Kinetic investigation on the oxidation of one of the aminotriazole derivatives, namely N,N-dimethyl-N’- (4H-1,2,4-triazol-3-yl) formamidine (ATF) by permanganate ion in alkaline medium has been performed at a constant ionic strength of 0.1 mol dm-3 and at 25 oC. The progress of the reaction was followed spectrophotometrically. Both spectroscopic and kinetic evidences reveal formation of a 1:1 intermediate complex between the oxidant and substrate. The influence of pH on the oxidation rate indicated that the reaction is base-catalyzed. The reaction shows first order dependence with respect to [MnO4 - ], and fractional-first order dependences on both [ATF] and [OH- ]. Increasing ionic strength and dielectric constant did not affect the reaction rate. Addition of small amounts of alkali-metal ion catalysts was found to accelerate the oxidation rate and the order of effectiveness of the ions was: Li+ > Na + > K + . The final oxidation products of ATF were identified as 3-aminotriazole, dimethyl amine and carbon dioxide. A plausible reaction mechanism consistent with the kinetic observations is proposed, and the reaction constants involved in the different steps of the mechanism have been evaluated. The activation parameters with respect to the slow step of the reaction, along with thermodynamic quantities of the equilibrium constants are calculated and discussed.

Kinetics and mechanistic investigations of copper(II)-catalyzed oxidation of L-asparagine (Asn) by hexachloroplatinate(IV) (HCP) was performed in alkaline medium at a constant ionic strength of 0.2 mol dm-3 and at 25 oC using a conventional spectrophotometric technique. A first order dependence in both [HCP] and [CuII] and fractional-first order kinetics with respect to both [Asn] and [OH- ] were observed. Increasing ionic strength and dielectric constant increases the oxidation rate. The proposed mechanism indicated that the reaction proceeds via formation of copper(II) _ asparagine intermediate complex, which reacts with the oxidant in the rate-determining step to give rise to the oxidation products which were identified as αformyl acetamide, ammonia and carbon dioxide. In this context, platinum(IV) is reduced to platinum(II) by the substrate in a one-step twoelectron transfer process. The rate law associated with the reaction mechanism is deduced. Activation parameters of the reaction have been evaluated and discussed.

Kinetic investigation on the hexachloroplatinate(IV) (HCP) oxidation of L-histidine (His) catalyzed by zirconium(IV) has been performed in sulfuric acid medium at constant ionic strength and temperature. The reaction has been followed spectrophotometrically. A first order dependence on [HCP] and fractional-first order dependences with respect to [His], [acid] and [Zr(IV)] are obtained. Increasing ionic strength and dielectric constant decreases the oxidation rate. On the basis of the experimental results, a suitable mechanism has been proposed. The reaction is suggested to proceed via formation of zirconium(IV)-histidine intermediate complex, which reacts with the oxidant by an inner-sphere mechanism leading to decomposition of the complex in the rate-determining step to give rise to the oxidation products which are identified as the corresponding aldehyde (2-imidazole acetaldehyde), ammonium ion and carbon dioxide. The appropriate rate law is deduced and the activation parameters are evaluated and discussed.

Kinetic investigations of Pt(IV) oxidation of L-asparagine catalyzed by transition metals with different valencies, namely Ag(I), Pd(II), Cr(III) and Zr(IV), were studied spectrophotometrically in sulfuric acid medium at constant ionic strength and temperature. The reaction was first order in [Pt(IV)], while the orders with respect to the concentrations of Asn, sulfuric acid and transition metal were less than unity over the concentration range studied. The rate constants decreased with increasing ionic strength and dielectric constant, while increasing temperature enhanced the rate. The order of catalytic efficiency was: Ag(I) [Cr(III) [Pd(II) [Zr(IV). A mechanism involving the formation of a complex between the catalyst and substrate is proposed. Oxidation by Pt(IV) is suggested to take place by an inner-sphere mechanism in which Pt(IV) is reduced to Pt(II) on the catalyst-bound substrate in a onestep two-electron transfer process. The oxidation products of Asn were identified as a-formyl acetamide, ammonium ion and carbon dioxide. The rate law associated with the reaction mechanism was deduced. Activation parameters of the reactions were evaluated and discussed

Kinetics of hexachloroplatinate(IV) (HCP) oxidation of L-histidine (His) in H2SO4 medium has been investigated in the absence and presence of silver(I) catalyst at constant ionic strength 2.0 mol dm-3 and temperature 25 C. The progress of both uncatalyzed and silver(I)-catalyzed oxidation reactions has been monitored spectrophotometrically. Both uncatalyzed and catalyzed paths show first-order dependence on [HCP] and fractionalfirst-order dependence each on [His] and [acid]. The catalyzed path is first order in [AgI ]. Increasing ionic strength and dielectric constant decreases the oxidation rates. The catalyzed reaction has been shown to proceed via formation of a silver(I)-histidine intermediate complex, which reacts with the oxidant by an inner-sphere mechanism leading to decomposition of the complex in the rate-determining step. The final oxidation products of histidine were identified as the corresponding aldehyde (2-imidazole acetaldehyde), ammonium ion and carbon dioxide. The mechanisms of these reactions have been proposed and the appropriate rate laws are deduced

