Understanding conformer equilibria in solution with the aid of calculated 13C NMR spectra.1 A density functional and molecular mechanics study

MM3 conformational analyses were performed for a series of diastereomeric 2,4,6-trimethylated alcohols. Using MM3 geometries and energies, 13C NMR chemical shifts of 15–40 low energy conformers were calculated by means of an SOS–DFPT/IGLO approach and Boltzmann weighted. A comparison of calculated and experimental shifts allows us to analyse the conformational equilibria in solution and to estimate the importance of intramolecular hydrogen bonds in CDCl3 solution.