Zinc polyoxometalate on activated carbon: an efficient catalyst for selective oxidation of alcohols with hydrogen peroxide

[PW₁₁ZnO₃₉]^5? was immobilized on activated carbon and characterized using Fourier transform infrared, X‐ray diffraction, Brunauer–Emmett–Teller and elemental analysis techniques. Effective oxidation of various alcohols with hydrogen peroxide was performed in the presence of this catalyst. Easy separation of the catalyst from the reaction mixture, cheapness, high activity and selectivity, stability as well as retained activity in subsequent catalytic cycles make this supported catalyst suitable for small‐scale synthesis. Copyright © 2015 John Wiley & Sons, Ltd.     

Cup products in Hopf-cyclic cohomology

We construct cup products of two different kinds for Hopf-cyclic cohomology. When the Hopf algebra reduces to the ground field our first cup product reduces to Connes' cup product in ordinary cyclic cohomology. The second cup product generalizes Connes–Moscovici's characteristic map for actions of Hopf algebras on algebras. To cite this article: M. Khalkhali, B. Rangipour, C. R. Acad. Sci. Paris, Ser. I 340 (2005).     

An effective modeling and solution approach for the generalized independent set problem

The generalized independent set (GIS) problem was first introduced by Hochbaum and Pathria (Forest Sci 43(4), 544–554, 1997) and independently explored in greater detail by Hochbaum (Manage Sci 50(6), 709–123, 2004). This problem, with applications in forest management and a variety of related areas, is a generalization of the classical maximum independent set problem. In this paper we highlight a natural, nonlinear formulation for the problem that is an attractive alternative to the linear model found in the literature. The effectiveness of this alternative formulation is demonstrated by computational experience on test problems of varying size and density, disclosing a dramatic reduction in the time to obtain optimal and near optimal solutions and an ability to solve much larger problems.     

The Importance of Polarity/Polarizability Interaction on the Acidity Behavior of 9,10-Anthraquinone and 9-Anthrone Derivatives in Methanol-Water Mixed Solvents Using Target Factor Analysis and QSPR Approaches

The influence of solvent properties on acidity constants of some newly synthesized 9,10-anthraquinone and 9-anthrone derivatives was studied in methanol-water mixtures in a composition range of 0.57 to 1.0 methanol mole fraction. The model was established by using both multiple linear regression and target factor analysis. Both methods revealed that the solvent polarity/polarizability parameter ^* is a major factor in controlling the acidity behavior of the anthraquinones and anthrones studied in binary methanol-water mixed solvents. A QSPR study was conducted to drive the relationships between the ^* coefficient s and the polarity/polarizability of molecules. Both dipole moment and polarizability were found to have a linear relationship with s. The results confirm that, in the dipolar protic solvents used, the dipole-dipole interaction (for neutral molecules) and the ion-dipole interaction (for ionized molecules) are the major factors controlling the acidity behavior of these compounds.     

Regio- and Stereoselective Reactions of 17-Phenyl-18,19,20-trinorprostaglandin F(2)(alpha) Isopropyl Ester

Novel prostaglandin F(2)(alpha) derivatives, functionalized at C13 and C14, have been prepared. 17-Phenyl-18,19,20-trinorprostaglandin F(2)(alpha) isopropyl ester [(15S)-1] and its epimer [(15R)-1] were stereoselectively epoxidized, using Sharpless conditions, to produce each of the four diastereomeric epoxides (15S)-2, (15S)-3, (15R)-2, and (15R)-3. Treatment of the four epoxides with LiOH stereospecifically-produced the pentahydroxy substituted analogues 12 and 13. Alternatively, epoxides 2 and 3were allowed to react with thiophenolate ion. The attack of the sulfur nucleophile on the epoxide occurred at either C13 or C14 depending on the stereochemistry of the epoxide and of C15.     

Spectrophotometric determination of beryllium in water samples after micelle-mediated extraction preconcentration

A new micelle-mediated phase preconcentration method for preconcentration of ultra-trace quantities of beryllium as a prior step to its determination by spectrophotometry has been developed. Chrome Azurol S (CAS) and cetyltrimethylammonium bromide (CTAB) were used as chelating agent and cationic surfactant, respectively. The method evaluates and eliminates the blank bias error present in such procedures using mean centering of ratio spectra. This procedure gives more accurate results than the traditional approach using absorbance values against reagent blank. The optimal extraction and reaction conditions were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration and improvement factors) were obtained. Linearity was obeyed in the range of 0.9-18.0 ng mL⁻¹ (1.00 × 10⁻⁷-2.00 × 10⁻⁶ mol L⁻¹) of beryllium. The detection limit of the method is 0.51 ng mL⁻¹ (5.66 × 10⁻⁸ mol L⁻¹) of beryllium. The interference effect of some anions and cations was also tested. The method was applied to the determination of beryllium in spring water samples.     

Synthesis and characterization of silica-coated magnetite nanoparticles modified with bis(pyrazolyl) triazine ruthenium(II) complex and the application of these nanoparticles as a highly efficient catalyst for the hydrogen transfer reduction of ketones

We present a facile and efficient method for modifying the surface of silica-coated Fe₃O₄ magnetic nanoparticles (MNPs) with bis(pyrazolyl) triazine ruthenium(II) complex [ MNPs@BPT–Ru (II) ] . Field emission-scanning electron microscopy, thermogravimetric/derivative thermogravimetry analysis, X-ray powder diffraction, Fourier-transform infrared spectroscopy, vibrating sample magnetometry, and energy-dispersive X-ray spectrometry analyses were employed for characterizing the structure of these nanoparticles. MNPs@BPT–Ru(II) nanoparticles proved to be a magnetic, reusable, and heterogeneous catalyst for the hydrogen transfer reduction of ketone derivatives. In addition, highly pure products were obtained with excellent yields in relatively short times in the presence of this catalyst. A comparison of this catalyst with those previously used for the hydrogen transfer reactions proved the uniqueness of MNPs@BPT–Ru(II) nanoparticle which is due to its inherent magnetic properties and large surface area. The presented method also had other advantages such as simple reaction conditions, eco-friendliness, high recovery ability, easy work-up, and low cost.