One-Pot,Catalyst-Free,Facile, and Efficient Sulfenylation of Electron-Rich Substrates with a Mild Sulfenium Carrier Azobenzene-2-sulfenyl Bromide

One-pot, catalyst-free, facile, and efficient sulfenylations of resorcinol, 1,3-diaminobenzene, 2-naphthol, 2-aminonaphthalene, indole, pentane-2,4-dione, etc., in aqueous and ethanolic solution by a mild sulfenium carrier azobenzene-2-sulfenyl bromide are described. Efficient sulfenylating reagent, mild reaction conditions, and excellent yields make this method quite simple, convenient, and practical.

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A comparative study on catalytic performance of modified nanocrystalline and microcrystalline zeolite X for synthesis of cumene by transalkylation of 1,4-diisopropylbenzene with benzene

Cumene is a commercially important product in the petrochemical industries. In isopropylation of benzene, 1,4-diisopropyl benzene (1,4-DIPB) is produced as low value by-product. This low value by-product DIPB is used to maximize the production of commercially important product cumene by transalkylation reaction. Reduction of crystal size in zeolite can increase surface area of the external surface and in this way bring about substantial changes in catalytic activity. Moreover modification with rare-earth metal enhances the acidity of zeolite. In this work, nanocrystalline and microcrystalline zeolite X were modified with cerium to study the combine effect of crystal size and ion modification of zeolite on selectivity of cumene in commercially important transalkylation reaction. Benzene and 1,4-diisopropylbenzene in a molar ratio of 1 to 12.5 were subjected to vapour-phase reaction in the temperature range of 498 to 593 K at atmospheric pressure with space time of 5.27–10.54 kg h/kmol. Nanosized crystalline zeolite gives much higher conversions of 1,4-DIPB than microcrystalline zeolite. Over cerium modified nanosized zeolite CeX_N 81.85% conversion of 1,4-DIPB and 97% cumene selectivity were achieved. It was found that stability and activity of CeX_N for cumene synthesis was much higher than that of CeX_M zeolite. Kinetic constants for the reactions were estimated and the activation energies for various reactions over CeX_M were determined. The activation enegy for transalkylation reaction was found to be 78.54 kJ/mol.     

Mixed saturated-unsaturated alkyl-chain assemblies: solid solutions of zinc stearate and zinc oleate

The linear saturated stearic acid and the bent mono-unsaturated oleic acid do not mix and form solid solutions. However, the zinc salts of these acids can. From X-ray diffraction and DSC measurements we show that the layered zinc stearate and zinc oleate salts form a homogeneous solid solution at all composition ratios. The solid solutions exhibit a single melting endotherm, with the melting temperature varying linearly with composition but with the enthalpy change showing a minimum. By monitoring features in the infrared spectra that are characteristic of the global conformation of the hydrocarbon chain, and hence can distinguish between stearate and oleate chains, it is shown that solid solution formation is realized by the introduction of gauche defects in a fraction of the stearate chains that are then no longer linear. This fraction increases with oleate concentration. It has also been possible from the spectroscopic measurements to establish a quantitative relation between molecular conformational order and the thermodynamic enthalpy of melting of the solid solutions.     

Tunable Molecular Logic Gates Designed for Imaging Released Neurotransmitters

Tunable dual‐analyte fluorescent molecular logic gates (ExoSensors) were designed for the purpose of imaging select vesicular primary‐amine neurotransmitters that are released from secretory vesicles upon exocytosis. ExoSensors are based on the coumarin‐3‐aldehyde scaffold and rely on both neurotransmitter binding and the change in environmental pH associated with exocytosis to afford a unique turn‐on fluorescence output. A pH‐functionality was directly integrated into the fluorophore π‐system of the scaffold, thereby allowing for an enhanced fluorescence output upon the release of labeled neurotransmitters. By altering the pH‐sensitive unit with various electron‐donating and ‐withdrawing sulfonamide substituents, we identified a correlation between the pK_a of the pH‐sensitive group and the fluorescence output from the activated fluorophore. In doing so, we achieved a twelvefold fluorescence enhancement upon evaluating the ExoSensors under conditions that mimic exocytosis. ExoSensors are aptly suited to serve as molecular imaging tools that allow for the direct visualization of only the neurotransmitters that are released from secretory vesicles upon exocytosis.     

