The semi - empirical method AM1 was used to study the reaction pathway
of the thermal isomerization of a homoazulene(1,5 - methano[10] annul
ene). The conclusion that there is a ground - state di - pi - methane
radical rearrangement in the reaction pathway is obtained. The geometr
y, energies of each stationary point in the reaction pathway and the a
ctivation energies of each step in the reaction pathway are also calcu
lated.