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NMR of terminal oxygen. 16 — 17 O NMR of amide‐analogous N ‐acyl derivatives of non‐basic nitrogen groups: The question of amide resonances
Author(s) -
Dahn Hans,
Van Toan Vien,
Péchy Peter
Publication year - 1995
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260330812
Subject(s) - chemistry , amide , group (periodic table) , nitrogen , oxygen , resonance (particle physics) , isocyanate , stereochemistry , crystallography , chemical shift , medicinal chemistry , organic chemistry , physics , particle physics , polyurethane
Natural abundance 17 O NMR data for six classes of N ‐acyl compounds RCONX are reported: acylazide, acylisocyanate, acylisothiocyanate, diacyldiimide, 1‐acylimidazole and N , N ′‐carbonyldiimidazole. Compared with the normal amide group, they all show strong deshielding (Δδ ≈ 70–130 ppm), which is attributed to diminished resonance of the CO group with the weaker electron donor NX. The high shielding of isocyanate oxygen is attributed to symmetry‐based anisotropy effects.