Molecular orbital calculations of excited state cyclobutanone and its photocarbene

Abstract

Ab initio molecular orbital calculations, at the MP2/6-31G *//6-31G * level are reported for cyclobutanone, acetone, and the isomeric oxacarbenes 2 and 3, the first excited singlet states (S 1) of acetone and cyclobutanone have been calculated at the 6–31G * level using the UHF method. The cyclic oxacarbene 2, lies 26 kcal mol below the S 1 state of the isomeric cyclobutanone while the acyclic oxacarbene 3 is 2 kcal mol above the S 1 state of acetone. Isodesmic reactions give the strain energies of cyclobutanone to be 24.9 kcal mol in the ground state and 31.4 kcal mol in the first excited singlet state.