Kinetic and mechanistic studies of oxidation of an antiallergic drug with bromamine-t in acid and alkaline media

Cetrizine dihydrochloride (CTZH) is widely used as an anti-allergic drug. Sodium N-bromo-p-toluenesulfonamide or bromamine-T (BAT) is the bromine analogue of chloramine-T (CAT) and is found to be a better oxidizing agent than CAT. In the present research, the kinetics of oxidation of CTZH with BAT in acid and alkaline media was studied at 313 K. The experimental rate laws obtained are: -dBAT/dt = kBAT CTZH0.80H+-0.48 in acid medium and -dBAT/dt = kBATCTZH0.48OH-0.52PTS-0.40 in alkaline medium where PTS is p-toluenesulfonamide. Activation parameters and reaction constants were evaluated. The solvent isotope effect was studied using D2O. The dielectric effect is positive. The stoichiometry of the reaction was found to be 1:1 and the oxidation products were identified as 4-chlorobenzophenone and (2- piperazin-1-yl-ethoxy)-acetic acid in both media. The rate of oxidation of CTZH is faster in acid medium. Suitable mechanisms and related rate laws have been worked out

Oxidation of tricyclic antidepressant drugs with chloramine-T in acidic solutions: Kinetic, mechanistic and thermodynamic studies

The kinetics of the oxidation of two tricyclic antidepressants (TCA) namely, imipramine (IMP) and clomipramine (CLM) with sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) in HClO4 medium was studied at 300 K. The two reactions followed identical kinetics with a first-order dependence of rate on CATo and fractional order dependence on TCAo. The reaction is catalyzed by H+ ions with a fractional order dependence. The reaction was studied at different temperatures and activation parameters were evaluated. The reaction constants involved in the mechanism were computed. The solvent isotope effect was studied using D2O. Addition of p-toluenesulfonamide retards the reaction rate. The rate increased with decreasing dielectric constant of the medium. Variation of ionic strength of the medium and addition of halide ions (Cl- or Br-) showed no effect on the rate. The stoichiometry of the reaction was found to be 1:1 and the oxidation products were identified as imipramine-5-N-oxide and clomipramine-5-N-oxide. The rate of oxidation of IMP is faster than CLM. The observed results have been explained in terms of a mechanism and a relevant rate law has been deduced. © 2013 Sukhdev and Puttaswamy; licensee Springer

Palladium(II)-catalyzed oxidation of tranexamic acid by bromamine-B in alkaline medium and uncatalyzed reaction in acid medium: A study of kinetic and mechanistic chemistry

Tranexamic acid (TA) possess antifibrinolytic properties and finds extensive applications in pharmaceuticals. Its oxidation-kinetic study is of much significance in understanding the mechanistic profile of TA in biological systems. In this context, a systematic kinetic study of palladium(II) (Pd(II)) catalyzed oxidation of TA by sodium N-bromobenzenesulfonamide or bromamine-B (BAB) in alkaline medium and uncatalyzed reaction in perchloric acid medium at 303 K was investigated. In acid medium, the reaction exhibits a first-order dependence of rate on BABo and less than unity order dependence on TAo. The reaction rate shows inverse less than unity order dependence with respect to H+. In alkaline medium, the reaction shows first-order dependence on both BABo and Pd(II) and zero-order with respect to TAo. The order with respect to OH - is less than unity. Activation parameters have been evaluated. The oxidation reactions are nearly 10-fold faster in acid medium in comparison with alkaline medium. In alkaline medium, the Pd(II) catalyzed reactions are about 6-fold faster than the uncatalyzed reaction. Further, the catalytic constant (KC) has been calculated at different temperatures and activation parameters with respect to Pd(II) catalyst have also been evaluated. The conjugate acid C6H5SO2NHBr and the anion C 6H5SO2N-Br of BAB have been postulated as the reactive oxidizing species in acid and alkaline media, respectively. The proposed mechanisms and derived rate laws are in agreement with the observed kinetics. © 2010 Elsevier B.V. All rights reserved

Oxidation of mephenesin and guaifenesin with chloramine-B in hydrochloric acid medium: Design of kinetic model

