The gas-phase oxidation of iso butene

The reaction which has been examined by a static method between 252 and 320 $^\circ$C, proceeded with an initial pressure decrease during which formaldehyde and acetone were produced in equivalent amounts. Isobutyraldehyde produced during this period was probably the isomerization product of isobutene oxide which was detectable at the lower temperature. Much of the pressure decrease is attributed to the overall process, $(CH_3)_2C=CH_2+\frac{1}{2}O\rightarrow(CH_3)_2CHCHO$, rather than to peroxide formation since under certain conditions the yield of peroxide is much too small to provide a satisfactory explanation. The more important primary products can be accounted for in terms of a radical addition mechanism initiated by addition of a hydroxyl radical to the terminal CH$_2$ group, and followed by peroxy radical formation and its subsequent decomposition (possibly following its addition to a further fuel molecule). The formation of methyl allyl hydroperoxide and methacrolein shows that some abstraction of methyl hydrogen occurs, although this seems to be less important than the addition attack. The carbon oxides, water and propylene are formed by reactions of the primary products, and it is suggested that branching occurs by aldehyde oxidation.