Journal of Molecular Catalysis A-Chemical, Vol.335, No.1-2, 38-45, 2011
Base-catalyzed oxidation of some sulfated macromolecules: Kinetics and mechanism of formation of intermediate complexes of short-lived manganate (VI) and/or hypomanganate (V) during oxidation of iota- and lambda-carrageenan polysaccharides by alkaline permanganate
The kinetics of formation of intermediate complexes during the oxidation of iota- and lambda-carrageenan sulfated polysaccharides (CAR) as natural polymers by alkaline permanganate at pH's >= 12 have been investigated using a conventional spectrophotometer. The reactions showed first-order dependences in permanganate and fractional-first-order kinetics with respect to carrageenans concentration. Kinetic and spectrophotometric evidences revealed the formation of intermediate complexes involving green manganate (VI) and/or blue hypomanganate (V) short-lived transient species. The influence of pH on the oxidation rates indicated that the formation of complexes is base-catalyzed. The kinetic parameters have been evaluated and mechanisms consistent with the experimental results are discussed. (C) 2010 Elsevier B.V. All rights reserved.
Keywords:Catalysis;Soluble-colloidal Mn-IV;Carrageenans;Polysaccharides;Permanganate;Kinetics;Oxidation;Mechanism