Thermolysis of a series of w-arylalkanoyl m-chlorobenzoyl (and acetyl) peroxides at-100 OC in cyclohexanone and in hexachloroacetone was studied by using 13C chemically induced dynamic nuclear polarization. Analysis of the observed I3C polarizations indicate that all the three radicals (8-arylethyl, y-arylpropyl and &arylbutyl) have open-chain structures with no evidence for aryl participation resulting in spirocycloalkylcyclohexadienyl radicals.
