One-pot synthesis of 1,2,4,5-tetrasubstituted and 2,4,5-trisubstituted imidazoles by zinc oxide as efficient and reusable catalyst

Abstract  

ZnO is an efficient, readily available, and reusable catalyst for the one-pot synthesis of 1,2,4,5-tetrasubstituted and 2,4,5-trisubstituted imidazoles. This procedure is very simple and affords excellent yields.     

Voltammetric Determination of Trace Antiepileptic Gabapentin with a Silver‐Nanoparticle Modified Multiwalled Carbon Nanotube Paste Electrode

For the first time, a novel carbon nanotube bed electrode impregnated with silver–nanoparticles (AgNPs) for the determination of trace amounts of gabapentin (GBP) is described. We synthesized the AgNPs via a new procedure. The voltammetric behavior of the electrode was investigated by cyclic voltammetry. There were linear relationships in the ranges from 3.1×10^?9 to 2.9×10^?2 M and from 1.0×10^?8 to 1.0×10^?2 GBP with square wave and differential pulse voltammetric peak currents, respectively. The detection limits were 5.6×10^?10 and 9.7×10^?9 M, respectively. The electrode showed excellent response over a period of 2 months and was successfully applied in human plasma and pharmaceutical capsular products.     

Synthesis and characterization of spinel-type CuAl<Subscript>2</Subscript>O<Subscript>4</Subscript> nanocrystalline by modified sol–gel method

Nanocrystalline Copper aluminate (CuAl₂O₄) was prepared by sol–gel technique using aluminum nitrate, copper nitrate, diethylene glycol monoethyl ether and citric acid were used as precursor materials. This method starts from of the precursor complex, and involves formation of homogeneous solid intermediates, reducing atomic diffusion processes during thermal treatment. The formation of pure crystallized CuAl₂O₄ nanocrystals occurred when the precursor was heat-treated at 600 °C in air for 2 h. The stages of the formation of CuAl₂O₄, as well as the characterization of the resulting compounds were done using thermo–gravimetric analysis, X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. The products were analyzed by transmission electron microscopy and ultraviolet–visible (UV–Vis) spectroscopy to be round, about 17–26 nm in size and E _g = 2.10 eV.     

Perovskite-type ferromagnetic BiFeO3 nanopowder: a new magnetically recoverable heterogeneous nanocatalyst for efficient and selective transfer hydrogenation of aromatic nitro compounds into aromatic amines under microwave heating

Perovskite-type ferromagnetic BiFeO₃ nanopowder was readily synthesized via thermal decomposition of Bi[Fe(CN)₆]·5H₂O complex and characterized using thermal analysis (TGA/DSC), X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT–IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), magnetic measurement and Brunauer–Emmett–Teller (BET) specific surface area measurements. The magnetic measurements show a ferromagnetic behavior for the BiFeO₃ nanoparticles at room temperature. This nanosized ferromagnetic oxide with an average particle size of approximately 20 nm and a specific surface area of 48.5 m²/g was used as a new magnetically recoverable heterogeneous nanocatalyst for the highly efficient and selective reduction of aromatic nitro compounds into their corresponding amines by using propan-2-ol as the hydrogen donor under microwave irradiation. This method is regio- and chemoselective, clean, inexpensive and compatible with the substrates having hydrogenlyzable or reducible functional groups. As compared with conventional heating, this method is very fast and suitable for the large-scale preparation of different substituted anilines as well as other arylamines. The catalyst can also be reused without loss of activity.     

Outward melting of ice enhanced by Cu nanoparticles inside cylindrical horizontal annulus: Lattice Boltzmann approach

Heat transfer enhancement of water-(Ice) as a phase change material (PCM) through dispersion of Cu-nanoparticles is the centerpiece of this research study. The nanoparticle-enhanced phase change material (NEPCM) demonstrates increased thermal conductivity and decreased melting time in comparison with the conventional PCM. An enthalpy-based lattice Boltzmann method (LBM) with a double distribution function (DDF) model is implemented to trace phase change front in a cylindrical-horizontal annul. The subcooling case is neglected and Prandtl number, Stefan number and Rayleigh number are fixed to 6.2, 1 and 10⁵, respectively. In addition, the effects of varying the position of heated cylinder and nanoparticle volume fractions on the transient isotherms and liquid fractions are discussed.     

