Wet carbon-based solid acid/NaNO_3 as a mild and efficient reagent for nitration of aromatic compound under solvent free conditions

Nitro aromatic compound can be obtained in high yields via nitration of aromatic compound with wet carbon-based solid acid and NaNO_3 under solvent free oxidation at room temperature.     

Diammonium Hydrogen Phosphate as an Efficient and Inexpensive Catalyst for the Synthesis of Bis(indolyl)methanes under Solvent-Free Conditions

Bis(indolyl)methanes were synthesized by the reaction of indole derivatives and aromatic and aliphatic aldehydes in the presence of diammonium hydrogen phosphate as a solid catalyst under solvent-free conditions. This methodology offers significant improvements for the synthesis of bis(indolyl)methanes with regard to the yield of products, simplicity in operation, and green aspects by avoiding toxic catalysts and solvents.     

Efficient and eco-friendly synthesis of dihydropyrimidinones, bis(indolyl)methanes, and N-alkyl and N-arylimides in ionic liquids

Dihydropyrimidinones, bis(indolyl)methanes, and N-alkyl and N-arylimides were synthesized efficiently under mild reaction conditions in the presence of two types of ionic liquids. In each section, effects of different ILs on the yield of reactions were investigated. The use of ionic liquids offer improvements for the synthesis of title compounds with regard to the yield of products, simplicity in operation, short reaction times and green aspects by avoiding toxic catalyst and organic solvents.     

Solid phase extraction of gold by sorption on octadecyl silica membrane disks modified with pentathia-15-crown-5 and determination by AAS

A simple and selective method for rapid and efficient concentration and determination of μg l⁻¹ levels of Au(III) ions in aqueous solution using octadecyl silica membrane disks modified by pentathia-15-crown-5 and flame atomic absorption spectrometry is presented. The influence of flow rates of eluent and sample solution, amount of ligand, types and least amount of eluent for elution of Au from disks were investigated. Break through volume and limit of detection of the membrane disks modified by 5 mg of the thiacrown ether was found to be 2.0 l and 1.0 μg l⁻¹, respectively. The effects of various cationic interferences on percent recovery of gold were studied. The method was successfully applied for the determinations of gold in some pharmaceutical samples and for the recovery of trace Au³⁺ ions from synthetic and water samples.     

A new approach to the facile synthesis of mono- and disubstituted quinazolin-4(3H)-ones under solvent-free conditions

Quinazolin-4(3H)-one derivatives were synthesized successfully via a one-pot, three component reaction of isatoic anhydride and an orthoester with ammonium acetate or a primary amine catalyzed by silica sulfuric acid under solvent-free conditions. This is the first report on the synthesis of 2-substituted quinazolin-4(3H)-ones by this procedure.     

Solvent extraction of mercury using Alamine 304

Summary A study has been undertaken to develop a solvent extraction system for mercury using Alamine 304 in aqueous chloride medium. The parameters investigated included reagent concentration, acid concentration, pH, aqueous to organic phase ratio, and rate of extraction and stripping. The study shows that mercury can be extracted rapidly and efficiently from aqueous chloride solutions. A number of aqueous stripping reagents removed more than 90% of the mercury from the organic phase with only one equilibrium. These include HNO₃, NaOH and EDTA.

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Extraktion von Quecksilber mit Alamin 304

Zusammenfassung Die Extraktion von Quecksilber aus der wäßrigen Lösung des Chlorids mit Alamin 304 wurde untersucht. Die Konzentration des Reagens, der Säure, das pH, das Verhältnis der wäßrigen zur organischen Phase sowie das Extraktionsverhältnis wurden geprüft. Die Extraktion verläuft rasch und wirkungsvoll. Eine Reihe wäßriger Reagenzien entzieht mehr als 90% des Quecksilbers aus der organischen Phase. Dazu gehören Salpetersäure, Natronlauge und EDTA.

     

Zein film as a novel natural biopolymer membrane in electrochemical detections

Permselective modifier films are very important in preparing highly sensitive electrochemical sensors. In this work, for the first time, the behavior of gold and glassy carbon electrodes coated with biocompatible zein film as a permselective membrane for the electrochemical detection of various compounds has been investigated. For this purpose, several electroactive cationic (methylene blue, brilliant green, and thionine) and anionic (potassium ferricyanide, alizarin red S, and riboflavin-5’-phosphate) compounds have been used as model. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) showed that zein membranes prepared from casting solution containing 1% zein in ethanol/water have porous structures with high nanometric roughness. The capacitance values of electrical double layers of electrodes modified with zein film were very high for hydrophilic ions in comparison with hydrophobic ions. Point of zero charge pH (pH_pzc) of zein membrane was 4.8. The results of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) as well as pH_pzc study indicated that zein permselective membrane acts as ion exchanger film for selected cationic compounds with fast electrochemical kinetics responses in aqueous solution (pH=7). This behavior was confirmed by circulating solutions containing model compounds from homemade continuous cell equipped with polyamide membranes modified with zein film.

Graphical Abstract

     

The role of charge distribution on the antimalarial activity of artemisinin analogues

In this work the calculated nuclear quadrupole coupling constants (NQCC; chi) of 17O in artemisinin and some of its derivatives and the effects of charge density due to the nature of ligands on NQCC of 17O were investigated. All calculations were performed at the HF/3-21G level using the Gaussian 98 program. The results show that the O-O linkage has a characteristic role in the antimalarial activity of artemisinin. In addition, various substitutions on C4 change the charge density on these oxygens and consequently change the pharmaceutical effect of artemisinin. Our results suggest that due to a larger charge density on O1, the heme iron approaches the endoperoxide moiety at the O1 position with preference to the O2 position.     

A novel ion selective membrane potentiometric sensor for direct determination of Fe(III) in the presence of Fe(II)

A new PVC membrane potentiometric sensor that is highly selective to Fe(III) ions was prepared by using 2-[(2-hydroxy-1-propenyl-buta-1,3-dienylimino)-methyl]-4-p-tolylazo-phenol [HPDTP] as a suitable carrier. The electrode exhibits a linear response for iron(III) ions over a wide concentration range (3.5 × 10⁻⁶ to 4.0 × 10⁻²) with a super Nernstian slope of 28.5 (±0.5) per decade. The electrode can be used in the pH range from 4.5 to 6.5. The proposed sensor shows fairly a good discriminating ability towards Fe³⁺ ion in comparison to some hard and soft metals such as Fe²⁺, Cd²⁺, Cu²⁺, Al³⁺ and Ca²⁺. It has a response time of <15 s and can be used for at least 2 months without any measurable divergence in response characteristics. The electrode was used in the direct determination of Fe³⁺ in aqueous samples and as an indicator electrode in potentiometric titration of Fe(III) ions.     

A facile procedure for the one-pot synthesis of unsymmetrical 2,5-disubstituted 1,3,4-oxadiazoles

Unsymmetrically 2,5-disubstituted 1,3,4-oxadiazoles were efficiently synthesized from the cyclization-oxidation reaction of acyl hydrazones. Also, the synthesis of the title compounds was achieved by the condensation of acyl hydrazides and aromatic aldehydes in the presence of ceric ammonium nitrate in dichloromethane.