Addition of 2,2,3,3-tetramethylbutane to slowly reacting mixtures of hydrogen and oxygen

Abstract

When 1 % of 2,2,3,3-tetramethylbutane (TMB) is added to slowly reacting mixtures of H₂+ O₂+ N₂ at 480°C, analysis of the reaction products shows that, even in the presence of half an atmosphere of O₂, 96 % of the tetramethylbutyl radical, formed by radical attack on TMB, decomposes by reaction (34) with k₃₄= 1.9 × 10⁶ s^–1; a value of 1.1 × 10⁴ s^–1 is obtained for the alternative decomposition reaction (38).,(CH₃)₃CC(CH₃)₂CH₂=t-C₄H₉+i-C₄H₈(34),(CH₃)₃CC(CH₃)₂CH₂=(CH₃)₃CC(CH₃)CH₂+CH₃(38),Small amounts (≈ 1 %) of propene, 2,3,3-trimethylbut-1-ene, 2,3-dimethyloxiran, formaldehyde and methane are also formed in addition to the main product, isobutene. Secondary formation of propene from isobutene is relatively rapid. There is no evidence for the formation of conjugate O-ring compounds, or for the further addition of O₂ molecules to the two QOOH radicals formed from the tetramethylbutylperoxy radicals.

The relative rates of consumption of TMB and H₂ have been determined using 0.025 % of the additive. Rate constants for H and OH attack on TMB have been obtained and compared with those for ethane and neopentane. The variation in the rate constants for the three alkanes is not quantitatively consistent with a simple additivity rule.