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RESEARCH PRODUCT
The tautomerism of nitraminopyridines
Erkki KolehmainenRyszard GawineckiReijo SuontamoDanuta Rasałasubject
NMR spectra databaseCrystallographyProtonChemistryStereochemistryChemical shiftOrganic ChemistryAtomNitroNuclear magnetic resonance spectroscopyPhysical and Theoretical ChemistryRing (chemistry)Tautomerdescription
1H, 13C and 15N NMR data for nitraminopyridines are discussed in terms of tautomeric equilibria in these compounds. The favoured tautomer is determined mainly from 15N NMR spectroscopy. The chemical shift of the nitrogen atom of the nitro group in nitraminopyridines and N-nitroanilines which cannot tautomerize vary from 28·0 to 35·4 ppm in DMSO solution. 3-Nitraminopyridine and 2-nitramino-3- and -5-nitropyridines behave similarly. In the 15N NMR spectra of nitrimino-1-methyldihydropyridines, used as models, an upfield shift of that atom, different from that observed for 2-nitraminopyridine, indicates the significance of the nitrimino tautomer. In contrast, a downfield shift of the ring nitrogen atom of some other compounds shows an increased weight of the nitramino tautomer. 3-Nitraminopyridine, when dissolved in DMSO, does not have the zwitterionic structure. Changes in the chemical shift of the amino nitrogen atom are not readily interpreted. Some proton and carbon chemical shifts and hydrogen–hydrogen and carbon–hydrogen spin–spin coupling constants can also be used to determine the predominant tautomer of 2- and 4-nitraminopyridines.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 1995-10-01 | Journal of Physical Organic Chemistry |