Experimental and Calculated Activation Parameters for Ring Opening of the 1-Bicyclopentyl Radical: The Effect of Bridgehead Substituents

Article abstract of DOI:10.1021/jo00015a018

Ring opening of the 1-bicyclo<1.1.1>pentyl, 3-phenyl-1-bicyclo<1.1.1>pentyl, and 3-carbomethoxy-1-bicyclo<1.1.1>pentyl radicals has been studied by experiment and by molecular orbital theory.Our results indicate that the parent system 1a is extremely reluctant to ring open, with an energy barrier of at least 26 kcal mol^-1.The ester- and phenyl-substituted radicals rearrange somewhat more readily, with barriers of about 25 and 21 kcal mol^-1, respectively.This trend is also observed in the molecular orbital treatment of these processes.Previous reports that include radical rearrangements of this type must now be reconsidered in light of our new data.