Oxyallyl biradical

Thomas and his coworkers have studied the gas-phase thermolysis and photolysis of cyclopropanone in detail" ". They have found that the thermal reaction of gaseous cyclopropanone follows a first-order rate to give only the polymerized product in what appears to be a surface-catalyzed process. The heat of formation of cyclopropanone was measured to be -f 3.8 kcal mol" and this value was used to predict an activation energy of 30.5 kcal mol" for its homogeneous decomposition via the oxyallyl biradical. 

Samuel provided the first example that the oxyallyl intermediate in the Type A rearrangement could be trapped intermolecularly with a diene in a (3-t4]-cycloaddition. Samuel found that the apparent lifetime of simple 4,4-dialkyl substituted cyclohexadienones was too short to permit intermolecular capture. However, irradiation of Schuster s 4-methyl-4-trichloromethyl-2.5-cyclohexadienone 1 (Rj = CHj, Rj = CCI3) in the presence of either furan or cyclopentadiene produced 1 1 adducts 7 (X = O or CHj). This type of [4-1-3]-cycloaddition reaction has long been considered as evidence for an oxyallyl transient and is compatible with either a biradical or zwitterionic species. ... 

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