Dimethyl Sulfoxide Pivaloyl Chloride: A New Reagent for Oxidation of Alcohols to Carbonyls

An efficient procedure for conversion of alcohols to the corresponding carbonyl compounds, an alternative to the classical Swern oxidation, is described. Pivaloyl chloride is employed as a mild and inexpensive electrophile. A possible reaction mechanism is proposed.     

Tubule Nanoclay‐Organic Heterostructures for Biomedical Applications

Natural halloysite nanotubes (HNTs) show unique hollow structure, high aspect ratio and adsorption ability, good biocompatibility, and low toxicity, which allow for various biomedical applications in the diagnosis and treatment of diseases. Here, advances in self‐assembly of halloysite for cell capturing and bacterial proliferation, coating on biological surfaces and related drug delivery, bone regeneration, bioscaffolds, and cell labeling are summarized. The in vivo toxicity of these clay nanotubes is discussed. Halloysite allows for 10–20% drug loading and can extend the delivery time to 10–100 h. These drug‐loaded nanotubes are doped into the polymer scaffolds to release the loaded drugs. The rough surfaces fabricated by self‐assembly of the clay nanotubes enhance the interactions with tumor cells, and the cell capture efficacy is significantly improved. Since halloysite has no toxicity toward microorganisms, the bacteria composed within these nanotubes can be explored in oil/water emulsion for petroleum spilling bioremediation. Coating of living cells with halloysite can control the cell growth and is not harmful to their viability. Quantum dots immobilized on halloysite were employed for cell labeling and imaging. The concluding academic results combined with the abundant availability of these natural nanotubes promise halloysite applications in personal healthcare and environmental remediation.     

Initial Carbon−Carbon Bond Formation during the Early Stages of Methane Dehydroaromatization

Methane dehydroaromatization (MDA) is among the most challenging processes in catalysis science owing to the inherent harsh reaction conditions and fast catalyst deactivation. To improve this process, understanding the mechanism of the initial C?C bond formation is essential. However, consensus about the actual reaction mechanism is still to be achieved. In this work, using advanced magic‐angle spinning (MAS) solid‐state NMR spectroscopy, we study in detail the early stages of the reaction over a well‐dispersed Mo/H‐ZSM‐5 catalyst. Simultaneous detection of acetylene (i.e., presumably the direct C?C bond‐forming product from methane), methylidene, allenes, acetal, and surface‐formate species, along with the typical olefinic/aromatic species, allow us to conclude the existence of at least two independent C?H activation pathways. Moreover, this study emphasizes the significance of mobility‐dependent host–guest chemistry between an inorganic zeolite and its trapped organic species during heterogeneous catalysis.     

Evaluation of transfer factor and ecological half life of 137Cs in terrestrial matrices around Kakrapar Gujarat Site,India during 1993–2019

Journal of Radioanalytical and Nuclear Chemistry - The activity of 137Cs was measured in different terrestrial samples around Kakrapar Gujarat site. Transfer Factor and Ecological half-life of...     

An improvement on the maximum number of -dominating independent sets

Erdős and Moser raised the question of determining the maximum number of maximal cliques or, equivalently, the maximum number of maximal independent sets in a graph on vertices. Since then there has been a lot of research along these lines. A -dominating independent set is an independent set such that every vertex not contained in has at least neighbors in . Let denote the maximum number of -dominating independent sets in a graph on vertices, and let . Nagy initiated the study of . In this study, we disprove a conjecture of Nagy using a graph product construction and prove that for any even we have We also prove that for any we have improving the upper bound of Nagy.     

