The kinetics of oxidation of vanillin (VAN) by chromium(VI) in sulfuric acid medium was studied by a spectrophotometric technique. The reaction exhibited a first order dependence with respect to [Cr(VI)] and fractionalfirst orders with respect to [VAN] and [H+]. Varying ionic strength or dielectric constant of the reaction medium had no significant effect on the oxidation rate. The proposed mechanism includes an intermediate complex formation between vanillin and chromium(VI) before the rate-determining step. The final oxidation product of vanillin was identified by both spectral and chemical analysis as vanillic acid. The suitable rate law has been deduced. The reaction constants included in the various steps of the suggested mechanism have been evaluated. The activation parameters of the rate constant of the rate-determining step of the mechanism and the thermodynamic quantities of the equilibrium constant have been evaluated and discussed.

The kinetics of oxidation of vanillin (VAN) by permanganate ion in neutral medium has been investigated spectrophtometrically. The stoichiometry of the reaction was found to be 3:2 (VAN: MnO4 - ). The oxidation reaction exhibited a first order dependence in [MnO4 - ] and less than unit order dependence with respect to vanillin concentration. Addition of small amounts of Ag(I), Co(II) and Ru(III) catalysts increased the oxidation rate and the catalytic efficiency increased in the order: Ru(III) > Ag(I) > Co(II). The proposed oxidation mechanism involves formation of a 1:1 intermediate complex between vanillin and permanganate ion in pre-equilibrium step. The final oxidation product of vanillin was identified by both spectral and chemical analysis as vanillic acid. The appropriate rate law was deduced. The reaction constants involved in the different steps of the mechanism were evaluated. The activation parameters associated with the rate constant of the slow step of the proposed mechanism along with the thermodynamic quantities of the equilibrium constant have been evaluated and discussed.

The kinetics of oxidation of one of the formamidine derivatives, namely, methylaminopyrazole formamidine (MAPF) by cerium(IV) has been investigated in aqueous perchlorate solutions at a constant ionic strength of 1.2 mol dm-3 and at 25°C. The progress of the reaction was followed spectrophotometrically. The reaction exhibited a first order kinetics with respect to [Ce(IV)], whereas the order with respect to [MAPF] was found to be less than unity. The reaction rate decreased with the increase in acid concentration with a negative less than unit order. The rate of reaction was not affected by increasing either ionic strength or dielectric constant of the medium. Furthermore, addition of cerium(III) product did not affect the reaction rate. The plausible oxidation mechanism involves formation of an intermediate complex between MAPF substrate and the kinetically active species of cerium(IV) in a pre-equilibrium step which decomposes in the slow step to give free radical derived from the substrate and Ce(III). The free radical is attacked by another Ce(IV) species to yield the final oxidation products which were identified by spectral and chemical analyses as methylaminopyrazole, dimethylamine and carbon dioxide. The activation parameters have been evaluated and discussed. The rate law associated with the reaction mechanism was derived.

The of kinetics of oxidation of a pyrimidine derivative, N,N-dimethyl-N’-(pyrimidin-2-yl) formamidine (Pym-F), by hexacyanoferrate(III) (HCF) was studied in aqueous alkaline medium in the presence of palladium(II) catalyst. The reaction did not proceed in the absence of Pd(II) catalyst. The progress of the catalyzed reaction was followed spectrophotometrically. The reaction showed a first order kinetics in both [HCF] and [Pd(II)], and less than unit orders with respect to both [Pym-F] and [OH- ]. Increasing ionic strength and dielectric constant of the medium increased the reaction rate. A mechanistic scheme for the catalyzed oxidation reaction has been proposed. The final oxidation products are identified as 2-aminopyrimidine, dimethylamine and carbon dioxide. The rate law expression associated with the reaction mechanism is derived and the reaction constants involved in the different steps of the mechanism are calculated. The activation parameters with respect to the ratedetermining step have been computed and discussed.

In alkaline medium, the kinetics of oxidation of two substituted benzazolylformamidines, namely N, N-dimethylN’-(1H-benzimidazol-2-yl) formamidine (BIF) and N, N-dimethyl-N’-(benzthiazol-2-yl) formamidine (BTF) by permanganate ion has been studied spectrophotometrically at a constant ionic strength of 0.1 mol dm-3 and at 25°C. The reactions exhibited first order kinetics with respect to [permanganate]. Fractional-first order dependences of both reactions on [reductants] and [alkali] were revealed. Increasing either ionic strength or solvent polarity of the medium had no significant effect on the rates. The final oxidation products of BIF and BTF were identified as 2-aminobenzimidazole and 2-aminobenzthiazole, respectively, in addition to dimethylamine and carbon dioxide. Under comparable experimental conditions, the oxidation rate of BIF was higher than that of BTF. The reaction mechanism adequately describing the kinetic results was proposed, and the reaction constants involved in the different steps of the mechanism have been evaluated. The activation parameters with respect to the rate-limiting step of the reactions, along with thermodynamic quantities were computed and discussed.