Kinetics of oxidation of mcphencsin and guaifenesin by sodium N-chlorobcnzcncsulfonamide (CAB) have been investigated in IIC1 medium at 303 K. The oxidation behaviour is similar for both the substrates. The rate shows a first order dependence on both CAB0 and HQ, and is fractional in substratc0. The orders individually in H* and CI - are fractional. The variation of ionic strength and addition of the reduction' product, benzcnes'ulibnamide, has no significant effect on the reaction rate. The solvent isotope effect has been studied using D20, and the oxidation products have been identified. Composite activation parameters for the reaction have been determined from Arrhcnius plots. Michaelis-Menten type of kinetics is observed and activation parameters for the rate limiting steps have also been computed. The proposed mechanism assumes the simultaneous catalysis by H+ and CI- ions. The reaction is found to be moderately faster in guaifenesin in comparison with mcphcnesin, which may be attributed to the involvement of methoxy and methyl^groups of the substrate. The observed results have been explained by a plausible mechanism and the related rate law has been proposed

Rhodium(III) catalyzed and uncatalyzed kinetic spectrophotometric oxidation of amodiaquine hydrochloride with chloramine-T in presence of alkaline buffer: A mechanistic chemistry

Amodiaquine hydrochloride (AQ) is a 4-aminoquinoline derivative commonly used to prevent and treat malaria. Sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) is a well-known oxidizing agent. In rhodium(III) chloride (Rh(III)) catalyzed oxidation, the rate law is -dCAT / dt = k CAT o AQo OH--x Rh(III) y and it takes the form -dCAT/dt = k CAToAQ oOH--x for uncatalyzed reaction, where x and y are less than unity. The rate constants revealed that the Rh(III) catalyzed reactions are about five fold faster than the uncatalyzed reactions. The catalytic constant (KC) and activation parameters with respect to Rh(III) catalyst have been deduced. Copyright © Taylor & Francis Group, LLC

Oxidative Cleavage of β-Lactam Ring of Cephalosporins with Chloramine-T in Alkaline Medium: A Kinetic, Mechanistic, and Reactivity Study

Cephalosporins are β-​lactam antibiotics, and the important drugs of this group are cephalexin, cefadroxil and cephradine. In the present research, the kinetics and mechanism of oxidn. of cephalexin (CEX)​, cefadroxil (CFL)​, and cephradine (CPD) with chloramine-​T (CAT) in alk. medium were investigated at 301 K. All the three oxidn. reactions follow identical kinetics with a first-​order dependence each on [CAT]​o and [substrate]​o. The reaction is catalyzed by hydroxide ions, and the order is found to be fractional. The dielec. effect is neg. Proton inventory studies in H2O-​D2O mixts. with CEX as a probe have been made. Activation parameters and reaction consts. have been evaluated. Oxidn. products were identified by mass spectral anal. An isokinetic relation was obsd. with β = 378 K, indicating that enthalpy factors control the rate. The rate increases in the following order: CPD > CFL > CEX. The proposed mechanism and the derived rate law are consistent with the obsd. kinetics

Decolorization of reactive orange 16 azo dye in wastewater using CAT/ IrCl3/HClO4 redox system: Delineation of kinetic modeling and mechanistic approaches

Reactive orange 16 (RO16) is a reactive azo dye, which is chiefly used in textile industry. In the present research, a simple and expeditious decolorization technique has been developed for the removal of this dye present in the wastewater. Kinetics and oxidative decolorization of RO16 dye with chloramine-T (CAT) in HClO4 medium catalyzed by iridium (III) chloride (IrCl3) have been investigated spectrophotometrically (λmax = 496 nm) at 303 K. The reaction exhibited a first-order dependence of rate on CATo and RO16o respectively. The rate of the reaction was retarded with increase in H+ and shows an order less than unity. The order with respect to IrCl3 was fractional. Oxidation products were identified as 6-acetamido-3,4-dioxo-3,4-dihydro naphthalene-2-sulfonic acid and 2-(phenyl sulfonyl)-ethyl hydrogen sulphate by mass spectral analysis. IrCl3 catalyzed decolorization reaction is about six times faster than the uncatalyzed reaction. Activation parameters have been computed. The kinetic modelings and mechanistic pathway have been worked out. The oxidative decolorization process has significantly reduced the COD. Phytotoxicity studies demonstrated that the treated dye was less toxic than untreated dye sample. Economic analysis was performed. Notably, the developed oxidative decolorization technique is expected to be helpful for treating RO16 dye present in industrial wastewater with suitable modifications. © 2016 Taiwan Institute of Chemical Engineer

Kinetics and reactivities of ruthenium(III)- and osmium(VIII)-catalyzed oxidation of ornidazole with chloramine-T in acid and alkaline media: A mechanistic approach

