Reactivity and Use of Sulfur–Oxygen Reducing Agents with C–S Bonds

The use of the reducing agents belonging to the group of hydroxy- and aminoalkanesulfinates (rongalite, thiourea dioxide, and their analogs) in chemistry and chemical technology is considered. The latest data on the mechanisms and kinetic models of homogeneous and heterogeneous reactions involving these compounds, the mechanism of catalysis of the redox reactions by cobalt dioximines, and the effect of the solid reagent prehistory and of atmospheric oxygen on the reducing properties of hydroxyalkanesulfinates are discussed.     

A form of the solution to the Mathieu equation

A special linear transformation is introduced to express the general solution to a second-order differential equation with a periodic coefficient in terms of a particular solution to an auxiliary second-order nonlinear system with a periodically perturbed right-hand side. It is numerically shown that there exist periodic solutions to the auxiliary system outside the instability regions of the solutions to the Mathieu equation. The estimates obtained for the instability regions are in agreement with known results.     

Heavy ion linear accelerator with high-frequency quadrupole focusing

Based on results of works on the NICA/MPD (Joint Institute for Nuclear Research, Dubna) project, the possibility of designing a heavy ion linear accelerator with high-frequency quadrupole focusing both in the input part and in the main part of the accelerator is shown. Parameters of the linear ¹⁹⁷Au³¹⁺ ion accelerator are presented. Special attention is paid to technical questions of calculating, designing, manufacturing, and tuning the accelerator.     

An unusual mechanism of polymerization of MMA initiated by ammonia-triisobutyl borane and atmospheric oxygen

The kinetics of polymerization of methyl methacrylate in vacuum initiated by ammonia-triisobutyl borane (iso-Bu₃B · NH₃) oxidized in air is studied. It is shown that the rate of reaction shows the first order with respect to the monomer concentration and a variable order with respect to the initiator concentration; the process is characterized by a low activation energy. It is demonstrated that polymerization proceeds according to a two-step mechanism. The mechanism of polymerization initiation and reinitiation is investigated via ESR spectroscopy, and it is found that one primary radical generated during initiation can form up to 200 substantial chains during the subsequent chain-transfer process.     

Peculiarities of azobenzene catalytic hydrogenation in 2-propanol aqueous solutions with acid or base additives

It is shown experimentally that the hydrogenation of azobenzenes over a nickel skeleton catalyst in 2-propanol aqueous solutions proceeds selectively with the formation of aniline. It is pointed out that during the reaction, considerable participation of hydrogen bonded with active centers of a catalyst surface was observed. The competitive character of adsorption between the initial azo compound and aniline formed as a result of reaction is established. It is concluded that purposeful change of the azo group hydrogenation rate is possible by introducing acid or base additives into 2-propanol aqueous solution.     

Correlations between the catalytic activity of heteropoly acids and the special features of their tunneling spectra

The electronic-vibrational spectra of phosphomolybdic acid, a classic heteropoly acid with a Keggin anion, were measured in an ultrahigh vacuum with the use of scanning tunneling microscopy. The dependences of the resonance characteristics of the spectra, so-called negative differential resistances (NDRs), on the vacuum gap, the polarity of applied voltage, and the direction of tunnel current were determined. A new mechanism of the formation of NDRs was proposed based on the quantum effect of the localization of the electronic states of multicenter systems in strong electric fields. The character of correlations between NDRs and the catalytic properties of heteropoly acid catalysts was established.     

Features of the phenylhydroxylamine catalytic hydrogenation in water solutions of 2-propanole on skeletal nickel

The kinetics of phenylhydroxylamine hydrogenation reaction on skeletal nickel catalyst in 2-propanole aqueous solutions was studied. It was shown that the value of phenylhydroxylamine and aniline adsorption increases with an increase in the molar fraction of water in the binary solvent 2-propanole-water. It was found experimentally that the hydrogenation reaction is of the first order with phenylhydroxilamine and of the zero order with hydrogen. It is noted that the amount of hydrogen absorbed in the reduction of phenylxydroxylamine in the initial phase of the reaction is considerably lower than the stehiometry of the reaction would indicate. The reasons for the effect of solvent on the features of phenylhydroxilamine hydrogenation are discussed.     

Reduction of the Mathieu equation to a nonlinear equation of the first order

A second order equation with periodic coefficients is considered. It is shown that its analysis can be reduced to the study of a nonlinear equation of the first order. The second approximation is obtained for the first resonance region of the Mathieu equation. This approximation describes the behavior of solutions inside this resonance region and near it.