Gas-phase oxidation of butene-2: The role of acetaldehyde in the reaction

The gas-phase oxidation of butene-2 has been studied under two different sets of conditions. At 184°C, the principal products, when butene-2 is co-oxidized with acetaldehyde, are the isomeric epoxybutanes. Between 277° and 400°C, butene-2-molecular oxygen mixtures yield acetaldehyde and oxides of carbon as the main products, although the eposides are still formed in significant yield. The proportion of acetaldehyde to epoxides does not change on increasing the temperature, while the proportion of carbon monoxide to carbon dioxide increases significantly. The results are explained in terms of addition reactions of oxygenated radicals to the alkene. Acetaldehyde is considered to be formed by addition of hydroxy, followed by oxygen, while, below 300°C, the principal source of epoxide is thought to be peracetyl attack on the alkene. Rate data for the addition of peracetyl to butene-2 at 184°C suggests that this reaction is as facile as the abstraction reaction between peracetyl and acetaldehyde.