Micelle-assisted cerium(IV) oxidation of L-sorbose in aqueous sulfuric acid

Spectrophotometric kinetic technique has been used to investigate the effect of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) surfactants on the redox reaction of cerium(IV)+l-sorbose in aqueous sulfuric acid media. The anionic SDS has no effect, whereas the reaction rate increases in the presence of cationic CTAB, which is due to favorable conditions provide by the cationic micelles. The reaction rate decreases with [H₂SO₄], and no acid-dependent path has been observed. At constant [H₂SO₄], the rate of the reaction is dependent on the first powers of the l-sorbose and cerium(IV) concentrations. The CTAB-assisted reaction is retarded by addition of electrolytes (Na₂SO₄, NaNO₃, and NaCl), which is attributed to the competition between electrolyte anions and cerium(IV)-sulfato species. Bromide ion (of CTAB or externally added in the form of NaBr) is not oxidized by the cerium(IV) (as a main or side reaction).