Stereochemical aspects of proton chemical shifts—IV: The cumulative nature of the geminal proton shift influenced by long chain substituents

Substituent shift effects on geminal protons are consistent with cumulative α‐, β‐ and γ‐effects of a long chain substituent, e.g. whereby not only the first, but also the subsequent β‐ and γ‐atoms of the sidechain should be taken into consideration. These shift contributions depend on rotational conformation in a way that lends itself to calculation where the necessary data are available. Therefore the shifts of the unsubstituted parent compound, the individual increment‐contributions of the β and γ groupings and the rotameric distribution must be known. This would enable, conversely, a semi‐quantitative prediction of one of these parameters if the others are accessible.