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Issue 5, 2000
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Tautomerism in Schiff bases derived from 3-hydroxysalicylaldehyde. Combined X-ray diffraction, solution and solid state NMR study

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Abstract

The crystal structure of six Schiff bases derived from 3-hydroxysalicylaldehyde has been determined by single crystal X-ray diffraction. In the solid state, these compounds form dimers linked by two strong intermolecular O–H  O bridges resulting in ten-membered pseudocycles. From the observed geometrical parameters together with previous results obtained for N-(3-hydroxysalicylidene)isopropylamine, it can be concluded that these compounds undergo a fast proton exchange between two forms, phenolimine and keto-amine. The tautomeric equilibrium mixture is greatly influenced by the physical state of the examined compounds. This is clearly seen when comparing results obtained from liquid and solid-state 13C NMR. For derivatives derived from aliphatic amines the keto-amine tautomer is always predominant; for compounds obtained from substituted anilines the tautomeric concentration is variable depending on the nature of the substituent. An excellent correlation between C–O bond lengths and 13C chemical shifts is observed.

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Publication details

The article was received on 27 Jan 2000, accepted on 16 Mar 2000 and first published on 13 Apr 2000


Article type: Paper
DOI: 10.1039/B000756K
Citation: J. Chem. Soc., Perkin Trans. 2, 2000, 935-939
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    Tautomerism in Schiff bases derived from 3-hydroxysalicylaldehyde. Combined X-ray diffraction, solution and solid state NMR study

    H. Pizzala, M. Carles, W. E. E. Stone and A. Thevand, J. Chem. Soc., Perkin Trans. 2, 2000, 935
    DOI: 10.1039/B000756K

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