RING-OPENING OF OXIRANYLMETHYL AND 3-METHYL-3-OXETHANYLMETHYL RADICALS

Oxiranylmethyl and 3-methyl-3-oxetanylmethyl radicals were generated f rom the corresponding bromides and their rearrangements to allyloxyl a nd 2-methylprop-2-enyloxymethyl radicals respectively, were studied by kinetic EPR spectroscopy. The former radical was shown to ring open w ith a rate constant of > 4 x 10(8) s-1 at 25-degrees-C. The following kinetic parameters were for ring opening of the latter radical: k(25-d egrees-C) = 8.9 x 10(2) s-1, log[A/s-1] = 13.97, E/kJ mol-1 = 63.3. Co mparison of this data with that of related radicals supported the prop osal that the transition state for beta-scission of three-membered and four-membered cycloalkylmethyl radicals has dipolar character.