NaIO4-mediated selective oxidation of alkylarenes and benzylic bromides/alcohols to carbonyl derivatives using water as solvent

A new transition-metal-free, sodium metaperiodate (NaIO4)-mediated direct oxidation of methylarenes and benzylic bromides to the corresponding aromatic carboxylic acids is described. Under the same reaction conditions, benzylic alcohols are selectively oxidized to afford the corresponding aldehydes in good yields without undergoing overoxidation. Unprecedentedly, oxidation of benzyl bromide, toluene, or benzyl alcohol with NaIO4 underwent nuclear bromination followed by oxidation to give 4-bromobenzoic acid in 60-79% yields.     

Redox magnetohydrodynamic enhancement of stripping voltammetry: toward portable analysis using disposable electrodes, permanent magnets, and small volumes

The use of redox magnetohydrodynamics (MHD) to enhance the anodic stripping voltammetry (ASV) response of heavy metals has been investigated, with respect to achieving portability: disposable electrodes consisting of screen-printed carbon (SPC) on a low temperature co-fired ceramic (LTCC) substrate, small volumes, and permanent magnets. The analytes tested (Cd(2+), Cu(2+), and Pb(2+)) were codeposited on SPC with Hg(2+) to form a Hg thin film electrode. High concentrations of Fe(3+) were used to produce a high cathodic current which generates a significant Lorentz force in the presence of a magnetic field. This Lorentz force induces solution convection during the deposition step, enhancing the mass transport of analytes to the electrode and increasing their preconcentrated quantity in the mercury thin film. Therefore, larger ASV peaks and improved sensitivities are obtained, compared to analyses performed without a magnet. The effects on ASV signal of varying Hg(2+) concentration (0.10 and 1.0 mM), deposition time (10-600 s), and electrode surface roughness were investigated. In addition, analyses were performed using a real lake water matrix. By using the disposable LTCC-SPC working electrodes in small volumes (150 microL) and with small permanent magnets (0.78 T), peak areas were increased by 75% when compared to the signal obtained in the absence of a magnetic field. A limit of detection of 25 nM for Cd(2+) was observed with only a 1 min preconcentration time.     

Acute and sub-acute toxicity study of hydroalcoholic fruit extract of Pithecellobium dulce

This study was carried out to evaluate the acute and sub-acute toxicity profile of the hydroalcoholic fruit extract (HAEPD) of Pithecellobium dulce (Leguminosae). Albino rats were treated orally with 100, 200 and 500?mg?kg(-1) bodyweight (BW) of HAEPD for 90 days to assess its sub-acute toxicity. HAEPD at single doses of 100, 500, 1000, 2000 and 4000?mg?kg(-1) BW was also administered to rats to assess its acute toxicity. The rats were observed for physical discomfort, BW change and feeding habits. Pithecellobium dulce did not cause any abnormal changes in haematological or biochemical parameters. Pathologically, no gross abnormality in the tissue architecture was observed. The LD(50) was found to be 3916?mg?kg(-1) BW and potential effective doses for efficacy studies are 100 and 300?mg?kg(-1) BW as the minimum and maximum doses, respectively. It is concluded that HAEPD can be used safely for experimental and clinical trials.     

Polyprotic acid catholyte for high capacity dual-electrolyte Li-air batteries

The polyprotic acid H(3)PO(4) in a Li(2)SO(4) supporting electrolyte has been effectively utilized as a catholyte donating three protons in dual-electrolyte Li-air cells. The cell offers a high capacity of 740 mA h g(-1) at an average cell voltage of 3.3 V with good rechargeability and stability.     

Synthesis of the anti-influenza agent (-)-oseltamivir free base and (-)-methyl 3-epi-shikimate

A new enantioselective synthesis of the anti-influenza agent (-)-oseltamivir free base (7.1% overall yield; 98% ee) and (-)-methyl 3-epi-shikimate (16% overall yield; 98% ee) has been described from readily available raw materials. Sharpless asymmetric epoxidation and diastereoselective Barbier allylation of an aldehyde are the key reactions employed in the incorporation of chirality, while the cyclohexene carboxylic ester core was constructed through a ring closing metathesis reaction.     

Microwave-solvothermal synthesis of various polymorphs of nanostructured TiO2 in different alcohol media and their lithium ion storage properties

The various polymorphs (anatase, rutile, and brookite) of TiO(2) with different nanomorphologies have been synthesized by a facile microwave-assisted solvothermal process without surfactants, employing TiCl(4) or TiCl(3) as precursors in various alcohol (ethanol, propanol, butanol, and octanol) media. The samples have been characterized by X-ray diffraction (XRD), electron microscopy, and Brunauer-Emmett-Teller (BET) surface area analysis. The Ti/Cl ion concentration, reaction pH, and size of the alcohol molecule are found to control the morphology, crystal structure, and crystallite size of the TiO(2) particles. Among the various TiO(2) polymorphs synthesized, the rutile TiO(2) spheres built up of nanorods that were synthesized with TiCl(4) in octanol have an average pore size and surface area of, respectively, 5 nm and 404 m(2)/g and exhibit the best electrochemical performance with a capacity of >200 mAh/g after 100 cycles and high rate capability. The excellent electrochemical properties originate from the nanorod-building morphology and mesoporosity of TiO(2) spheres that provide good electrical contact, accommodates the strain smoothly, and facilitates facile lithium-ion diffusion.     

