Clocking tertiary cyclopropylcarbinyl radical rearrangements

摘要

Three independent methods have been employed to estimate the rate constant, k_1, for ring-opening of the 2-cyclopropyl-2-propyl radical, 1, at room temperature. These three estimates are based on chemical trapping of 1 and the ring-opened 4-methylpent-3-ene-1-yl radical by thiophenol (k_1= (1. 6_5±0.4_1)x10~7M~1 s~1), 9-azabicyclo[3.3.1]nonane-N-oxyl (k_1=(1.7_6±0.3_4)x10~7M~1s~1) and 2,2,6,6-tetramethylpiperidine-N-oxyl (k_1=(2.1±0.4)x10~7M~1s~1) and absolute rate constants for nonrearranging radicals structurally related to 1.