Retrieval and analysis of transition states in electrophilic substitution reactions of the carborane(12) series

The transition states of the reaction of electrophilic substitution in a series of ortho-, meta-, and para-carboranes were found by calculations in the B3PW91/6-31G(d,p) and B3LYP/6-31G(d,p) approximations. The key role of catalyst was demonstrated in the reactions of halogenation and alkylation. The reaction selectivity of electrophilic alkylation by CH₃Br in the presence of AlCl₃ should be lower than that of the chlorination reaction.     

Adsorption and conversion of ethylene glycol on the surface of Ag-containing catalyst modified with phosphate

The interaction of ethylene glycol with the surface of Ag-containing catalysts modified with phosphates was studied by IR spectroscopy. It was found that ethylene glycol was adsorbed at the surface phosphate groups; the presence of water vapor increased the stability of adsorbed ethylene glycol to a temperature of 400°C. A study of the kinetics of oxidation of ethylene glycol showed that it was consecutively converted into glycolaldehyde and glyoxal at 400°C. At 500–550°C, glyoxal was formed upon both the consecutive and direct conversion of ethylene glycol. The presence of a stage of the consecutive conversion of ethylene glycol into glycolaldehyde and glyoxal was caused by the participation of surface phosphate groups in the adsorption of alcohol molecules to be oxidized.     

Doping of graphite by an alkaline-earth metal to reduce the work function

A technique for reducing the work function of a field-emission graphite cathode by doping it by an alkaline-earth metal (barium) is suggested. A model of formation of a barium monolayer on the cathode surface is proposed. Field-emission tests show that the operating voltage of the doped cathode is lower than that of the undoped one with the same emission current.     

Classical trajectories and RRKM modeling of collisional excitation and dissociation of benzylammonium and <Emphasis Type="Italic">tert</Emphasis>-butyl benzylammonium ions in a quadrupole-hexapole-quadrupole tandem mass spectrometer

Collision-induced dissociation of the benzylammonium and the 4-tert-butyl benzylammonium ions was studied experimentally in an electrospray ionization quadrupole-hexapole-quadrupole tandem mass spectrometer. Ion fragmentation efficiencies were determined as functions of the kinetic energy of ions and the collider gas (argon) pressure. A theoretical Monte Carlo model of ion collisional excitation, scattering, and decomposition was developed. The model includes simulation of the trajectories of the parent and the product ions flight through the hexapole collision cell, quasiclassical trajectory modeling of collisional activation and scattering of ions, and Rice-Ramsperger-Kassel-Marcus (RRKM) modeling of the parent ion decomposition. The results of modeling demonstrate a general agreement between calculations and experiment. Calculated values of ion fragmentation efficiency are sensitive to initial vibrational excitation of ions, scattering of product ions from the collision cell, and distribution of initial ion velocities orthogonal to the axis of the collision cell. Three critical parameters of the model were adjusted to reproduce the experimental data on the dissociation of the benzylammonium ion: reaction enthalpy and initial internal and translational temperatures of the ions. Subsequent application of the model to decomposition of the t-butyl benzylammonium ion required adjustment of the internal ion temperature only. Energy distribution functions obtained in modeling depend on the average numbers of collisions between the ion and the atoms of the collider gas and, in general, have non-Boltzmann shapes.     

Application of adhesive materials for the repair of acting gas pipelines

The materials and equipment developed to eliminate damage in the pipelines that transmit hydro-carbons are presented. The properties of the adhesive materials and processing methods used in the repairs are described.     

Effect of change in structural and magnetic states of Pt<Subscript>74.1</Subscript>Fe<Subscript>25.9</Subscript> alloy on its optical properties

The effect of atomic disordering on the optical properties of Pt_74.1Fe_25.9 alloy, whose stoichiometry is close to that of Pt₃Fe, has been investigated. The optical constants of ordered and plastically deformed alloys, which are, respectively, in the paramagnetic and ferromagnetic states, have been measured by the polarimetric method. The frequency dispersions of the permittivity, optical conductivity, and reflectivity, as well as the microscopic characteristics of conduction electrons (plasma and relaxation frequencies), have been calculated. The energy dependences of the optical conductivity are compared to the calculated energy-band structure of atomically ordered and disordered Pt₃Fe compounds.     

Evolution of the optical properties of DyNi<Subscript>5 − <Emphasis Type="Italic">x</Emphasis></Subscript>Al<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> compounds in dependence of aluminum concentration

The refractive (n) and absorption (k) indices of intermetallic DyNi_{5 ? x} Al _x compounds (x = 0, 0.5, 1, 1.5, 2) have been measured by ellipsometry at room temperature in the spectral range of 0.22–15 μm. It is established that the replacement of nickel by aluminum atoms leads to significant changes in the dispersion relations of the optical conductivity σ(E) in the interband absorption range. With an increase in Al content, the spectrum σ(E) (containing three maxima for DyNi₅) is gradually transformed into a single-peak structure. The results obtained are discussed on the basis of the data on the electronic spectrum of these compounds. Concentration dependences of the plasma and relaxation frequencies of conduction electrons are determined.     

Low-energy peculiarities of the optical properties of inhomogeneous alloys

The optical properties of PdMn_0.7Fe_0.3, Pd₂AuFe and GdCu alloys of different homogeneity have been investigated. Possible reasons for the peculiarities typical of all alloys studied (deviation from the Drude behavior and low-energy absorption of light at ?ω < 0.5 eV) are discussed. Occurrence of these anomalies is related to general features of studied objects microstructure (phase inhomogeneity of medium in the form of presence in high-resistivity matrix of alloys of small inclusions of metal type.     

Electronic Structure and Optical Spectra of GdFeAl and GdFeSi Compounds

Physics of the Solid State - The results of studies of the electronic structure and optical properties of intermetallic compounds GdFeAl and GdFeSi are presented. The spin-polarized densities of...