17O NMR investigation of acetyl and formylthiophenes,furans and pyrroles

The ¹⁷O nmr chemical shifts of 20 acetyl and formylthoiphenes, furans, and pyrroles are reported. The chemical shifts qualitatively correlate with the electronic character of the heterocyclic rings. The effect of steric factors are noted for the ¹⁷O chemical shifts of alkyl substituted acetylthiophenes and for N-methylpyr-roles.