Addition of n-butane to slowly reacting mixtures of hydrogen and oxygen at 480°C. Part 2.—Formation of oxygenated products

Abstract

By measuring the relative yields of alkenes and oxygenated products when n-C₄H₁₀, but-1-ene, and cis- and trans-but-2-ene, are added to slowly reacting H₂+ O₂+ N₂ mixtures at 480°C, overall velocity constants have been obtained for the reactions of n- and s-C₄H₉ radicals with O₂ to give 1,2-epoxybutane, cis- and trans-2,3-epoxybutane, methyl ethyl ketone and tetrahydrofuran. Mechanisms for the production of CH₃CHO, C₂H₅CHO and CH₃COCH₃ from n-C₄H₁₀ are discussed and evidence favouring the reaction of alkylhydroperoxide radicals (QOOH) with O₂ is presented. Comparison of the relative yields of 2,3-epoxybutane and C₄H₈–2 provides strong evidence that conjugate alkenes are formed directly from R + O₂, or from RO₂, rather than from QOOH. On this assumption, velocity constants for 1,3 to 1,6 isomerisations of RO₂→ QOOH for primary, secondary and tertiary hydrogen atom abstraction have been suggested. The values suggest that the activation energies are significantly different from those previously suggested.