Mechanical mixtures of Me (Ni, Pd) Ce oxides and silica-supported heteropolyacids: Role and optimal concentration of each active species in n-hexane isomerization

Catalytic properties of silica-supported heteropolyacids (HPA) in a mechanical mixture with reduced Me-Ce oxides (Me = Ni, Pd) in n-hexane isomerization are studied. The role of each component of the mixed oxides (Ce and, typically, Ni and Pd) and their optimum content has been illuminated: cerium is not only beneficial for eliminating or preventing coke deposition but is also effective for maintaining the Keggin structure of the highly-organized HPA during the reaction and probably allows a better dispersion of the second metal species. Nickel and palladium, present as Ni⁰ and Pd⁰, reinforce the activation of the alkane, which is difficult to obtain by means of a direct attack by an acid, and, thus, enhance noticeably the activity of the catalyst. The best mechanical mixtures are obtained with 30–70 wt % NiCeO-HPW/SiO₂ and 50–50 wt % Pd_0.1CeO-HPW/SiO₂. These mixtures have the highest efficiency for a Ni/(Ni + W) atomic ratio of 0.66 and a Pd/(Pd + W) ratio of 0.40, respectively. Finally, the conversion of n-hexane is in the order HPW > HSiW > HBW, which seems to be consistent with the order of their acid strength as per the literature, but the isomerization selectivity appears to be slightly higher on HSiW. Published in Russian in Kinetika i Kataliz, 2006, Vol. 47, No. 1, pp. 24–28. The text was submitted by the authors in English.     

Rapid determination of 5-hydroxytryptamine in whole blood by liquid chromatography with fluorimetric detection.

A rapid and simple reversed-phase (using muBondapak C18 as the stationary phase) liquid chromatographic method with fluorimetric detection is described for the quantitation of 5-hydroxytryptamine in whole blood. The rapidity and simplicity of the method are explained by the absence of a pretreatment. 5-Fluoro-dl-tryptophan was used as internal standard. The mobile phase was 0.01 M phosphate buffer (pH 4.5) with 0.0025 M 1-heptanesulfonic acid and 20% methanol. The detection wavelength were 302 nm for excitation and 340 nm for emission. Analysis time was 10 min with retention times for 5-hydroxytryptamine of 9 min and for 5-fluoro-dl-tryptophan of 7 min. This method is proposed for biological exploration of psychiatric disorders involving 5-hydroxytryptamine and would be useful for tryptophan.     

Efficient nickel-mediated intramolecular amination of aryl chlorides

The use of an in situ generated Ni(0) catalyst associated with 2,2'-bipyridine or N,N'-bis(2,6-diisopropylphenyl)dihydroimidazol-2-ylidene (SIPr) as a ligand and NaO-t-Bu as the base for the intramolecular coupling of aryl chlorides with amines is described. The procedure has been applied to the formation of five-, six-, and seven-membered rings. [reaction: see text]     

Dual phosphorescence from 5-methylbicyclo[4.3.01,5]non-1-en3-one

Phosphorescence has been simultaneously observed from both a ³π, π* and a ³n,π* level of 5-methylbicyclo-[4.3.0^1,5non-1-en-3-one. The emission from the higher energy ³n,π* state, which is in thermal equilibrium with the ³π,π* state, is quenched by lowering the temperature and also quenched by increasing the solvent polarity so as to raise the energy of the ³n,π* state relative to the ³π,π* state.     

Issue Information ‐ TOC

Numerical modeling of multiphase flow generally requires a special procedure at the solid wall in order to be consistent with Young's law for static contact angles. The standard approach in the lattice Boltzmann method, which consists of imposing fictive densities at the solid lattice sites, is shown to be deficient for this task. Indeed, fictive mass transfer along the boundary could happen and potentially spoil the numerical results. In particular, when the contact angle is less than 90 degrees, the deficiencies of the standard model are major. Various videos that demonstrate this behavior are provided (Supporting Information). A new approach is proposed and consists of directly imposing the contact angle at the boundaries in much the same way as Dirichlet boundary conditions are generally imposed. The proposed method is able to retrieve analytical solutions for static contact angles in the case of straight and curved boundaries even when variable density and viscosity ratios between the phases are considered. Although the proposed wetting boundary condition is shown to significantly improve the numerical results for one particular class of lattice Boltzmann model, it is believed that other lattice Boltzmann multiphase schemes could also benefit from the underlying ideas of the proposed method. The proposed algorithm is two‐dimensional, and the D2Q9 lattice is used. Copyright © 2016 John Wiley & Sons, Ltd.     

On the reduction of S-alkyl-thionocarbonates (xanthates) with phosphorus compounds

[reaction: see text] Reductive cleavage of the carbon-sulfur bond present in S-alkyl-thionocarbonates (xanthates) was achieved by high-yielding, tin-free radical reactions based on phosphorus reagents. The combination hypophosphorous acid/triethylamine/AIBN led to fast, efficient, and smooth formation of the alkane. Reduction with diethyl phosphite was sufficiently slow to permit sequential intermolecular addition of a 2-oxoalkyl xanthate onto an olefin followed by cleavage of the newly formed carbon-sulfur bond.     

Prodrugs of aza nucleosides based on proton transfer reaction

DFT calculation results for intramolecular proton transfer reactions in Kirby’s enzyme models 1–7 reveal that the reaction rate is quite responsive to geometric disposition, especially to distance between the two reactive centers, r _GM, and the angle of attack, α (the hydrogen bonding angle). Hence, the study on the systems reported herein could provide a good basis for designing aza nucleoside prodrug systems that are less hydrophilic than their parental drugs and can be used, in different dosage forms, to release the parent drug in a controlled manner. For example, based on the calculated log EM, the cleavage process for prodrug 1ProD is predicted to be about 10¹⁰ times faster than that for prodrug 7ProD and about 10⁴ times faster than prodrug 3ProD: rate _1ProD  > rate _3ProD  > rate _7ProD . Hence, the rate by which the prodrug releases the aza nucleoside drug can be determined according to the structural features of the linker (Kirby’s enzyme model).     

Existence and Nonexistence of Weak Positive Solution for a Class of p-Laplacian Systems

In this work, we are interested to obtain some result of existence and nonex- istence of positive weak solution for the following p-Laplacian system
{-△piui=λifi（u1,^…,um）,inΩ, i=1,...,m, ui=0,
on δΩ,Vi=1,…,m,
where △piz = div（｜△z｜^pi-2△Z）, Pi ≥ 1,λi,1 ≤ i ≤ m are a positive parameter, and Ω is a bounded domain in IR^N with smooth boundary δΩ. The proof of the main results is based to the method of sub-supersolutions.