Ornidazole is an antiparasitic drug having a wide spectrum of activity. Literature survey has revealed that no attention has been paid towards the oxidation of ornidazole with any oxidant from the kinetic and mechanistic view point. Also no one has examined the role of platinum group metal ions as catalysts in the oxidation of this drug. Such studies are of much use in understanding the mechanistic profile of ornidazole in redox reactions and provide an insight into the interaction of metal ions with the substrate in biological systems. For these reasons, the Ru(III)- and Os(VIII)-catalyzed kinetics of oxidation of ornidazole with chloramine-T have been studied in HCl and NaOH media, respectively at 313 K. The oxidation products and kinetic patterns were found to be different in acid and alkaline media. Under comparable experimental conditions, in Ru(III)-catalyzed oxidation the rate law is -dCAT/dt = k CAToornidazoleoxH+ -yRu(III)z and it takes the form -dCAT/dt = k CAToornidazoleoxOH- yOs(VIII)ArSO2NH2-z for Os(VIII)-catalyzed reaction, where x, y and z are less than unity. In acid medium, 1-chloro-3-(2-methyl-5-nitroimidazole-1-yl)propan-2-one and in alkaline medium, 1-hydroxy-3-(2-methyl-5-nitroimidazole-1-yl)propan-2-one were characterized as the oxidation products of ornidazole by GC-MS analysis. The reactions were studied at different temperatures and the overall activation parameters have been computed. The solvent isotope effect was studied using D2O. Under identical set of experimental conditions, the kinetics of Ru(III) catalyzed oxidation of ornidazole by CAT in acid medium have been compared with uncatalyzed reactions. The relative rates revealed that the catalyzed reactions are about 5-fold faster whereas in Os(VIII) catalyzed reactions, it is around 9 times. The catalytic constant has been calculated for both the catalysts at different temperatures and activation parameters with respect to each catalyst have been evaluated. The observed experimental results have been explained by plausible mechanisms. Related rate laws have been worked out. © 2009 Elsevier B.V. All rights reserved

Kinetic and mechanistic investigation of S-oxidation of ranitidine hydrochloride with chloramine-T in acid and alkaline media

Ranitidine hydrochloride (RNH), chemically known as N-dimethyl-5-2-(1- methylamino-2-nitro-vinyl)-ethylthiomethylfurfuryl amine hydrochloride, is an antiulcer drug and its oxidation-kinetic study is of much significant in understanding its mechanistic chemistry in redox reactions. Consequently, the kinetics of oxidation of RNH by sodium N-chloro-p-toluenesulfonamide (chloramine-T or CAT) have been examined in HClO 4 and NaOH media at 298 K. The stoichiometry and oxidation products of RNH-CAT reaction are the same in both media, however, their kinetic patterns were found to be different. The reaction rate exhibits first-order kinetics with respect to CAT o and RNH o in both media. The rate of reaction increases with increase in H +, but it decreases with respect to OH - with a slope of unity in both the cases. Decrease of the dielectric constant of the medium decreases the reaction rate in both media. Variation of the ionic strength of the medium, and addition ofp-toluenesulfonamide or NaCl, have no significant effect on the rate. The reaction was studied at different temperatures and activation parameters have been deduced. Ranitidine-S-oxide was identified as the oxidation product of RNH by GC-MS in both media. The conjugate free acid CH 3C 6H 4SO 2NHCl of CAT is postulated as the reactive oxidizing species in both cases. The observed results have been explained by plausible mechanisms and related rate laws have been deduced. © 2012 Science Reviews 2000 Ltd

Oxidative decolorization of methyl red dye with chloramine-T - Kinetic and mechanistic chemistry

A simple and expeditious oxidative decolorization technique has been developed for the removal of Methyl Red dye (MR; C.I. Acid Red 2) present in the wastewater. The kinetic and mechanistic aspects of the present redox system have also been investigated. Kinetics and oxidative decolorization of MR dye with sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) in HClO4 medium at 303 K has been investigated spectrophotometrically at λmax 524 nm. The reaction shows a first-order dependence of rate each on CATo and MRo. The reaction is catalyzed by HClO4 and the order with respect to H+ is found to be fractional (0.75). Activation parameters have been evaluated. The oxidation products of MR dye are identified as N-(4-dimethylamino-phenyl)-hydroxylamine and 4-nitroso-benzoic acid by GC-MS analysis. The observed results have been explained by a plausible mechanism and the related rate law is deduced. Further, the present redox system can be adopted for treating MR dye present in industrial effluents with suitable modifications to reduce the toxicity caused by MR dye