Biacetyl pyrolysis

It is now clearly demonstrated through the use of free radical traps that all organic liquids will undergo cavitation and generate bond homolysis, if the ambient temperature is sufficiently low (i.e., in order to reduce the solvent system s vapor pressure) (89,90,161,162). The sonolysis of alkanes is quite similar to very high temperature pyrolysis, yielding the products expected (H2, CH4, 1-alkenes, and acetylene) from the well-understood Rice radical chain mechanism (89). Other recent reports compare the sonolysis and pyrolysis of biacetyl (which gives primarily acetone) (163) and the sonolysis and radiolysis of menthone (164). Nonaqueous chemistry can be complex, however, as in the tarry polymerization of several substituted benzenes (165). 

Estimated by the author from pyrolysis data, thermal data, and data on the photolj sis of biacetyl. 

Biacetyl has often been used for sensitizing the pyrolysis of organic compounds" . Radicals, resulting from the thermal decomposition of biacetyl, initiate the chain decomposition of such substances. However, NO causes no inhibition of notable significance in such systems . Nevertheless, this cannot be considered as an evidence against the occurrence of chains, since the sensitized decompositions are definitely inhibited by, for instance, propene . 

Szwarc et alP have studied the pyrolysis of biacetyl by the toluene carrier technique. For the CO formation, they gave the first-order rate coefficient as... 

The present discussion is by no means exhaustive. It is designed to provide a summary of the most significant and reliable kinetic data, at least those that appear so to the author. There is a variety of methods for producing alkyl radicals, and, naturally, there will be certain restrictions on experimental conditions depending on the method chosen. Some of the common methods for generation of methyl radicals, for example, include photolysis of acetone, pyrolysis of di-ferf-butyl peroxide, photolysis of biacetyl, photolysis of azomethane and decarbonylation of acetaldehyde. In the majority of cases discussed here, the reactions were followed by product determinations, employing gas chromatography. 

Pyrolysis of 5,6-dimethylenebicyclo[2,2,l]hept-2-ene (251) yields indane, whereas the similar treatment of the analogous compounds (252)—(254) resulted in Diels-Alder retrogression to afford 1,2,3-butatriene. When a solution of the endo-epoxide (255) was injected directly into the inlet of a gas-liquid chromatograph, it was found that biacetyl and hexamethylcyclohexa-2,4-dienone could be detected as components of the eluted mixture. The presence of the dienone can be explained by assuming Diels-Alder retrogression, and the biacetyl could arise from intermediate dimethyl-oxiren (256) formed concomitantly. Since, however, neither dimethylketene nor its... 

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