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 ΔfH°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)