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Barriers to rotation about CN bonds—I: Rotation about the CN bond in mono‐, di‐ and trifluoroacetamide, and deuterium isotope effects upon 19 F shielding
Author(s) -
Pendlebury M. H.,
Phillips L.
Publication year - 1972
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270040412
Subject(s) - deuterium , kinetic isotope effect , chemistry , isotope , rotation (mathematics) , spectral line , electromagnetic shielding , analytical chemistry (journal) , computational chemistry , atomic physics , physics , nuclear physics , organic chemistry , geometry , mathematics , astronomy , quantum mechanics
The 19 F NMR spectra of mono‐ and difluoroacetamide are used to derive the activation parameters for rotation about the CN bond; it is not possible to obtain useful results for trifluoroacetamide. A total line shape analysis is used. Unusually large deuterium isotope effects upon the shielding of the 19 F nucleus are observed for N ‐deuterated derivatives. The magnitude of the isotope effect is different for mono‐, di‐ and trifluoroacetamides, and in the mono‐deuterated species the isotope effect is different for cis and trans rotational isomers.