Prof. Dr. Hans Dahn, Dr. Peter Péchy and Dr. Vien Van Toan
Contrary to the consensus of opinion13C-NMR spectroscopy is not suitable for the determination of electron density at the carbonyl C-atom. However, by measurement of the 17O-chemical shift in aromatic carbonyl compounds Y-C6H4-COX, X = CF3, H, CH3, CO2R, Br, Cl, F, OCOAryl, SR, OR, NH2, OH, O⊖, reliable statements could be made about the electrophilicity of the carbonyl C-atom. It is gratifying that the results are in agreement with classical chemical rules. There is much to be said for 17O-NMR spectroscopy being given more attention than hitherto.