σ-Alkynylcopper(i) and σ-alkynylpalladium(ii) complexes as intermediates in catalytic oxidative carbonylation of alkynes to alkynoates

Hypothetical mechanisms of oxidative carbonylation of alkynes to alkynoates in the PdCl₂-CuCl₂-base system are discusssed. σ-Alkynylcopper(i) and σ-alkynylpalladium(ii) complexes are considered to be the most probable intermediates in the process. A kinetic model of the reaction is proposed. The oxidative carbonylation of RC≡CCu in the PdCl₂-CuCl₂-base system leads to the formation of RC≡CCOOR'. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1806–1809, October, 1993.     

Topological structure of mechanisms of complex reactions

A new concept is proposed, the topological structure of the mechanism of chemical reactions (TS), reflecting the set of interrelations of intermediates and reactants. In order to identify the TS of a mechanism, topological information must be obtained through kinetic methods for describing the process, through certain chemical and physical methods of identifying individual links in the TS and through chemical modeling of the stages. Feasibility has been demonstrated for application of graph theory methods in classifying, codifying, and determining the complexity of TS of reaction mechanisms. Techniques are described for identifying the TS of mechanisms of catalytic reactions, involving analysis of the structure of hypothetical nodes of conjugation of stage sequences in the formation of products, and also techniques for purposeful changes in the TS of the mechanism of a complex reaction.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 3, pp. 282–291, May–June, 1988.     

Synthesis and structure of a product of interaction of acetonitrile with hydrogen bromide, [H2N=C(Me)−NH−C(Me)Br2]Br

A mixture of solid products was obtained upon absorption of dry HBr by MeCN. One of the products, [H₂N=C(Me)−NH−C(Me)Br₂]Br, was isolated as white single crystals and characterized by X-ray diffraction analysis. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2274–2277, November, 1998.     

Palladium(II,I, 0) Complexes in Catalytic Reactions of Oxidative Carbonylation

The mechanisms of carbonylation of alkenes, alkynes, and alcohols, including the mechanism of oxidative carbonylation of alkynes in the regime of self-oscillations catalyzed by Pd(II), Pd(I), or Pd(0) complexes, are analyzed. It is shown that the main reasons for the appearance of self-oscillations in the oxidation reactions are nonlinear and autocatalytic steps of generation and termination of active centers. The results of studying the functions of para-benzoquinone as an oxidant, ligand, and catalyst in the oxidative reactions are generalized. It is found that Pd(0) complexes with para-benzoquinone can catalyze oxidation reactions.     

Analysis of ESR spectra of fluorocarbon radicals in irradiated tetrafluorethylene

ESR spectra in irradiated tetrafluoroethylene were studied. It was found that during radiolysis at 77 K several types of radicals are formed. The spectra of two types of radicals were established and were preliminarily interpreted as the spectra of fluorine atoms and CF₃-CF₂ radicals.     

Properties of thin poly(tetrafluoroethylene) films deposited on solid substrates by electron beam polymerization from vapor phase

The deposition of thin poly(tetrafruoroethylene) films on silicon substrates via the polymerization of tetrafluoroethylene from the vapor phase by means of an electron beam with an electron energy of 20–40 eV and the current density varied in the range 1–10⁴ μA/cm² has been studied. It has been shown that a variation in the current density during deposition allows one to widely vary the properties of the films being formed, in particular, their heat resistance. The crosslinked poly(tetrafluoroethylene) films prepared at a current density of 10² to 10³ μA/cm² demonstrate heat resistance up to 400–450°C. This opens wide prospects for the use of these films as dielectric layers in microelectronics.     

Formation of masking pattern by electron beam-induced vapor deposition

The dry resist-free process of electron beam-induced masking via chemical vapor deposition from a hydrocarbon precursor was studied. It was shown that the obtained mask exhibited a low selectivity during ion beam etching with SF₆ ions. It was found that, during mask deposition, a thin (of the order of 1 nm) boundary layer is formed on the SiO₂ plate surface; the layer had a substantially higher plasma resistance and, hence, high selectivity upon ion beam etching of SiO₂. Certain features of the masking process and the properties of the mask material were studied.     

Features of resist-free formation of masking pattern by electron beam-induced vapor deposition

Certain features of masking-pattern formation via electron beam-induced deposition from undecane vapor onto a copper substrate were considered. It was shown that the width of pattern bands formed on copper is substantially greater than that on SiO₂ and is almost independent of their height (mask layer thickness). A strong dependence of the mask growth rate on the beam scan time was revealed, indicating the diffusion regime of the mask formation process. Through the mask, the substrate was etched with Ar ions. It was shown that the mask material is etched at a 1.3 times lower rate than copper.     

Kinetics and Mechanism of Allyl Alcohol Epoxidation with Hydrogen Peroxide on a Titanium Silicalite Catalyst TS-1. Formulation and Discrimination between Hypothetical Mechanisms

Kinetics and Catalysis - The kinetics of epoxidation of allyl alcohol with hydrogen peroxide in the presence of a titanium-containing zeolite catalyst TS-1 has been studied. The hypothetical...