A mechanistic study on the synthesis of branched functional polyethylene through reactive co-polymer approach

The reactive co-polymer approach is one of the most promising techniques for the synthesis of functional polyolefins. Following this concept, 1-hexene and p-methylstyrene are co-polymerized in the presence of a generic Brookhart-type catalyst. The microstructures of the co-polymers imply the tendency of p-methylstyrene co-monomers to place at the end of the structural branches formed by the chain walking reaction. The molar masses of the co-polymers decrease, not only at higher levels of co-monomer but surprisingly by decreasing reaction temperature. A mechanism consisting of a highly stable η³ metal–benzyl intermediate, which is quantitatively approved by density functional theory calculations, can delicately justify all the aforementioned observations. A series of the produced co-polymers is selectively functionalized by maleic anhydride at the benzylic position of p-methylstyrene, under very mild reaction conditions. Such a reactive intermediate opens the path for the introduction of different types of functionalities in polyolefins. Namely, the grafted co-polymers were further functionalized by a triazole ring, which provides a transient supramolecular network through intermolecular hydrogen bonding.     

Efficient synthesis of β-aminoketones catalyzed by Fe3O4@ quillaja sapogenin/Ni (II) as a novel magnetic nano-catalyst

A new nano-magnetic core–shell Fe₃O₄@quillaja sapogenin/Ni (II) was synthesized and characterized thoroughly using various tests including energy-dispersive X-ray spectroscopy (EDS), Brunauer–Emmett–Teller (BET), thermo-gravimetric analysis (TGA), high-resolution transmission electron microscopy (HR-TEM), vibrating sample magnetometer (VSM), Fourier transform infrared (FT-IR) spectroscopy, inductively coupled plasma (ICP), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The achievements demonstrated that the proposed agents were beneficial to synthesis the derivatives of β-aminoketone. Moreover, it was possible to recover the catalyst by means of simple magnetic decantation quickly. Besides, no reduction in the activity of the catalyst occurred, even though it was utilized in various reactions.     

Spectral and molecular docking studies of nucleic acids/protein binding interactions of a novel organometallic palladium (II) complex containing bioactive PTA ligands: Its synthesis,anticancer effects and encapsulation in albumin nanoparticles

The organometallic palladium complex with nitrogen-containing heterocycles is a potent antitumor agent. Coordination of phosphorus ligands to organometallic complexes increases their hydrophilicity, promotes ligand−DNA interactions and damage level to cancer cells, and blocks division in target cells. In this study, a phosphaadamantane palladium complex ([Pd{(C,N)- (C₁₂H₈NH₂)} (PTA) Cl], PTA = 1,3,5-Triaza-7-phosphaadamantane) ( 2 ) was synthesized via the reaction of biologically active PTA with binuclear palladacycles [Pd₂{(C,N)-(C₁₂H₈NH₂)}₂(μ-Cl)₂] ( 1 ). In vitro studies of the complex with DNA (calf-thymus) explored by UV–Vis, emission titration, circular dichroism and helix melting methods showed that the complex interacts with DNA via an intercalative mechanism. Furthermore, competitive binding studies using warfarin, digoxin and ibuprofen site markers containing definite binding sites revealed the binding of the complex to site I on bovine serum albumin. The in vitro release mechanism of the palladium complex exhibited a biphasic pattern characterized by an initial burst release followed by a slower sustained release. Ultimately, in vitro evaluation of cytotoxicity and cell death showed that the complexes were able to decrease the viability of human cancer cell lines (MCF-7 and Jurkat) in a dose-dependent manner, but lower decreases were observed in the viability of normal fibroblast cells ASF-4 at the dosages evaluated. Finally, the order of in vitro anticancer activities was found to be consistent with the DNA-binding affinities.     

Choline chloride-urea deep eutectic solvent as an efficient media for the synthesis of propargylamines via organocuprate intermediate

A facile method for the synthesis of various propargylamines derivatives with different structural parts has been reported. The reaction has consisted of one-pot coupling between aldehydes, secondary amines and terminal alkynes using CuCl as a catalyst and choline chloride/urea DES as a cheap and biocompatible reaction media. The procedure is free of using toxic solvents and used CuCl as an available, inexpensive and non-toxic catalyst. Using this methodology, 15 different propargylamine derivatives were successfully synthesized at 60 °C in 15 hr, mostly in good yields.     

