THERMAL STABILITY OF LARGER CARBONYL COMPOUNDS: 2-METHYLBUTYRALDEHYDE

摘要

Oxygenated fuels as alternatives to conventional petroleum based fuels must be critically evaluated from different practical perspectives, for instance, undesirable aldehyde emissions.[l] The aim of this study is to determine the mechanism and rate expressions for the decomposition of larger organic compounds in the gas phase and in the absence of radical induced processes. Alkanes, alkenes, alkynes, branched aromatics, alcohols, ketones, amines and alkyl halides have shown that they decompose by various molecular and bond cleavage processes. The rate expressions for the latter are consistent with the bond energies of the C-C bond being broken and the A-factors demonstrate a lowering of their value as the temperature increases. The other processes involve the direct formation of stable molecular products which are characterized by smaller rate parameters. For unsaturated hydrocarbons there are processes involving six center transition states, usually termed the retro-ene reaction. In the case of alcohols there is a juxtaposition of dehydration and C-C bond cleavage. We have recently established the rate rules for these processes.[2, 3] In the case of the ketones[4] we have found that C-C bond cleavage processes are the predominant decomposition mechanism with only a minor retro-ene decomposition channel. One would expect that the aldehydes will be a simple extension of these observations.