A comparative study of the reactions of fluorinated oxi- and thiiranes with acyl chlorides

The CoCl₂-catalyzed reactions of fluorinated 1,2-oxi- and thiiranes with acyl chlorides were studied. It was found that a regioselective heterocycle opening reaction resulted in two isomers having normal and abnormal structure in a ratio predetermined by the substituents in both the starting heterocycles and acyl chlorides.     

<Emphasis Type="Italic">N</Emphasis>-Allyl-substituted aminomethylene-1,1-bisphosphonates in 1,3-dipolar cycloaddition reaction with aromatic nitrile <Emphasis Type="Italic">N</Emphasis>-oxides

A reaction of N-allyl-substituted aminomethylene-1,1-bisphosphonates with aromatic nitrile N-oxides was used to obtain new aminomethylenebisphosphonates with one or two 3-arylisoxazoline rings at the nitrogen atom. NMR spectroscopy studies showed that the bisphosphonates with two isoxazoline fragments in the molecule exist in solution as a mixture of two diastereomers.     

Synthesis and properties of 1-(R-adamant-1-yl)-3-(1-propionylpiperidin-4-yl)ureas and 4-({4-[3-(R-adamant-1-yl)ureido]cyclohexyl}oxy)benzoic acids,efficient target-oriented human soluble epoxide hydrolase inhibitors

A reaction of R-adamant-1-yl isocyanates with 4-[(4-aminocyclohexyl)oxy]benzoic acid and 1-(4-aminopiperidin-1-yl)propan-1-one in DMF afforded corresponding ureas in 90—95% yield, the target-oriented inhibitors of epoxide hydrolase sEH. The ureas are characterized by reduced melting points and increased solubility in water, as well as by inhibitory activity in the range of 0.5—4.0 nmol L^–1.     

Heterocyclization of carboxy- and sulfonamides in the course of oxidative addition to unsaturated substrates

Formation of heterocyclic compounds in the course of oxidative addition of carboxamides and sulfonamides to alkenes and dienes is reviewed. Main attention is focused on reactions proceeding in the presence of halo-containing oxidative systems and reagents. Features of behavior of fluorine-substituted sulfonamides and carboxamides are discussed.     

One-Electron Bonds in Frustrated Lewis Pair TPB Ligands: Boron Behaving as a Lewis Base

Owing to its versatility in synthetic chemistry, TPB (tris[2-diisopropylphospino)phenyl]borane) is a very important frustrated Lewis Pair. The unusual stability of the neutral radical (TPB)Cu has been related to the presence of a one-electron B−Cu bond. Herein we show, through the use of different computational chemistry methods, that the existence and nature of this kind of A⋅⋅⋅M bond (A=donor atom, M=transition metal) depends on the surrounding chemical structure, and can be genuine one-electron sigma bonds only if appropriate metal ligands (Y), able to trap the charge in the desired region, are chosen. This ability is modulated by the subtle balance between the electronegativity of the different atoms along the A⋅⋅⋅M⋅⋅⋅Y bond paths. Most importantly, contrary to many TPB complexes in which boron acts as a Lewis acid, in one-electron-bond-containing structures boron behaves as a Lewis base.     

Non-Pincer-Type Manganese Complexes as Efficient Catalysts for the Hydrogenation of Esters

Catalytic hydrogenation of carboxylic acid esters is essential for the green production of pharmaceuticals, fragrances, and fine chemicals. Herein, we report the efficient hydrogenation of esters with manganese catalysts based on simple bidentate aminophosphine ligands. Monoligated Mn PN complexes are particularly active for the conversion of esters into the corresponding alcohols at Mn concentrations as low as 0.2 mol % in the presence of sub-stoichiometric amounts of KO^tBu base.     

