Rapid conversion of cellulose to 5-hydroxymethylfurfural using single and combined metal chloride catalysts in ionic liquid

Direct conversion of cellulose into 5-hydroxymethylfurfural(HMF) was performed by using single or combined metal chloride catalysts in 1-ethyl-3-methylimidazolium chloride(Cl) ionic liquid.Our study demonstrated formation of 2-furyl hydroxymethyl ketone(FHMK),and furfural(FF) simultaneously with the formation of HMF.Various reaction parameters were addressed to optimize yields of furan derivatives produced from cellulose by varying reaction temperature,time,and the type of metal chloride catalyst.Catalytic reaction by using FeCl3 resulted in 59.9% total yield of furan derivatives(HMF,FHMK,and FF) from cellulose.CrCl3 was the most effective catalyst for selective conversion of cellulose into HMF(35.6%) with less concentrations of FHMK,and FF.Improving the yields of furans produced from cellulose could be achieved via reactions catalyzed by different combinations of two metal chlorides.Further optimization was carried out to produce total furans yield 75.9% by using FeCl3/CuCl2 combination.CrCl3/CuCl2 was the most selective combination to convert cellulose into HMF(39.9%) with total yield(63.8%) of furans produced from the reaction.The temperature and time of the catalytic reaction played an important role in cellulose conversion,and the yields of products.Increasing the reaction temperature could enhance the cellulose conversion and HMF yield for short reaction time intervals(5~20 min).     

Identification of ligands that target the HCV-E2 binding site on CD81

Hepatitis C is a global health problem. While many drug companies have active R&D efforts to develop new drugs for treating Hepatitis C virus (HCV), most target the viral enzymes. The HCV glycoprotein E2 has been shown to play an essential role in hepatocyte invasion by binding to CD81 and other cell surface receptors. This paper describes the use of AutoDock to identify ligand binding sites on the large extracellular loop of the open conformation of CD81 and to perform virtual screening runs to identify sets of small molecule ligands predicted to bind to two of these sites. The best sites selected by AutoLigand were located in regions identified by mutational studies to be the site of E2 binding. Thirty-six ligands predicted by AutoDock to bind to these sites were subsequently tested experimentally to determine if they bound to CD81-LEL. Binding assays conducted using surface Plasmon resonance revealed that 26 out of 36 (72 %) of the ligands bound in vitro to the recombinant CD81-LEL protein. Competition experiments performed using dual polarization interferometry showed that one of the ligands predicted to bind to the large cleft between the C and D helices was also effective in blocking E2 binding to CD81-LEL.     

Prearranged Glycosides,Part 10. Intramolecular Glycosylation with Cellobiosyl,Lactosyl, and Maltosyl Donors

ABSTRACT

Acetyl protected 1,2-O-(1-methoxyethylidene)-disaccharides 1 of maltose, cellobiose, and lactose, respectively were converted via the corresponding benzyl protected couterparts 2, the benzyl protected phenyl 2-O-acetyl- 3 and 2-O-unprotected 1-thio-glycoside disaccharides 4 into 2-O-succinoylated disaccharides 5. The latter were esterified with benzyl 2-O-benzoyl-4,6-di-O-benzylidene-α-D-glucopyranoside (6) to afford succinyl linked derivatives 7 the benzylidene groups of which were regioselectively opened to give prearranged glycoside trisaccharides 8. Intramolecular glycosylation of the latter with N-iodosuccinimide resulted in exclusive formation of the corresponding α-(1→4)-linked trisaccharides 9. No influence of the donor moiety on the diastereoselectivity of the intramolecular glycosylation was observed.     

Inhibition effect of horehound (Marrubium vulgare L.) extract towards C38 steel corrosion in HCl solution

The corrosion inhibition properties of horehound (Marrubium vulgare L.) extract (HE) in 1 M hydrochloric acid medium was carried out using electrochemical methods (polarization curve and electrochemical impedance spectroscopy). Experiments were performed by concentration of the inhibitor and temperature effect. The results showed variation in inhibition performance of this plant extract. The Langmuir model was tested to describe the adsorption behavior of the inhibitor on the C38 steel surface. Some thermodynamic functions of dissolution processes were also determined.     

Synthesis of two-dimensional gallium nitride via spin coating method: influences of nitridation temperatures

This paper reports the synthesis and characterization of gallium nitride (GaN) thin films deposited on p-type silicon (100) substrates by using low cost spin coating method under various nitridation temperatures. This work demonstrated that spin coating with the new prepared precursor solution can be used as a versatile method for the successfully growth of GaN thin films. Furthermore, the influence of varying nitridation temperatures on the structural, morphological, and optical properties of synthesized GaN thin films were studied in this work. The GaN thin films were characterized by X-ray diffraction, field-emission scanning electron microscopy, atomic force microscopy, photoluminescence and Raman spectroscopy. All the characteristics of the GaN thin films were effectively improved with the increasing of the nitridation temperatures from 750 to 950 °C and degraded at temperature of 1,050 °C. The measured results show that nitridation temperature plays an important role in improving the crystalline quality of the GaN thin films and the most efficient nitridation temperature was at 950 °C.     

