Knowledge Bank

We have measured the vibrational circular dichroism (VCD) spectrum of $3,4-d2$-tetrahydrofuran ($d2$-THF) using an FTIR spectrometer. These spectra were broad and weak compared to previously studied isotopically chiral molecules but reliable features could be identified for several mid-ir bands. To interpret these spectra, a new force field for THF was developed based on an ab initio calculated force field with $C2$ symmetry. For comparison, force fields with $Cs$ and $C2v$ symmetries were also calculated. The $C2$ geometry is calculated to be lowest in energy, and that force field gives the best fit after scaling to the ir and Raman data we have re-obtained from five isotopomers. Calculated VCD spectra obtained using Stephen's a priori model agree with experiment for many but not all modes. Fixed partial charge results are worse.