ALKYL RADICAL GENERATION USING CYCLOHEXA-1,4-DIENE-3-CARBOXYLATES AND2,5-DIHYDROFURAN-2-CARBOXYLATES

3-Methylcyclohexa-1,4-diene-3-carboxylic acid and 2-methyl-2,5-dihydro furan-2-carboxylic acid were prepared by Birch reduction and alkylatio n of benzoic and furoic acid respectively and converted to alkyl ester s, Cyclohexadienyl and 2,5-dihydrofuranyl radicals were generated by h ydrogen abstraction and characterised by EPR spectroscopy, The esters decomposed thermally in the presence of a radical initiator to generat e alkyl radicals which could be trapped with moderate efficiency by ha logen donors or alkenes, Loss of methyl to afford an alkyl benzoate wa s an important side reaction at higher temperatures, From the thermal reaction of hex-5-enyl 3-methylcyclohexa-1,4-diene-3-carboxylate the r ate constant for hydrogen abstraction from the ester by hexenyl radica ls was determined to be 0.82 x 10(5) dm(3) mol(-1) s(-1) at 140 degree s C.