Y, and X
Y
Z stretching region
VCD spectroscopy in the 1900–2400 cm−1 region has less often been studied. This article briefly summarises VCD studies in this spectral region and discusses the properties of 1900–2400 cm−1 chromophores.
VCD spectroscopy associated with DFT calculations is a powerful tool to unambiguously assign both the absolute configurations and conformations of chiral secondary metabolites directly in solution.
C
C stretching VCD signal
VCD spectroscopy was applied to allenic natural products to elucidate their axial chirality. The sign and intensity of C
C
C antistretching VCD signal were found to be affected by substituents on the allene.
The VCD signal observed in a crystal for the stretching vibration of hydroxyl groups is entirely determined by the crystal symmetry, whereas it vanishes at the molecular level.
The absolute configuration of cyclic peptides with two chiral centers can be unambiguously assigned with VCD. This is however not possible with three or four chiral centers. Hence, other techniques are needed to supplement VCD.