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Nitrogen-15 nuclear magnetic resonance spectroscopy. Pyridine N-oxides and quinoline N-oxides

✍ Scribed by Issa Yavari; John D. Roberts

Publisher
John Wiley and Sons
Year
1979
Tongue
English
Weight
545 KB
Volume
12
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

The noise‐decoupled nitrogen‐15 NMR spectra of ten pyridine N‐oxides and two quinoline N‐oxides have been obtained at the natural‐abundance level by high‐resolution NMR spectroscopy. Substituents at the 4‐ring position of pyridine N‐oxide, capable of resonance interaction with the N‐O moiety, give fairly large shifts in the expected directions. Spectra taken in dimethyl sulfoxide solution give 5–20 ppm and 33–55 ppm downfield shifts with respect to the solutions of the same substances in 2,2,2‐trifluoroethanol and trifluoroacetic acid. Solvent influences are discussed in terms of hydrogen bonding and protonation of the N‐oxide oxygen. Carbon‐13 chemical shifts and one‐bond carbon‐hydrogen coupling constants of some substituted pyridine N‐oxides are reported and discussed.

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