Ring opening of oxiranylmethyl and 3-methyl-3-oxetanylmethyl radicals

Oxiranylmethyl and 3-methyl-3-oxetanylmethyl radicals were generated from the corresponding bromides and their rearrangements to allyloxyl and 2-methylprop-2-enyloxymethyl radicals respectively, were studied by kinetic EPR spectroscopy. The former radical was shown to ring open with a rate constant o≫ 4 x 108 s-1 at 25°C. The following kinetic parameters were measured for ring opening of the latter radical: k(25°C) = 8.9 x 102 s-1, log[A/s-1] = 13.97, E/kJ mol-1 = 63.3. Comparison of this data with that of related radicals supported the proposal that the transition state for β-scission of three-membered and four-membered cycloalkylmethyl radicals has dipolar character.