Rate enhancement via sodium dodecyl sulfate (SDS) encapsulation of metal-mediated cerium(IV) oxidation of d-mannitol to d-mannose at room temperature and pressure: a kinetic and mechanistic approach

Abstract

d-mannitol is a sweet-tasting hexitol widely distributed in nature, and is found in olive trees, plane trees, fruits, and vegetables. However, production of mannitol and mannose by extraction of plant raw materials is no longer economical. Selective oxidation of d-mannitol gives d-mannose. Oxidation kinetics of d-mannitol by Ce(IV) in an aqueous medium in the presence of sodium dodecyl sulfate (SDS) has been carried out to observe the micellar effect on rate. The oxidation kinetics was studied by UV–Vis spectrophotometry. Five different metal ions Cr(III), Mn(II), Fe(II), Cu(II), and Ag(I) are used. Both Cr(III) and Mn(II) are active catalysts for the d-mannitol oxidation in the presence and absence of anionic surfactants. The substrate undergoes effective collision with the expected positive reactive species Ce(SO4)2+ resulting enhancement of rate. The presence of SDS surfactant was found to accelerate the reaction rate and this effect has been explained by the partitioning of the reactants in micelle. The effect of sodium dodecyl sulfate (SDS) on rate also indicate that Ce(SO4)2+ was the main reactive form of cerium(IV). The main product d-mannose was identified by the FTIR spectroscopy and spot test. The combination of Mn(II) and SDS is the most suitable combination for the conversion of d-mannitol to d -mannose.