Polyethylenimine and tris(2-aminoethyl)amine modified p(GA–EGMA) microbeads for sorption of uranium ions: equilibrium,kinetic and thermodynamic studies

Poly(glycidyl methacrylate-ethyleneglycol dimethacrylate), p(GA–EGMA), microbeads were prepared through suspension polymerization. It was decorated with polyethylene imine (PEIM) and tris(2-aminoethyl)amine (TAEA) ligands to decorate with polyamine groups. These microbeads were used for sorption of uranium ions from aqueous solution. The maximum sorption of uranium ions on the PEIM and TAEA modified microbeads was observed at pH 6.0. The maximum sorption capacity of acid hydrolyzed p(GA–EGMA)–OH, p(GA–EGMA)–PEIM and p(GA–EGMA)–TAEA microbeads was found to be 7.21, 87.8 and 64.3 mg g^?1. The sorption process conforms to the pseudo-second order kinetic model and the Langmuir and Temkin isotherm models well.     

Sulphur content estimation of Venezuelan heavy oil by fast neutron and gamma transmission technique

A compact and modern equipment for implementing the fast neutron and γ-ray transmission technique (FNGT) has been developed in order to estimate the sulphur content of crude oil. FNGT is employed for non- destructive analysis of different kinds of samples. The compact system presented in this work represents an improvement of our previous experimental set-up [1, 2]. It makes use of a ²⁵²Cf source, an EJ-301 liquid scintillator detector (2″ × 2″) with excellent n/γ discrimination capabilities, and modern nuclear electronics based on fast digitizers. The fast neutron and gamma transmission technique was employed to study a system for on-line sulphur concentration measurement in Venezuelan heavy sour oil. The range of sulphur concentrations investigated is between 0.1 and 6.5 wt%. The equipment performances and limitations are compared with those predicted by a Monte Carlo model built in GEANT4 v10.01. The results show the possibility to implement a compact unit for on-line determination of sulphur concentration in crude oil.

     

DRBEM solution of biomagnetic fluid flow and heat transfer in cavities-CMMSE2016

In this paper, we investigate the fully developed, laminar, forced convection flow of an electrically non-conducting, viscous, biomagnetic fluid in the 2D cross-section (cavity) of a long impermeable pipe. The fluid is under the influence of a point magnetic source placed below the cavity. The dual reciprocity boundary element method (DRBEM) with constant and linear elements is used for solving the governing equations resulting from the Navier–Stokes and energy equations together with magnetization and buoyancy forces. The fundamental solution of Laplace equation is made use of converting differential equations to boundary integral equations by taking all the terms other than Laplacian as inhomogeneity in the Poisson’s equations for the velocity components, pressure and the temperature of the fluid. The unknown pressure boundary conditions are approximated through momentum equations by using finite difference approximation for the pressure gradients and DRBEM coordinate matrix for the other terms. All the space derivatives are also calculated by DRBEM coordinate matrix which is one of the main advantages of DRBEM. Pipe axis velocity is also computed. The effects of magnetization and the buoyancy force on the fluid with or without viscous dissipation term in the energy equation are investigated in square and lid-driven cavities for several values of magnetic (Mn) and Rayleigh (Ra) numbers. It is observed that the flow and heat transfer are significantly affected with increasing values of Mn and Ra. DRBEM gives small sized linear systems due to its boundary only nature at a considerably low computational expense.     

On the geometric–arithmetic index by decompositions-CMMSE

The concept of geometric–arithmetic index was introduced in the chemical graph theory recently, but it has shown to be useful. There are many papers studying different kinds of indices (as Wiener, hyper–Wiener, detour, hyper–detour, Szeged, edge–Szeged, PI, vertex–PI and eccentric connectivity indices) under particular cases of decompositions. The main aim of this paper is to show that the computation of the geometric-arithmetic index of a graph G is essentially reduced to the computation of the geometric-arithmetic indices of the so-called primary subgraphs obtained by a general decomposition of G. Furthermore, using these results, we obtain formulas for the geometric-arithmetic indices of bridge graphs and other classes of graphs, like bouquet of graphs and circle graphs. These results are applied to the computation of the geometric-arithmetic index of Spiro chain of hexagons, polyphenylenes and polyethene.