Molecular decomposition of 2,2,3,3-tetramethylbutane

Abstract

In the presence of O₂, the decomposition of 2,2,3,3-tetramethylbutane (TMB) gives 98 % of isobutene in the temperature range 420–540°C through reactions (4) and (5). (CH₃)₃ CC(CH₃)₃= 2(CH₃)₃C (4). (CH₃)₃C + O₂=(CH₃)₂CCH₂+ HO₂(5). Approximately 1 % of isobutane is also obtained, and the rate of isobutane formation at a given temperature is directly proportional to [TMB], and is independent of [O₂], N₂ addition, and vessel diameter. It is shown that these results require the molecular reaction (3). (CH₃)₃ CC(CH₃)₃=(CH₃)₃ CH +(CH₃)₂ CCH₂(3). Studies over the range 420–540°C give log₁₀(A₃/s^{– 1})= 13.89 ± 0.10, E₃= 275 ± 1.4 kJ mol^{– 1}. The A factor is consistent with a four-centre transition state.