Conformational transferability of the sulfenyl carbonyl group -SC(O)- in cyclic thioesters

The molecular and crystal structure of two dithiolactones (formally dimers of ε-caprothiolactone and ω-hexadecathiolactone) have been determined by X-ray diffraction at low temperature, revealing that the thioester group is planar with a synperiplanar orientation of the C═O double bond with respect to the S-C single bond. This conformational behavior is in contrast to that found for the smaller cyclic members of this family, where the antiperiplanar conformation is enforced. It is hypothesized that strain effects play a major role for the energy balance in the conformational preference. In this context, the molecular, vibrational (infrared and Raman), and electronic properties of ε-caprothiolactone have also been analyzed by using a combined experimental, including gas-phase helium I photoelectron spectroscopy, and computational approach.