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Analysis of long-range through-space couplings via an intramolecular hydrogen bond

✍ Scribed by Ian D. Rae; Josephine A. Weigold; Rubén H. Contreras; Rodolfo R. Biekofsky

Book ID
102951499
Publisher
John Wiley and Sons
Year
1993
Tongue
English
Weight
521 KB
Volume
31
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

2‐Fluorobenzamide and its N‐methyl derivative show spin‐spin couplings between the aromatic fluorine and the nitrogen and carbon of the amide group, which are absent in the corresponding N,N‐dimethylamide. The N‐methyl compound, in which there is a hydrogen bond between the fluorine and the amide hydrogen, also shows fluorine couplings to the nuclei of the methyl group, and these are diminished for solutions of the amide in polar solvents. Such couplings are absent in the N,N‐dimethylamide, which does, however, show fluorine couplings to the proximate methyl group. Calculations at the INDO level employing the IPPP method give reasonable agreement with the magnitudes of the observed ^4^J(F,N) values in the N‐methylamide and show that the Fermi contact contributions are dominant and that the spin information is transmitted mainly through the hydrogen bond.

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