Industrial Chemistry
Open Access

Abstract

The oxidation of [CrIII(HNTA)(Hist) (H2O)]- and [CrIII(HNTA)(Asp)(H2O)]- (NTA=nitrilotriacetate, Hist=L-histidine and Asp=DL-aspartate) by periodate in aqueous medium has been studied spectrophotometrically between 15.0 and 35.0�°C under pseudo-first-order conditions, [IO4]- [complex]. The rate increases over the pH range 3.40-4.45 in both cases, but the two complexes give different rate laws, in aqueous solutions, [CrIII(HNTA)(Hist)(H2O)]- is oxidized by IO4- according to the following rate law: d[CrVI]/dt =(k1K2+k2K3K1/[H+])[IO4-][CrIII]T/{1+ (K1/[H+]) +(K2+K1K3/[H+])[IO4-]}. The other case is [CrIII(HNTA)(Asp)(H2O)]- the derived rate law is given by equation: Rate=k1K2[CrIII]T[IVII]T/{1+ ([H+]/K1) + K2[IVII]T}. Electron transfer, outer-sphere and inner-sphere mechanisms have been discussed. The nature, properties, chemical behavior and different species in aqueous solutions of periodate have been reported. A literature survey on the oxidation of organic and inorganic compound in aqueous solutions and in aqueous organic solvent was reported. The nature of �±-amino acids and their metal complexes have been briefly discussed, it is clear that [CrIII(NTA)(Asp)(OH)]2- may be the reactive species, an inner-sphere process may be still accommodating through replacement of coordinated H2O in two species by IO4-. The rate of reaction increases with the increasing of complex concentration and ionic strength. The thermodynamic activation parameters were calculated, and we propose that electron transfer proceeds through an inner-sphere mechanism, via coordination of IO4- to chromium (III). A common mechanism for the oxidation of some to chromium(III) complexes by periodate is proposed by an excellent isokinetic relationship between and values for these reactions. MohamedHabib952@gmail.com

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