Oxidation of amoxicillin by hexacyanoferrate(III) in aqueous alkaline medium—A kinetic and mechanistic approach

1085-1091The kinetics and mechanism of oxidation of amoxicillin by hexacyanoferrate(III) in aqueous alkaline medium at constant ionic strength of 0.10 mol dm-3 is studied spectrophotometrically at 25 °C. The reaction exhibits 2:1 ([Fe(CN)6]3-: amoxicillin) stoichiometry. The reaction products have been identified with the help of TLC and characterized by FT-IR, GCMS and LCMS. The reaction is first order in hexacyanoferrate(III) concentration but fractional order in both amoxicillin and alkali concentrations. The effects of ionic strength and dielectric constant have been investigated. In a composite equilibrium step, amoxicillin binds to hexacyanoferrate(III) to form a complex that subsequently decomposes to the products. Based on investigation of the reaction at different temperatures, computation of the activation parameters with respect to the slow step of the proposed mechanism was evaluated

Binding of fexofenadine hydrochloride to bovine serum albumin: structural considerations by spectroscopic techniques and molecular docking

<p>The binding interaction of peripheral H₁ receptor antagonist drug, fexofenadine hydrochloride to bovine serum albumin (BSA) is investigated by fluorescence spectroscopy in combination with UV-absorption spectroscopy under physiological conditions. The Stern–Volmer plots at different temperatures and the steady state fluorescence suggested a static type of interaction between fexofenadine and BSA. Binding constants were determined to provide a measure of the binding affinity between fexofenadine and BSA. It was found that BSA has one binding site for fexofenadine. On the basis of the competitive site marker experiments and thermodynamic results, it was considered that fexofenadine was primarily bound to the site I of BSA mainly by hydrogen bond and van der Waals force. Utilising Förster resonance energy transfer the distance, <i>r</i> between the donor, BSA and acceptor fexofenadine was obtained. Furthermore, the results of circular dichroism and synchronous fluorescence spectrum indicated that the secondary structure of BSA was changed in the presence of fexofenadine. Molecular docking was applied to further define the interaction of fexofenadine with BSA.</p

KINETICS AND MECHANISM OF OXIDATION OF AN ANTIARRHYTHMIC DRUG PROCAINAMIDE HYDROCHLORIDE BY MN (VII) IN AQUEOUS SULPHURIC ACID MEDIUM: A STOPPED FLOW TECHNIQUE

Objective: To understand the kinetics and mechanism of oxidation of procainamide hydrochloride by Mn(VII) in aqueous sulfuric acid medium at 298K and at constant ionic strength, I= 3.0×10-3 mol dm-3 and to identify its oxidation products.Methods: Kinetic measurements were performed on a Varian CARRY 50 Bio UV- visible spectrophotometer connected to a rapid kinetic accessory (HI-TECHSFA-12 unit). The products are characterized by FT-IR, GC-MS and NMR studies.Results: The reaction stoichiometry was determined and the results indicate that five moles of procainamide require four moles of Mn(VII). The oxidation products were identified as Mn(II), p-aminobenzoic acid and N,N-diethyl-2-nitrasoethanamine. The reaction shows first-order kinetics with respect to MnO4-and fractional order with respect to procainamide. Increase in sulphuric acid concentration increased the rate of reaction with fractional order dependence on H+ion concentration. The effect of added products, ionic strength, and dielectric constant of the medium were studied on the rate of reaction.Conclusion: A suitable mechanism is proposed on the basis of experimental results. The activation parameters with respect to the slow step of the mechanism were evaluated and the thermodynamic parameters are also determined and discussed.Â

Free-radical-induced oxidative degradation of antibacterial drug, methylparaben by permanganate in alkaline medium: A kinetic and mechanistic approach

<p>The kinetics of oxidation of an antibacterial drug, methylparaben by permanganate in alkaline medium at a constant ionic strength of 0.80 mol dm⁻³ was studied spectrophotometrically at 25°C. The stoichiometric ratio between permanganate and methylparaben was found to be 2:1 in alkaline medium. The main products were identified by NMR, IR, and GC–MS spectral studies. The reaction showed first-order kinetics in permanganate, fractional order in methylparaben, and OH⁻ concentrations under the experimental conditions. Ionic strength and dielectric constant did not affect the rate of reaction. The added products did not have any significant effect on the rate of reaction. Based on the rate experimental results, a suitable mechanism is proposed. Investigations at different temperatures allowed the determination of the activation parameters with respect to the slow step of the proposed mechanism. The reaction constants involved in the mechanism were evaluated. The results of this study provide fundamental mechanistic parameters and degradation efficiencies of drug by advanced oxidation processes.</p

Investigation of electron-transfer reaction between alkaline hexacyanoferrate(III) and ranitidine hydrochloride – a histamine H₂ receptor antagonist, in the presence of homogenous ruthenium(III) catalyst

