Theoretical calculation of vibrational circular dichroism spectra

We report calculations of the mid-IR unpolarized absorption and circular dichroism spectra of 4-methyl-2-oxetanone, 6,8-dioxabicyclo[3.2.1]octane and 1,7,7-trimethylbicyclo[2.2.1]heptan-2-one (camphor) based on harmonic force fields calculated using density functional theory (DFT). A hybrid density functional, Becke3LYP, is used. The basis set is 6-31G*. The results are in impressive agreement with experimental spectra. Calculations using the LSDA and BLYP functionals are much less successful. Our results using Becke3LYP/DFT are compared with the predictions of SCF and MP2 calculations. At the present time, the Becke3LYP/DFT methodology is clearly to be preferred in predicting mid-IR vibrational spectra.