The anticorrosion characteristics of sulfachloropyridazine (SCP) as an eco-friendly inhibitor for the corrosion of mild steel in 0.5 M H2SO4 solution has been studied, for the first time, using potentiodynamic measurements and electrochemical impedance spectroscopy (EIS). The possible synergistic effect of halide ions on the inhibitive effect of SCP has been investigated. Thermodynamic calculations indicated that SCP adsorption on steel surface obeyed Langmuir adsorption isotherm. Electrochemical measurements showed that the SCP acted mainly as an anodic inhibitor. Halides significantly promoted the inhibition performance of SCP through the pre-adsorption on the electrode surface which is positively charged under the present conditions.

The catalytic effect of copper(II) ions toward the oxidation of L-asparagine (Asn) by an anticancer platinum(IV) complex in the form of hexachloroplatinate(IV) (HCP) has been investigated in aqueous acid medium at the constant ionic strength and temperature. The progress of both uncatalyzed and copper(II)-catalyzed oxidation reactions has been monitored spectrophotometrically. The stoichiometry in both cases is [Asn]/[HCP] = 1:1. The kinetics of both redox reactions is first order with respect to [oxidant] and less than the unit order in [acid]. The order with respect to [Asn]T decreases from unity in the uncatalyzed path to less than unity in the catalyzed one. The catalyzed path is first order in [CuII]T. Increasing ionic strength and dielectric constant decreases the oxidation rates. The final oxidation products of L-asparagine are identified as the corresponding aldehyde (α-formyl acetamide), ammonium ion, and carbon dioxide. Tentative mechanisms of both reactions have been suggested.

The kinetics of oxidation of L-histidine (His) by platinum(IV) in the absence and presence of copper(II) catalyst was studied using spectrophotometry in alkaline medium at a constant ionic strength of 0.1 mol dm-3 and at 25 C. In both cases, the reactions exhibit a 1:1 stoichiometry ([His]:[PtIV]). The rate of the uncatalyzed reaction is dependent on the first power of each of the concentrations of oxidant, substrate and alkali. The catalyzed path shows a first-order dependence on both [PtIV] and [CuII], but the order with respect to both [His] and [OH-] is less than unity. The rate constants increase with increasing ionic strength and dielectric constant of the medium. The catalyzed reaction has been shown to proceed via formation of a copper(II)_ histidine intermediate complex, which reacts with the oxidant by an inner-sphere mechanism leading to decomposition of the complex in the rate-determining step. Platinum(IV) is reduced to platinum(II) by the substrate in a one-step two-electron transfer process. This is followed by other fast steps, giving rise to the oxidation products which were identified as 2-imidazole acetaldehyde, ammonia and carbon dioxide. A tentative reaction mechanism is suggested, and the associated rate laws are deduced. The activation parameters with respect to the slow step of the mechanism are reported and discussed.

: The reaction kinetics for the oxidation of L-histidine by permanganate ions have been investigated spectrophotometrically in sulfuric acid medium at constant ionic strength and temperature. The order with respect to permanganate ions was found to be unity and second in acid concentration, whereas a fractional order is observed with respect to histidine. The reaction was observed to proceed through formation of a 1:1 intermediate complex between oxidant and substrate. The effect of the acid concentration suggests that the reaction is acid catalyzed. Increasing the ionic strength has no significant effect on the rate. The influence of temperature on the rate of reaction was studied. The presence of metal ion catalysts was found to accelerate the oxidation rate, and the order of effectiveness of the ions was Cu2+ > Ni2+ > Zn2+. The final oxidation products were identified as aldehyde (2-imidazole acetaldehyde), ammonium ion, manganese(II), and carbon dioxide. Based on the kinetic results, a plausible reaction mechanism is proposed. The activation parameters were determined and discussed with respect to a slow reaction step. C 2014 Wiley Periodicals, Inc. Int J Chem Kinet 46: 370–381, 2014

The kinetics and mechanism of oxidation of silver (I) by permanganate ion in aqueous perchlorate solutions at a constant ionic strength of 1.0 mol dm-3 have been studied spectrophotometrically. The reaction time curves of the pseudo first-order plots were found to be of sigmoidal shape throughout the entire course of reaction. The initial rates were found to be relatively fast in the early stages, followed by a more slow reaction over longer time periods. The experimental results indicated a first-order dependence in [MnO4 - ] and fractional first-order kinetics with respect to [Ag+ ] for both stages. The results showed that the oxidation reaction was acid-catalyzed in which the reaction rates were increased with increasing the [H+ ]. Kinetic and spectrophotometric evidences for formation of 1:1 binuclear intermediate complex have been revealed in both two -stages. The activation parameters have been evaluated and a tentative reaction mechanism consistent with the kinetic results was discussed.