The kinetics of formation of intermediate complexes during the oxidation of iota- and lambdacarrageenan
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.