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Effect of the ortho ‐nitro group on the 13 C NMR chemical shifts of substituted pyridines
Author(s) -
Rasala Danuta,
Gawinecki Ryszard
Publication year - 1993
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.1260310108
Subject(s) - substituent , chemical shift , chemistry , nitro , ring (chemistry) , carbon 13 nmr , group (periodic table) , nuclear magnetic resonance spectroscopy , computational chemistry , nmr spectra database , stereochemistry , medicinal chemistry , spectral line , organic chemistry , alkyl , physics , astronomy
The 13 C NMR spectra of 40 vicinally substituted 2‐ and 3‐nitropyridines were recorded. The observed chemical shifts are, in general, non‐additive. These results are discussed in terms of the effects of 2‐, 3‐ and 4‐substitutents on the ring carbons and of the position of the fixed nitro group and the substituent. The chemical shifts of the para carbon, with respect to the substitutent, follow well the dual substituent parameter approach, which shows their electronic origin. However, the substituent chemical shifts of both ipso and ortho positions can be rationalized, in terms of multiple parameter substituent correlation analysis, only on a approximate level.