Torsion angle relationship of the (17)O NMR chemical shift in alpha,beta-unsaturated carbonyl compounds.

The torsion angle effect on the isotropic shielding of (17)O nucleus in alpha,beta-unsaturated carbonyl groups is studied by means of density functional theory (DFT) calculations using a polarizable continuum model (PCM) for the solvent, employing the PBE0 functional together with the 6-311G(d,p) basis set for geometry optimization, and the 6-311+G(2d,p) basis set for calculating the NMR shielding with the gauge-including atomic orbitals (GIAO) method.This study adds new information on the sensitivity of the (17)O nucleus to conformational changes, revealing a strong dependence of the (17)O NMR chemical shift on the dihedral angle between the carbonyl and the vinyl moiety in all studied compounds; remarkable differences are observed with the data reported for alpha-diketones.