Effect of Methyl Group Substitution on the Kinetics of Vinyl Radical + O-2 Reaction

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Joshi , S P , Pekkanen , T T , Timonen , R S & Eskola , A J 2019 , ' Effect of Methyl Group Substitution on the Kinetics of Vinyl Radical + O-2 Reaction ' , Journal of Physical Chemistry A , vol. 123 , no. 49 , pp. 10514-10519 . https://doi.org/10.1021/acs.jpca.9b08028

Title: Effect of Methyl Group Substitution on the Kinetics of Vinyl Radical + O-2 Reaction
Author: Joshi, Satya P.; Pekkanen, Timo T.; Timonen, Raimo S.; Eskola, Arkke J.
Contributor organization: Department of Chemistry
Date: 2019-12-12
Language: eng
Number of pages: 6
Belongs to series: Journal of Physical Chemistry A
ISSN: 1089-5639
DOI: https://doi.org/10.1021/acs.jpca.9b08028
URI: http://hdl.handle.net/10138/321155
Abstract: The kinetics of (CH3)(2)CCH + O-2 (1) and (CH3)(2)CCCH3 + O-2 (2) reactions have been measured as a function of temperature (223-600 K) at low pressures (0.4-2 Torr) using a tubular laminar flow reactor coupled to a photoionization mass spectrometer (PIMS). These reactions are important for accurate modeling of unsaturated hydrocarbon combustion. Photolysis of a brominated precursor by a pulsed excimer laser radiation at 248 nm wavelength along the flow reactor axis was used for the production of radicals. The measured bimolecular rate coefficient of reaction 1 shows a negative temperature dependence over the temperature range 223-384 K and becomes temperature independent at higher temperatures. The bimolecular rate coefficient of reaction 2 exhibits a negative temperature dependence throughout the experimental temperature range. The bimolecular rate coefficients of reactions 1 and 2 are expected to be at the high-pressure limit under the current experimental conditions, and the following values are obtained at 298 K: k(1)(298 K) = (4.5 +/- 0.5) x 10(-12) cm(3) s(-1) and k(2)(298 = (8.9 +/- 1.0) x 10(-12) cm(3) s(-1). The observed products for reactions 1 and 2 were CH3COCH3 and CH3 + CH3COCH3, respectively. Substituting both beta-hydrogens in the vinyl radical (CH2CH) with methyl groups decreases the rate coefficient of the CH2CH + O-2 reaction by about 50%. However, the rate coefficient of the triply substituted (CH3)(2)CCCH3 radical reaction with O-2 is almost identical to the CH2CH + O-2 rate coefficient under the covered temperature range.
Subject: THERMOCHEMISTRY
BIODIESEL
MECHANISM
OXYGEN
CH3CO
O-2
116 Chemical sciences
Peer reviewed: Yes
Rights: unspecified
Usage restriction: openAccess
Self-archived version: acceptedVersion


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