The kinetics of oxidation of iota- and lambda-carrageenan as sulfated carbohydrates by permanganate
ion in aqueous perchlorate solutions at a constant ionic strength of 2.0 mol dm3 have been investigated
spectrophotometrically. The pseudo-first-order plots were found to be of inverted S-shape throughout
the entire courses of reactions. The initial rates were found to be relatively slow in the early stages, followed
by an increase in the oxidation rates over longer time periods. The experimental observations
showed first-order dependences in permanganate and fractional first-order kinetics with respect to both
carrageenans concentration for both the induction and autoacceleration periods. The results obtained at
various hydrogen ion concentrations showed that the oxidation processes in these redox systems are
acid-catalyzed throughout the two stages of oxidation reactions. The added salts lead to the prediction
that MnIII is the reactive species throughout the autoacceleration periods. Kinetic evidence for the formation
of 1:1 intermediate complexes was revealed. The kinetic parameters have been evaluated and tentative
reaction mechanisms in good agreement with the kinetic results are discussed.