Internal rotation in acetone

The geometrical structure of the ground state of acetone obtained by ab initio SCF energies is compared with experimental structures mainly from microwave spectroscopy. The potential function for the internal rotational motions in acetone obtained from SCF energies is compared with experimental. It is shown that the top-top coupling constants are not negligible in acetone, and that at least three constants are required to give realistic potential functions for internal rotation in dimethyl molecules. Torsional potential constants for acetone of V₃ = 452, V₃₃ = 174, V′₃₃ = −171, and V₆ = 1 cm⁻¹ are calculated with the DZ basis.