Knowledge Bank

The experimental infrared absorption and vibrational circular dichroism (VCD) spectra of a series of methyl substituted 6,8-dioxabicyclo[3,2,1]octanes are reported in the region $800-1500cm-1$. Vibrational intensities were calculated with the models of atomic polar tensor (APT), fixed partial charge (FPC), and charge flow (CF), based on the scaled and refined SCF ab initio 3-21G force fields. In general, APT and FPC reproduce the intensities satisfactorily and poorly, respectively, in accord with the results for the parent compound $6,8-dioxabicyclo[3,2,1]octane.1$ In order to correct for the major shortcoming of the FPC model, different sets of charge flow parameters were employed, derived originally for propane, dimethyl ether and ethanol. It is demonstrated that only few parameters are necessary for reasonably accurate predictions of the absorption and VCD intensities. It appears that the charge flow parameters may be transferable between structurally related molecules