Producing highly linear polyethylenes by using t‐butyl‐functionalized 2,6‐bis(imino)pyridylchromium(III) chlorides

A new family of t‐butyl substituted chromium(III) chloride complexes ( Cr1 – Cr6 ), bearing 2‐(1‐(2,6‐dibenzhydryl‐4‐t‐butylphenylimino)ethyl)‐6‐(1‐(arylimino)ethyl)pyridine (aryl = 2,6‐Me₂C₆H₃ Cr1 , 2,6‐Et₂C₆H₃ Cr2 , 2,6‐i‐Pr₂C₆H₃ Cr3 , 2,4,6‐Me₃C₆H₂ Cr4 and 2,6‐Et₂‐4‐MeC₆H₂ Cr5 ) or 2,6‐bis(1‐(2,6‐dibenzhydryl‐4‐t‐butylphenylimino)ethyl)pyridine ( Cr6 ), has been synthesized by the reaction of CrCl₃·6H₂O in good yield with the corresponding ligands ( L1 – L6 ), respectively. The molecular structures of Cr2 and Cr6 were characterized by X‐ray diffraction highlighted a distorted octahedral geometry with the coordinated N,N,N ligand and three bonded chlorides around the metal center. On activation with modified methylaluminoxane or triisobutyl aluminum, most of the chromium precatalysts exhibit good activities toward ethylene polymerization and produce linear polyethylenes with high‐molecular weight. In addition, an in‐depth catalytic evaluation of Cr2 was conducted to investigate how cocatalyst type and amount, reaction temperature, and run time affect the catalytic activities and polymer properties. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1049–1058     

A New Oxynitride Compound of Molybdenum,Na3MoO3N — Synthesis via the Azide Route and Structure

The new oxynitride compound of molybdenum, Na₃MoO₃N was prepared via the azide route. Its crystal structure was solved and refined from X‐ray powder data (orthorhombic, Pmn2₁, a = 724.63(1), b = 624.98(1), c = 563.86(1) pm, R_p: 9.04 %; R_wp: 9.83 %). The structure consists of isolated [MoO₃N]^3— tetra‐hedra which are separated by Na⁺ cations, also in a tetrahedral coordination. It is isostructural to Na₃WO₃N which is a lower symmetry derivative of the Cu₃AsS₄ structure. Due to the small difference in the scattering lengths of nitrogen and oxygen, we were unable to distinguish between fully ordered, fully disordered, or partially ordered anions. However, from the positive SHG responses, we can deduce the acentric space group being the correct one and based on the lattice energy calculations, we have been able to identify the position most probably being occupied by nitrogen.     

Pressure Transients in Gas Phase Adsorptive Reactors

The role of pressure and flow transients caused by strong adsorption on the behavior of gas phase adsorptive reactors was studied using a staged model. The general gas phase reaction A + B C is considered for two cases: (1) the product C is adsorbed and (2) both reactants A and B are adsorbed. Strong adsorption of one or more components causes a decrease in the pressure(s) in the stage(s). The pressure decrease causes variations in the inlet and outlet flow rates and in the case of multiple stages, it causes variations in the flows between tanks. In accordance with Le Chatelier's principle, the pressure decrease aids or inhibits product formation depending on whether there is an increase or decrease in total moles by reaction. Reactant flow into the section where adsorption occurs increases because of increased pressure drop behind the adsorption front. However, the residence time of the reactants behind the adsorption front is lower because of the higher velocity. The flow variations can aid or hinder product formation depending on the specific conditions. Thus, the adsorption-caused pressure variations directly modify reaction rates and product concentrations and, also indirectly, by causing flow variations which affect reaction rates and product concentrations. This study highlights the need to include pressure variations when modeling gas phase adsorptive reactors if adsorption is strong irrespective of the net change in the total moles by reaction. It also demonstrates a method to incorporate axial pressure drop in staged models.     

Thirteenth IUPAC Conference on Chemical Thermodynamics Joint Meeting with the Twenty-fifth AFCAT Conference July 17–22, 1994 Clermont-Ferrand,France

Meeting Notice

Thirteenth IUPAC Conference on Chemical Thermodynamics Joint Meeting with the Twenty-fifth AFCAT Conference July 17–22, 1994 Clermont-Ferrand, France