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Spectroscopy
Volume 13 (1997), Issue 4, Pages 251-256
http://dx.doi.org/10.1155/1997/304503

Nitrogen NMR shieldings of 2-amino-5-nitro-6-methylpyridines

B. Palasek,1 A. Puszko,1 Z. Biedrzycka,2 W. Sicinska,2 and M. Witanowski2

1Department of Chemistry, Academy of Economics, 53–345 Wroclaw, Poland
2Institute of Organic Chemistry, Polish Academy of Sciences, 01–224 Warsaw, Poland

Received 1 February 1997; Revised 1 March 1997

Copyright © 1997 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Nitrogen NMR shieldings (chemical shifts) of 2-amino-5-nitro-6-methylpyridine derivatives are assessed from the point of view of substituent-induced effects under conditions where alkyl, aryl, nitro, and nitroso moieties are substituents at the amino nitrogen. The nitro nitrogen shielding reveals only little variation upon varying the substituents, and this seems to indicate that steric hindrance which is likely to force the nitro group out of the plane of the aromatic ring reduces the π-electron conjugation with the latter, and with the amino group as well. On the other side, the pyridine nitrogen shielding shows large effects of substituents at the amino moiety, which suggests a significant conjugation between the ring and the amino group. The latter effects produce a remarkable deshielding of the pyridine nitrogen in the case of nitro and nitroso substituents at the amino group.