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)2C[double bond, length as m-dash]CH2+ 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 C[double bond, length as m-dash]CH2(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.
