Ab initio hybrid DFT-GIAO calculations of the shielding produced by carbon-carbon bonds and aromatic rings in 1H NMR spectroscopy

Theoretical calculations of H-1 shieldings by single, double and triple CC bonds as well as by aromatic rings (benzene, cyclopropenyl cation and hexafluorobenzene) have been performed using ab initio MO theory. As an illustration of the methodological approach, absolute chemical shieldings of H-1-, C-13-, O-17- and F-19-containing molecules have been calculated. The results, both inter- and intramolecular, range from good to excellent. The relative chemical shifts of some large molecules having strongly shielded protons are conveniently reproduced.