Kinetics of the Thermal Skeletal Inversion of Bicyclopentane and Methylbicyclopentanes

Article abstract of DOI:10.1021/jo00323a027

cis-exo-2,3-Dideuteriobicyclo<2.1.0>pentane, cis-exo-2,3-dideuterio-1-methylbicyclo<2.1.0>pentane, and the endo and exo isomers of 5-methylbicyclo<2.1.0>pentane have been prepared; rate constants for the gas-phase equilibrations between these substrates and the corresponding ring-inverted isomers have been determined between 153 and 208 deg C.The parent hydrocarbon and 1-methylbicyclo<2.1.0>pentane have equal or nearly equal activation energies, 37.8 +/- 0.1 and 38.0 +/- 0.4 kcal/mol; the 2-methyl and 5-methyl systems have slightly higher E_a values, 38.7 to 39.2 kcal/mol.These data and related information from the literature are assessed in terms of electronic and steric substituent effects on ground-state bicyclopentanes and transition states leading to planar 1,3-cyclopentadiyl diradicals.