AB-INITIO HYBRID DFT-GIAO CALCULATIONS OF THE SHIELDING PRODUCED BY CARBON-CARBON BONDS AND AROMATIC RINGS IN H-1-NMR SPECTROSCOPY

Theoretical calculations of H-1 shieldings by single, double and tripl e 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 be en calculated. The results, both inter- and intramolecular, range from good to excellent. The relative chemical shifts of some large molecul es having strongly shielded protons are conveniently reproduced.