Studies on kinetics and mechanism of oxidation of D∼sorbitol and D∼mannitol by cerium(IV) in aqueous micellar sulfuric acid media

The kinetics and mechanism of cerium(IV) oxidation of hexitols, i.e. D-sorbitol and D-mannitol, in aqueous sulfuric acid media have been studied in the presence and absence of surfactants. Under the kinetic conditions, vertical bar S vertical bar(T) >> vertical bar Ce(lV)vertical bar(T), where vertical bar S vertical bar(T) is the total substrate (D-sorbitol or D-mannitol) concentration, the overall process shows a first-order dependence on vertical bar Ce(IV)vertical bar(T) and vertical bar S vertical bar(T). The process is acid catalyzed and inhibited by vertical bar HSO4-vertical bar. From the vertical bar HSO4-vertical bar dependence, it has been noted that the both Ce(SO4)(2+) and Ce(SO4)(2) have been found kinetically active. The different rate constants in the presence and absence of surfactants have been estimated with the activation parameters. N-cetylpyridinium chloride has been found to retard the oxidation process of hexitols, whereas sodium dodecyl sulfate has been found to accelerate the rate process. All these findings including the micellar effects have been interpreted in terms of the proposed reaction mechanism and partitioning behavior of the kinetically active different species of Ce(IV) between the aqueous and pseudomicellar phase. (C) 2008 Wiley Periodicals, Inc.