Reactions of Benzoyl Isothiocyanate with Active Methylene Reagents: A Novel Synthesis of Thiophene,Thiazoline and Thieno[2,3-d]Pyrimidine Derivatives

Various derivatives of thiophene, thiazoline and thienopyrimidine have been synthesized via the reaction of active methylene reagents (la-j) with benzoyl isothiocyanate in the presence of potassium hydroxide, followed by the subsequent treatment of the potassium salt intermediates 2a-j with phenacyl bromide or ethyl chloroacetate. The stability of the formed adducts 3 and 12 or their selective cyclization depends on both the nature of the active methylene reagent and the α-halocarbonyl compounds.     

Antitumor,cytotoxic, and antioxidant evaluation of six heterocyclic compounds containing different heterocycle moieties

Heterocyclic compounds with different heterocycle moieties, namely benzoxazinone, benzimidazole, quinazolinone, and benzofuranone heterocyclic rings, were synthesized, characterized, and evaluated for their anticancer activity against human hepatocellular carcinoma cell line (HepG2) using sulforhodamine B (SRB) and dimethylthiazol-diphenyltetrazolium bromide (MTT) assays. Also, their cytotoxic activities were tested against human epithelioid carcinoma (Hela) cell line in comparison with normal cell, amniotic epithelial (WISH) cell line, as an in vitro toxicity estimation model. The results showed clearly that 2-(2-benzyl-4-oxoquinazolin-3(4H)-yl)acetohydrazide 4 is the most potent antioxidant and anticancer agents. Although, 3-amino-2-benzylquinazolin-4(3H)-one 5 is less potent anticancer agent against Hela but it is more safe against normal cell (WISH).     

Preparation of Homogeneous Hydrogels by Controlling the Crosslinker Reactivity and Availability

Network microstructures of polyacrylamide (PAAm) hydrogels were investigated by static light scattering measurements. The gels were prepared by free‐radical crosslinking polymerization of acrylamide (AAm). To suppress the degree of gel inhomogeneity, the crosslinker reactivity during gelation was controlled by decreasing its availability in the reaction system. Our first approach was the addition of the crosslinker N,N′‐methylenebis(acrylamide) (BAAm) in one or three portions during the course of the gelation reactions. As a second approach, a slightly water soluble crosslinker, namely ethylene glycol dimethacrylate (EGDM) was used as a crosslinker in AAm polymerization. Due to the low water solubility of EGDM, EGDM phase in the gelation system act as a reservoir of crosslinker so that the crosslinker can be supplied continuously to the aqueous reaction zone during the course of gelation. It was found that the delayed crosslinker addition technique further increases the degree of inhomogeneity of PAAm hydrogels. The results were explained with increasing viscosity of the reaction solution at the time of the crosslinker addition so that the crosslinking reactions are limited to local regions in the reaction system. The second approach, namely use of the slightly water soluble crosslinker EGDM significantly increases the degree of structural homogeneity of PAAm hydrogels.     

Sodium, ammonium, calcium, and magnesium forms of zeolite Y for the adsorption of glucose and fructose from aqueous solutions

The kinetics of adsorption by sodium, ammonium, calcium and magnesium forms of zeolite Y from aqueous solutions containing 25% w/v of either one or an equimolar mixture of glucose (G) and fructose (F) have been studied batch-wise at 50 degrees C. The adsorption of aqueous pure G was fast, while that of aqueous pure F depended on the cationic form, approaching that of G on the Mg-Y, and slowing down in the sequence of Mg2+ > NH4+ > Ca2+ > Na+ of the cations. The adsorption behavior from solutions containing both G and F indicated significant hindering effects of F on G on Na-Y. Na-Y and Mg-Y did not exhibit rate-based selectivity, while Ca-Y an NH4-Y adsorbed G faster than F. Addition of CaCl2 to the mixture of Ca-Y and aqueous solution of G and F improved the separation, by hindering the adsorption of F. Addition of NH4Cl to the mixture of the sugar solution and NH4-Y, on the other hand, had a negative effect on the separation. NH4-Y was found to be desorbing about 30% of the adsorbed sugars and this value was found to be around 50% for Ca-Y. Re-adsorption experiments resulted in similar or somewhat higher percentages of amounts adsorbed compared to adsorption on fresh samples. Both NH4-Y and Ca-Y were found to be re-adsorbing around 50% of the sugars they adsorbed on fresh samples.     

Conduction mechanism of an infrared emitting diode: Impedance spectroscopy and current-voltage analysis

The bias dependent complex impedance spectra of a conventional GaAs based infrared emitting diode have been studied in the temperature range 150–300 K. It is found that for bias voltages lower than 0.7 V, the device behaves like a pure capacitor. However for V _dc ≥ 0.7 V, an equivalent circuit model composed of a parallel resistor (R _p ) and capacitor (C _p ) network connected with a series resistance (R _s ) can be used to describe the individual impedance contributions from interfacial and bulk regions of the diode. Fitting of experimental data to the proposed ac model reveal that the value of parallel device capacitance C _p increases with temperature whereas the parallel resistance R _p component decreases. The tendency of parallel resistance and parallel capacitance as a function of temperature is expected that thermally activated current transport mechanism dominates in the forward bias, which coincides with the analysing results of the dark forward current-voltage (I–V) characteristics. The temperature dependent I–V variations suggest that recombination in the depletion region has a paramount role.     

