Silica-supported boric acid with ionic liquid: a novel recyclable catalytic system for one-pot three-component Mannich reaction

A rapid and efficient silica-supported boric acid/ionic liquid ([bmim][PF?]), catalyzed, one-pot three-component Mannich reaction has been carried out to synthesize β-amino carbonyl compounds at room temperature. The reaction afforded desired products in excellent yields with moderate to good diastereoselectivity. The method provides a novel modification of three-component Mannich reaction in terms of mild reaction conditions, clean reaction profiles, low amount of catalyst, recyclability of catalyst and a simple workup procedure. The present report first time describes the preparation of H?BO?-SiO? catalyst and its use with [bmim][PF?], to synthesize Mannich products. The catalyst can be reused at least seven times.     

Mesogenic quinazolone derivatives: synthesis and characterisation

Two new mesogenic homologous series of quinazolone derivatives have been synthesised by condensation of 4-n-alkoxybenzoyloxy benzaldehyde (for series I) / 4-n-alkoxy-3-methoxybenzoyloxy benzaldehyde (for series II) with 3-amino-2-methyl quinazolone in alcohol. The synthesised compounds are characterised by a combination of elemental analysis and standard spectroscopic methods. In series I, all the synthesised members exhibit the nematic mesophase. An enantiotropic smectic A phase is observed from the n-decyloxy derivative onward to the last homologue synthesised. Methoxy to n-propyloxy derivatives of series II are non-mesogenic, whereas the rest of the members exhibit a monotropic nematic mesophase. The mesomorphic properties of the present series I and II are compared with each other and with the other structurally related mesogenic homologous series to evaluate the effect of lateral methoxy substituent and quinazolone moiety on mesomorphism.     

Porous‐Organic‐Framework‐Templated Nitrogen‐Rich Porous Carbon as a More Proficient Electrocatalyst than Pt/C for the Electrochemical Reduction of Oxygen

Porous nitrogen‐rich carbon (POF‐C‐1000) that was synthesized by using a porous organic framework (POF) as a self‐sacrificing host template in a nanocasting process possessed a high degree of graphitization in an ordered structural arrangement with large domains and well‐ordered arrays of carbon sheets. POF‐C‐1000 exhibits favorable electrocatalytic activity for the oxygen‐reduction reaction (ORR) with a clear positive shift of about 40 mV in the onset potential compared to that of a traditional, commercially available Pt/C catalyst. In addition, irrespective of its moderate surface area (785 m² g^?1), POF‐C‐1000 showed a reasonable H₂ adsorption of 1.6 wt % (77 K) and a CO₂ uptake of 3.5 mmol g^?1 (273 K).     

Simultaneous Quantification of Aliskiren, Valsartan and Sitagliptin by LC with Fluorescence Detection: Evidence of Pharmacokinetic Interaction in Rats

A sensitive, precise and simple LC method for the simultaneous quantification of aliskiren, valsartan and sitagliptin in rat plasma has been developed and validated. The chromatographic separation was achieved on a C₁₈ column (250 mm × 4.6 mm, 5 μm) maintained at room temperature, using isocratic elution with acetonitrile/20 mM ammonium acetate buffer (35:65, v/v), pH adjusted to 4.85 with glacial acetic acid, and detected using a fluorescence detector. Liquid–liquid extraction of the aliskiren, valsartan and sitagliptin from the rat plasma with t-butyl methyl ether resulted in their high recoveries. LC calibration curves based on the extracts from the rat plasma were linear in the range of 25–2,000 ng mL^?1 for aliskiren and sitagliptin and 50–4,000 ng mL^?1 for valsartan. The limits of quantification were 25 ng mL^?1 for aliskiren and sitagliptin and 50 ng mL^?1 for valsartan. The precision and accuracy of the method were well within the generally accepted criteria for biomedical analysis. The described method was successfully applied to study the pharmacokinetics of aliskiren, valsartan and sitagliptin following oral administration, individually as well as in combination in Sprague–Dawley rats. The results of the study implied the occurrence of pharmacokinetic interaction upon the co-administration of these three drugs.     

Chemical composition and larvicidal activity of Zanthoxylum armatum against diamondback moth,Plutella xylostella

The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Yponomeutidae) is the most serious pest of cruciferous crops grown in the world causing economic yield loss. Several synthetic insecticides have been used against P. xylostella but satisfactory control was not achieved due to development of resistance to insecticides. Therefore, the present study was carried out to screen different fractions of Zanthoxylum armatum for their insecticidal activities against second instar larvae of P. xylostella. Results indicate, all the fractions showed activity to P. xylostella. However, n-hexane fraction of Z. armatum showed maximum larvicidal activity with minimum LC₅₀ value of 2988.6 ppm followed by ethanol (LC₅₀ = 12779.7 ppm) and methanol fraction (LC₅₀ = 12908.8 ppm) whereas chloroform fraction was least toxic (LC₅₀ = 16750.6 ppm). The GC–MS analysis of n-hexane fraction of leaf extract showed maximum larvicidal activity, which may be due to two major compounds i.e. 2-undecanone (19.75%) and 2-tridecanone (11.76%).     

