Studies of Reaction Mechanisms with All-valence Electron Semi-empirical SCF MO Theories. IX. The Role of Tetracyclo[4.2.0.02,805,7]oct-3-ene on the Ground State Potential Energy Hypersurfaces of (CH)8 Isomers

Abstract

Abstract Tetracyclo[4.2.0.02,805,7]oct-3-ene (1) is estimated by a MINDO MO calculation to be moderately strained. Interaction between the ethylenic π orbital and the Walsh orbitals of the two cyclopropane rings is extensive in the ground state structure of 1. The third highest occupied MO is an out-of-phase combination of the ethylenic 2pπ AO’s on C3 and C4, while the corresponding in-phase combination appears in the lower unoccupied MO’s. The interconversion between 1 and bicyclo[4.2.0]octa-2,4,7-triene (2) is a typical symmetryallowed reaction as revealed by a smooth change in bond indices along the reaction coordinates. The isomerization of substituted cyclooctatetraenes via 1 and 2 (Eq. (2)) is predicted to be possible at elevated temperatures. The symmetry-allowed degenerate valence isomerization of 1 (Eq. (3)) is energetically less favorable due to skeletal constraint.