Acid-catalyzed oxidation of some sulfated polysaccharides: Kinetics and mechanism of oxidation of kappa-carrageenan by cerium(IV) in aqueous perchlorate solutions

The kinetics of oxidation of kappa-carrageenan (KCAR) as a sulfated polysaccharide by cerium(IV) in aqueous perchlorate solutions at a constant ionic strength of 2.0 mol dm−3 have been investigated, spectrophotometically. The results showed a first-order dependence in [CeIV] and fractional-first-order kinetics in carrageenan concentration. A kinetic evidence for the formation of 1:1 complex has been revealed. The hydrogen ion dependence of the reaction rate indicated that the oxidation process is acid catalyzed. The oxidation product was identified by the spectral data and elemental analysis. The activation and thermodynamic parameters have been evaluated and a relevant reaction mechanism is suggested and discussed.

Graphical abstract. The kinetics of oxidation of kappa-carrageenan (KCAR) by cerium(IV) in aqueous perchlorate solutions have been investigated, spectrophotometically. A kinetic evidence for the formation of 1:1 complex has been revealed. The oxidation product was identified by the spectral data and microanalysis as diketo-acid derivative (DKA-KCAR).Figure optionsDownload full-size imageDownload high-quality image (41 K)Download as PowerPoint slideResearch highlights▶ The kinetics of oxidation of some sulfated macromolecules in acidic solutions by cerium(IV) ion. ▶ Novel synthesis of keto-acid derivatives of kappa-carrageenan by an oxidation process. ▶ Behavior of sulfated polysaccharides in aqueous acidic solutions. ▶ Elucidation of reaction mechanistics for the oxidation.