A Convenient Method for Kinetic Studies of Fast Radical Rearrangements. Rate Constants and Arrhenius Function for the Cyclopropylcarbinyl Radical Ring Opening

Article abstract of DOI:10.1021/ja00183a041

An indirect method for studying the kinetics of radical rearrangements employing N-hydroxypyridine-2-thione esters as radical precursors and hydrogen atom transfer from thiophenol as the basis trapping reaction is demonstrated in a study of an archetypal fast radical reaction, the cyclopropylcarbinyl radical ring opening.Rate constants measured over the temperature range -37 to 50 deg C gave a temperature-dependent function for the ring opening of log(k/s^-1)=(13.0+/-0.14)-(6.8+/-0.2)/θ and a rate constant for ring opening at 25 deg C of 1.0E8 s^-1.The kinetic values from this work were combined with rate data from low-temperature ESR studies and higher temperature nitroxyl radical trapping studies to give an Arrhenius function of log(k/s^-1)=13.15-7.05/θ that is recommended for calculations of rate constants for the title ring opening.