13C‐ and 1H‐NMR Shielding Effects in Aliphatic gauche/trans Fragments

On the basis of improved calculation models, of new NMR measurements with bicyclo[2.2.1]heptyl and cyclohexyl compounds, and of literature data it is shown that classical mechanisms of sterically induced charge polarizations, of linear electric field, and of anisotropy effects can account for many substituent‐induced shielding (SIS) differences. The rǒle of steric distortions on α‐and β‐SIS is discussed; bond angle variations generated by a methyl group introduction at C‐α and subsequent hybridization changes are correlated with Cα‐Me SIS values as well as with the eq/ax shielding in cyclohexanes.