Determination of hydroxyl groups in epoxy resins by potentiometric titration using a reaction with maleic anhydride

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"

m-Aminophenylarsonic acid as an analytical form for the photometric determination of phenol in water

The azocoupling reaction of diazonium salts of o- and m-aminophenylarsonic acids with phenol was studied. On the basis of quantum-chemical calculations of the reagents, conformation analysis of resulting azo compounds, and experimental data, it was found that the meta isomer of aminophenylarsonic acid is of practical interest as an analytical reagent for the determination of phenol. The advantage of the proposed reagent is a high stability of the diazonium salt. A procedure was developed for the spectrophotometric determination of phenol in water at a level of 0.06 μg/mL. The error in the determination is no higher than 5.5%

Determination of Epoxide and Hydroxyl Groups in Epoxide Resins by IR Spectrometry

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)

m-Aminophenylarsonic acid as a reagent for the extraction preconcentration of phenol

The azocoupling reaction of phenol with the diazonium salt of m-aminophenylarsonic acid was used for the determination of phenol in water at a level of maximum permissible concentrations. The resulting compound is stable in a wide pH range, which made it possible to develop a procedure for the determination of phenol with the preconcentration of the azo compound by extraction to isobutanol at pH 2 and subsequent back extraction to the aqueous phase at pH ≥ 10. The high concentration coefficient of phenol (65) provides for determination of phenol down to 0.9 μg/L

Determination of epoxy and isocyanate groups in the presence of each other

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

Determination of epoxy groups in the presence of carboxylic acids of the acryl series and aromatic amines

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

Determination of functional groups in 2,4,6-tris[(dimethylamino)methyl] phenol by potentiometric titration

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

Photometric determination of octadecylamine with methyl orange

The reaction of octadecylamine with Methyl Orange in water at pH 2.5-4.0 was studied. Linear relationships were revealed between the decrease in the absorbance of an aqueous solution of Methyl Orange and the concentration of octadecylamine. Optimal conditions of the reaction were found. It was demonstrated that 50- to 200-fold amounts of lower aliphatic and aromatic amines and salts of lower quaternary ammonium bases do not interfere with the determination. Procedures were developed for the photometric determination of 0.083-1.0 μg/mL and 0.74-10 μg/mL octadecylamine

Determination of phenylurethane and isocyanate groups in isocyanates

Reactions of phenylurethane and isocyanate groups of arylisocyanates with secondary amines are studied by IR spectrometry and potentiometric titration. It is found that the rate of the reaction between isocyanate groups and diethylamine is nearly independent of the solvent nature. When protophilic solvents are used, solvent molecules and isocyanate groups form associates, which interfere with the determination. Optimal conditions are determined for the determination of phenylurethane and isocyanate groups. Procedures are developed for determining mass fractions of isocyanate and phenylurethane groups when they are present simultaneously. © 1999 MAEe Cyrillic signK "Hayκa/Interperiodica"

Study of Adducts in the Photometric Determination of Maleic Anhydride by Its Reaction with 2-Methylimidazole

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