Radical Intermediates in the Thermal Decomposition of 1,1-Bis(t-butyldioxy)cyclohexane

Article abstract of DOI:10.1246/bcsj.65.664

The thermolysis mechanism of 1,1-bis(t-butyldioxy)cyclohexane (6) has been studied in solutions.The activation parameters obtained in cumene are ΔH^<*>=139.5 kJ mol^-1 and ΔS^<*>=44.8 J K^-1 mol^-1, and the volatile products are t-butyl alcohol, t-butyl peroxyhexanoate, and 2,3-dimethyl-2,3-diphenylbutane along with minor products of acetone, cyclohexanone, and t-butyl 1-methyl-1-phenylethyl peroxide.The thermolysis of 6 in benzene gave acetone and t-butyl alcohol as major volatile products.The polyester of 2-hydroxyhexanoic acid was obtained both in cumene and benzene as a non-volatile product, and the yield was as high as 76percent in benzene.These facts indicate that <1(t-butyldioxy)cyclohexyl>oxyl radical (7) undergoes a facile ring-opening reaction yielding 5-(t-butyldioxycarbonyl)pentyl radical (8).The resulting radicals abstract hydrogen atoms either intra- or intermolecularly.The former reaction is predominant in the absence of good hydrogen donors, affording 2-hexanolide and ultimately the corresponding polyesters.