Ring Opening of Cyclopropanone

We report the results of INDO and ab initio SCF calculations on cyclopropanone, oxyallyl, and aliene oxide, and the con- and disrotatory openings of the closed ketone. The ab initio results indicate that singlet oxyallyl is 83 kcal/mol less stable than cyclopropanone, while aliene oxide is 21 kcal/mol less stable. The internal C₃C₁C₂ angle in singlet oxyallyl is predicted to be near 105°. Although the conrotatory opening of cyclopropanone passes through a true transition state, the disrotatory opening is the lower energy pathway, and oxyallyl appears to be at, or near, the disrotatory energy maximum.