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Structural investigation on phenyl‐ and pyridin‐2‐ylamino(methylene)naphthalen‐2(3 H )‐one. Substituent effects on the NMR chemical shifts
Author(s) -
Venkatachalam Taracad K.,
Pierens Gregory K.,
Campitelli Marc R.,
Reutens David C.
Publication year - 2010
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.2626
Subject(s) - chemistry , tautomer , schiff base , moiety , substituent , proton nmr , methylene , chemical shift , hydrogen bond , solvent , proton , amine gas treating , ring (chemistry) , nmr spectra database , carbon 13 nmr , medicinal chemistry , stereochemistry , molecule , organic chemistry , spectral line , physics , quantum mechanics , astronomy
Schiff bases bearing phenyl and pyridyl groups were synthesized by condensation of appropriate amines with 2‐hydroxynaphthaldehyde. These Schiff bases were obtained as colored crystalline solids. The proton NMR spectra of these compounds showed a doublet for the NH protons indicating a keto tautomer for these Schiff bases. The pyridyl‐substituted Schiff bases containing hydroxyl moiety were found to show the most downfield shift for the NH protons in DMSO solvent, and this was rationalized due to the formation of a six‐ and five‐membered ring using hydrogen bonds for these two compounds. Correspondingly, the olefinic proton of the Schiff bases is also found to be a doublet due to coupling to the amine proton. These Schiff bases exhibited thermochromic properties. Detailed NMR spectral analysis for both the phenyl‐ and pyridyl‐substituted Schiff bases is presented. Copyright © 2010 John Wiley & Sons, Ltd.