TMSCl-promoted selective oxidation of sulfides to sulfoxides with hydrogen peroxide

Selective oxidation of sulfides to sulfoxides is achieved using H₂O₂ and TMSCl as the promotor. Aromatic and aliphatic sulfides are oxidized to sulfoxides in excellent yields and in short reaction times. Different functional groups including ketone, alkene, ester, and alcohol are tolerated.     

Electrochemical determination of meloxicam in pharmaceutical preparation and biological fluids using oxidized glassy carbon electrodes

The adsorptive and electrochemical behaviors of meloxicam (MLC) was investigated on a glassy carbon electrode that was electrochemically treated by anodic oxidation at +1.8 V, following potential cycling in the potential range from -0.8 to 1.0 V vs. Ag/AgCl reference electrode. The resulting electrode showed a good activity to improve the electrochemical response of the drug. MLC was accumulated at an electrochemically activated glassy carbon electrode (phosphate buffer pH 6) in a certain time and then determined by linear sweep voltammetry. The oxidative peak currents showed a linear function in the concentration ranges of 0.02 to 10 microM using a 240 s preconcentration time. The preconcentration medium-exchange approach was utilized for the selective determination of the drug in spiked urine and plasma samples with satisfactory results. The recovery values of the proposed method obtained 105% (RSD 2.5%) and 100% (RSD 1.8%) for urine and plasma samples, respectively. Also, the proposed method has been successfully used for determination of MLC in tablets.     

Numerical study of Prandtl effect on MHD flow at a lid‐driven porous cavity

In this paper, the lattice Boltzmann method is used to study the Prandtl number effect on flow structure and heat transfer rates in a magnetohydrodynamic flow mixed convection in a lid‐driven cavity filled with a porous medium. The right and left walls are at constant but different temperatures (θ_h and θ_c), while the other walls are adiabatic. Gallium and salt water (0.02 < Pr < 13.4) are used as samples of the electroconducting fluids in the cavity. Typical sets of streamlines and isotherms are presented to analyze the flow patterns set up by the competition among the forced flow created by the lid‐driven wall, the buoyancy force of the fluid and the magnetic force of the applied magnetic field. Mathematical formulations in the porous media were constructed based on the Brinkman–Forchheimer model, while the multidistribution‐function model was used for the magnetic field effect. Numerical results were obtained and the effects of the Prandtl number and the other effective parameters such as Richardson, Hartman, and Darcy numbers were investigated. It was found that the fluid fluctuations within the cavity were reduced by increasing the Hartman number. A similar pattern was observed for the Darcy number reduction. Heat transfer was essentially dominated by the conduction for the low Prandtl number and forced convection dominated as the Prandtl number increased. Also, the average Nusselt number was raised by increasing the Prandtl number. It was discovered that a remarkable heat transfer enhancement of up to 28% could be reached by increasing the Prandtl number (from 0.02 to 13.4) at constant Richardson and Darcy numbers. Copyright © 2011 John Wiley & Sons, Ltd.     

Highly selective catalytic Friedel–Crafts sulfonylation of aromatic compounds using a FeCl3-based ionic liquid

Friedel–Crafts sulfonylation of aromatic compounds was carried out using FeCl₃-based ionic liquid. These liquids serve as efficient media as well as Lewis acid catalyst.     

New Correlation between Electric Spark and Impact Sensitivities of Nitramine Energetic Compounds for Assessment of Their Safety

Electric spark and impact sensitivities of nitramine energetic compounds are two important sensitivity parameters, which are closely related to many accidents in working places. For nitramines, in contrast to electric spark sensitivity, their impact sensitivity can be easily measured or predicted by various methods. A new approach is introduced to correlate electric spark and impact sensitivities of nitramine energetic compounds by the use of three structural parameters. The predicted results of the novel model for 20 nitramines are compared with two of the best available models, which are based on complex quantum mechanical approach and the measured values of activation energies of thermolysis. The root‐mean‐square (rms) and maximum deviations of the new model are 1.06 and 2.41 J, respectively. For further 14 nitramines, where the measured electric spark or impact sensitivities were not available, the estimated electric spark sensitivities by the new model are close to those predicted based on experimental data of activation energies of thermolysis.