Acetaldehyde pyrolysis free radicals

Whereas acetone shows little tendency to undergo chain decomposition in photolysis or pyrolysis, acetaldehyde has been found to decompose by a chain mechanism which tends to quite sizable chain lengths as the temperature is raised. As a consequence of this behavior, the dec(3mposition has been found to be remarkably sensitive to the presence of small amounts of substances that can form free radicals more readily than pure acetaldehyde does. A further result of this sensitivity is that the data on the pyrolysis obtained under different conditions or in different laboratories show quite important discrepancies. In compensation for these difficulties the stoichiometry of the pyrolysis seems to be quite simple, the products being CO + CH4, together with very small amounts of C2H6 and also some II2 at temperatures near 500°C. These can be represented by ... 

The occurrence of free radicals in the pyrolysis of acetaldehyde was proved by Rice etal. as early as in 1932, and later also by others using the Paneth... 

It was proved by a separate experiment that isotope mixing in a mixture of methane and methane-i proceeds very slowly even above 600 °C. Thus, it must be concluded that, in the pyrolysis, the formation of the partially deuterated methanes is a result of free radical reactions and not of the secondary exchange of the methanes. Consequently, these results support the free radical mechanism of the acetaldehyde decomposition. 

As shown in the pyrogram of poly(L-lactide), the main pyrolysis products are CO and acetaldehyde. The pyrolysis probably takes place by a free radical mechanism including the following reactions ... 

Free radical addition of acetaldehyde to perfluoro-3,4-dimethyl-3-hexene 74 under y-irradiation followed by the pyrolysis of the product leads to furan 75. 2... 

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