<div><p>The ruthenium(III)-catalyzed electron-transfer reaction between hexacyanoferrate(III) and ranitidine hydrochloride is studied in alkaline medium at 25°C and at an ionic strength of 1.10 mol/dm³. The reaction stoichiometry is established and is found to be 1:4, that is, for the oxidation of one mole of ranitidine, four moles of hexacyanoferrate(III) are consumed. The reaction products were characterized by spectral studies such as IR, GC-MS, ¹H-NMR and ¹³C-NMR. The reaction rate shows a less than unit order in substrate and alkali and a first-order dependence in oxidant, [Fe(CN)₆]³⁻ and the catalyst, ruthenium(III) concentrations. The active species of ruthenium(III), [Ru(H₂O)₅OH]²⁺, forms an intermediate complex with the substrate. The attack of complex by hexacyanoferrate(III) in the rate determining step produces a radical cation, which is further oxidized in the subsequent step to form the oxidation product. The effect of the reaction environment on the rate constant upon adding varying concentrations of KNO₃ and <i>t</i>-butanol was studied. The initially added products did not have any significant effect on the reaction rate. A plausible mechanism is proposed based on the experimental results. The effect of varying temperature on the reaction rate was also studied. The activation parameters for the slow step and the thermodynamic quantities for the equilibrium steps were evaluated.</p><p>The mechanism of title reaction has been studied and one mole of ranitidine consumes four moles of [Fe(CN)₆]³⁻, as shown in the following equation:</p></div

Oxidation of captopril by hexacyanoferrate(III) in aqueous hydrochloric acid medium – A kinetic and mechanistic study

159-166The oxidation of captopril by hexacynoferrate(III) in hydrochloric acid<span style="mso-bidi-font-weight: bold"> and 50% acetic acid-water(v/v) at a constant ionic strength (I = 3.10 mol dm-3) has been studied spectrophometrically at 25 °C. The reactions are initiated by mixing previously thermostated solutions of hexacyanoferrate(III) and captopril containing the required amounts of hydrochloric acid and sodium perchlorate. The kinetics have been followed under pseudo-first order conditions with captopril in excess. The stoichiometry is found to be 2:2, i. e., two moles of hexacyanoferrate(III) react with two moles of captopril. The reaction products have been identified as [Fe(CN6)]4- and captopril disulfide. The product, captopril disulfide, has been confirmed by IR and GC-MS analysis. The reaction is of first order with respect to hexacyanoferrate(III) and fractional order with respect to captopril concentration. Increase in hydrochloric acid concentration accelerates the rate of reaction at constant ionic strength and at other conditions constant. The order with respect to acid concentration is nearly two. The added product, [Fe(CN6)]4-, does not show any significant effect on the rate of the reaction. The effects of ionic strength and dielectric constant on the rate of reaction have also been studied. Based on the experimental results, a suitable mechanism is proposed and the rate law is derived. The reaction constants involved in the different steps of mechanism are calculated. The activation parameters with respect to limiting step of the mechanism and also the thermodynamic quantities are determined and discussed. </span

Kinetics and mechanistic studies of oxidation of fluoroquionoline antibacterial agent norfloxacin by diperiodatocuprate(III) in aqueous alkaline medium

Abstract: The kinetics of the oxidation of norfloxacin by diperiodatocuprate(III) in aqueous alkaline medium has been studied spectrophotometrically at 300 K and at constant ionic strength of 0.20 mol dm −3 . The oxidation products were identified by LC-ESI-MS technique and other spectral studies. The stoichiometry was found to be 1:2 ([NOR]: [DPC]. The active species of DPC is understood to be as monoperiodatocuprate(III). A suitable mechanism was proposed on the basis of experimental results. The reaction constants involved in the different steps of the reaction mechanism were calculated. The activation parameters with respect to the slow step of mechanism were determined and discussed

Multi-spectroscopic investigation of the binding interaction of fosfomycin with bovine serum albumin

The interaction between fosfomycin (FOS) and bovine serum albumin (BSA) has been investigated effectively by multi-spectroscopic techniques under physiological pH 7.4. FOS quenched the intrinsic fluorescence of BSA via static quenching. The number of binding sites n and observed binding constant KA were measured by the fluorescence quenching method. The thermodynamic parameters ÎG0, ÎH0 and ÎS0 were calculated at different temperatures according to the vanât Hoff equation. The site of binding of FOS in the protein was proposed to be Sudlowâs site I based on displacement experiments using site markers viz. warfarin, ibuprofen and digitoxin. The distance r between the donor (BSA) and acceptor (FOS) molecules was obtained according to the Förster theory. The effect of FOS on the conformation of BSA was analyzed using synchronous fluorescence spectra (SFS), circular dichroism (CD) and 3D fluorescence spectra. A molecular modeling study further confirmed the binding mode obtained by the experimental studies. Keywords: Fosfomycin, Serum albumin, Spectroscopic methods, Synchronous fluorescence, 3D spectr