Aerobic {Mo72V30} nanocluster‐catalysed heterogeneous one‐pot tandem synthesis of benzimidazoles

A novel heterogeneous one‐pot protocol is developed for tandem aerobic synthesis of benzimidazoles through dehydrogenative coupling of primary benzylic alcohols and aromatic diamines co‐catalysed by Keplerate‐type {Mo₇₂V₃₀} polyoxometalate and N‐hydroxyphthalimide (NHPI). The catalytic system also works well for the synthesis of benzimidazoles using benzaldehydes, as commonly used starting materials, in the absence of NHPI. The high activity of the solid nanocluster provides standard conditions avoiding current limitations of oxidation methods including high catalyst loadings. The spectral results and leaching experiments revealed that the nanocapsule preserved its structural integrity after being reused in consecutive runs.     

Performance enhancement of thin‐film composite membranes in water desalination process by wood sawdust

In this study, polysulfone/wood sawdust (PSf/WSD) mixed matrix membrane (MMM) was prepared as a novel substrate layer of thin‐film composite (TFC) membrane in water desalination. The main aim was to evaluate how different amounts of WSD (0‐5 wt%) and PSf concentrations (12‐16 wt%) in the porous substrate affect the properties of the final TFC membranes in the separation of organic and inorganic compounds. Morphological and wettability studies demonstrated that the addition of small amount of WSD (less than or equal to 1 wt%) in the casting solution resulted in more porous but similar hydrophobic substrates, while high loading (greater than or equal to 2 wt%) of WSD not only changed the substrate wettability and morphology but also increased and decreased the swelling and mechanical properties of substrate layer. Therefore, PA layer formed thereon displayed extensively varying film morphology, interfacial properties, and separation performance. Based on approximately stable permeate flux (ASPF) and apparent salt rejection efficiency (ASRE), the best TFC membrane was prepared over the substrate with 12 to 14 wt% of PSf and around 0.5 to 1 wt% of WSD. Although notable improvements in permeate flux were obtained by adding a small amount of sawdust, the results clearly indicate that the salt rejection mechanism of TFC membrane was different from the glycerin rejection mechanism. Furthermore, durability results of TFC membranes showed that in continuous operation for 30 days, TFC‐14/0.5 and TFC‐14/01 have the maximum plateau levels of stable permeate flux and salt rejection among the all TFC membranes.     

Synthesis and crystal structure of a new N-(2,6-dichlorobenzoyl)-N′,N″-bis(pyrrolidinyl)-phosphoric triamide as a carrier and competitive bulk liquid membrane transport of six metal cations

The competitive metal ion transport experiments of Co⁺², Cd⁺², Ag⁺, Pb⁺², Ni⁺², and Cu⁺² were carried out by N-(2,6-dichlorobenzoyl)-N′,N″-bis(pyrrolidinyl)-phosphoric triamide as a carrier in organic membrane phase. 2,6-Cl₂C₆H₃C(O)NHP(O)[NC₄H₈]₂ has been synthesized and characterized by mass spectrometry IR spectroscopy and single crystal X-ray diffraction. The asymmetric unit of title phosphoric triamide contains one symmetrically independent molecule. The source phase contained equimolar concentrations of metal ions at pH 5 and the receiving phase being buffered at pH 3. The following solvents were examined as membrane: chloroform (CHCl₃), nitrobenzene (NB), 1,2-dichloroethane (1,2-DCE), dichloromethane (DCM), dichloromethane/1,2-dichloroethane (DCM/1,2-DCE). The obtained results show that the selectivity and efficiency of transport for these heavy metal cations change with the nature of the ligand and also the organic solvents, which were used as liquid membrane in these experiments. A good selectivity was observed for Pb⁺² cation by this ligand in all membrane systems. Moreover, the selectivity of metal cations in DCM is higher than other solvents. A non-linear relationship was found between the percent of transport of Pb⁺² cation by this ligand and the compositions of DCM/1,2-DCE and binary solution by this ligand. The effect of several factors such as the nature of carboxylic acids (stearic, fumaric and maleic acid) as surfactant in the membrane phase and the time of transport on transport efficiency of Pb⁺² cation were investigated.     

