Flame photometric determination of cesium ion after its preconcentration with nanoparticles imprinted with the cesium-dibenzo-24-crown-8 complex

We report on the synthesis of cesium ion-imprinted polymer nanoparticles that were prepared by a precipitation polymerization strategy using dibenzo-24-crown-8 ether as a selective crown ether, methacrylic acid as the functional monomer, ethyleneglycol dimethacrylate as the crosslinker, and AIBN as the radical initiator. The prepared sorbents have a diameter of 50–90 nm and display highly selective binding capability for Cs(I) ion, with rapid adsorption and desorption. The maximum adsorption capacity is 50 mg g^?1, and the preconcentration factor is around 100 at pH 9.0. Cesium ion was then determined by flame photometry with a detection limit (3σ) of 0.7 ng mL^?1 and with a standard deviation of 0.9 %.

Silica-Supported Perchloric Acid (HClO4-SiO2): An Efficient Catalyst for the Preparation of β-Amido Carbonyl Compounds Using Multicomponent Reactions

A new, one-pot, efficient, three-component condensation of benzaldehyde derivatives, enolizable ketones, acetyl chloride, and acetonitrile or benzonitrile in the presence of silica-supported perchloric acid as an effective catalyst for the synthesis of β-amido carbonyl compounds is described. The present methodology offers several advantages, such as good yields, short reaction times, and simple workup procedure.     

Facile,efficient and diastereoselective synthesis of α-hydrazine tetrazoles through a novel one-pot four-component reaction

A novel and efficient method for the diastereoselective synthesis of α-hydrazine tetrazoles via an isocyanide-based multicomponent reaction is reported in good yields. The α-hydrazine tetrazoles were obtained by a facile azide Ugi four-component reaction (U-4CR) using cyclic ketones, trimethylsilyl azide, hydrazides, and corresponding isocyanide without any catalyst and with high bond forming efficiency at room temperature.     

Synthesis of Tungsten Oxide Nanorods by the Controlling Precipitation Reaction: Application for Hydrogen Evolution Reaction on a WO3 Nanorods/Carbon Nanotubes Composite Film Modified Electrode

Tungsten trioxide nanorods (WO₃) were prepared by controlling the precipitation reaction of sodium tungstate dehydrates solution and hydrothermal process. The synthesized tungsten trioxide nanorods have been characterized by X‐ray diffraction (XRD), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), cyclic voltammetry (CV) and linear sweep voltammetry (LSV). Electrochemical activity for hydrogen evolution reaction (HER) on WO₃ nanorods / carbon nanotube (WO₃/CNT) composite electrocatalyst was first studied in acid solution (0.1 M H₂SO₄) at room temperature. The overall experimental results revealed that the electrocatalytic activity for HER on WO₃/CNT is two order magnitude higher than those obtained with WO₃ nanorods and is four times than in the case of commercial WO₃ in 0.1 M H₂SO₄. On the other hand, the kinetic reaction mechanisms were discussed on WO₃/CNT electrocatalysts in acid solution for HER. However, the rate‐determining step carries through Tafel reaction on commercial WO₃, CNT, WO₃ nanorods and WO₃/CNT electrocatalysts in acidic solution was introduced.     

Intermolecular interactions in uracil–nitrous acid complexes: structures,binding energy,topological properties,and nuclear magnetic resonance study

