Lanthanide-induced shifts in proton NMR spectra—IV: Praseodymium-induced shifts to lower applied fields and obscured chemical shifts from lanthanide-induced shift (LIS) data
✍ Scribed by J. R. Hlubucek; B. L. Shapiro
- Publisher
- John Wiley and Sons
- Year
- 1972
- Tongue
- English
- Weight
- 291 KB
- Volume
- 4
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
Praseodymium(II1) tris(dipiva1omethanato) [Pr(DPM),] reduces the complex overlapping aromatic absorptions in the proton NMR spectrum of a monosubstituted naphthalene, cis-3-(1- naphthyl)-l,3,5,5-tetramethylcyclohexan-l-ol(l) to a virtually first-order pattern, whereas Eu(DPM), at the same and higher molar concentrations does not completely resolve the aromatic proton signals. Plots of the Pr(DPM),-induced shifts measured in carbon tetrachloride solution versus molar equivalents of Pr(DPM), added may be extrapolated to provide accurate chemical shifts in the absence of added lanthanide shift reagent (LSR). The qualitativeconformationalconclusions from the Pr(DPM), shifts agree with those from the Eu(DPM),-induced shifts, but there are detailed differences in the relative lanthanide-induced shifts (LIS) for different proton types in the molecule.