Zeta potential and electroosmotic mobility in microfluidic devices fabricated from hydrophobic polymers: 1. The origins of charge

This paper combines new experimental data for electrokinetic characterization of hydrophobic polymers with a detailed discussion of the putative origins of charge at water-hydrophobe interfaces. Complexities in determining the origin of charge are discussed in the context of design and modeling challenges for electrokinetic actuation in hydrophobic microfluidic devices with aqueous working fluids. Measurements of interfacial charge are complicated by slip and interfacial water structuring phenomena (see Part 2, this issue). Despite these complexities, it is shown that (i) several hydrophobic materials, such as Teflon and Zeonor, have predictable electrokinetic properties and (ii) electrokinetic data for hydrophobic microfluidic systems is most consistent with the postulate that hydroxyl ion adsorption is the origin of charge.     

Determination of aliphatic amines by high-performance liquid chromatography-amperometric detection after derivatization with naphthalene-2,3-dicarboxaldehyde

A simple and sensitive liquid chromatographic method has been developed for the determination of low molecular weight aliphatic amines after their pre-column derivatization with naphthalene-2,3-dicarboxaldehyde (NDA). Derivatization conditions, including the NDA concentration, reaction pH and reaction time have been investigated for method optimization. The chromatographic separation of five amines was performed on ABZ PLUS column using mobile phase of methanol-water (80:20, v/v) at a flow rate of 0.2 mL min⁻¹. The detection was carried out with a 6 mm glassy carbon electrode at the applied potential of 0.7 V versus Ag/AgCl reference electrode. The detection limits were between 23.3 and 34.4 nmol L⁻¹ of amines with a sample injection volume of 2 μL. The present method was applied for the determination of aliphatic amines in lake water. The recovery ranged 52.2-127.9%. The RSD in analytes retention time was less than 0.3% and 2.4% for intra- and inter-day analyses, respectively. The RSD in peak area was below 5.8% for both intra-day and inter-day analyses. The total analysis was completed within 20 min.     

Surface structural,morphological, and catalytic studies of homogeneously dispersed anisotropic Ag nanostructures within mesoporous silica

Highly dispersed anisotropic Ag nanostructures were synthesized within the channels of 3-aminopropyltrimethoxysilane (APTMS)-modified mesoporous SBA-15 for catalyzing the reduction of p-dinitrobenzene, p-nitrophenol, and p-nitroacetophenone, respectively. A green templating process without involving any reducing agent, by varying the amount (1–10 wt.%) of Ag loading followed by calcination at 350 °C under H₂ led to change in the morphology of Ag nanoparticles from nanospheres (~7–8 nm) to nanorods (aspect ratio ~12–30 nm) without any deformation in mesoporous sieves. In comparison to white bare SBA-15, gray-colored samples were formed with Ag impregnation exhibiting absorption bands at 484 and 840 nm indicating the formation of anisotropic Ag nanostructures within mesoporous matrix. TEM and FE-SEM micrographs confirmed the presence of evenly dispersed Ag nanostructures within as well as on the surface of mesoporous matrix. AFM studies indicated a small decrease in the average roughness of SBA-15 from 20.59 to 19.21 nm for 4 wt.% Ag/m-SBA-15, illustrating the encapsulation of majority of Ag nanoparticles in the siliceous matrix and presence of small amount of Ag nanoparticles on the mesoporous support. Moreover, due to plugging of mesopores with Ag, a significant decrease in surface area from 680 m²/g of SBA-15 to 385 m²/g was observed. The Ag-impregnated SBA-15 catalyst displayed superior catalytic activity than did bare SBA-15 with 4 wt.% Ag-loaded catalyst exhibiting optimum activity for selective reduction of p-nitrophenol to p-aminophenol (100 %), p-nitroacetophenone to p-aminoacetophenone (100 %), and p-dinitrobenzene to p-nitroaniline (87 %), with a small amount of p-phenylenediamine formation.

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Graphical abstract This paper demonstrates the spontaneous formation of uniformly dispersed Ag nanospecies of various morphologies (nanospheres, size ~7–8 nm and nanorods, aspect ratio ~12–30 nm), both within as well as on the surface of the mesoporous SBA-15, as a function of increased Ag loading. Surface structural and other physiochemical properties of Ag/m-SBA-15 nanocomposites were considerably influenced w.r.t change in Ag loading. Ag/m-SBA-15 nanocomposites with 4 wt.% Ag loading exhibited the highest selectivity (87 %) for the selective reduction of p-dinitrobenzene to p-nitroaniline and 100 % selectivity for p-nitrophenol to p-aminophenol and p-nitroacetophenone to p-aminoacetophenone, respectively.

     

Liquid–liquid extraction of thorium(IV) with N-n-heptylaniline from acid media

The extraction behavior of thorium(IV) from sulphuric acid medium with N-n-heptylaniline in xylene. Various parameters like reagent concentration, acid concentration, equilibration time, diverse ions and effect of diluents were studied. Thorium(IV) was selectively extracted and separated from many metal ions. The nature of the extracted species was determined. Thorium(IV) was analyzed from monazite ore and gas mantle.

     

High performance liquid chromatographic separation of <Superscript>228,229</Superscript>Th and <Superscript>232,233</Superscript>U and their estimation by α- and γ-ray spectrometry

The activities of ^228,229Th and ^232,233U from an irradiated ThO₂ sample were radiochemicaly separated by using high performance liquid chromatography. Plancheted sources of the separated samples were made and the amount of ^232,233U and ^228,229Th were estimated by using alpha and gamma-ray spectrometric techniques. These estimations are important for the Th–U fuel reprocessing cycle of advanced heavy water reactor and accelerator driven sub-critical system.