Carbon-13 nuclear magnetic resonance spectra—XII: Through-bond and through-space interactions of substituents in β-substituted ketones and related compounds

Abstract

Intramolecular substituent interactions in β-substituted ketones, thioketones, methoximes and olefines can be detected by considering non-additivities of the individual substituent effects on the 13C chemical shifts. When the substituent X is in equatorial (anti) position, the interaction is hyperconjugative, if the central atom of X is a hetero atom. It affects the two substituted C atoms and may influence unsubstituted carbons also, provided that the latter are in β position to both of the substituted carbons in the same ring. When X is axial ( syn) there are mutual through-space bond polarizations and, if X is anisotropic, additional field effects can be monitored. Unsubstituted C atoms are not influenced in the axial case. Investigations of this kind allow a deep insight into transmission mechanisms of substituent effects and may be applicable to stereochemical problems.