Oxidative Transformations of Phenylacetylene on a Manganese(IV) Oxide Adsorbent-Catalyst

It is shown by IR spectroscopy and thermally programmed surface reactions that the complete oxidation of phenylacetylene on hydrated manganese dioxide in an adsorption catalytic regime occurs via dissociation of the CC bond (during chemisorption) with the formation of formate and benzoate on the surface.     

Low-dimensional chainlike assemblies of TiO2 nanorod-stabilized Au nanoparticles

A simple and versatile light-based strategy to grow low-dimensional gold superstructures is presented; prolonged UV-irradiation of TiO2 nanorod-stabilized Au nanoparticles in organic media promotes the progressive formation of distinctive chainlike metal assemblies, namely segments of a few gold particles, 2D or quasi-1D large structures composed of interlacing lines of hundreds of metal units over areas of about 500 nm2.     

Diffusion Boundary Layers in Transport of Aliphatic Acids in Electromembrane Systems

The regularities of the formation of diffusion boundary layers during the transport of aliphatic acids in electromembrane systems are studied and their characteristics obtained experimentally are analyzed. It is shown that their concentration profiles in solutions of the electrodialyzer sections are asymmetric near membranes of different polarity. Experimental values of diffusion layer thicknesses are compared with those following from the known theoretical relations. The equation, which is proposed for the surface concentration, permits the prediction of the operation mode of apparatus during electrodialysis of solutions of aliphatic acids and other weak electrolytes. Specific features characterizing the emergence of a limiting state and the character of the distribution of limiting current densities over the height of the membrane channel are revealed.     

Coordination of aza heterocycles with macroheterocyclic metal complexes in amphiprotic media: III. Kinetics and mechanism of inner-sphere ligand exchange in (tetraphenylporphyrinato)chromium(III)

Inner-sphere replacement of alcohols by imidazole and its derivatives in the complex (acetato)-(tetraphenylporphyrinato)chromium(III) was studied by electronic absorption spectroscopy. The rate constants and activation parameters of the process were calculated. The entering ligand structure was shown to affect the reaction rate, while the alcohol nature (departing ligand) does not influence the kinetic parameters of the process to an appreciable extent. Regression analysis revealed participation of imidazole and ethanol in the rate-determining stages. The kinetic equation for the inner-sphere axial substitution implies interaction of a free alcohol molecule with that coordinated to chromium, followed by replacement of the associate by the heteroring. Mathematical processing of the kinetic data in terms of the proposed solvolytic association-dissociation mechanism gave the rate constants for particular stages of the process and showed an extremal relation between the rate constant and composition of the solvent.     

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