Oxygen-17 NMR spectroscopy: basic principles and applications. Part II.

17O NMR spectroscopy: Assessment of steric perturbation of structure in organic compounds

Substituent Effects on Chemical Shifts in the Sidechains of Aromatic Systems

17O-NMR. Aliphatic aldehydes and ketones, additivity of substituent effects and correlation with 13C-NMR.



The 17O-chemical shifts of 9 aldehydes, 22 aliphatic and 4 alicyclic ketones, in the natural abundance FT.-NMR. spectra followed a good correlation with the 13C-chemical shifts of the terminal C-atoms of corresponding methylene compounds. An additivity relation involving 6 parameters represents the 17O-shifts of 28 of the measured products with a standard deviation of 2.5 ppm. The additivity parameters are discussed with respect to the modifications of the polarity of the carbonyl group induced by the hyperconjugative interaction of π and π* orbitals with the πCH3 orbitals of the alkyl substituent groups.

Résonance Magnétique Nucléaire de 17O. Aldéhydes et cétones aliphatiques: additivité des effets de substitution et corrélation avec la 13C‐RMN

The 17O and 13C chemical shifts (δ) of 14 α,β-unsaturated aldehydes and ketones and 33 acyl derivatives RXC = O (X = Cl, OH, OMe, OEt, NH2 and R = H or alkyl) have been measured. In the unsaturated carbonyl series, a correlation exists between δ 17O and the π electron density at the β-carbon atom. From this correlation, an δ 17O of 530 ppm was extrapolated for the loss of one electron at the oxygen atom. In the acyl series, the δr 17O were also sensitive to changes in the polarity of the carbon-oxygen bond. A partial correlation between 17O-NMR. chemical shifts and the nuclear quadrupole coupling constants exists for aldehydes, ketones, esters and amides but not for acyl chlorides.

Oxygen‐17 and Carbon‐13 Nuclear Magnetic Resonance. Chemical shifts of unsaturated carbonyl compounds and acyl derivatives

The 17O spectra of some ortho- and para-substituted acetophenones were determined to examine the effect of substituent polarity and steric hindrance on the acetyl oxygen shieldings. The results are...

D. J. Sardella

Papers

Nuclear magnetic resonance studies. XVI. Oxygen-17 shieldings of some substituted acetophenones