Transition State Geometry and Polar Effect in the Addition of Peroxyl Radicals to Olefins

Transition-state interatomic distances in the addition of peroxyl radicals to the double bond of olefins are estimated from experimental data (activation energies and rate constants) using a new algorithm combining quantum chemical and parabolic model calculations. An aromatic ring in the α-position with respect to the double bond elongates the ⋯ distance by 0.02 × 10−10 m. Polar groups adjacent to the double bond affect this distance considerably. The geometric parameters of the transition states in the abstraction and addition of peroxyl radicals are compared.