Isotopic difference spectra as an aide in determining absolute configuration using vibrational optical activity: vibrational circular dichroism of 13C- and 2H-labelled nonamethoxy cyclotriveratrylene.

The use of isotopic difference spectra in vibrational optical activity is demonstrated as a supplemental aide in determining the absolute configuration of chiral molecules. It is shown that IR and VCD difference spectra associated with isotopic substitution observed in experimental spectra can be accurately reproduced by density functional theory calculations when the IR and VCD spectra of the original isotopomer are calculated to reasonable accuracy. Results for isotopically substituted nonamethoxy cyclotriveratrylene are presented to illustrate the degree of agreement between measured and calculated IR and VCD difference spectra for several isotopomers of this molecule. These findings highlight the utility of isotoptic substitution as an aide to verifying the determination of absolute configuration using vibrational optical activity.