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http://crossmark.crossref.org/dialog/?doi=10.1007/s00396-016-3921-8&domain=pdf
Web End = http://crossmark.crossref.org/dialog/?doi=10.1007/s00396-016-3921-8&domain=pdf
Web End = Colloid Polym Sci (2016) 294:16111622
DOI 10.1007/s00396-016-3921-8
ORIGINAL CONTRIBUTION
Kinetic study of oxidation of paracetamol by water-soluble colloidal MnO2 in the presence of an anionic surfactant
Ajaya Kumar Singh1 & Neelam Sen1 & Som Kumar Chatterjee2 &
Md. Abu Bin Hasan Susan3
Received: 1 October 2015 /Revised: 26 May 2016 /Accepted: 11 July 2016 /Published online: 28 July 2016 # Springer-Verlag Berlin Heidelberg 2016
Abstract The kinetics of the oxidation of paracetamol [PCM] by water-soluble colloidal MnO2 was investigated spectrophotometrically at 298 K in the absence and presence of an anionic surfactant, sodium dodecyl sulphate (SDS), in aqueous solution. The reaction was first order with respect to [MnO2], [PCM] and [H2SO4]. The effects of [Mn(II)], [salt], dielectric constant and ionic strength of the medium on the kinetics of the reaction have also been examined. Micelles of SDS in aqueous solution accelerated the reaction rate, and partitioning of MnO2 in favour of the micellar pseudophase was remarkable. The catalytic effect of SDS in aqueous solutions has been treated by well-defined mathematical (Tuncay), Menger and Portnoy, and Piszkiewicz models. The binding constant (7.59 102 mol1 dm3), dissociation constant(32.43), rate constant in the micellar phase (5.15 104 s1), cooperativity index (1.98) and various thermodynamic activation parameters have been evaluated, and on the basis of the observed kinetic data, possible reaction mechanism and rate law have been proposed.
Keywords Kinetics . Colloidal MnO2 . Paracetamol . Sodium dodecyl sulphate . Oxidative degradation
Introduction
Micellar catalysis has been an intriguing domain of research for the last few decades. There has been a surge of interest on catalysis of reactions by micelles of surfactants with a view to their widespread applications in chemical, industrial, pharmaceutical, environmental and biological fields. Surfactants are amphiphilic substances, and formation of micelles in aqueous solution is induced by the hydrophobic interaction among the hydrophobic moiety of the surface-active agent balanced by their hydration and electrostatic repulsive effects [15]. Hydrophobic substrates when dissolved in aqueous micellar solutions result in high localized concentration inside the core of the micelles and may interact with micellar aggregates (incorporated inside the core and/or bound on the surface of micelles) to enhance apparent reactivity, and as a consequence, the kinetics of a reaction may...