Abstract
Three structurally analogous radical clock substrates with a 100-fold span in their rearrangement rates are hydroxylated by the diiron oxygenase AlkB to afford similar amounts of rearranged and unrearranged products. Such a result is predicted by a mechanistic scheme by which radical rebound competes with cage escape of the geminate substrate radical. The results show that radical clocks can measure both the radical life-time and the kinetics of cage escape.