Ultrasonic degradation of solutions of poly(vinyl acetate) in dioxan: The effects of the temperature and polymer concentration

The ultrasonic degradation of poly(vinyl acetate) (PVAc) solutions was carried out in dioxan at 25, 30, 35, 40, and 45 °C to investigate the effects of the temperature and solution concentration on the rate of degradation. The kinetics of degradation were studied by viscometry. The calculated rate constants indicated that the degradation rate of the PVAc solutions decreased as the temperature and solution concentration increased. The calculated rate constants were correlated in terms of the concentration, temperature, vapor pressure of dioxan, and relative viscosity of the PVAc solutions. This degradation behavior was interpreted in terms of the vapor pressure of dioxan, the viscosity, and the concentration of the polymer solutions. With increasing temperature, the vapor pressure of the solvent increased, and so the vapor entered the cavitation bubbles during their growth. This caused a reduction in collapsing shock because of a cushioning effect; therefore, the rate of degradation decreased. As the solution concentration increased, the viscosity increased and caused a reduction in the cavitation efficiency, and so the rate of degradation decreased. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 445–451, 2004     

PVA-clay nanocomposite hydrogels for wound dressing

Polymer gels as soft biomaterials have found diverse applications in biomedical field, e.g. in management and care of wound as wound dressing.The recent researches on nanocomposite materials have shown that some properties of polymers and gels significantly improve by adding organoclay into polymeric matrix. In this work, in order to obtain wound dressing with better properties, nanocomposite hydrogel wound dressing was prepared using combination of polyvinyl alcohol hydogel and organoclay, i.e. Na-montmorillonite, via the freezing-thawing method. The effect of organoclay quantity on the structural, swelling, physical and mechanical properties of nanocomposite hydrogel wound dressing was investigated. The results showed that the nanocomposite hydrogels could meet the essential requirements for the reasonable wound dressing with some desirable characteristics such as relatively good swelling, appreciated vapour transmission rate, excellent barrierity against microbe penetration and mechanical properties. The results also indicated that the quantity of the clay added to the nanocomposite hydrogel is the key factor in obtaining such suitable properties required for wound dressing.     

<Emphasis Type="Italic">Stachys lavandulifolia</Emphasis> and <Emphasis Type="Italic">Lathyrus</Emphasis> sp. Mediated for Green Synthesis of Silver Nanoparticles and Evaluation Its Antifungal Activity Against <Emphasis Type="Italic">Dothiorella sarmentorum</Emphasis>

In this study, silver nanoparticles (AgNPs) were biosynthesized using Stachys lavandulifolia and Lathyrus sp. The first sign of the reduction of silver ions to AgNPs was the change in color of S. lavandulifolia and Lathyrus sp. extracts changed into dark brown and auburn after treating with silver nitrate, respectively. The UV–Vis spectroscopy of reaction mixture (extract+silver nitrate) produced by S. lavandulifolia and Lathyrus sp. showed the strong adsorption peaks at ?440 and 420 nm, respectively. The transmission electron microscope images showed the synthesis of AgNPs using S. lavandulifolia and Lathyrus sp. with an average size of 7 and 11 nm, respectively. The result of X-ray diffraction pattern showed four diffraction peaks at 38°, 44°, 64°, and 77° for both types of biosynthesized AgNPs. Fourier transform infrared spectroscopy showed the possible role of involved proteins and polyhydroxyl functional groups in the synthesis process of AgNPs. Inductively coupled plasma analysis determined the conversion rate (percentage) of silver ions to silver nanoparticles in reaction mixtures of S. lavandulifolia and Lathyrus sp. 99.73 and 99.67 %, respectively. In addition, antifungal effect of AgNPs, synthesized by both extracts, was studied separately on mycelial growth of Dothiorella sarmentorum, in a completely randomized design on potato dextrose agar (PDA) medium. The inhibition rate of mycelial growth was strongly depended on the density of AgNPs and it strongly increased with increasing the density of AgNPs in the PDA medium. AgNPs more than 90 % of them inhibited from the mycelia growth of the fungus at the concentration of 40 µg/mL and higher.     

