COMBUSTION OF METHYL ISOPROPYL KETONE AND METHYL T-BUTYL KETONE

It is shown that in the combustion (between 270°C and 400°C) of methyl isopropyl ketone and methyl t-butyl ketone (pinacolone) there was ready abstraction of a hydrogen atom from the methyl group. Oxidation then followed by the two mechanisms already reported3 for acetone and methyl ethyl ketone. {A figure is presented}. Thus formaldehyde and the oxides of carbon were important primary products. Other products, such as acetone, methanol and acetaldehyde can plausibly be explained as arising from the oxidation of alkyl or alkoxy groups also formed. However, at the higher temperatures the initial yields of 1,2-propene and isobutene in the combustion of methyl isopropyl ketone and pinacolone respectively exceeded the yields of carbon dioxide so it is likely that abstraction of hydrogen atoms to form β ketonyl radicals [e.g. CH3COC(R1)(R2)CH2] should also be postulated. These unstable radicals would decompose to give the large proportions of olefins which are observed. {A figure is presented}. At lower temperatures oxidation of the ketonyl radicals may occur to give the corresponding oxides {A figure is presented}. The products showed no apparent difference in type of propagation reaction between pinacolone and the simpler ketones which, unlike pinacolone, are said to have low temperature oxidation mechanisms and give rise to cool flames. © 1969.