Influence of sodium dodecyl sulfate/TritonX-100 micelles on the oxidation of d-fructose by chromic acid in presence of HClO4 Original Research Article

The kinetics of oxidation of d-fructose by chromic acid in aqueous and aqueous surfactant (sodium dodecyl sulfate, SDS, and alkylphenyl polyethylenglykol, TX-100) media have been investigated in the presence of HClO4. The reaction is acid catalyzed and is associated with an induction period which is dependent on [H+], [surfactant] and temperature. The order of oxidation during induction under [d-fructose]>[chromic acid] conditions is fractional in each reagent in both media. The rate constant was found to increase with [Mn(II)]. A mechanism has been proposed for the reaction. The micelles produce a catalytic effect in the range of SDS and TX-100 concentrations used, and the effect is explained by means of the pseudo-phase mass-action model. In the presence of SDS, the reaction is inhibited by electrolytes (NH4Br, NaBr, LiBr), and the inhibition order Na+>Li+>NH4+ is explained on the basis of electrostatic considerations. The rate constant (km), binding constants (KS and KF), and corresponding activation parameters (Ea, ΔH≠ and ΔS≠) have been evaluated and discussed. The order of reactivities of different sugars is found as: d-fructose>d-arabinose>d-xylose≈d-glucose.