Is the VCD spectrum a fingerprint of the conformational population?: the conformation of perezone in the spotlight

Abstract

The M06e2X, B3LYP,uB97XD and B97D functionals with the 6e311þþG(2d,2p) and DGDZVP basis setswere used to describe the stationary points of minimum energy of the potential energy surface ofperezone. The inability of theoretical methods to predict a consistent conformational order, including theeffects of zero point energy and dielectric constant was highlighted. Perezone was used as a model ofstudy since it is known that weak interactions are involved in its conformation and represent a challengeof study for theoretical methods. Each level of theory here employed generated a significantly differentconformational population, ranging from 75% participation of folded conformers (where ap/pstabilizinginteraction was predicted) to less than 5%, without producing a uniform conformational order. Sur-prisingly, in every case, the constructed Vibrational Circular Dichroism (VCD) spectrum with each level oftheory was able to reproduce the experimental spectrum with high level of confidence. The correctRconfiguration of the stereogenic center of perezone was predicted in all cases.