Oxidative Dehydrogenation of 2,3,5-Trimethyl-1,4-hydroquinone in the Presence of Titanium Dioxide Hydrogel

Liquid-p[hase oxidative dehydrogenation of 2,3,5-trimethyl-1,4-hydroquinone in the presence of titanium dioxide hydrogel was studied by a kinetic method. Associative interactions between the substrate, oxidant, and gel were detected by voltammetry and ESR and IR spectroscopy.     

Nickel(II) and copper(II) complexes based on N-(2-carboxyethyl)alkanolamines: Influence of the amino alcohol structure on the coordination sphere of the metal center

New nickel(II) complexes based on N-(3-hydroxypropyl)-β-alanine, N-(bis(hydroxymethyl)methyl)-β-alanine, and N-(tris(hydroxymethyl)methyl)-β-alanine are synthesized, and their structures are studied by X-ray diffraction analysis. The coordination spheres of the nickel and copper metal centers in the condensed phase are compared for a series of N-substituted β-alaninate ligands with the regularly changed dentate mode. In the case of the copper(II) complexes, an increase in the size of the alkanolamine chelate ring or the number of hydroxymethyl groups provides the formation of achiral coordination structures, whereas the structures of the nickel(II) complexes are independent of the size of the alkanolamine chelate ring or the number of hydroxymethyl groups, thus providing the formation of the complexes as racemic modifications.     

Synthesis of oxocyclohexenecarboxylic acids and podands derived therefrom under heterogeneous catalysis

Nanosized Al, Mg, and Ti-Si oxides, as well as barium hydroxide, have been tested as heterogeneous catalysts in the Robinson reaction with 2-ethoxy-substituted chalcone and podands based thereon. Barium hydroxide catalyzes the first step of the Robinson reaction, Michael addition, while its activity in the second step involving intramolecular cyclization and dehydration is lower. Nanosized oxides effectively catalyze the second step of the Robinson reaction and hamper elimination of the carboxy group. Procedures have been developed for the synthesis of oxocyclohexenecarboxylic acid derivatives and symmetric and asymmetric podands based thereon.     

Synthesis of TiO2-SiO2 and TiO2-SiO2-Cu(II) xerogels by cohydrolysis of precursors in the absence of a solvent and redox catalysts

Cohydrolysis of tetrabutoxytitanium and tetraethoxysilane in a desiccator in the presence of water vapor produced a TiO₂-SiO₂ binary xerogel and its Cu(II)-containing analog. The hydrolysis was performed without using either a solvent, or redox catalysts. The effect of the synthesis conditions on the physicochemical properties of the obtained material was studied.     

Synthesis of SiO2-TiO2 binary composites with cellulose as the substrate

A procedure for the synthesis of the SiO₂-TiO₂ binary material was developed. The procedure includes the formation of the silica matrix by impregnating cellulose plates with tetraethoxysilane followed by hydrolysis of the organometallic compound and burning-out of the cellulose constituent; activation of silica with HF; and deposition of titanium dioxide on the surface of the silica matrix by impregnating it with a solution of tetrabutoxytitanium, which is hydrolyzed in water-ammonia atmosphere. The physicochemical properties of the obtained material were studied.     

Development of the method of polystyrene chloromethylation using the synthesis in gel approach

Russian Chemical Bulletin - A new method for the preparation of poly(chloromethylstyrene) by synthesis in a gel via treating of linear polystyrene with cyclic formals in thionyl chloride has been...     

Physicochemical properties of TiO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript> xerogel modified by hydrogen peroxide

How the specific surface area and the amorphous-to-crystalline titania phase ratio in TiO₂–SiO₂ (14 mol % TiO₂) xerogels change during the fivefold repeated cycles comprising the hydrogen peroxide treatment of the xerogel followed by drying and calcining of the binary material, was traced by the BET method, X-ray powder diffraction, and IR spectroscopy.     

The effect of the structure of a cross-linking reagent of the alkylating type on the properties of chitosan granules

Russian Chemical Bulletin - The reactivity of chitosan in the form of granules towards a series of cross-linking reagents of alkylating type is compared. The following cross-linking reagents were...