Experimental study of dimerization of radical anions of aromatic carbonyl compounds

The rate constants of dimerization (k₁) of radical anions of acetophenone, 1-acetylnaphthalene, 9-acetylanthracene, 9-formylanthracene, and anthracene in DMF containing 0.02 M tetrabutylammonium bromide were determined by differential cyclic voltammetry. It was shown that the values of k₁ of the radical anions investigated are correlated with the values of the boundary electron density on the reaction sites, which in turn increase symbatically with an increase in the size of the aryl fragment or on incorporation of electron-acceptor functional groups in the anthracene nucleus.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1777–1782, August, 1991.     

Experimental simulation of meteorite impact

The author presents the results of experiments on the impact of a compact mass with a density of about 1 g/cm³ against polystyrene and steel targets at a velocity of 24 km/sec. Contrary to expectation, the impact left deep and narrow holes in the target, i. e., did not create the effect of a point surface explosion.     

Equilibrium shapes and stability of rotating drops

Direct variational methods are used to obtain nonaxisymmetric equilibrium shapes of a rotating drop. The results are given of experiments on the interaction of freely floating drops of viscous fluid. It is shown that if the dimensionless angular momentum of the system is > 3.4, then a sequence of three-dimensional shapes similar to ellipsoids bifurcates from the sequence of axisymmetric shapes The stability of these shapes is studied in Poincaré's scheme.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 13–20, July–August, 1982.     

Anti‐Stokes Luminescence of Cadmium Telluride Nanocrystals

For the first time, the antiStokes luminescence in colloidal solutions of CdTe nanocrystals on excitation below the absorption edge has been discovered. The maximum spectral shift to the shortwave region relative to the excitation energy E _con ^max = 319 meV is obtained for meansized nanocrystals (2.5 nm). The conversion efficiency of the absorbed radiant energy is 1.3·10^–2%. The rise in the antiStokes photoluminescence intensity with increasing temperature and the linear dependence on the exciting radiation intensity have been established. It is shown that the effect observed cannot be caused by twophoton excitation or by Auger recombination. It is assumed that the basic mechanism of the luminescence observed is the radiative recombination through the energy levels of the states attributable to the disturbance of the crystal structure in the nanocrystals.     

Fokker-Planck operator for free-molecular,nonspherical, thermally nonequilibrium Brownian particles

The Fokker-Planck collision operator entering into the kinetic equation for the velocity distribution function of convex nonspherical rigid homogeneous Brownian particles in a traveling inhomogeneous monatomic gas is derived. The regime of flow past the particles is free-molecular, i.e., the characteristic particle dimensions are much smaller than the average free path of the gas molecules, the interaction between the particles and their effect on the gas phase can be neglected, and a specular-diffuse law of interaction between the molecules and the particle surface holds. The particle temperatures T _p are the same and differ from the local gas temperature T. Thermal nonequilibrium (T _p ≠ T) leads to violation of the well-known relations between the diffusion coefficients in the spaces of the translational and angular velocities and the coefficients of forces and moments exerted on a particle. The coefficients in the unknown operator are calculated for the particles in the form of bodies of revolution with longitudinal symmetry. Data characterizing the effect of the nonsphericity of the particles, i.e., spheroids and sphere-cylinders, on the degree of violation are given.     

Effect of microheterogeneity on the kinetics of oxidation of methyl linoleate in micelles

The kinetic results of the radical chain oxidation of methyl linoleate (LH) in micelles were given. The oxidation rate depends on the average number of substrate molecules in the micelle and is almost independent of the micelle concentration under the given conditions. The chain propagation and termination were assumed to predominantly occur inside the micelle. Possible reasons for linear chain termination during the oxidation of polyunsaturated fatty esters in microheterogeneous systems were discussed.     

Stereochemical study of the sterically crowded phenylselanylalkenes by means of 77Se?1H spin–spin coupling constants

Stereochemical study of five sterically crowded phenylselanylalkenes obtained via the hydroselenation of either terminal or internal alkynes with benzeneselenol catalyzed by the nanosized Ni complexes has been carried out based on the experimental HMBC measurements and theoretical second order palarization propagator approach (SOPPA) calculations of their ⁷⁷Se? ¹H spin–spin coupling constants across double bond in combination with the energy‐based theoretical conformational analysis performed at the MP2/6‐311G** level. It has been found that studied phenylselanylalkenes adopt mainly skewed s‐cis conformation with the noticeable out‐of‐plane deviations of the phenylselanyl and phenyl groups. Copyright © 2011 John Wiley & Sons, Ltd.     

Stereochemical behavior of geminal and vicinal 77Se–13C spin–spin coupling constants studied at the SOPPA(CC2) level taking into account relativistic corrections

A systematic theoretical study of geminal and vicinal ⁷⁷Se–¹³C spin–spin coupling constants in the series of the open‐chain selenides and selenium‐containing heterocycles revealed that relativistic effects play an essential role in the selenium–carbon coupling mechanism, especially when the coupling pathway includes a triple bond, contributing to about 10–15% of their total values and noticeably improving the agreement of the calculated couplings with experiment. Both geminal and vicinal ⁷⁷Se–¹³C spin–spin coupling constants show marked stereochemical behavior as documented by their calculated dihedral angle dependence that could be used as a practical guide in stereochemical studies of organoselenium compounds. Copyright © 2014 John Wiley & Sons, Ltd.     

Relativistic effects of chlorine in 15N NMR chemical shifts of chlorine-containing amines

Russian Journal of Organic Chemistry - Quantum-chemical calculations by DFT method demonstrated that the accounting is necessary of the shielding by chlorine of nitrogen atom in practical...     

Applying the photonuclear technique to fissile materials detection

Application of a photonuclear technique is considered as a nondestructive method for detecting the unauthorized transporting of camouflaged fissile nuclear material in cargo containers. The advantages of the technique (the use of time selection and the analysis of energy distributions of delayed neutrons) are demonstrated. The operating modes of the accelerator were optimized by modeling. A version of a neutron scintillation spectrometer based on a stylbene monocrystal is presented along with its schematic and main parameters.