Indian Journal of Chemistry Vol. 48A, February 2009, pp. 189-193 Kinetics of permanganate oxidation of synthetic macromolecule poly(vinyl alcohol) Maqsood Ahmad Malik, Mohammad Ilyas & Zaheer Khan* ,† a Department of Chemistry, Jamia Millia Islamia (Central University), Jamia Nagar, New Delhi, 110 025, India Email: drkhanchem@yahoo.co.in Received 22 July 2008; re-revised and accepted 27 December 2008 Oxidation of poly(vinyl alcohol) (PVA) by permanganate has been studied spectrophotometrically at 525 and 420nm. Under pseudo-first order conditions ([PVA] >> [MnO 4 - ]), the reaction rate increases with [PVA] and the kinetics reveals complex order dependence on [PVA]. The second-order kinetics with respect to [H 2 SO 4 ] at low concentration shifts to first- order at higher concentration. Water soluble colloidal MnO 2 has been identified as an intermediate in the reduction of MnO 4 - by PVA. The hydrogen ions decrease the stability of colloidal MnO 2 . Poly(vinyl ketone) is found to be the final oxidation product of PVA. Inorganic electrolytes like NaF, Na 4 P 2 O 7 and MnCl 2 (a product of the reaction), have inhibitory and composite effects (inhibition and catalysis) on the reaction rate. Arrhenius and Eyring equations have been used to evaluate the activation parameters. The observed results are discussed in terms of Michaelis-Menten kinetic model. A mechanism has been proposed on the basis of experimental findings. Keywords: Kinetics, Reaction mechanisms, Oxidations, Poly(vinyl alcohol), Permanganate oxidations IPC Code: Int Cl. 8 C07B33/00 The science of polymer (macromolecule) behavior in solution is a rapidly developing field with regard to their wide applications in the preparation of colloidal and nano-size metal particles 1-5 . Stabilizers (polymers, surfactants, complexing agents) have a significant effect on orientation and interaction of metal particles 1-7 . It has been established that the most important role of the stabilizing polymer is to protect the nanoparticles from coagulation. Poly(vinyl alcohol) is one of the favoured macromolecule for carrying out synthesis of polymer-nanoparticle composite 8 . Preparation of colloidal- and nano-metal particles depends upon the reduction of metal salt by suitable reducing agent as well as the presence of stabilizers 9-12 . PVA and its oxidation product (polyvinyl ketone) have reducing and complexing properties, res- pectively, towards various transition metal ions 13-15 . It has been established 5,6,16 that secondary –OH groups in the macromolecule skeleton are responsible for the oxidation of PVA by permanganate and chromic acid in aqueous alkaline and acidic media. It has been reported on several occasions that the possible intermediate(s) species are Mn(VI), Mn(V), Mn(IV), and Mn(III) if permanganate serves as an oxidizing agent in alkaline, neutral and /or acidic medium 14,17,18 . Mn(II) (reaction product) acts as an autocatalyst. Permanganate is used as oxidizing agent for removing organic molecules and heavy metals from the nuclear wastes 19 . Due to this, permanganate oxidations provide chemical kinetics with challenging mechanism. As a part of our investigations on the preparation, characterization and catalytic behavior of water soluble colloidal MnO 2 9,10,20-23 , we report herein the kinetics of the formation of water soluble colloidal MnO 2 as an intermediate during the permanganate oxidation of poly(vinyl alcohol) in presence of H 2 SO 4 medium and examine the inferences drawn from the inorganic electrolytes (NaF, Na 4 P 2 O 7 and MnCl 2 ) trapping experiments. Materials and Methods CO 2 -free, deionized and doubly distilled water (first distillation from alkaline permanganate) was used as solvent for the preparation of stock solutions of all the reagents (PVA, potassium permanganate, sodium fluoride, sodium pyrophosphate and manganese(II) chloride; all from Merck, India, 99%). Permanganate and PVA solutions were prepared by literature methods 13 . Permanganate solutions were standardized by titration against a standard sodium _________ † Present address: Department of Chemistry, Faculty of Science, King Abdul Aziz University, P.O. Box 80203, Jeddah, 21589, Saudi Arabia