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Multinuclear magnetic resonance and x‐ray diffraction studies of aminonitropyridines
Author(s) -
Kolehmainen Erkki,
Laihia Katri,
Rissanen Kari,
Rasala Danuta,
Gawinecki Ryszard
Publication year - 1992
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.1260300613
Subject(s) - chemistry , chemical shift , tautomer , crystallography , nmr spectra database , pyridine , crystal structure , nuclear magnetic resonance spectroscopy , aryl , nuclear magnetic resonance , stereochemistry , spectral line , medicinal chemistry , organic chemistry , alkyl , physics , astronomy
The 15 N NMR spectra for 21 aminonitropyridines were measured and their chemical shifts assigned. The 1 H and 13 C NMR chemical shifts and spin–spin coupling constants were also determined for 16 compounds of this series. In order to relate the structural properties of nitramino groups and their 15 N NMR chemical shifts in 2‐ and 4‐nitramino‐3‐nitropyridines, which differ remarkably from all other amino groups studied, low‐temperature 1 H NMR, 17 O NMR, comparative INEPT and IR spectroscopic studies were carried out. In addition, the x‐ray crystal structure of 2‐nitramino‐3‐nitropyridine was determined. Comparative spectroscopic studies showed that the nitramino derivatives exhibit different characteristics to the other compounds studied. Based on the x‐ray structural data, the nitramino group differs markedly from separate aryl‐bound amino and nitro groups. The nitramino group does not exhibit prototropic tautomerism in the crystalline state. This is in agreement with the small variation in the 15 N NMR chemical shifts of the pyridine nitrogen, which excludes the prevalence of pyridinium ions. Among the four NMR nuclei studied, 15 N seems to possess the best predictive power regarding the exceptional properties of the nitramino group.