The thermal unimolecular isomerization of bicyclo[3,2,0]hept-1(5)-ene

Abstract

The gas-phase thermal isomerization of bicyclo[3,2,0]hept-1(5)-ene has been studid between 121 and 162°. The reaction is homogeneous and kinetically first order and yields 1,2-dimethylenecyclopentane as the sole product. In the pressure range 0·5–100 Torr the rate constants are independent of pressure and fit the Arrhenius equation k= 10^13·29 exp (–31,560/RT) sec.^–1(R= 1·987 cal. deg.^–1 mole^–1). The experimental evidence suggests that the isomerization like that of simple alkylcyclobutenes is a unimolecular process occurring by a concerted mechanism.