17O NMR Spectra of α,β-Unsaturated Carbonyl Compounds RCH=CHCOX: the Influence of Group X on the δ(17O) Value of the Carbonyl Oxygen and on the Shielding Effect of Group R

Abstract

17O NMR spectra of RCOX (R = Me, Ph), RCH=CHCOX (R = H, Ph, Me, CO2Et) and Me2C=CHCOX (X = H, Me, Et, i-Pr, t-Bu, Ph, PhCH=CH, OMe, OEt, Cl, CN, CF3, CO2Et) are reported. The 17O shift values of these carbonyl compounds depend mainly on the electron donating power of X and correlate well with the resonance constants sR+ of X. This suggests that the d(17O) values can be used to reflect qualitatively the electrophilicity of the carbonyl group. The shielding effect of the substituent R in RCH=CHCOX is diminished with increasing the electronic donating power of X and correlates with s+ values of X.

Keywords

• 17O NMR
• carbonyl groups
• a
• b-unsaturated carbonyl compounds
• resonance effects