Tautomeric transformations of piroxicam in solution: a combined experimental and theoretical study

Piroxicam tautomerism was studied in solution by using UV-Vis spectroscopy, NMR measurements and advanced chemometrics. It has been found that in ethanol and DMSO the enol-amide tautomer is present mainly as a sandwich type dimer. The addition of water leads to distortion of the aggregate and to gra...

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Bibliographic Details
Published in:RSC advances 2015-01, Vol.5 (40), p.31852-31860
Main Authors: Ivanova, D., Deneva, V., Nedeltcheva, D., Kamounah, F. S., Gergov, G., Hansen, P. E., Kawauchi, S., Antonov, L.
Format: Article
Language:English
Subjects:
Agglomeration
Distortion
Ethanol
Ethyl alcohol
Mathematical analysis
Solvents
Tautomers
Transformations
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Summary:Piroxicam tautomerism was studied in solution by using UV-Vis spectroscopy, NMR measurements and advanced chemometrics. It has been found that in ethanol and DMSO the enol-amide tautomer is present mainly as a sandwich type dimer. The addition of water leads to distortion of the aggregate and to gradual shift of the equilibrium towards the zwitterionic tautomer. Quantitative data for the aggregation and the tautomeric equilibria are presented. Quantum chemical calculations (M06-2X/TZVP) have been used to explain stability of the tautomers as a function of the solvent and concentration.
ISSN:2046-2069
2046-2069
DOI:10.1039/C5RA03653D