Vibrational circular dichroism of (S,S)-[2,3-2H2]oxirane in the gas phase and in solution

Abstract

Vibrational circular dichroism (VCD) spectra of an exceptionally simple chiral three-membered ring molecule, (S,S)-[2,3-2H2]oxirane, have been obtained for samples in the gas phase and in C2Cl4 and CS2 solution. The VCD band contours for the gas phase samples of this molecule with C2 symmetry follow those of the absorption spectra, with the modes of A symmetry species giving rise to bands with two sharp Q-branch maxima on either side of a distinct minimum, and the modes of B symmetry species giving rise to bands with a strong central Q-branch. The signs and relative intensities of the VCD bands can be understood in terms of chiral perturbation by the deuterium substitution of the vibrational modes of the parent oxirane molecule, which mixes modes of A1 and A2 symmetry, and modes of B1 and B2 symmetry, thus introducing angular charge oscillation about the direction of linear charge oscillation. Key words: vibrational circular dichroism, oxirane, chiral perturbation.