17O NMR Spectroscopy of Benzoyl Compounds YC6H4COX: Sensitivity to Ring Substituents as a Measure of the Electron Demand of the Carbonyl Group

Contrary to the consensus of opinion 13C‐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.