Catalytic reduction of 4-nitrophenol by means of nanostructured polymeric Schiff base complexes

Polymeric Schiff base ligands were synthesized using 2-hydroxybenzaldehyde (L²), 4-hydroxy-3-methoxybenzaldehyde (L⁴), and 5-aminoisophthalic acid. The nanostructured complexes were then synthesized using Ni²⁺, Cu²⁺, and Mn³⁺. The ligands and complexes thus synthesized were characterized using Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis (TGA), and field-emission scanning electron microscopy. The thermal stability of the complexes was confirmed using TGA. The synthesized complexes were used as catalysts in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol in an aqueous phase in the presence of sodium borohydride. In this work, the catalytic reactivity of nanostructured complexes was compared using the rate constant (k) of the reaction. The reaction time for the reduction of 4-NP was 5–14 min for different complexes. The catalytic system based on Ni²⁺/2-hydroxybenzaldehyde was the most active and displayed reusability in the reduction of 4-NP.     

An inorganic–organic hybrid material based on a Keggin-type polyoxometalate@Dysprosium as an effective and green catalyst in the synthesis of 2-amino-4H-chromenes via multicomponent reactions

A novel inorganic–organic hybrid, [Dy₄(PDA)₄(H₂O)₁₁(SiMo₁₂O₄₀)]·7H₂O denoted as (POM@Dy-PDA), based on a lanthanide cluster, a Keggin-type polyoxomolybdate, and PDA (1,10-phenanthroline-2,9-dicarboxylic acid) was prepared and fully characterized by elemental analysis, Fourier-transform infrared and UV–Vis spectroscopies, thermogravimetric analysis, powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction. The structural analysis study showed that the [SiMo₁₂O₄₀]⁴⁻ ions reside in the interspace between two cationic layers as discrete counterions and are not coordinated to the rare-earth ions. Significantly, this hybrid catalyst is a rare case of an inorganic–organic hybrid polyoxometalate (POM) with a PDA ligand based on CSD search (CSD version 5.40/November2018). The hybrid catalyst was further characterized via powder X-ray diffraction (PXRD) pattern at room temperature which indicated the good phase purity of the catalyst. BET and Langmuir surface area analysis indicate surface area of POM@Dy-PDA 6.6 and 51.3 m2g-1, respectively. The catalytic activity of the hybrid catalyst was successfully examined in the synthesis of 2-amino-4H-chromene derivatives through a multicomponent reaction. A three-component, one-pot reaction involving differently substituted benzaldehydes, resorcinol/α-naphthol/β-naphthol/4-hydroxycoumarin/3-methyl-4H-pyrazole-5(4H)-one, and malononitrile or ethyl cyanoacetate in the presence of a catalytic quantity of the aforementioned hybrid catalyst in EtOH/H₂O under reflux condition gave the corresponding highly functionalized 2-amino-4H-chromenes in satisfactory yields. The catalyst can be reused several times without appreciable loss in its catalytic activity.     

Thermally stimulated depolarization current spectra of cross-linked polyethylene and the influence of cross-linking byproducts

Cross-linked polyethylene (XLPE) is notable for its use as power cable insulation. Its longevity is limited by space charge buildup linked to impurities such as the byproducts left behind by the cross-linking agent dicumyl peroxide (DCP). The goal of this work is to determine the impacts of these byproducts on charge trapping and detrapping in XLPE using the thermally stimulated depolarization current technique. XLPE with byproducts has one source of trapped charge, which originates from the byproducts. XLPE that was thermally treated via degassing exhibits two other sources of trapped charge, which are charge injection and dipolar relaxations. Oxidation from degassing was shown to control the trapping from these sources, which is useful knowledge for processing this material prior to its use. Reintroducing acetophenone, one of the major byproducts of DCP, suppresses those two peaks once more, showing that it controls the overall space charge buildup characteristics in XLPE.     

Naturally occurring organic acids for organocatalytic synthesis of pyrroles via Paal–Knorr reaction

Research on Chemical Intermediates - In this study, common naturally occurring organic acids, namely oxalic, malonic, succinic, tartaric and citric acid (as safe, inexpensive, and biodegradable...     

Technological and economical analysis of flare recovery methods,and comparison of different steam and power generation systems

Journal of Thermal Analysis and Calorimetry - One of the most important environmental issues in the oil, gas, and petrochemical industries is the appropriate disposal of waste hydrocarbon gases in...     

Heat transfer enhancement of a microchannel heat sink with the combination of impinging jets,dimples, and side outlets

Journal of Thermal Analysis and Calorimetry - With the rapid increasing heat fluxes released from micro electronic devices, thermal management of electric components faces huge challenge. High...