Oxidative transformation of ciprofloxacin by alkaline permanganate - A kinetic and mechanistic study

Kiran A. Thabaj, Suresh D. Kulkarni, Shivamurti A. Chimatadar, Sharanappa T. Nandibewoor

Research output: Contribution to journalArticle

37 Citations (Scopus)

Abstract

This spectroscopic study presents the kinetics and degradation pathways of oxidation of ciprofloxacin by permanganate in alkaline medium at constant ionic strength of 0.04 mol-3. Orders with respect to substrate, oxidant and alkali concentrations were determined. Effect of ionic strength and solvent polarity of the medium on the rate of the reaction was studied. The oxidation products were identified by LC-ESI-MS technique. Product characterization of ciprofloxacin reaction mixtures indicates the formation of three major products corresponding to m/z 263, 306, and 348 (corresponding to full or partial dealkylation of the piperazine ring). The piperazine moiety of ciprofloxacin is the predominant oxidative site to KMnO4. Product analyses showed that oxidation by permanganate results in dealkylation at the piperazine moiety of ciprofloxacin, with the quinolone ring essentially intact. The reaction kinetics and product characterization point to a reaction mechanism that likely begins with formation of a complex between ciprofloxacin and the KMnO4, followed by oxidation at the aromatic N1 atom of piperazine moiety to generate an anilinyl radical intermediate. The radical intermediates subsequently undergo N-dealkylation. Investigations of the reaction at different temperatures allowed the determination of the activation parameters with respect to the slow step of proposed mechanism. The proposed mechanism and the derived rate laws are consistent with the observed kinetics.

Original languageEnglish
Pages (from-to)4877-4885
Number of pages9
JournalPolyhedron
Volume26
Issue number17
DOIs
Publication statusPublished - 30-10-2007

Fingerprint

Ciprofloxacin
Oxidation
oxidation
Kinetics
kinetics
products
Ionic strength
rings
Reaction products
Oxidants
Reaction kinetics
reaction products
Quinolones
Alkalies
alkalies
polarity
reaction kinetics
Chemical activation
activation
degradation

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

Cite this

Thabaj, Kiran A. ; Kulkarni, Suresh D. ; Chimatadar, Shivamurti A. ; Nandibewoor, Sharanappa T. / Oxidative transformation of ciprofloxacin by alkaline permanganate - A kinetic and mechanistic study. In: Polyhedron. 2007 ; Vol. 26, No. 17. pp. 4877-4885.
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Oxidative transformation of ciprofloxacin by alkaline permanganate - A kinetic and mechanistic study. / Thabaj, Kiran A.; Kulkarni, Suresh D.; Chimatadar, Shivamurti A.; Nandibewoor, Sharanappa T.

In: Polyhedron, Vol. 26, No. 17, 30.10.2007, p. 4877-4885.

Research output: Contribution to journalArticle

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AU - Kulkarni, Suresh D.

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AB - This spectroscopic study presents the kinetics and degradation pathways of oxidation of ciprofloxacin by permanganate in alkaline medium at constant ionic strength of 0.04 mol-3. Orders with respect to substrate, oxidant and alkali concentrations were determined. Effect of ionic strength and solvent polarity of the medium on the rate of the reaction was studied. The oxidation products were identified by LC-ESI-MS technique. Product characterization of ciprofloxacin reaction mixtures indicates the formation of three major products corresponding to m/z 263, 306, and 348 (corresponding to full or partial dealkylation of the piperazine ring). The piperazine moiety of ciprofloxacin is the predominant oxidative site to KMnO4. Product analyses showed that oxidation by permanganate results in dealkylation at the piperazine moiety of ciprofloxacin, with the quinolone ring essentially intact. The reaction kinetics and product characterization point to a reaction mechanism that likely begins with formation of a complex between ciprofloxacin and the KMnO4, followed by oxidation at the aromatic N1 atom of piperazine moiety to generate an anilinyl radical intermediate. The radical intermediates subsequently undergo N-dealkylation. Investigations of the reaction at different temperatures allowed the determination of the activation parameters with respect to the slow step of proposed mechanism. The proposed mechanism and the derived rate laws are consistent with the observed kinetics.

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