The Influence of Sulphur on Anharmonic Features of Vibrational Circular Dichroism, on Electronic Circular Dichroism and on Optical Rotatory Dispersion: A Study of (R)-2-Chloromethyl-Oxirane, (R)-2-Methyl-Oxirane, (R)-2-Chloromethyl-Thiirane, and (R)-

The vibrational circular dichroism (VCD) spectra of (R)-2-chloromethyl-oxirane and (R)-2-chloromethyl-thiirane have been recorded in a vast spectral region including mid-IR, CH-stretching fundamentals and bending-CC/CO(CS) overtone/combination regions in the mid-IR, and CH-stretching overtone/combination regions in the near infrared (NIR). The presence of sulfur is associated with intensification of the NIR-VCD spectra, similarly to what is monitored with electronic circular dichroism (ECD) and optical rotatory dispersion (ORD). DFT calculations, dealing with anharmonicity at the GVPT2 level or based on the local mode approximation, permit to correctly predict the large majority of observed VCD and IR/NIR bands and to explain the role of various molecular moieties. Also, ORD data are better interpreted by including anharmonic vibrational contributions.