Effect of dissolved organic matter from Guangzhou landfill leachate on sorption of phenanthrene by montmorillonite

To investigate the effect of dissolved organic matter (DOM) on the adsorption of phenanthrene (PHE) by montmorillonite (MMT), organic clay complex was prepared by associating montmorillonite with DOM extracted from landfill leachate. Both the raw MMT, DOM, and MMT complex (DOM-MMT) were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), X-ray photo-emission spectroscopy (XPS), and scanning electron microscope (SEM). Batch adsorption studies were carried out on the adsorption of PHE as a function of contact time, temperature, and adsorbent dose. The sorption of PHE on complex was rapid, and the kinetics could be described well by the Pseudo-first-order model (R(2)>0.99), with an equilibrium time of 120 min. The adsorption isotherm was in good agreement with the Henry equation and Freundlich equation. Also, thermodynamic studies showed that the adsorption process was exothermic and spontaneous in nature. Compared with MMT, the adsorption capacity of DOM-MMT complex for PHE was greatly enhanced. The effects of DOM on PHE sorption by MMT may be attributed to the changes in the surface structure, the specific surface area, the hydrophobic property, and the average pore size of MMT. A series of atomistic simulations were performed to capture the structural and functional qualities observed experimentally.     

Unsaturated iridium pyridinedicarboxylate pincer complexes with catalytic activity in borylation of arenes

Unsaturated σ,π-cyclooctenyl and hydrido Ir(III) complexes bearing an unusual tridentate dianionic ONO pincer-type ligand have been straightforwardly obtained from 2,6-pyridinedicarboxylic acid and standard Ir(I) starting materials. These complexes efficiently catalyzed the arene C-H borylation under thermal conditions.     

Supported Au nanoparticles as efficient catalysts for aerobic homocoupling of phenylboronic acid

Au nanoparticles with small sizes (1-4 nm) were effectively formed on Mg-Al mixed oxides (Au/MAO), which showed superior catalytic performances and good recyclability in aerobic homocoupling of phenylboronic acid.     

Autocatalytic Intermolecular versus Intramolecular Deprotonation in C?H Bond Activation of Functionalized Arenes by Ruthenium(II) or Palladium(II) Complexes

The activation of the C? H bond of 1‐phenylpyrazole ( 2 ) and 2‐phenyl‐2‐oxazoline ( 3 ) by [Ru(OAc)₂(p‐cymene)] is an autocatalytic process catalyzed by the co‐product HOAc. The reactions are indeed faster in the presence of acetic acid and water but slower in the presence of a base K₂CO₃. A reactivity order is established in the absence of additives: 2‐phenylpyridine>2‐phenyl‐2‐oxazoline>1‐phenylpyrazole (at RT). The accelerating effect of added acetate ions reveals an intermolecular deprotonation after C? H bond activation by a cationic Ru^II center (S_E3 mechanism). The reactions of 1‐phenylpyrazole and 2‐phenyl‐2‐oxazoline first lead to the neutral cyclometalated complexes A₂ and A₃ ligated by one acetate. The latter dissociate to the cationic complexes B₂ ⁺ and B₃ ⁺ , respectively, and acetate. A slow incorporation of one or two D atoms into 2 , 3 , and 2‐phenylpyridine ( 1 ) was observed in the presence of deuterated acetic acid. The “reversibility” of the C? H bond activation/deprotonation takes place from the cationic complexes B _n ⁺ (n=1–3). They are also involved in oxidative additions to PhI, which are rate‐determining and lead to the mono‐ and bis‐phenylated products at high temperatures. A general mechanism is proposed for the arylation of arenes 1–3 catalyzed by [Ru(OAc)₂(p‐cymene)]. In contrast, the reaction of Pd(OAc)₂ with 2‐phenylpyridine ( 1 ), is much faster: Pd(OAc)₂>[Ru(OAc)₂(p‐cymene)]. Since the kinetics is not affected by added acetates, the reaction proceeds through a CMD mechanism assisted by a ligated acetate (intramolecular process) and is irreversible. A bis‐cyclometalated Pd^II^Pd^II dimer D′₁ is formed whose bielectronic electrochemical oxidation leads to a [Pd^III^Pd^III]²⁺ dimer, in agreement with the result of a reported chemical oxidation used in arene functionalizations catalyzed by Pd(OAc)₂.     

