Multinuclear magnetic resonance and x-ray diffraction studies of aminonitropyridines

✍ Scribed by Erkki Kolehmainen; Katri Laihia; Kari Rissanen; Danuta Rasala; Ryszard Gawinecki

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 621 KB
• Volume: 30
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260300613

✦ Synopsis

Abstract

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.