 Â 10 À11 cm 3 mol À1 s À1 . 35,36 As a consequence the major consumption of acetyl is in reaction with methyl to form acetone. Using a GEPASI simulation model it can easily be shown that this is indeed the case for our experimental conditions and that the 'time constant' for the loss of acetyl in these reactions is in the order of 10 2 s À1 .…”

Section: Determination Of the Co Quantum Yieldmentioning

confidence: 99%

Pressure dependence for the CO quantum yield in the photolysis of acetone at 248 nm: A combined experimental and theoretical study

Somnitz

Fida

Ufer

et al. 2005

Phys. Chem. Chem. Phys.

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The quantum yield of CO in the laser pulse photolysis of acetone at 248 nm and at 298 K in the pressure range 20-900 mbar (N2) has been measured directly using quantitative infrared diode laser absorption of CO. It is found that the quantum yield of CO shows a significant dependence on total pressure with Phi(CO) decreasing with pressure from around 0.45 at 20 mbar to approximately 0.25 at 900 mbar. From a combination of ab initio quantum chemical calculations on the molecular properties of the acetyl (CH3CO) radical and its unimolecular fragmentation as well as the application of statistical (RRKM) and dynamical calculations we show that CO production results from prompt secondary fragmentation (via(2a)) of the internally excited primary CH3CO* photolysis product with an excess energy of approximately 62.8 kJ mol(-1). Hence, our findings are consistent with a consecutive photochemically induced decomposition model, viz. step (1): CH3COCH3+hv--> CH3CO*+ CH3, step (2a): CH3CO*--> CH3+ CO or step (2b) CH3CO*-(+M)--> CH3CO. Formation of CO via a direct and/or concerted channel CH3COCH3+hv--> 2CH(3)+ CO (1') is considered to be unimportant.

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“…Where possible, we have recalculated values of k , and k-' using current knowledge of the rate constants of the competing reactions that were needed to reduce the data in these older studies. In particular, the CH, + CH3 rate constant was taken from the study of Walter et al [37], and that of the CH, + CH,CO as well as the CH3C0 + CH,CO reaction from the investigation of Hassinen et al [38]. One reference rate constant was reestimated since it has not been determined experimentally, that of the reaction…”

Section: Reanalysis Of Prior Studies Of Fall-off Behavior Of Reactionmentioning

confidence: 99%

“…) Fall-off curve Experimental rate constants are higher than those calculated using the strong collision Methyl-t-butyl ketone.Rate constant for CHI + CH,CO -CH'COCH, (6.97 . lo-" cm' molec-l S K I ) used in recalculation of k , taken from[38]. h' Rate constant for CH'CO Rate constant for 2 CHICO -(CH3C0)2 (3.52 .…”

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Weak Collision Effects in the Reaction CH₃CO → CH₃ + CO

Bencsura

Knyazev

Slagle

et al. 1992

Ber Bunsenges Phys Chem

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Rate constants for the unimolecular decomposition of CH3CO have been obtained as a function of temperature (420 ‐ 500 K) and helium density (3 ‐ 18 · 1016 atom cm−3), conditions which are in the second order region of the fall‐off curve. An Arrhenius expression for the low‐pressure limit unimolecular rate constant was obtained from the results, k1±(He) = (6.7 ± 1.8) · 10−9 exp[(‐6921 ± 126 K)/T] cm3 molecule−1 s−1. Using a Master Equation formalism to calculate values of k1, a set of the two energy parameters needed in the calculations, E± and ΔE)down (including its temperature dependence), was found that is within the range of expected values (including a temperature dependence in the case of ΔEdown), which, when incorporated into the Master Equation, provides calculated rate constants which agree well with the measured ones. They are E± = 65.3 ± 4.0 kJ mol−1 and ΔEdown = 65.6 + 0.271 T cm−1 (the latter, a parameterized expression, is valid only in the temperature range of this study). A transition state model for the unimolecular decomposition of CH3CO was produced which provides high‐pressure limit rate constants for this reaction (k1±(CH3CO ± CH3 + CO) = 2.50 · 1013 exp(‐8244 K/T) s−1 and k−1±(CH3 + CO ± CH3CO) = 7.64 · 10−13 exp(‐3073 K/T) cm3 molecule−1 s−1) and k(E) values for solving the Master Equation for reaction conditions that are in the fall‐off region. Fall‐off behavior of k1 and k−1 reported by others for several different bath gases was reproduced within the uncertainty limits of the experimental results using the Master Equation formalism incorporating the transition state model, the energy parameter E± given above, and reasonable values for ΔEdown for the different bath gases used. This Master Equation formalism and transition state model should provide unimolecular rate constants for reaction (1, ‐ 1) in the fall‐off region for additional bath gases using reasonable estimates of ΔEdown (e. g., values obtained for this energy‐transfer parameter for collisions between other polyatomic radicals and the bath gases of interest).

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Kinetics of reactions between methyl and acetyl radicals in gas phase produced by flash photolysis of acetic anhydride

Cited by 19 publications

References 14 publications

Branching Fractions for H₂O Forming Channels of the Reaction of OH Radicals with Acetaldehyde

Branching Fractions for H₂O Forming Channels of the Reaction of OH Radicals with Acetaldehyde

Pressure dependence for the CO quantum yield in the photolysis of acetone at 248 nm: A combined experimental and theoretical study

Weak Collision Effects in the Reaction CH₃CO → CH₃ + CO

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Kinetics of reactions between methyl and acetyl radicals in gas phase produced by flash photolysis of acetic anhydride

Cited by 19 publications

References 14 publications

Branching Fractions for H2O Forming Channels of the Reaction of OH Radicals with Acetaldehyde

Branching Fractions for H2O Forming Channels of the Reaction of OH Radicals with Acetaldehyde

Pressure dependence for the CO quantum yield in the photolysis of acetone at 248 nm: A combined experimental and theoretical study

Weak Collision Effects in the Reaction CH3CO → CH3 + CO

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Product

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Branching Fractions for H₂O Forming Channels of the Reaction of OH Radicals with Acetaldehyde

Branching Fractions for H₂O Forming Channels of the Reaction of OH Radicals with Acetaldehyde

Weak Collision Effects in the Reaction CH₃CO → CH₃ + CO