Lanthanide-induced shifts of diastereotopic groups

The chemical shift differences of diastereotopic protons in aliphatic acyclic alcohols, mostly of the type R? CH₂? CR′R″? (CH₂)_nOH, have been investigated. Fairly small amounts of Eu(dpm)₃ cause the spectra of these materials to simplify dramatically; indeed, even diastereotopic protons rather far removed form the hydroxyl group give discrete signals in the presence of the shift reagent. Large shift differences were realized in the γ-protons (n = 1) and the δ-protons (n = 2), particularly if R is bulky and R' and R″ have different steric requirements. Semi-quantitative conformational preferences can be determined from the data obtained.