Addition of 2,3-dimethylbutane to slowly reacting mixtures of hydrogen and oxygen at 480 °C. Rate constants of the elementary reactions involved
- 1 January 1986
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions 2: Molecular and Chemical Physics
- Vol. 82 (2) , 251-267
- https://doi.org/10.1039/f29868200251
Abstract
The oxidation of 2,3-dimethylbutane (DMB) has been studied by adding traces of the alkane to slowly reacting H2–O2 mixtures in an aged boric acid coated vessel at 480 °C. Rate constants have been obtained for H and HO2 attack on DMB, and Arrhenius parameters of log10(A/dm3 mol–1 s–1)= 9.45 (per C—H bond) and E= 67 kJ mol–1 are suggested for HO2 attack at the tertiary C—H bond in DMB. Combination with data at room temperature gives log10(A22/dm3 mol–1 s–1)= 11.45 and E22= 30 kJ mol–1 for the overall reaction H + DMB → H2+ C6H13. (22) Methane, propene, 2,3-dimethylbut-1-ene, 2,3-dimethylbut-2-ene, 2-methylbut-2-ene, and the two O-heterocyclic compounds, 2,2,3-trimethyl-oxetane and tetramethyloxirane, are the major initial products. The proportions of the two species of dimethylbutyl radicals formed in each mixture used has been estimated by computer treatment in order to facilitate interpretation of the product distribution. Detailed mechanisms for the two radicals are discussed quantitatively. Rate constants are determined for the 1,4t H atom transfer involved in reaction (5A) and for the 1,5t transfer involved in reaction (5B). No other experimentally derived value is available for a 1,5t H atom transfer in alkylperoxy radicals (CH3)2C(O2)CH(CH3)2→(CH3)2C(O2H)C(CH3)2(5A), (CH3)2CHCH(CH3)CH2O2→(CH3)2CCH(CH3)CH2O2H. (5B) The role of reaction (X) in the mechanism of autoignition of alkanes is discussed R + O2→ conjugate alkene + HO2. (X)Keywords
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