Intrinsic adsorption properties of CO2 on 5A and 13X zeolite

Data for the adsorption of CO₂ on 5A (CaA) and 13X (NaX) zeolite are critically evaluated. In addition, fresh data for the adsorption of CO₂ on 13X zeolite is reported. Three intrinsic properties are examined: q _max , the saturation loading, K _H , the Henry constant, and (?ΔH) _q , the isosteric heat of sorption. Below a reduced temperature T _r , of 0.9, the q _max values for both 5A and 13X zeolites are similar to theoretical values that may be derived using zeolitic crystallographic properties and the sorbate density calculated using the Rackett equation. For the region 0.9 ≤ Tr ≤ 1.0, the calculated q _max values exceed the theoretical values similarly calculated, indicating that the molecules have a smaller molar volume than in a similar liquid phase. This is a similar result to that observed in ionic liquids. Linear regressed equations are derived for q _max for the region 0.9 ≤ Tr ≤ 1.25. The Henry constant values for 5A are remarkably consistent for the five studies examined, with a correlation coefficient, R, of 0.999 for the van’t Hoff equation, but for the seven studies examined in 13X the data is more disperse as indicated by a correlation coefficient R of 0.899 for the van’t Hoff equation. The values of (?ΔH) _q , the isosteric heat of sorption are in agreement with the literature. An explanation is advanced for the discrepancy between the higher heats of sorption values obtained calorimetrically from those obtained from isosteric adsorption studies. Finally, the fresh data is observed to fit the Toth model with regression coefficients of 0.999. However, the parameters obtained for the Toth equation by regression are significantly different from the intrinsic properties derived earlier, indicating the difficulty of deriving intrinsic parameters from isotherm fits.     

Q‐symmetry and conditional Q‐symmetries for Drinfel'd–Sokolov–Wilson system

We study in this paper the Q‐symmetry and conditional Q‐symmetries of Drinfel'd–Sokolov–Wilson equations. The solutions which we obtain in this paper take the form of convergent power series with easily computable components. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and performance of electroless Ni–P–TiCN composite coatings on Al substrate

Electroless Ni–P and Ni–P–TiCN composite coatings have been deposited successfully on Al substrates. Scanning electron microscopy (SEM) and energy dispersive X‐ray (EDX) techniques were applied to study the surface morphology and the chemical composition of the deposited films. Moreover, X‐ray diffraction (XRD) proved that Ni–P and Ni–P–TiCN deposits have amorphous structures. The properties of Ni–P–TiCN/Al composite films such as hardness, corrosion resistance and electrocatalytic activity were examined and compared with that of Ni–P/Al film. The results of hardness measurements reveal that the presence of TiCN particles with Ni–P matrix improves its hardness. Additionally, the performance against corrosion was examined using Tafel lines and electrochemical impedance spectroscopy techniques in both of 0.6 M NaCl and a mixture of 0.5 M H₂SO₄ with 2 ppm HF solutions. The results indicate that the incorporation of high dispersed TiCN particles into Ni–P matrix led to a positive shift of the corrosion potential and an increase in the corrosion resistance for all aluminum substrates after their coating with Ni–P–TiCN. In addition, Ni–P–TiCN/Al electrodes showed a higher electrochemical catalytic activity and stability toward methanol oxidation in 0.5 M NaOH solution compared with that of Ni–P/Al. Copyright © 2014 John Wiley & Sons, Ltd.     

Dynamic Interfacial Behavior of Poly(oxyethylene) Lauryl Ether Based Surfactant Mixtures

The adsorption behavior of binary mixtures comprising nonionic surfactants at the air–water interface has been studied by bubble pressure tensiometry at concentrations above and below their critical micelle concentrations. Surfactants with the same hydrocarbon chains but different degree of ethoxylations were chosen as the components to understand their mixing behavior at equilibrium and dynamic conditions. At short times, the adsorption is found to be diffusion limited for individual components as well as for the mixtures, as predicted by the Ward and Tordai model. The effective diffusion coefficient of the monomers in the mixed state displays a dynamic synergism, consistent with the molecular thermodynamic model for dynamic surface tension. However, the equilibrium surface tension and micellar diffusion coefficient of the mixtures exhibit ideal behavior.     

5‐O‐Caffeoylshikimic acid from Solanum somalense leaves: Advantage of centrifugal partition chromatography over conventional column chromatography

Solanum somalense leaves, used in Djibouti for their medicinal properties, were extracted by MeOH. Because of the high polyphenol and flavonoid contents of the extract, respectively, determined at 80.80 ± 2.13 mg gallic acid equivalent/g dry weight and 24.4 ± 1.01 mg quercetin equivalent/g dry weight, the isolation and purification of the main polyphenols were carried out by silica gel column chromatography and centrifugal partition chromatography. Column chromatography led to 11 enriched fractions requiring further purification, while centrifugal partition chromatography allowed the easy recovery of the main compound of the extract. In a solvent system composed of CHCl₃/MeOH/H₂O (9.5:10:5), 21.8 mg of this compound at 97% purity was obtained leading to a yield of 2.63%. Its structure was established as 5‐O‐caffeoylshikimic acid by mass spectrometry and NMR spectroscopy. This work shows that S. somalense leaves contain very high level of 5‐O‐caffeoylshikimic acid (0.74% dry weight), making it a potential source of production of this secondary metabolite that is not commonly found in nature but could be partly responsible of the medicinal properties of S. somalense leaves.