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Proximity effect in the 13 C NMR spectra of alkylpyridines: An aid in structure elucidation
Author(s) -
Holík Miroslav,
Turečková Milena,
Vymětal Jan
Publication year - 1984
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270221005
Subject(s) - chemistry , chemical shift , substituent , steric effects , ring (chemistry) , additive function , alkyl , molecule , carbon 13 nmr , nmr spectra database , stereochemistry , spectral line , computational chemistry , organic chemistry , mathematics , physics , mathematical analysis , astronomy
The structures of seven polysubstituted alkylpyridines, recently isolated from coal tar, were elucidated using their 13 C NMR spectra. For tri‐ and tetra‐substituted derivatives the correct isomeric structure was found from their conformity with the proximity effect, i.e. the deviations from additivity when calculating chemical shifts from substituent increments (SCS) for sterically crowded molecules. This effect manifests itself both on the ring and on the alkyl carbon signals, and in most cases shifts their position upfield.