Rate constants for the formation of oxiranes by γ-scission in secondary β-t-butylperoxyalkyl radicals

Abstract

Rate constants for the title reactions have been determined from the ratios of oxirane to peroxide obtained in the reductions of β-bromoalkyl t-butyl peroxides with tributyltin hydride. At ca. 298 K the rate constants are 0.32, 1.12, 1.96, 2.0, and 6.2 × 10⁶ s^–1 for β-t-butylperoxy derivatives of trinorbornan-2-yl (exo) cyclohexyl, 1-methylpropyl, cyclopentyl, and 1-ethylbutyl, respectively. The results are discussed in terms of steric and electronic effects in the transition state leading to ring closure of the radicals.