Diketoacid derivative of kappa-carrageenan (KCAR) was synthesized as an oxidation product of oxidation of KCAR with potassium permanganate in alkaline solution at pH's > 12 with a yield of 96.2%. The chemical structure of the coordination biopolymer macromolecule (DKA-KCAR) has been elucidated by elemental analysis and IR spectroscopy. The product has a high efficiency for removal of toxic heavy metal cations from the contaminated matters in environment. Suggested models for chelation were presented. A tentative reaction mechanism consistent with the experimental results for oxidation is suggested

The kinetics of oxidation of L-asparagine (Asn) by hexacyanoferrate(III) (HCF) has been investigated in alkaline medium in the absence and presence of silver(I) catalyst at a constant ionic strength of 0.5 mol dm−3 and at 20°C. The progress of both uncatalyzed and silver(I)-catalyzed oxidations was followed spectrophotometrically. Both reactions showed a first order dependence with respect to [HCF], whereas the orders with respect to [Asn] and [OH− ] were less than unity. The catalyzed reaction exhibited a first order dependence in [AgI ]. Increasing both ionic strength and dielectric constant of the reaction medium increased the rate of uncatalyzed reaction and did not affect significantly the rate of catalyzed reaction. Addition of the reaction product, HCF(II) to the reaction mixture had no affect on the rate. Appropriate reaction mechanisms for both uncatalyzed and catalyzed oxidations explaining all of the observed kinetic results has been proposed. The catalyzed reaction has been shown to proceed via formation of a silver(I)-asparagine intermediate complex, which reacted with the oxidant by an inner-sphere mechanism leading to decomposition of the complex in the rate-determining step to yield the final oxidation products which were identified as α-formyl acetamide, ammonia, and carbon dioxide. The rate law expressions associated with the reaction mechanisms were derived.

In aqueous alkaline medium, the kinetics of oxidation of methylaminopyrazole formamidine (MAPF) by hexacyanoferrate(III) (HCF)has been studied spectrophotometrically under the conditions, MAPF >> HCF at a constant ionic strength of 0.1 mol dm-3 and at 25°C. The reaction showed first order dependence on [HCF] while it exhibited fractional-first order kinetics with respect to [MAPF] and [OH- ]. The oxidation rate increased with increasing ionic strength and dielectric constant of the reaction medium. Addition of small amounts of some divalent transition metal ions accelerates the oxidation rate and the order of catalytic efficiency was: Cu(II) > Ni(II) > Zn(II) > Co(II) > Cd(II). The suggested mechanism involves formation of a 1: 1 intermediate complex between HCF and the deprotonated MAPF species in a pre-equilibrium step. The final oxidation products were identified as methylaminopyrazole, dimethylamine and carbon dioxide. The appropriate rate law was deduced. The reaction constants involved in the mechanism were evaluated. The activation and thermodynamic parameters were determined and discussed.

The kinetics of oxidation of N, N-dimethyl-N’-(pyridin-2-yl) formamidine (Py-F) by cerium(IV) was studied spectrophotometrically in aqueous perchloric acid solutions at a constant ionic strength of 1.0 mol dm-3 and at 20°C. The reaction showed first order dependence with respect to [Ce(IV)] and less than unit order with respect to [Py-F]. The reaction exhibited negative fractional-first order kinetics with respect to [H+ ]. The rate of reaction was not significantly affected by variation of either ionic strength or dielectric constant of the reaction medium. Addition of cerium(III) product did not affect the reaction rate. A suitable mechanistic scheme for the oxidation reaction has been proposed. The final oxidation products were identified as 2-aminopyridine, dimethylamine and carbon dioxide. The activation parameters have been evaluated and discussed. The rate law associated with the reaction mechanism was derived.

The kinetics of oxidation of iota- and lambda-carrageenans as sulfated polysaccharides by cerium(IV) was studied spectrophotometrically in aqueous perchlorate solutions at a fixed ionic strength of 2.0 mol dm-3 and a temperature of 25 oC. The reactions showed a first order dependence on [CeIV], whereas the orders with respect to each carrageenan concentration were less than unity. The reactions exhibited fractional-first order kinetics with respect to [H+ ]. Increasing ionic strength increased the oxidation rates. The oxidation products of carrageenans were characterized by elemental analysis and IR spectra as their diketo-acid derivatives. The oxidation products were found to have high tendencies to form coordination polymer complexes with some metal cations such as BaII, CdII, PbII and AgI . Kinetic evidences for the formation of 1:1 complexes were revealed. Plausible mechanistic scheme for cerium(IV) oxidations of carrageenans were proposed. The activation parameters with respect to the slow step of the reactions were evaluated and discussed. The rate laws have been derived and the reaction constants involved in the different steps of the mechanisms were calculated. The activation parameters associated with the ratedetermining step of the mechanism along with thermodynamic quantities of the equilibrium constants were computed and discussed.