Synthesis and characterization of lead oxide nano-powders by sol–gel method

Our goal in this research was to obtain lead oxide nano-powders by sol–gel method. In this method, lead oxide nano-powders were synthesized through the reaction of citric acid (C₆H₇O₈·H₂O) solution and lead acetate [Pb(C₂H₃O₂)₂] solution as stabilizer and precursor, respectively. The effect of different parameters including calcination temperature, (molar ratio of citric acid to lead acetate) and drying conditions were investigated. The prepared lead oxide nano-powders were characterized by FT-IR spectroscopy, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. The prepared PbO samples consist of the particles in the range of 50–120 nm or the thick plate like structures with thickness of 53 nm depending on the drying conditions.     

Generalization of a theorem of Carlitz

We generalize Carlitz? result on the number of self-reciprocal monic irreducible polynomials over finite fields by showing that similar explicit formula holds for the number of irreducible polynomials obtained by a fixed quadratic transformation. Our main tools are a combinatorial argument and Hurwitz genus formula.     

Phase Equilibrium Modeling of Clathrate Hydrates of Carbon Dioxide + 1,4-Dioxine Using Intelligent Approaches

In this work, an adaptive neuro-fuzzy inference system (ANFIS) and a couple of fuzzy logic approach and genetic algorithms are utilized to serve robust inverse-based approaches for determination/prediction of the clathrate hydrate formation pressure of carbon dioxide in the presence of 1,4-dioxine, which is a most-widely implemented water “soluble” organic promoter. The gained outcomes prove the reliability and accuracy of the suggested ANFIS approach with the mean square error of 0.0034 and squared correlation coefficients of 0.9969. Thanks to the results generated by the aforementioned intelligent approaches, the models proposed in the current research contribute to high accuracy for the estimations of the phase equilibria clathrate hydrates of carbon dioxide +1,4-dioxane.      

DFT study of the dissociative adsorption of HF on an AlN nanotube

We have investigated the adsorption of hydrogen fluoride (HF) on the AlN nanotube surface using density functional theory in terms of energetic, structural and electronic properties. By overcoming energy barriers of 27.90–52.30 kcal/mol, HF molecule is dissociated into H and F species on the tube surface and its molecular structure is not preserved after the adsorption process. Dissociation energies have been calculated to be −52.57 and −70.10 kcal/mol. The process has negligible effect on the electronic and field emission properties of the AlN nanotube. This process may increase the solubility of AlN nanotubes.     

Determination of fluoxetine in pharmaceutical preparations and biological samples using potentiometric sensors based on polymeric membranes

The construction and general performance of four novel potentiometric membrane sensors for the determination of fluoxetine have been described. The sensors are based on the formation of the ion association complex of fluoxetine with sodium tetraphenylborate and phosphotungstic acid as electroactive materialles, dispersed in a PVC matrix with dibuthyl sebacate (or diethyl sebacate) as a plasticizer. These sensors exhibit fast, stable and near-Nernstian response for the monocharged fluoxetine cation over wide concentration range from 3.0 × 10^?6 to 1.2 × 10^?2 M and pH 4.0–7.5. No interferences are caused by many inorganic and organic species. Direct potentiometric determinations of 5–100 μg/mL of fluoxetine in drug and urine samples show good recovery of fluoxetine. The developed membrane electrodes have been used as an end point indicator electrode; the potentiometric titration of fluoxetine with sodium tetraphenylborate as a titrant has been monitored.     

MICROWAVE INDUCED STEREOSELECTIVE CONVERSION OF DIALKYL 2-(IMIDO-N-YL)-3- (TRIPHENYLPHOSPHORANYLIDENE)BUTANEDIOATES TO ELECTRON-POOR (Z)-N-VINYLIMIDES IN THE PRESENCE OF IRON(II) SULFATE POWDER IN SOLVENT-FREE CONDITIONS

Microwave was found to catalyze stereoselective conversion of dialkyl 2-(imido-N-yl)-3-(triphenylphosphoranylidene)butanedioates to electron-poor (Z)-N-vinylimides in the presence of iron(II) sulfate powder in solvent-free conditions in 4 min.     

CONVERSION OF IN SITU GENERATED STABILIZED PHOSPHORUS YLIDES TO CHROMENE DERIVATIVES IN SOLVENT-FREE CONDITIONS

Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylates, by phenols (1-hydroxynaphthalene, 2-hydroxynaphthalene, 4-bromophenol, 2-hydroxybenzaldehyde, and 5-bromo-2-hydroxyben- zaldehyde) leads to vinyltriphenylphosphonium salts, which undergo electrophilic substitution reaction with conjugate base to produce corresponding stabilized phosphorus ylides. Microwave was found to catalyze conversion of the stabilized phosphorus ylides to chromene derivatives in the presence of solid catalysts in solvent-free conditions at microwave power 0.4 KW in 3 min.     

Triphenylphosphine-Catalyzed Preparation of Sterically Congested,Electron-Poor N-Vinylimidazole Derivatives from Acetylenic Esters and Imidazole-Containing NH-Acids

Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and alkyl acetylenecarboxylates (or ethyl 3-phenyl-2-propynoate), by azathioprine or imidazole leads to vinyltriphenylphosphonium salts, which undergo a Michael addition reaction with a conjugate base to produce phosphorus ylides. Dipotassium hydrogen phosphate, potassium dihydrogen phosphate, and potassium iodide were found to catalyze the conversion of the phosphorus ylides to electron-poor N-vinyl imidazoles in solvent-free conditions under thermal (90°C, 1 h) conditions. The structural analysis of the products indicated that the reaction is regio- and stereoselective.     

One-Pot,Three-Component Synthesis of Dialkyl 1,2-Dihydroquinoline-2,3-Dicarboxylates from Triphenylphosphine,Acetylenic Esters,and Amide Derivatives of 2-Aminobenzaldehyde in Aqueous Acetone

Abstract

Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylates by amide derivatives of 2-aminobenzaldehyde in the mixture of acetone-water (3:1) leads to vinyltriphenylphosphonium salts, which undergo a Michael addition reaction with a conjugate base to produce the corresponding stabilized phosphorus ylides. An intramolecular Wittig reaction of the stabilized phosphorus ylide group with the aldehyde group leads to the corresponding dialkyl 1,2-dihydroquinoline-2,3-dicarboxylates.     

N-Isocyaniminotriphenylphosphorane as an Efficient Reagent for the Synthesis of Disubstituted 1,3,4-Oxadiazoles Via In-Situ Generation of Sterically Congested Iminophosphorane Derivatives

Abstract

Reaction of N-isocyaniminotriphenylphosphorane with benzaldehyde derivatives in the presence of 3-phenyl-2-propynoic acid and secondary amines proceeds smoothly at room temperature and under neutral conditions to afford sterically congested 1,3,4-oxadiazole derivatives in high yields. The reaction proceeds smoothly and cleanly under mild conditions and no side reactions are observed.