Dipolar cycloaddition based multi-component reaction: Synthesis of spiro tethered acenaphthylene–indolizine–pyridinone hybrids

The stereoselective syntheses of novel dispiro acenaphthylene–indolizine–pyridinone hybrid heterocycles have been achieved through one-pot four-component domino 1,3-dipolar cycloaddition–Michael addition–air oxidation sequence of reactions.     

Synthesis of magnetically modified mesoporous nanoparticles and their application in simultaneous determination of Pb(II), Cd(II) and Cu(II)

In this study, a novel adsorbent from a mesoporous family (MCM-41) coating with CoFe₂O₄ and piperazine was synthesized by a simple and easy route. Its application for simultaneous preconcentration of three heavy metals including lead, cadmium and copper in real samples followed by a flame atomic absorption spectroscopy was investigated. The central composite design was employed for investigating the most effective factors of pH, amount of adsorbent, the equilibrium time and their interactions. Under the optimum conditions, the detection limits for lead, cadmium and copper were 0.50, 0.30 and 0.25 μg L^?1, respectively, and the preconcentration factor (PF) was 33. The presented method was successfully employed for the simultaneous determination of the three mentioned heavy metals in real samples with recoveries of 90%–105%. The accuracy of the suggested methods was also investigated through spiking samples and a reasonable range for recoveries from 90.3% to 107% was acquired. The isotherm models and thermodynamic parameters have also been studied. The new adsorbent showed fast adsorption kinetics within 10 min and maximum Langmuir monolayer capacities of 238.09, 178.57 and 208.33 mg g^?1 for lead, cadmium and copper, respectively.     

Kinetic spectrophotometric determination of the macrolide antibiotic josamycin in formulations

A simple kinetic spectrophotometric method was developed for the determination of josamycin in its dosage forms. The method is based on oxidation of the drug with alkaline potassium permanganate at room temperature for a fixed time of 20 min and measuring the produced green color at 611 nm. The absorbance-concentration plot is rectilinear over the range of 2-10 microg/mL (2.4 x 10(6)-1.2 x 10(-5)M) with minimum detectability of 1.0 microg/mL (1.2 x 10(-6)M). The determination of josamycin by fixed concentration and the rate-constant methods is also feasible with the calibration equations obtained, but the fixed-time method proved to be more applicable. The procedure was applied successfully to commercial tablets, and statistical analysis showed that the results compared favorably with those obtained by reference methods. The effect of sensitizers and surfactants on the performance of the proposed method was also studied. A proposal of the reaction pathway was presented.     

Kinetics and Mechanism of the Autocatalytic Oxidation of L-Asparagine in a Moderately Concentrated Sulfuric Acid Medium

The reaction kinetics of the Autocatalytic Oxidation of L-asparagine by permanganate ions has been investigated in moderately strong acid medium using the spectrophotometric technique. In all cases studied, an autocatalytic effect due to Mn²⁺ ions formed as a reaction product was observed. Both catalytic and noncatalytic processes were determined to be first order with respect to the permanganate ions while a first and a fractional order with respect to the amino acid for noncatalytic and catalytic reactions were obtained, respectively. The overall rate equation for this process may be written asd[MO₄ ^–]/dt= k´₁[MnO₄ ^–]+k´₂[MnO₄ ^–][Mn⁺²],where k´₁ and k´₂ are rate pseudoconstants for noncatalytic and catalytic reactions, respectively. The influence of some factors such as temperature and reactant concentration on the rate constants has been studied, and the activation parameters have been calculated. Reaction mechanisms satisfying observations for both catalytic and noncatalytic routes have been presented.