REACTIONS OF TERT-BUTOXYL RADICALS WITH CYCLIC ETHERS STUDIED BY THE RADICAL TRAPPING TECHNIQUE

The pattern and relative rate of abstraction reactions of tert-butoxyl radicals with fourteen cyclic alkanes and cyclic ethers have been inv estigated by the aminoxyl radical trapping technique. Oxygen alpha to C-H strongly enhances abstraction, but beta to C-H generally retards a bstraction. The rate of abstraction of hydrogens alpha to oxygen in cy clic ethers was found to decrease with ring size in the order 5 > 7 >> 6 > 4. The results are discussed in terms of ring size, abstraction p osition relative to ethereal oxygen atoms in the ring and aliphatic su bstitution. Factors such as polarity, torsional strain, hybridisation of the oxygen (whether sp(2) or sp(3)) and the anomeric effect are con sidered.