Decomposition of 2,2,3,3-tetramethylbutane in the presence of oxygen

Abstract

The oxidation of 2,2,3,3-tetramethylbutane in KCl-coated vessels has been studied between 440 and 540°C, and over the pressure range 60–500 Torr. The results are consistent with a simple mechanism comprising reactions (1)-(3)(CH₃)₃C—C(CH₃)₃→ 2t-C₄H₉(1) t-C₄H₉+O₂→ i-C₄H₈+HO₂(2), HO₂[graphic omitted]½ H₂O +¾ O₂(3) After allowance for a small (< 20 %) contribution from a chain process, accurate Arrhenius parameters A₁= 6.0 × 10¹⁶ s^–1, E₁= 290.4 kJ mol^–1 have been obtained by combination with Tsang's results. From the thermochemistry of reaction (1) and literature values for k_–1, values of Δ_fH^°₂₉₈(t-Bu)= 44.0±4.0 kJ mol^–1 and S^°₂₉₈(t-Bu)= 304.2±4.0 J K^–1 mol^–1 are recommended.

Analysis of the products shows that ∼1 % of the t-butyl radicals give isobutene oxide and over the temperature range 470–542°C, A₂/A₁₃= 13.8 and E₁₃–E₂= 13.0 kJ mol^–1 where reaction (13) is the overall process, t-C₄H₉+O₂= C₄H₈O+OH.(13) Reaction (13) is discussed in terms of the peroxy radical isomerisation and decomposition theory and Arrhenius parameters are suggested for the (1, 4p) H atom transfer reaction (17) in t-butylperoxy radicals (CH₃)₃CO₂→(CH₃)₂C(OOH)CH₂. (17)