Mechanism of adsorption,electroreduction and hydrogenation of compounds with ethylenic bonds on platinum and rhodium: Part II. Comparison of the electroreduction and catalytic hydrogenation processes

The catalytic liquid-phase hydrogenation of maleic acid on platinum and rhodium has been investigated. It is shown that the rate-determining step of this process as well as of the electroreduction process of maleic acid is the interaction of the chemisorbed particle of maleic acid with the adsorbed hydrogen which is formed at the preceding rapid stage of either the dissociative adsorption of molecular hydrogen, or the electrochemical stage of hydrogen ion discharge. The rate of the process with the same degree of surface coverage with hydrogen and chemisorbed particles of maleic acid does not depend on whether the process is carried out catalytically or electrochemically, on whether maleic acid and hydrogen were preliminarily adsorbed on the surface of the electrode-catalyst or not. With due regard for the mutual influence of chemisorbed particles participating in the rate-determining stage, the main kinetic equations for the electroreduction and catalytic hydrogenation processes have been derived. The difference in the rates of electroreduction of maleic acid on platinum and rhodium, with the same degree of electrode surface coverage with reactants, is shown to be the result of differences in the adsorption heats (or bonding strength with the surface) of hydrogen and maleic acid on these two metals. Experimental procedures are described in Part I [1].     

Use of enyne compounds in the synthesis of insect pheromones

A new approach has been developed to the synthesis of monogenic insect pheromones with acetogenin and macrolide structures, using the low reactivity of ozone and of 9-borabicyclo[3.3.1]nonane towards an acetylenic function as compared with a vinyl function.Institute of Organic Chemistry, Ufa Scientific Center of the Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, Vol. 33, No. 1, pp. 34–41, January–February, 1997.     

Nuclear magnetic isoscreening lines for O-O and O-H bonds: The second-order magnetic parameters of the H2O2 molecule

A variational method has been used with a basis of Gaussian atomic orbitals and an additive scheme based on localized molecular fragments to calculate the molar magnetic susceptibility and nuclear magnetic isoscreening line diagrams for O-O and O-H bonds, as well as and (for the protons) in the H₂O₂ molecule for the cis, trans, and twisted configurations. The molecular wave functions have been calculated by the INDO method and localized ones by the Edmiston-Rudenberg method, together with ab initio ₀ localized by Boys' method. It is found that and are substantially dependent on the bond lengths.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 4, pp. 482–487, July–August, 1986.     

Grain Boundary Wetting in Polycrystals: 1. Probability of Wetting of Structural Elements

A model describing the wetting of structural elements in polycrystals such as grain boundaries (faces), triple lines (edges), and quaternary nodes (vertices) is proposed. It is assumed that the only driving force during wetting is the tendency of a system to the energy minimization due to the substitution of low-energy liquid–solid interfaces for high-energy grain boundaries. In this case, the anisotropy of grain boundary energy caused by the differences in misorientation of adjacent grains is taken into account, whereas the liquid–solid interface energy is assumed to be independent of the orientation. The well-known condition of grain boundary wetting (the Gibbs–Smith condition) is extended to the triple lines and quaternary nodes by introducing parameters determined as characteristic free energy of these elements.     

The model U(5) of the triatomic molecule

Rotation-vibration spectra of a triatomic molecule can be classified by the irreducible representations of the group U(5). The dynamical symmetry U(5) ? O(5) ? O(3) is discussed. Its application to the spectrum of HCN is considered.     

Theoretical conformational analysis of some agonists of the H1- and H2-receptors of histamine

The conformational equilibrium of -(aminoethyl)pyridines has been studied by molecular-mechanics using the geometry optimization. It has been determined that the equilibrium is characterized by the nearly statistical distribution of the ap- and sc-conformers about the bond. Substitution of the dimethylamino-group for the amino-group results in a slight shift of the equilibrium toward the ap-rotamers. The global minimum in -(ammoniumethyl)pyridines corresponds to the conformation with the +sc-orientation about the central C-C bond and the -sc-orientation (in the case of the dimethylammonium derivatives) about the bond. In the latter conformation, the bond of the ammonium group is oriented toward the pyridine cycle. For charged compounds, the regular orthogonal conformation of the aromatic-ring plate is distorted (the vicinal C-C bond becomes eclipsed).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1833–1840, August, 1991.The authors are grateful to P. P. Shagidullin and A. Kh. Plyamovatyi for their interest in this work and for fruitful discussions.     

Anodic synthesis and molecular structure of dodecaethylhexaamidobisphosphonium diperchlorate

The electrochemical oxidation of hexaethyl triamidophosphite in the absence of nucleophiles specially introduced into the electrolyte was studied by anodic voltamperometry and preparative electrolysis. The reversible one-electron oxidation of the triamidophosphite molecule gives an unstable radical-cation, which reacts with a molecule of the starting compound to give a dimeric radical-cation, whose subsequent oxidation leads to dodecaethylhexaamidobisphosphonium diperchlorate. This product is the first example of an acyclic, doubly charged bisphosphonium cation with a . The crystal structure of this compound was obtained by x-ray diffraction structure analysis.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 664–669, March, 1990.     

Catalytic decomposition of ozone over cupric oxide catalysts

Kinetic regularities of the catalytic decomposition of ozone over IC-12-1 and ICT-12-9 cupric oxide catalysts in wetted gases have been studied. These catalysts are suggested to be effective for ozone decomposition.

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-12-1 -12-9 . .

     

Three-dimensional structures of phosphorus-containing heterocycles. Communication 34. 2-Phenoxy-2-oxo-1,3,2-oxathiaphosphorinanes

Conclusions According to the data from the¹H NMR spectra, the dipole moments, and the Kerr effect, the preferred conformation of 2-aroxy-2-oxy-1,3,2-oxathiaphosphorinanes is a chair conformation with an axial orientation of the aroxy grouping and a gauche orientation of the aryl group relative to the P=O bond on the side of the cyclic oxygen atom. In the investigated compounds the p- conjugation is disrupted, as evidenced by the orthogonal orientation of the unshared pair of p electrons of the exocyclic oxygen atom and the orbitals of the benzene ring.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 570–575, March, 1985.     

Influence of oxygen substitution by =NSO2CF3 groups on structure and reactivity of aryl sulfochlorides

Institute of Organic Chemistry, Ukrainian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 4, pp. 161–168, July–August, 1994.