Molecular interactions between uracil and nitrous acid (U–NA) [C₄N₂O₂H₄? NO₂H] have been studied using B3LYP, B3PW91, and MP2 methods with different basis sets. The optimized geometries, harmonic vibrational frequencies, charge transfer, topological properties of electron density, nucleus‐independent chemical shift (NICS), and nuclear magnetic resonance one‐ and two‐bonds spin–spin coupling constants were calculated for U–NA complexes. In interaction between U and NA, eight cyclic complexes were obtained with two intermolecular hydrogen bonds N(C)HU…N(O) and OH_NA…O_U. In these complexes, uracil (U) simultaneously acts as proton acceptor and proton donor. The most stable complexes labeled, UNA1 and UNA2, are formed via NH bond of U with highest acidity and CO group of U with lowest proton affinity. There is a relationship between hydrogen bond distances and the corresponding frequency shifts. The solvent effect on complexes stability was examined using B3LYP method with the aug‐cc‐pVDZ basis set by applying the polarizable continuum model (PCM). The binding energies in the gas phase have also been compared with solvation energies computed using the PCM. Natural bond orbital analysis shows that in all complexes, the charge transfer takes place from U to NA. The results predict that the Lone Pair (LP)(O)_U → σ*(O? H) and LP(N(O)_NA → σ*(N(C)? H)_U donor–acceptor interactions are most important interactions in these complexes. Atom in molecule analysis confirms that hydrogen bond contacts are electrostatic in nature and covalent nature of proton donor groups decreases upon complexation. The relationship between spin–spin coupling constant (^1hJ_H…_Y and ^2hJ_H…_Y) with interaction energy and electronic density at corresponding hydrogen bond critical points and H‐bonds distances are investigated. NICS used for indicating of aromaticity of U ring upon complexation. © 2013 Wiley Periodicals, Inc.     

Environmentally Friendly Preparation of Amidoalkyl Naphthols

A new, facile, and cost-effective process involving the solvent-free synthesis of amidoalkyl naphthols using a three-component, one-pot condensation reaction of β-naphthol, aromatic aldehyde, and amides in the presence of Al(H₂PO₄)₃ as heterogeneous catalyst under thermal conditions and microwave irradiation has been described. This new approach has the advantage of consistently excellent yields and short reaction times. The catalyst has shown a very stable catalytic activity in the reaction conditions and also can be recovered and recycled.     

Electro-Organic Synthesis of 2-Amino-3-cyano-benzofuran Derivatives Using Hydroquinones and Malononitrile

Abstract

In this work, electrochemical oxidation of hydroquinones has been studied in the presence of malononitrile as a nucleophile in aqueous solution using cyclic voltammetry and controlled potential coulometry. The results indicate that the quinones derived from hydroquinones participate in Michael addition and then intramolecular nucleophilic addition to yield benzofuran derivatives. The electrochemical synthesis of these new 2-amino-3-cyano-benzofuran derivatives has been performed successfully at a carbon-rod electrode in an undivided cell in good to excellent yields at room temperature.     

Microwave Irradiation for Accelerating the Synthesis of Thioglycosides

A simple and efficient procedure for the synthesis of thioglycosides has been achieved from the reaction of glycosylisothiouronium salts with alkyl or heteroaryl halides under microwave irradiation, in much shorter times and in yields comparable with conventional methods.     

Novel ZnO-Al2O3 composite particles as sorbent for low temperature H2S removal

ZnO-Al₂O₃ composite particles composed of ZnO nanosheets（thickness of 40-80 nm） on alumina particles were prepared by heterogeneous precipitation method using bayerite seed particles.The asprepared composite particles were characterized in terms of crystal structure,morphology,surface area and pore volume.The composite particles were used as sorbent for H₂S adsorption at low temperature, and were compared with pure ZnO sorbent.The composite sorbent showed a greater sulfur adsorption capacity（0.052 g/g） than pure form of ZnO（0.028 g/g）.This significant improvement was mainly attributed to higher surface area,more pore volume and unique morphology in nanoscale,which were also obtained by low cost presented method in this work for synthesis of ZnO sorbent supported on alumina particles.     

Alumina Perchloric Acid (Al 2 O 3 -HClO 4 ) as an Efficient Heterogeneous Catalyst for Modified Preparation of Trimethylsilyl Ethers

A highly efficient and mild procedure for the trimethylsilylation of a wide variety of alcohols, including primary, benzylic, secondary, hindered secondary, tertiary, phenols, and oximes with hexamethyldisilazane (HMDS) using alumina perchloric acid (Al ₂ O ₃ -HClO ₄ ) as recyclable heterogeneous catalyst in excellent yields with short reaction times (3?65 min) under ambient conditions is described.