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1 H and 13 C NMR studies of substituted nitropyridines and nitrobenzenes
Author(s) -
Nudelman N. S.,
Cerdeira S. B.
Publication year - 1986
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.1260240607
Subject(s) - chemistry , steric effects , nitro , cyclohexylamine , nmr spectra database , pyridine , medicinal chemistry , stereochemistry , nitrobenzene , carbon 13 nmr , proton nmr , hydrogen bond , crystallography , spectral line , molecule , organic chemistry , catalysis , alkyl , physics , astronomy
The 1 H and 13 C NMR spectra of 3‐nitro‐, 5‐nitro‐ and 3,5‐dinitro‐2‐methoxypyridines have been determined. The results show the preferred cis conformation for the 2‐methoxy group, and the importance of steric repulsion between the oxygen atom of this group and those of the o ‐nitro group which hinders conjugation in the 3‐nitro‐substituted derivatives. Similar steric inhibition of resonance is observable with 2‐ N ‐butylamine‐, 2‐ N ‐cyclohexylamine‐ and 2‐( N ‐piperidyl)‐substituted nitropyridines, whose 1 H and 13 C NMR spectra were also determined. In the case of the secondary amines, a hydrogen bond between the amino proton and the 3‐nitro group was clearly detected. 1 H and 13 C NMR spectra of 2,6‐dinitro‐, 2,4‐dinitro‐ and 2,4,6‐trinitro‐2‐R‐benzenes (R = OCH 3 , NHC 4 H 9 , NH‐cyclo‐C 6 H 11 , NC 5 H 10 ) were also recorded and compared with those of the pyridine derivatives. The electronic aza and nitro group effects are comparable if conjugation of the nitro group is not hindered.