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NMR of enaminones. part 6— 17 O and 13 C NMR study of tautomerization in Schiff bases
Author(s) -
Zhuo JinCong
Publication year - 1999
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/(sici)1097-458x(199904)37:4<259::aid-mrc442>3.0.co;2-6
Subject(s) - tautomer , chemistry , schiff base , carbon 13 nmr , nmr spectra database , base (topology) , proton nmr , computational chemistry , stereochemistry , spectral line , mathematical analysis , physics , mathematics , astronomy
13 C and 17 O NMR spectra are reported for three series of Schiff bases: 2‐(aminomethylene)cyclohexanones (1), salicylideneamines (2) and N ‐(2‐hydroxy‐1‐naphthalenylmethylene)amines (3). The 13 C and 17 O NMR data show that Schiff bases 1 exist in ketoenamine form, 2 in enolimine form and 3 as an equilibrium mixture of both forms. The tautomeric composition of Schiff base 3 was estimated. Alkylamines slightly favoured the ketoenamine form; aromatic amines favoured the enolimine form. The tautomeric equilibria are shifted towards the enolimine form in non‐polar solvents and with increase in temperature. Copyright © 1999 John Wiley & Sons, Ltd.