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Tautomerism in 2‐hydroxy‐1‐naphthaldehyde schiff bases in solution and the solid state investigated using 13 C NMR spectroscopy
Author(s) -
Salman S. R.,
Lindon J. C.,
Farrant R. D.,
Carpenter T. A.
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.1260311107
Subject(s) - tautomer , chemistry , chemical shift , schiff base , imine , amine gas treating , nmr spectra database , nuclear magnetic resonance spectroscopy , phenol , carbon 13 nmr , proton nmr , spectroscopy , solid state , spectral line , crystallography , computational chemistry , medicinal chemistry , organic chemistry , catalysis , physics , quantum mechanics , astronomy
13 C and 1 H NMR spectra of six Schiff bases formed from 2‐hydroxy‐1‐naphthaldehyde and substituted anilines were measured and assigned in a variety of solvents. Based on the 13 C chemical shifts and 3 J (CH,NH), the ratio of the keto‐amine and phenol‐imine tautomers was derived using both 13 C chemical shifts and 1 H− 1 H coupling constants, the two methods giving comparable results. The solid‐state 13 C NMR spectra of two of these Schiff bases were also measured and interpreted. Based on chemical shift assignments from solution NMR, which showed a relationship between certain shifts and the proportions of the tautomers, it has been shown that these compounds exist essentially as the keto‐amine form in the solid, the tautomer previously shown to be the more thermodynamically stable.