Electrochemical reduction of ZnBr<Subscript>2</Subscript> in the presence of organic halides

Electrochemical reduction of zinc bromide in dimethylformamide, acetonitrile, and tetrahydrofuran in the presence of organic halides (RX) results in the formation of organozinc compounds by oxidative addition of RX to electrochemically generated Zn(0). Effects of the solvent and the nature of organic halides on the electrochemical reduction of zinc (II) ions are analyzed.     

Reaction of phosphorus pentachloride with 2,6-dichloro-4-phenylbenzo[ e ][1,2λ5]oxaphosphinine 2-oxide. Synthesis and steric structure of 2,2,6-trichloro-4-phenylbenzo[ e ][1,2λ5]oxaphosphinin-2-ylium hexachlorophosphate

2,2,2,6-Tetrachloro-4-phenylbenzo[e][1,2]oxaphosphinine and 2,2,6-trichloro-4-phenylbenzo[e][1,2λ⁵]-oxaphosphinin-2-ylium hexachlorophosphate were prepared by treatment of 2,6-dichloro-4-phenylbenzo[e][1,2λ⁵]-oxaphosphinine 2-oxide with phosphorus pentachloride. The structure of the latter compound was proved by means of X-ray diffraction analysis. Original Russian Text ? V.F. Mironov, E.N. Varaksina, D.A. Tatarinov, A.A. Shtyrlina, A.B. Dobrynin, I.A. Litvinov, 2008, published in Zhurnal Obshchei Khimii. 2008, Vol. 78, No. 2, pp. 210–215.     

Molecular dynamics simulations of grafted layers of bottle-brush polyelectrolytes

Using molecular dynamics simulations, we study the effect of the brush grafting density and degree of polymerization of the side chains on conformations of brush layers made of charged bottle-brush macromolecules. The thickness of the brush layer first decreases with increasing brush grafting density; then, it saturates and remains constant in the wide interval of the brush grafting densities. The brush layers consisting of the bottle-brush macromolecules with longer side chains have a larger layer thickness. The elongation of the side chains of the bottle-brush macromolecules decreases with increasing brush grafting density. This contraction of the side chains is due to counterion condensation inside the volume occupied by bottle-brushes. Our simulations showed that counterion condensation is a multiscale process reflecting different symmetries of the bottle-brush layer.     

Magnetic correlations in a layered iridate, Na(2)IrO(3)

Analysis of published data gathered on a sample of Na(2)IrO(3), held deep inside the antiferromagnetic phase at 1.58?K, shows that iridium magnetic dipole moments, measured in resonant x-ray Bragg diffraction, lie in the a-c plane of the monoclinic crystal and enclose an angle ≈118°?with the c-axis. These findings, together with bulk measurements, are united in a plausible magnetic ground state for an iridium ion constructed from a Kramers doublet. A magnetic space group, derived from the chemical space group C2/m (unique axis b), possesses an anti-translation, to accommodate antiferromagnetic order, and an odd, two-fold axis of rotation symmetry on the b-axis, [Formula: see text], placing Ir magnetic dipoles perpendicular to the b-axis. Anapoles (toroidal dipoles) are predicted to be likewise confined to the a-c plane, and magnetic charges forbidden.     

2-chloro-3,3,5-trimethyl-2,3-dihydro-1,2λ5-oxaphosphole 2-oxide as precursor in a new synthesis of dialkyl(diaryl)-(2-methyl-4-oxopent-2-yl)phosphine oxides

A new approach has been developed to the synthesis of dialkyl(diaryl)(2-methyl-4-oxopent-2-yl)-phosphine oxides that are structural analogs of the drug dimephosphon. This approach is based on the reaction of 2-chloro-3,3,5-trimethyl-3H-1,2λ⁵-oxaphosphole 2-oxide with Grignard compounds, and it ensures high yields of the target products. The structure of bis(2-methoxyphenyl)(2-methyl-4-oxopent-2-yl)phosphine oxide was determined by X-ray analysis. (2-Methyl-4-oxopent-2-yl)dipropylphosphine oxide with magnesium bromide formed a 4: 1 complex whose structure was also determined by X-ray analysis.     

Friction between brush layers of charged and neutral bottle-brush macromolecules. molecular dynamics simulations

Using molecular dynamics simulations, we study the lubricating properties of neutral and charged bottle-brush coatings as a function of the compression and shear stresses and brush grafting density. Our simulations have shown that in charged bottle-brush systems under shear there is a layer with excess counterions located in the middle between brush-bearing surfaces. The main deformation mode of the charged bottle-brush layers is associated with the backbone deformation, resulting in the backbone deformation ratio, α, and shear viscosity, η, being universal functions of the Weissenberg number. In the case of neutral bottle-brush systems, in addition to the backbone deformation there is also side chain deformation. The coupling between backbone and side chain deformation violates universality in the deformation ratio, α, dependence on the Weissenberg number and results in scaling exponents varying with the compression stress and brush grafting density. The existence of different length scales controlling deformation of neutral bottle brushes manifests itself in the shear viscosity, η, dependence on the shear rate, ?γ. Shear viscosity, η, as a function of the shear rate, ?γ, has two plateaus and two shear thinning regimes. The low shear rate plateau and shear thinning regime correspond to the backbone deformation, while the second plateau and shear thinning regime at moderate shear rates are due to side chain deformation. For both systems the value of the friction coefficient increases with increasing shear rate. The values of the friction coefficient for charged bottle-brush systems are about ten times smaller than corresponding values for neutral systems at the same shear rate.     

On 4-chromatic edge-critical regular graphs of high connectivity

New examples of 4-chromatic edge-critical r-regular and r-connected graphs are presented for r = 6,8,10.     

Electrochemical Properties of N-Substituted α-Diphenylphosphinoglycines

Russian Journal of Electrochemistry - The electrochemical properties of the N-substituted α-diphenylphosphinoglycines N-(2-methoxybenzyl) diphenylphosphinoglycine (1), N-(pyrazin-2-yl)...     

On 2-Connected Transmission Irregular Graphs

The transmission of a vertex v in a graph is the sum of the distances from v to all other vertices of the graph. In a transmission irregular graph, the transmissions of all vertices are pairwise distinct. It is known that almost all graphs are not transmission irregular. Some infinite family of transmission irregular trees was constructed by Alizadeh and Klav?ar [Appl.Math. Comput. 328, 113–118 (2018)] and the following problemwas formulated: Is there an infinite family of 2-connected graphs with the property? In this article, we construct an infinite family of 2-connected transmission irregular graphs.