APPLICATION OF EPR SPECTROSCOPY TO THE DETERMINATION OF THE RATES OF REACTION AND SELECTIVITY OF ATTACK OF THE TERT-BUTOXYL RADICAL ON ESTERS - THE INTERPLAY OF ELECTRONIC, POLAR, STERIC AND STEREOELECTRONIC FACTORS

Rate constants have been determined by steady-state EPR spectroscopy e xperiments for hydrogen-atom abstraction by Bu'O' from a variety of es ters. The values, which range over two orders of magnitude (5 x 10(3)- 5 x 10(5) dm(3) mol(-1) s(-1) at ca. 300 K) are significantly lower th an those for related ketones and ethers and reflect, at least in part, the importance of the appropriate C-H bond dissociation energies and the stabilization of carbonyl-conjugated radicals, The relative lack o f reactivity of C-H bonds in unsubstituted five-membered rings is beli eved to reflect ring-strain in the derived radicals;possible stereoele ctronic effects are discussed.