Comparative Kinetic and Mechanistic study of oxidation of B-Cyclodextrin by Potassium Dichromate

*1 R. Naz, 1 R. Azmat, 2 N. Qamar, 1 H. Jaffery and 1 S. Nisar *1 Department of Chemistry, University of Karachi, 75270, Karachi, Pakistan. 2 Department of Chemistry, Jinnah University for Women, 74600 Karachi, Pakistan E-mail: * drr.nazz@gmail.com ABSTRACT A comparative kinetic and mechanistic study of oxidation of β-Cyclodextrin (β-CD) by Potassium Dichromate (K2Cr2O7) in presence of aqueous H2SO4 medium was monitored at λmax 350 nm spectrophotometrically. The oxidation reaction follows first order kinetics with respect to [β-CD] and [Cr2O7 ] and markedly increased by increasing [H]. The slow reaction was accelerated with Fe (III) as a catalyst that enhances the rate significantly. The results of varying temperature were used to compute different activation parameters. The values of activation energy Ea were 37.70KJ mol -1 for catalysed and 50.183 KJ molfor uncatalysed reactions. These clearly indicate that Fe (III) greatly reduced the activation barrier thereby increases the rate of reaction. Oxidation product results due to the oxidation of -CH2OH group present on each glucose monomer of β-CD.A mechanism consistent with kinetic and thermodynamic data is also proposed that involves two-electron reduction of Cr (VI).