| Abstract: | The electronic structure of 4-H-pyran-4-one and its sulfur analogues were studied using ab initio wave-functions. Bond lengths and overlap populations suggest low aromaticity for this group of compounds. Examination of Jorgensen plots of the lowest π orbitals of I--IV leads to the aromaticity order 4H-thiopyran-4-thione (IV) > 4H-thiopyran-4-one (II) > 4H-pyran-4-thione (III) > 4H-pyran-4-one (I). The effects of including d orbitals were studied using the 3-21G, 3-21G* (6d), and 3-21G* (5d) basis sets. Optimized bond lengths, vibrational frequencies, ionization energies, and dipole moments were also obtained, and results for different basis sets were compared. |
