Dynamic isotope dilution kinetic study of the thermal conversions of bicyclo[3.2.0]hept‐2‐ene to bicyclo[2.2.1]hept‐2‐ene and to cyclopentadiene and ethene

Mixtures of bicyclo[3.2.0]hept‐2‐ene and bicyclo[2.2.1]hept‐2‐ene, with one isomer labeled with two deuterium atoms, were isomerized in the gas phase at 276 °C. By following the concentration ratios of d₀ and d₂ versions of bicyclo[2.2.1]hept‐2‐ene as functions of time one finds that the partitioning of bicyclo[3.2.0]hept‐2‐ene between the primary products bicyclo[2.2.1]hept‐2‐ene and cyclopentadiene plus ethene is 2:1. This and earlier stereochemical results permit the calculation of the partitioning of the [3.2.0] olefin between the orbital symmetry allowed [1,3] carbon shift‐with‐inversion product and several forbidden or non‐concerted reaction channels (approximately 1:1) and the stereochemistry of the ethene d₂ formed from exo,exo‐[6,7‐²H₂]bicyclo[3.2.0]hept‐2‐ene directly (1:1 E: Z).