Isopiestic Determination of Osmotic and Activity Coefficients for Solutions of LiCl, LiBr, and LiNO3 in 2-Propanol at 25°C

The osmotic coefficients of lithium chloride, lithium bromide, and lithium nitrate in 2-propanol have been measured by the isopiestic method at 25^°C. Sodium iodide was used as the isopiestic standard. The molality ranges covered were from 0.2 to 1.5 for LiCl and LiBr, and to 1.9 mol-kg^-1 for LiNO₃. The system of equations developed by Clegg–Pitzer and Pitzer were used to fit each set of osmotic coefficients. The experimental osmotic coefficient data are successfully correlated with these models. The parameters from the fit were used to calculate the mean molal activity coefficients.     

Puckering behavior in six new phosphoric triamides containing aliphatic six- and seven-membered ring groups and a database survey of analogous ring-containing structures

The influence of a N heteroatom on the ring conformations of six- and seven-membered aliphatic rings in six new C(O)NHP(O)-based phosphoric triamide structures (analysed by X-ray crystallography) is investigated. Additionally the influence of steric and crystal packing effects is also studied by the analysis of Hirshfeld surfaces. The results are compared to analogous structures with three- to seven- aliphatic membered rings deposited in the Cambridge Structural Database. In the newly determined structures, the six-membered rings only show the near-chair conformation with a maximum deviation of the θ puckering parameter of 4.4° from the ideal chair value of 0°/180°, while the seven-membered rings are found in different conformations such as near-chair, twist chair and twist sofa.     

Evaluation of lithium separation by dispersive liquid–liquid microextraction using benzo-15-crown-5

In this article a dispersive liquid?Cliquid microextraction method was applied for evaluation of lithium separation from aqueous solution. Benzo-15-crown-5 (B15C5) was used as a chelating agent prior to extraction. An appropriate mixture of disperser solvent and extraction solvent were added rapidly into the aqueous sample containing lithium ion; as a result, a cloudy solution was formed which consisted of fine droplets of extraction solvent dispersed entirely into aqueous phase. The mixture was centrifuged and the lithium complex with B15C5 was sedimented at the bottom of the conical sample holder. Then, 2.0?mL of enriched phase containing lithium complex was used for determination of lithium ion by flame atomic absorption spectrometry. The conditions for the microextraction performance were investigated. Under the best optimized conditions, the accepted recovery factors for the lithium obtained, ranged from 37.24 to 99.63?%. Furthermore, high preconcentration factors (7.46?C19.93) were also achieved. The relative standard deviation for three replicate measurements of 0.127?mg?L^?1 of lithium was 2.83?%.     

Chemical Composition of the Essential Oils of <Emphasis Type="Italic">Bunium elegans</Emphasis> and <Emphasis Type="Italic">Bunium caroides</Emphasis>

Analyses of the essential oils of Bunium elegans (Fenzl) Freyn and B. caroides (Boiss.) Hausskn. ex Bornm., using GC, GC/MS, and¹³ C-NMR spectroscopy resulted in identification of their chemical constituents. The oils of both species contain mainly the sesquiterpene hydrocarbons germacrene-D and E-caryophyllene, which amounted to 24.1% and 38% for B. elegans and 22.1% and 26.6% for B. caroides respectively. The oil of B. caroides contained the monoterpenes α-pinene and Z-β-ocimene in 4.1 and 5.9% respectively, while traces of monoterpenes were detected for B. elegans. On the other hand, in B. caroides the phenylpropanoid derivatives asaricin (7.5%) and dillapiole (10.2%) were among the major constituents. __________ Published in Khimiya Prirodnykh Soedinenii, No. 4, pp. 335–336, July–August, 2005.