Orbital topology. II. Orbital mapping of unsymmetrical molecules. A survey of the thermal isomerizations of dewar isomers of isoelectronically substituted benzenes, cyclopentadienes, and cyclopentadienyl ions

Orbital mapping analysis, based on EHT and CNDO/2 semiempirical molecular orbitals, has been used to survey the thermal, disrotatory, ring‐opening isomerizations of bicyclo[2.2.0]hexa‐2,5‐dienes (Dewar benzenes), bicyclo[2.1.0]pent‐2‐enes, and bicyclo[2.1.0]pent‐2‐en‐5‐yl ions to their planar isomers. Results indicate that isoelectronic substitution (CH replaced by C−, O+, N, NH+, etc.) in the molecular framework may favor allowed thermal reactions in some cases, in contrast to the disallowed reaction predicted for the parent hydrocarbons.