Synthesis and characterization of multiblock copolymers based on hydrophilic disulfonated poly(arylene ether sulfone) and hydrophobic partially fluorinated poly(arylene ether ketone) for fuel cell applications

Sulfonated fluorinated multiblock copolymers based on high performance polymers were synthesized and evaluated for use as proton exchange membranes (PEMs). The multiblock copolymers consist of fully disulfonated poly(arylene ether sulfone) and partially fluorinated poly(arylene ether ketone) as hydrophilic and hydrophobic segments, respectively. Synthesis of the multiblock copolymers was achieved by a condensation coupling reaction between controlled molecular weight hydrophilic and hydrophobic oligomers. The coupling reaction could be conducted at relatively low temperatures (e.g., 105 °C) by utilizing highly reactive hexafluorobenzene (HFB) as a linkage group. The low coupling reaction temperature could prevent a possible trans‐etherification, which can randomize the hydrophilic‐hydrophobic sequences. Tough ductile membranes were prepared by solution casting and their membrane properties were evaluated. With similar ion exchange capacities (IECs), proton conductivity and water uptake were strongly influenced by the hydrophilic and hydrophobic block sequence lengths. Conductivity and water uptake increased with increasing block length by developing nanophase separated morphologies. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) experiments revealed that the connectivity of the hydrophilic segments was enhanced by increasing the block length. The systematic synthesis and characterization of the copolymers are reported. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 214–222, 2010     

Efficient One-pot Zeolite Synthesis Protocol from the Metastable *BEA to MTW Topology and Its Impact on the Methanol-to-Hydrocarbons Process

The inter-zeolite conversion is a method to convert one meta-stable zeolite to a thermodynamically stable zeolite. Despite the enormous interest, this method is yet to be popularized or standardized in the zeolite community. Intending to provide more insights into hydrothermal conversions from one zeolite to another, this work developed a novel one-pot and flexible synthetic protocol to efficiently obtain the meta-stable *BEA topology and its derived MTW topology by varying the hydrothermal crystallization time. This inter-zeolite conversion process led to changes in the zeolite framework and modified physicochemical properties during the process. Such a transformation was feasible by forming hierarchical zeolite phases sharing a similar “mtw”-based common building units, possibly driving such conversion. The structure-reactivity relationship of four different zeolite materials, synthesized from this one-pot inter-zeolite conversion method, was established concerning their performance in the methanol-to-hydrocarbon (MTH) process, which has been well supported by operando UV-vis diffuse reflectance spectroscopic study coupled with online mass spectrometry and solid-state NMR spectroscopy. As a result, the pathway to synthesize various target zeolites from an identical initial synthesis gel with desired physicochemical properties has been scrutinized.     

Magnetism and transport studies in off-stoichiometric metallic perovskite compounds GdPd3Bx (x=0.25, 0.50 and 0.75)

We report the magnetic and transport properties of the off-stoichiometric metallic perovskite like compounds GdPd₃B_x (x=0.25, 0.50 and 0.75). Our results show that doping with boron in the lattice of parent binary-compound GdPd₃ leads to lattice expansion. Which in turn manifests in contrasting magnetic and transport behaviors of the doped compounds in comparison with the undoped GdPd₃. An attempt has been made to compare and correlate the results of magnetic and transport measurements of GdPd₃B_x with that of stoichiometric compositions GdPd₃B_xC_1−x. The comparative study of GdPd₃B_x and GdPd₃B_xC_1−x confirms that there is a strong correlations between the structural, magnetic and transport properties of these compounds.     

Thiamin biosynthesis in eukaryotes: characterization of the enzyme-bound product of thiazole synthase from Saccharomyces cerevisiae and its implications in thiazole biosynthesis

The biosynthesis of thiamin pyrophosphate in eukaryotes is different from the prokaryotic biosynthesis and is poorly understood to date. Only one thiazole biosynthetic gene has been identified (Thi4 in Saccharomyces cerevisiae). Here we report the identification and characterization of a Thi4-bound metabolite that consists of the ADP adduct of 5-(2-hydroxyethyl)-4-methylthiazole-2-carboxylic acid. The unexpected structure of this compound yields the first insights into the mechanism of thiamin thiazole biosynthesis in eukaryotes.