Hartree−Fock and Density Functional Theory ab Initio Calculation of Optical Rotation Using GIAOs:  Basis Set Dependence

Ab initio Hartree−Fock (HF) and density functional theory (DFT) calculations of the electric dipole−magnetic dipole polarizability β αβ are reported for the chiral molecules methyloxirane ( 1 ) and trans -dimethylthiirane ( 2 ) in the static limit. Values of β = 1 / 3 Tr [β αβ ] obtained thence are used to predict the specific optical rotations [α] D of 1 and 2 . Gauge-including atomic orbitals (GIAOs) are used to ensure origin independence of β and [α] D . β and [α] D values converge slowly to the complete basis set limit. Basis sets including diffuse functions are required to achieve reliable results. HF and DFT values of β αβ differ generally by 10−30%. Calculated [α] D values for 1 and 2 obtained using large basis sets agree well with experimental values in sign and magnitude. The deviations can be attributed in part to the neglect of the frequency dependence of β and of solvent effects.