Electrochemical behaviour of dipyrone (metamizole) and others pyrazolones

The electrochemical oxidation of dipyrone (MTM) in aqueous medium was characterized using antipyrine (AA), 4-aminoantipyrine (4AA), 4-methyl-aminoantipyrine (MAA) and 4-dimethyl-aminoantipyrine (DMAA) as model molecules for the elucidation of all MTM voltammetric signals. The MTM and the other pyraz...

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Bibliographic Details
Published in:Electrochimica acta 2018-05, Vol.273, p.358-366
Main Authors: Bacil, Raphael P., Buoro, Rafael M., Campos, Othon S., Ramos, Matesa A., Sanz, Caroline G., Serrano, Silvia H.P.
Format: Article
Language:English
Subjects:
Analgesics
Antipyrines
Aqueous solutions
Computer simulation
Dypirone
Electrochemical analysis
Electrochemical oxidation
Mechanism
Metamizole
Molecular chains
Oxidation
Pyrazolones
Stabilization
Thermodynamics
Voltammetry
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Summary:The electrochemical oxidation of dipyrone (MTM) in aqueous medium was characterized using antipyrine (AA), 4-aminoantipyrine (4AA), 4-methyl-aminoantipyrine (MAA) and 4-dimethyl-aminoantipyrine (DMAA) as model molecules for the elucidation of all MTM voltammetric signals. The MTM and the other pyrazolones show up to four oxidation electrochemical processes. The voltammograms obtained in AA solutions presented an irreversible electrochemical oxidation process involving one electron at Eap3, which is common to all pyrazolone derivatives, while the amino pyrazolones present electrochemical oxidation processes at Eap0 or Eap1. The stabilization of the oxidation products depends on different effects: the proton release added to the thermodynamic stability, in the case of the imine formation at Eap0 (4AA and MAA) and the hyperconjugation (σ-stabilization) in the case of iminium formation (DMAA and MTM) at Eap1. The process observed at Epa0 corresponds to the pH-dependent oxidation of the primary and secondary enamines, while the process observed at Eap1 occurs in the tertiary enamines, is pH independent. The oxidation peak potential follows the order: MAA < 4AA  DMAA > MTM > AA.
ISSN:0013-4686
1873-3859
DOI:10.1016/j.electacta.2018.04.082