Eco-friendly synthesis of 1,4-benzodiazepine-2,5-diones in the ionic liquid [bmim]Br

The green reaction of isatoic anhydrides with α-amino acids in presence of the ionic liquid 1-butyl-3-methylimidazolium bromide afforded 1,4-benzodiazepine-2,5-diones in excellent yields in absence of a catalyst. The reaction workup is simple and the ionic liquid was easily recovered from the reaction and reused. The methodology was quite general and a range of cyclic and acyclic α-amino acids were examined to produce 1,4-benzodiazepine-2,5-diones.     

Eco-friendly synthesis of 1,4-benzodiazepine-2,5-diones in the ionic liquid [<Emphasis Type="Italic">bmim</Emphasis>]Br

The green reaction of isatoic anhydrides with α-amino acids in presence of the ionic liquid 1-butyl-3-methylimidazolium bromide afforded 1,4-benzodiazepine-2,5-diones in excellent yields in absence of a catalyst. The reaction workup is simple and the ionic liquid was easily recovered from the reaction and reused. The methodology was quite general and a range of cyclic and acyclic α-amino acids were examined to produce 1,4-benzodiazepine-2,5-diones. Correspondence: Khosrow Jadidi, Department of Chemistry, Shahid Beheshti University, PO Box 1983963113, Tehran, Iran.     

Spectrophotometric study of anionic azo-dye light yellow (X6G) interaction with surfactants and its micellar solubilization in cationic surfactant micelles

Solubilization and interaction of azo-dye light yellow (X6G) at/with cationic surfactants cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC) was investigated spectrophotometricaly. The effect of cationic micelles on solubilization of anionic azo dye in aqueous micellar solutions of cationic surfactants was studied at pH 7 and 25 degrees C. The binding of dye to micelles implied a bathochromic shift in dye absorption spectra that indicates dye-surfactant interaction. The results showed that the solubility of dye increased with increasing surfactant concentration, as a consequence of the association between the dye and the micelles. The binding constants, K(b), were obtained from experimental absorption spectra. By using pseudo-phase model, the partition coefficients between the bulk water and surfactant micelles, K(x), were calculated. Gibbs energies of binding and distribution of dye between the bulk water and surfactant micelles were estimated. The results show favorable solubilization of dye in CTAB micelles.     

Application of in-situ formed polymer-based dispersive solid phase extraction in combination with solidification of floating organic droplet-based dispersive liquid–liquid microextraction for the extraction of neonicotinoid pesticides from milk samples

An in-situ formed polymer–based dispersive solid phase extraction in combination with solidification of floating organic droplet-based dispersive liquid–liquid microextraction was developed for the extraction of neonicotinoid pesticides from milk samples. The extracted analytes were determined using high-performance liquid chromatography–diode array detector. In this approach, after precipitating the proteins of milk using a zinc sulfate solution, the supernatant phase (containing sodium chloride) was transferred into another glass test tube, and a homogenous solution of polyvinylpyrrolidone and a suitable water-miscible organic solvent was rapidly injected into it. By this step, the polymer particles were re-produced and the analytes were extracted onto the sorbent surface. In the following step, the analytes were eluted with an appropriate organic solvent to use in the following solidification of floating organic droplet-based dispersive liquid–liquid microextraction step that was done to acquire the low limits of detection. Under the optimized conditions, satisfactory results consisting of low limits of detection (0.13–0.21 ng/ml) and quantification (0.43–0.70 ng/ml), high extraction recoveries (73%–85%), and enrichment factors (365–425), and good repeatability (relative standard deviations equal or less than 5.1% and 5.9% for intra- and inter-day precisions, respectively) were obtained.     

Ce (III) - Porphyrin Sandwich Complex Ce<Subscript>2</Subscript>(TPP)<Subscript>3</Subscript>: A Rod-Like Nanoparticle as a Fluorescence Turn-Off Probe for Detection of Hg (II) and Cu (II)

In this study the researcher reports a novel, one step synthesized rod-like nanoparticles of cerium (III)—tetraphenylporphyrin sandwich complex as a spectrofluorometric sensor to measure trace amount of Hg (II) and Cu (II) metal ions. Moreover, the synthesized fluorescent probe was able to detect higher amounts (>10^?4 M) of Hg (II) in aqueous media by changing the color which can also be used as a selective mercury naked-eye sensor. The selectivity and sensitivity of the sensor based on its fluorescence quenching in the presence of Hg (II) and Cu (II) were studied according to the Stern-Volmer equation. The detection limit of the sensor was 16 nM for Hg (II) and about 2.34 μM for Cu (II) ions.

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Graphical Abstract Ce₂(TPP)₃ sandwich complex application as a fluorescent probe for measuring trace amounts of mercury and copper in real samples

     

Local Clique Covering of Claw‐Free Graphs

A clique covering of a simple graph G is a collection of cliques of G covering all the edges of G such that each vertex is contained in at most k cliques. The smallest k for which G admits a clique covering is called the local clique cover number of G and is denoted by lcc(G). Local clique cover number can be viewed as the local counterpart of the clique cover number that is equal to the minimum total number of cliques covering all edges. In this article, several aspects of the local clique covering problem are studied and its relationships to other well‐known problems are discussed. In particular, it is proved that the local clique cover number of every claw‐free graph is at most , where Δ is the maximum degree of the graph and c is a constant. It is also shown that the bound is tight, up to a constant factor. Moreover, regarding a conjecture by Chen et al. (Clique covering the edges of a locally cobipartite graph, Discrete Math 219(1–3)(2000), 17–26), we prove that the clique cover number of every connected claw‐free graph on n vertices with the minimum degree δ, is at most , where c is a constant.     

增强LPG催化裂化催化剂ZSM-5稳定性的新方法：脱铝和负载硅

以碳纳米管为模板合成的带有介孔和微孔的ZSM-5分子筛具有不同的复合结构。用三氯乙酸(TCA)可选择性地将中孔的铝脱除。基于TCA分子大小,它可能只扩散到中孔中,因而使得微孔部分不脱铝。从分子筛结构中脱除铝原子导致催化剂中出现中空的空间。若将硅原子填充到空位中,那么介孔部分的结构会变得与硅酸盐类似,不具有催化性能。本文使用含硅的溶液来填充空位,将硅原子直接取代中孔结构中的铝原子。通过此特殊方法改变微孔和介孔的几何形状和性质,从而使改性HZSM-5上的积碳量从14%降低至3%。     

Adsorptive desulfurization of model diesel fuel over mono-functionalized nickel/γ-alumina and bi-functionalized nickel/cerium/γ-alumina adsorbents

Research on Chemical Intermediates - In this study, the S–M direct interaction and π-complexation mechanisms for selective adsorption of 4,6-dimethyldibenzothiophene (4,6-DMDBT) onto the...     

Modified iteration method for solving fractional gas dynamics equation

This paper is devoted to the time‐fractional gas dynamics equation with Caputo derivative. Fractional operators are very natural tools to model memory‐dependent phenomena. Modified iteration method is proposed to obtain the approximate and analytical solution of the fractional gas dynamics equation. This method is a combined form of the new iteration method and Laplace transform. Modified iteration method really is powerful and simple method compared with other methods. Existence and uniqueness of solution are proven. Numerical results for different cases of the equation are obtained. Copyright © 2016 John Wiley & Sons, Ltd.