Stabilizing the unstable: In textbooks barbituric acid is always drawn in its keto tautomeric form, which is indeed preferred in solution and in most polymorphic phases. However, phase IV, obtained by grinding, consists of molecules in the enol form, as shown by neutron powder diffraction. This phase is found to be the most stable one at room temperature; the “unstable” enol tautomer is stabilized by a higher number of hydrogen bonds.

The Thermodynamically Stable Form of Solid Barbituric Acid: The Enol Tautomer

CHIEROTTI, Michele Remo;GOBETTO, Roberto
2011-01-01

Abstract

Stabilizing the unstable: In textbooks barbituric acid is always drawn in its keto tautomeric form, which is indeed preferred in solution and in most polymorphic phases. However, phase IV, obtained by grinding, consists of molecules in the enol form, as shown by neutron powder diffraction. This phase is found to be the most stable one at room temperature; the “unstable” enol tautomer is stabilized by a higher number of hydrogen bonds.
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http://onlinelibrary.wiley.com/doi/10.1002/anie.201101040/abstract
barbituric acid; lattice-energy minimizations; neutron diffraction; NMR spectroscopy; tautomerism; polymorphism
M.U. Schmidt; J. Brüning; J. Glinnemann; M.W. Hützler; P. Mörschel; S.N. Ivashevskaya; J. van de Streek; D. Braga; L. Maini; M.R. Chierotti; R. Gobetto
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/93481
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