Rate constants for the rearrangement of 1-bicyclo [3.1. 0] hexanylmethyl radical (2) to 3- methylenecyclohexenyl radical (3) and 2-methylenecyclopentyl-1-methyl radical (1) were measured using the PTOC-thiol competition method. The ring-expansion pathway is described by the rate equation, log (k/s-1)=(12.5±0.1)-(4.9±0.1)/θ; the non-expansion pathway is described by log (k/s-1)=(11.9±0.6)-(6.9±0.8)/θ. Employing the slower trapping ...