Study of variation of soil radon exhalation rate with meteorological parameters in Bakreswar–Tantloi geothermal region of West Bengal and Jharkhand,India

Radon gas is the predominant ionizing radiation on earth. Its occurrence is controlled by the presence of uranium in all types of rocks in the earthcrust, apart from local geological features and atmospheric factors which influence its release into the atmosphere. The present work deals with 24 h observation of the dependence of radon exhalation rate from soil on local meteorological parameters at four locations in Bakreswar–Tantloi geothermal region, located in the highly faulted Chhotanagpur Plateau of eastern India. This study is the primary step towards the determination of soil radon exhalation dynamics in this geothermal area.

     

A study on the synthesis of alkaline copper(III)-periodate (DPC) complex with an overview of its redox behavior in aqueous micellar media

Research on Chemical Intermediates - In the present study the copper(III)-periodate (DPC) has been synthesized in an alkaline medium. The stability of this complex is significantly dependent on the...     

Structural and electronic properties of Snn-1Pb and Pbn-1Sn clusters: a theoretical investigation through first principles calculations

Here we report a systematic theoretical study of the structure and electronic properties of Sn_n-1Pb and Pb_n-1Sn (n = 2-13) clusters and compare these results with pure Sn_n and Pb_n to understand the influence of the dopant elements. The calculations were carried out using the density functional theory with generalized gradient approximation for the exchange-correlation potential. Extensive search based on large number of initial configurations has been carried out to locate the stable isomers of Sn_n-1Pb and Pb_n-1Sn (n = 2-13) clusters. The relative stability of Sn_n-1Pb and Pb_n-1Sn (n = 2-13) clusters is analyzed based on the calculated binding energies and second difference in energy. The stability analysis of these clusters suggests that, while the substitution of Sn by Pb lowers the stability of Sn_n clusters, presence of Sn enhances the stability of the Pb_n clusters. The results suggest that while for Sn_n-1Pb, n=4, 7, 10, 12 clusters are more stable than their respective neighbors, Pb_n-1Sn clusters with n = 4, 7 and 9 are found to be more stable. Based on the fragmentation pattern it is seen that for Sn_n-1Pb and Pb_n-1Sn clusters favor monomer evaporation of the Pb atom up to n =11 and n =12, respectively. Unlike this trend, the Sn₁₁Pb undergoes fission type fragment into Sn₅Pb and Sn₆ clusters. A comparison between our theoretical results and surface induced dissociation experiment shows good agreement, which gives confidence on the prediction of the ground state geometries.     

Rapid,Label-free Optical Spectroscopy Platform for Diagnosis of Heparin-Induced Thrombocytopenia

The use of surface-enhanced Raman spectroscopy (SERS) to determine spectral markers for the diagnosis of heparin-induced thrombocytopenia (HIT), a difficult-to-diagnose immune-related complication that often leads to limb ischemia and thromboembolism, is proposed. The ability to produce distinct molecular signatures without the addition of labels enables unbiased inquiry and makes SERS an attractive complementary diagnostic tool. A capillary-tube-derived SERS platform offers ultrasensitive, label-free measurement as well as efficient handling of blood serum samples. This shows excellent reproducibility, long-term stability and provides an alternative diagnostic rubric for the determination of HIT by leveraging machine-learning-based classification of the spectroscopic data. We envision that a portable Raman instrument could be combined with the capillary-tube-based SERS analytical tool for diagnosis of HIT in the clinical laboratory, without perturbing the existing diagnostic workflow.