Nitriles in organic synthesis: The reaction of trichloroacetonitrile with active methylene reagents

The reaction of trichloroacetonitrile with active methylene reagents such as acetylacetone, benzoylacetone, cyanoacetamide and cyanoacethydrazide is reported. A new simple route for the synthesis of polysubstituted phenols, pyrazoles and pyrroles is also described.

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Nitrile bei organischen Synthesen: Die Reaktion von Trichloracetonitril mit aktiven Methylen-Reagentien

Zusammenfassung Es wird über die Reaktionen von Trichloracetonitril mit aktiven Methylen-Reagentien wie Acetylaceton, Benzoylaceton, Cyanacetamid und Cyanacethydrazid berichtet. Ein neuer einfacher Weg für die Synthese polysubstituierter Phenole, Pyrazole und Pyrrole wird beschrieben.

     

Modified Diatomaceous earth as a principal stationary phase component in TLC

Modified natural diatomaceous earth (DE) is a principal component of the stationary phase in normal thin-layer chromatography (TLC) applications and is mixed with commercial silica gel 60GF254 (Si-60GF254). Modification is carried out by flux calcination and refluxing with acid. Natural DE, modified DEs [flux calcinated (FC)DE and FCDE-I), and Si-60GF254 are characterized by scanning electron microscopy and Fourier-transform-IR spectroscopy. Particle size, specific surface area, pore distribution, pore volume, and surface hydroxyl group density parameters of materials are determined by various techniques. FCDE-I and Si-60GF254 are investigated for their usefulness in the stationary phase of TLC both individually and in composition. Commercially available red and blue ink samples are run on layers of Si-60GF254 and FCDE-I individually, and on various FCDE-I and Si-60GF254 mixtures. Butanol-ethanol-2M ammonia (3:1:1, v/v) and butanol-acetic acid-water (12:3:5, v/v) mixtures are used as mobile phases. The polarities of stationary phases decrease, and the retention factor (Rf) values of ink components increase when the FCDE-I content of the stationary phase increases. The properties of the stationary phase can be optimized by adding FCDE-I to Si-60GF254. This study may be useful in understanding both the systematic effects of stationary phase properties [e.g., specific surface area and surface hydroxyl group density, aOH(s)] and those of the mobile phase (e.g., polarity and acidity) on Rf values and the separability of components.     

Evaluation of some new 14- and 15-crown-formazans as carriers in cesium ion selective electrodes

A number of new crown-formazans with 14 and 15 membered rings have been investigated as selective neutral carriers in cesium ion selective electrodes. Two plasticizers (NPOE and NPBnE) were studied. The new 14-crown-formazan 4a containing the 4-pyridyl N-oxide at the formazyl carbon exhibited the highest selectivity in cesium ion selective electrodes, especially towards the two low selectivity monovalent ions K⁺ and NH4⁺. Also, membranes containing the plasticizer NPBnE showed better cesium selectivity relative to most ions than those containing NPOE. Membranes containing 4a and variable compositions of plasticizers, potassium tetrakis-(p-chlorophenyl)borate (KTpClPB), and trioctylphosphine oxide (TOPO) were studied in order to prepare an electrode with the optimum cesium selectivity. The highest selectivity for cesium was achieved with the two electrodes designated d and e with membranes containing the ionophore 4a, NPBnE and KTpClPB with and without TOPO. Selectivities are reported relative to sodium, potassium, barium, calcium, ammonium, lithium, cobalt, and magnesium.     

Maximizing the lifetime of energy‐constrained cooperative spectrum sensing sensor network

Adding the cognitive capability to wireless sensor networks allows the sensors to monitor the spectrum and identify the spectrum holes to operate in different frequencies according to the radio environment which result in better spectrum utilization. Spectrum sensing is a main component in any cognitive radio network. In this paper, we propose a new cooperative sensing scheme based on energy detection for cognitive sensor networks which is constrained by the energy limitation of the wireless sensor elements. The proposed scheme minimizes the sensing energy for individual sensor and carefully selects the suitable participant sensors in each cooperative sensing process. This results in maximizing the lifetime of energy‐constrained wireless sensor networks. The proposed scheme also takes into consideration the constraints on the detection accuracy. The simulation results show that the proposed scheme prolonged the lifetime of the cognitive network, makes efficient usage of available spectrum by secondary users, and satisfy the target detection performance.     

Ab initio calculation of structural, electronic and phonon properties of ZrRu and ZrZn in B2 phase

The structural, electronic and dynamic properties of cesium chloride, ZrRu and ZrZn were studied by employing an ab initio pseudopotential method and a linear response scheme, within the generalized gradient approximation. The calculated lattice constant, bulk modulus and first-order pressure derivative of the bulk modulus were reported in B2 structure and compared with available experimental and other theoretical results. The electronic band structure, partial and total density of states were determined by using the Quantum-Espresso ab initio simulation package based on pseudopotential method. Phonon dispersion curves and density of states were calculated by employing a density functional perturbation theory.