Molecular dynamics simulations of the solution-air interface of aqueous sodium nitrate

Molecular dynamics simulations have been used to investigate the behavior of aqueous sodium nitrate in interfacial environments. Polarizable potentials for the water molecules and the nitrate ion in solution were employed. Calculated surface tension data at several concentrations are in good agreement with measured surface tension data. The surface potential of NaNO3 solutions at two concentrations also compare favorably with experimental measurements. Density profiles suggest that NO3- resides primarily below the surface of the solutions over a wide range of concentrations. When the nitrate anions approach the surface of the solution, they are significantly undercoordinated compared to in the bulk, and this may be important for reactions where solvent cage effects play a role such as photochemical processes. Surface water orientation is perturbed by the presence of nitrate ions, and this has implications for experimental studies that probe interfacial water orientation. Nitrate ions near the surface also have a preferred orientation that places the oxygen atoms in the plane of the interface.     

An efficient entry to furo[2,3-d]pyrimidines via inverse electron demand Diels–Alder reactions of 2-aminofurans with 1,3,5-triazines

Furo[2,3-d]pyrimidines were readily prepared via an inverse electron demand Diels–Alder (IDA) reaction between 2-aminofurans and 1,3,5-triazines. 2-Aminofurans proved to be productive dienophiles leading to the IDA product in moderate to good yields. This study further expanded the scope of 1,3,5-triazine IDA reactions with five-membered aromatic heterocycles as dienophiles.     

Electronic structure, statistical mechanical simulations, and EXAFS spectroscopy of aqueous potassium

We investigate the solvation structure of aqueous potassium ions, using a combination of electronic structure calculations, statistical mechanical simulations with a derived polarizable empirical potential and experimental measurement of the extended X-ray absorption fine structure (EXAFS) spectra. The potassium K-edge (at 3,608 eV) EXAFS spectra were acquired on the bending magnet of sector 20 at the Advanced Photon Source, at ambient conditions and for the concentrations of 1 and 4 m KCl. We focus on the coordination distances and the degree of disorder of the first hydration shell as determined by electronic structure calculations, molecular dynamics simulations and experimental measurement. Finally, we characterize the changes of the structure in the first hydration shell with increasing temperature as predicted by molecular simulation     

Benzaldehyde derivatives from Eurotium rubrum, an endophytic fungus derived from the mangrove plant Hibiscus tiliaceus

Four new (1-4) and seven known (5-11) benzaldehyde derivatives were characterized from the liquid fermentation cultures of Eurotium rubrum, an endophytic fungus that was isolated from the inner tissue of stems of the mangrove plant Hibiscus tiliaceus. The structures of these compounds were determined by extensive analysis of their spectroscopic data. Among these metabolites, compound 1, which was named as eurotirumin, possesses a new carbon skeleton with a cyclopentabenzopyran ring system.     

Modification of Rubber by Cardanol-Formaldehyde Resins and Epoxidized Cardanol

Abstract

Cardanol-formaldehyde resin (CF) and cardanol glycidylether (CGE) have been synthesized for reinforcing natural rubber (NR), a blend of NR and styrene-butadiene rubber (SBR), and nitrile-butadiene rubber (NBR). The novolac CF resin reinforced the NR, SBR, and NBR. The resolic CF is not only a reinforcing agent but also a hardener (crosslinking agent) for NBR by means of the methylol groups of CF with the CN- group of NBR. The CGE resin was synthesized by the epoxidation of cardanol by epichlorohydrin; it could be used as a reinforcing agent for NR and for crosslinking maleinized NR. The results of estimates of the physical properties of the vulcanisate, their DSC diagrams, and SEM showed the enhanced properties of the final products.     

Characterization and antimicrobial activity of silver nanoparticles prepared by a thermal decomposition technique

Recently, there has been an increasing need of efficient synthetic protocols using eco-friendly conditions including low costs and green chemicals for production of metal nanoparticles. In this work, silver nanoparticles (silver NPs) with average particle size about 10 nm were synthesized by using a thermal decomposition technique. Unlike the colloidal chemistry method, the thermal decomposition method developed has advantages such as the high crystallinity, single-reaction synthesis, and easy dispersion ability of the synthesized NPs in organic solvents. In a modified synthesis process, we used sodium oleate as a capping agent to modify the surface of silver NPs because the oleate has a C₁₈ tail with a double bond in the middle, therefore, forming a kink which is to be effective for aggregative stability. Importantly, the as-synthesized silver NPs have demonstrated strong antimicrobial effects against various bacteria and fungi strains. Electron microscopic studies reveal physical insights into the interaction and bactericidal mechanism between the prepared silver NPs and tested bacteria in question. The observed excellent antibacterial and antifungal activity of the silver NPs make them ideal for disinfection and biomedicine applications.