Decomposition of 2,2,3-trimethylbutane in the presence of oxygen
- 1 January 1980
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases
- Vol. 76, 825-837
- https://doi.org/10.1039/f19807600825
Abstract
The decomposition of 2,2,3-trimethylbutane in the presence of O2 in KCl-coated vessels has been studied at 480 and 500 °C over the pressure range 60–500 Torr. At low alkane pressures, where the chain contribution is small, the results are consistent with a simple mechanism comprising reactions (10), (11), (2) and (3). (CH3)3CCH(CH3)2→ t-C4H9+i-C3H7(10), i-C3H7+O2→ C3H6+HO2(11), t-C4H9+O2→ i-C4H8+HO2(2), HO2 [graphic omitted] ½H2O+¾O2(3), From measurements of the i-butene yields, accurate rate constants may be obtained for reaction (10) which, when combined with Tsang's results, give log10(A10/s–1)= 16.46 ± 0.12 and E10= 305.0 ± 1.5 kJ mol–1 over the temperature range 480–925 °C. Following a discussion of the thermo-chemistry of reaction (10) and the value of k–10, values of ΔfH° 298(t-Bu)= 37.6 ± 2.0 and ΔfH° 298(i-Pr)= 80.8 ± 4.0 kJ mol–1 are recommended, which correspond to D° 298(t-Bu—H)= 390.2 ± 2.0 and D° 298(i-Pr—H)= 402.5 ± 4.0 kJ mol–1, respectively. Two of the three species of radicals formed by radical attack on 2,2,3-trimethylbutane appear to react solely by C—C homolysis of the central C—C bond. The third radical, (CH3)3CC(CH3)2, reacts mainly by homolysis, but also forms the minor initial products 2,3,3-trimethylbut-1-ene, acetone and 2,3-dimethylbut-2-ene. A value of k17= 1.4 × 103 s–1 at 480 °C has been obtained. (CH3)3CC(CH3)2→(CH3)2CC(CH3)2+CH3(17).Keywords
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