Search

The interaction of maleic anhydride with 2-methylimidazole in different solvents and without solvents was studied using electronic, IR, and 1H NMR spectrometry; differential scanning calorimetry; and potentiometric titration. On the basis of experimental data and quantum-chemical calculations, it was demonstrated that molecular complexes can be formed as intermediates in the chain of consecutive reactions. It was found that, depending on the nature of anhydride, complex formation can be absent (in the case of phthalic anhydride). Because of the formation of the molecular complex between maleic anhydride and 2-methylimidazole, the nucleophilic addition of the latter at the double bond of anhydride yielding amide of the succinic acid derivative is possible.

The IR spectra of 40% acetone solutions of epoxy resins with different molecular mass were studied. A correlation was found between the intensities of some absorption bands for the determination of epoxide (920 cm-1) and hydroxyl (3450 cm-1) groups and for the estimations of the average molecular mass of the resin (1108 cm-1).

A method is proposed for the determination of anhydride groups by their reaction with piperidine in acetonitrile. This method exhibits some advantages over those known previously, which are determined by the use of a more basic amine as the amide-forming agent and of acetonitrile, which is indifferent to anhydride groups and miscible with water, as solvent. It is demonstrated that solvents that were previously used for the determination of anhydrides are not indifferent to the latter. This method provides the titrimetric determination of strong acids. © 1998 MAHK Hayka/Interperiodica Publishing.

A reaction of maleic anhydride with epoxy-dian resins in methyl ethyl ketene was investigated. It was shown by potentiometric titration that the resulting maleic esters are stable to hydrolysis in acid and weakly acid organic solutions. This reaction can be used for the quantitative determination of hydroxyl groups in epoxy resins. Epoxy groups do not interfere with the formation of maleic esters under the conditions of determination. The optimal reaction conditions were found. The reaction kinetic was investigated, the reaction rate constants were determined at various temperatures, and the activation energy was found. The value of the activation energy indicates that the reaction is characterized by a low potential barrier. © 2001 MAIK "Nauka/Interperiodica".

The reactions of the formation of monosubstituted titanium ethylene, diethylene, and triethylene glycolates based on the interaction of glycols with tetrabutoxytitanium in solutions were investigated. It was shown that ethylene glycol predominantly forms cyclic structures: diethylene glycol, a mixture of cyclic and linear structures, and triethylene glycol, mainly linear structures. The comparative analysis of the reaction products showed that the most promising precursor for the synthesis of TiO2 is a titanium compound based on triethylene glycol. © 2010 Pleiades Publishing, Ltd.

This article reviews the latest advances in the production and investigation of the properties of TiO2-based nanomaterials as photocatalysts for water decomposition into molecular oxygen and hydrogen, a component of disinfecting, photooxidative, and self-cleaning surfaces, and materials for sensors and catalysts. © 2011 Pleiades Publishing, Ltd.

The optical and protolytic properties of 2,4,6-tris[(dimethylamino)methyl] phenol were studied. The use of nonaqueous solvents provides the determination of the ratio of functional groups by potentiometric titration. A procedure is proposed for the determination of the functional composition of the compounds.

Different mechanisms of the catalytic action of tetrabutoxytitanium in esterification and transesterification reactions are analyzed. New evidence is obtained in favor of the nonionic mechanism of ester formation catalysis by glycol-tetrabutoxytitanium adducts in esterification reactions. © 2009 Pleiades Publishing, Ltd.

Analytical reactions for the determination of epoxy and isocyanate groups in the presence of each other in epoxy-isocyanate compositions were studied. For the determination of epoxy groups in the presence of isocyanate groups, a test with HBr in glacial acetic acid was proposed; acetic acid reacts with isocyanate groups and, hence, masks them. Isocyanate groups in the presence of epoxy groups were determined by potentiometric titration with a solution of piperidine in ethyl methyl ketone. The addition of toluene to the test solution decreases the fraction of the enol form of ethyl methyl ketone, which interferes with the determination.

Selective reactions for the determination of epoxy groups in the presence of acrylic acids and aromatic amines were studied. Factors affecting results of the determination of epoxy groups were revealed. Procedures were developed for the determination of epoxy and carboxylic groups and epoxy and amine (aromatic) groups in the presence of each other. The reaction is conducted in excess HCl in the former case and in excess tetraethylammonium bromide in the latter case. Performance characteristics of the procedures were estimated.