Study of the base-catalysed oxidation of the anti-bacterial and anti-protozoal agent metronidazole by permanganate ion in alkaline medium Aftab Aslam Parwaz Khan • Anish Khan • Abdullah M. Asiri • Naved Azum • Malik Abdul Rub • Sher Bahadar Khan • Mohammed M. Rahman • Abdulrahman O. Al-Youbi Received: 17 December 2012 / Accepted: 23 January 2013 / Published online: 10 February 2013 Ó Springer Science+Business Media Dordrecht 2013 Abstract The mechanism of dismutation of MnO 4 2- via the complex [MTZ– MnO 4 OH] 2- , formed during the oxidation of metronidazole (MTZ), has been investigated spectrophotometrically at different temperatures. The stoichiometry of the reaction is 1:1, i.e. 1 mol MTZ reacts with 1 mol Mn(VII).The reaction is first order in permanganate, less than first order in [MTZ] and [alkali]. The effects of added products and the dielectric constant and ionic strength of the reaction medium were investigated. The main products were identified by spot test and FT-IR. A mechanism involving a free radical has been proposed. In the equilibrium step MTZ binds to the MnO 4 - species to form a complex (C). Investigation of the reaction at different temperatures enabled determination of the activation data for the slow step of proposed mechanism. The proposed mechanism and the derived rate laws are consistent with the observed kinetics. Keywords MTZ  Rate laws  Free radicals  Permanganate  Oxidation  Mechanism  Complex and thermodynamic data A. A. P. Khan  A. Khan  A. M. Asiri  N. Azum  M. A. Rub  S. B. Khan  M. M. Rahman  A. O. Al-Youbi Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia A. A. P. Khan (&)  A. Khan  A. M. Asiri  N. Azum  M. A. Rub  S. B. Khan  M. M. Rahman  A. O. Al-Youbi Center of Excellence for Advanced Materials Research, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia e-mail: draapk@gmail.com 123 Res Chem Intermed (2014) 40:1703–1714 DOI 10.1007/s11164-013-1075-6