Issue 9, 1993

Proton transfer in rubazoic acid derivatives in solution and in the solid state. An NMR study

Abstract

Solution 1H and 13C, and solid-state 13C CPMAS NMR data are reported for the rubazoic acid derivatives 4-(5-hydroxy-1,3-dimethylpyrazol-4-ylmethylidene)-1,3-dimethyl-2-pyrazolin-5-one 1, 4-(5-hydroxy-1,3-dimethylpyrazol-4-ylimino)-1,3-dimethyl-2-pyrazolin-5-one 2, 4-(5-hydroxy-1-phenyl-3-aminopyrazol-4-ylmethylidene)-1-phenyl-3-amino-2-pyrazolin-5-one 3, and 4-(5-hydroxy-1-p-sulfophenylene-3-methylpyrazol-4-ylmethylidene)-1-p-sulfophenylene-3-methyl-pyrazolin-5-one 4. Solution 15N NMR chemical shifts have also been measured, lsotopic 2H shifts for the OH signal in CDCI3 for the first two compounds were found to be +0.28 ± 0.03 and +0.40 ± 0.03 ppm respectively. AM1-calculated molecular geometries are also reported. The overall results support the idea of a fast proton transfer equilibrium between two enolic tautomers both in solution and in the solid state. The degeneracy of the tautomers is removed in crystals.

Article information

Article type
Paper

J. Chem. Soc., Perkin Trans. 2, 1993, 1597-1601

Proton transfer in rubazoic acid derivatives in solution and in the solid state. An NMR study

A. C. Olivieri, D. Sanz, R. M. xmlns="http://www.rsc.org/schema/rscart38"> <. Claramunt and J. Elguero, J. Chem. Soc., Perkin Trans. 2, 1993, 1597 DOI: 10.1039/P29930001597

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