NMR chemical shift substituent effects. 3—α-Monosubstituted N,N-diethylacetamides; bifunctional compounds in LSR experiments

✍ Scribed by Maria Alejandra Gutierrez; Marcos A. P. Martins; Roberto Rittner

• Publisher: John Wiley and Sons
• Year: 1982
• Tongue: English
• Weight: 606 KB
• Volume: 20
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1270200106

✦ Synopsis

Abstract

Lanthanide‐induced shifts have been measured for some α‐heterosubstituted N,N‐diethylacetamides, using Eu(fod)~3~ in CCl~4~ solution. The resonances for the syn‐ and anti‐methylene and ‐methyl protons have been assigned unambiguously for some of these bifunctional amides. A simplified approach to the analysis of the geometry of the LSR–amide complexes is advanced, yielding average conformations which differ from the rotamers previously proposed. It demonstrates that the conformational equilibria are strongly perturbed by the lanthanide addition. The lanthanide was found to complex with the carbonyl oxygen atom lone‐pair in the less hindered position for some of the amides investigated, whereas the geometry of the complexes could not be determined for α‐(NN‐dimethyl)amino‐ and α‐methoxy‐N,N‐diethylacetamide. Mono‐ and bifunctional model compounds have also been measured to confirm the resonance assignments and the amide complexing site.