Yu. G. Khabarov

Spectrophotometric determination of hydrazine, methylhydrazine, and 1,1-dimethylhydrazine with preliminary derivatization by 5-nitro-2-furaldehyde

Abstract5-Nitro-2-furaldehyde, a new derivatizing agent for the spectrophotometric determination of hydrazine, methylhydrazine, and 1,1-dimethylhydrazine is proposed. It is characterized by high solubility in water and by a substantial difference in the positions of absorption bands of the formed colored derivatives. The kinetics of the reaction of analyte derivatization is studied, and reaction conditions (pH 5, concentration of derivatizing agent 2 mM, 60° C, duration 40 min) are optimized. The limits of detection are 5, 3, and 1.5 μg/L for hydrazine, methylhydrazine, and 1,1-dimetlhydrazine, respectively. A possibility of the spectrophotometric determination of analytes in their simultaneous presence using the Firordt method is shown. The developed approach is successfully applied to the analysis of polluted peat bog soil selected at a place of impact of the first step of a carrier rocket.

Characterisation of oxidation products of 1,1-dimethylhydrazine by high-resolution orbitrap mass spectrometry

1,1-Dimethylhydrazine is used as a fuel for carrier rockets in the majority of countries implementing space exploration programs. Being highly reactive, 1,1-dimethylhydrazine easily undergoes oxidative transformation with the formation of a number of toxic, mutagenic, and teratogenic compounds. The use of high-resolution mass spectrometry for the study of the reaction of 1,1-dimethylhydrazine oxidation with hydrogen peroxide in aqueous solution allowed us to find hundreds of nitrogen-containing products of the CHN and CHNO classes, formed via radical processes. The vast majority of the compounds have not been previously considered as possible products of the transformation of rocket fuel. We have shown that the oxidation of 1,1-dimethylhydrazine proceeds in two stages, with the formation of a great number of complex unstable intermediates that contain up to ten nitrogen atoms. These intermediates are subsequently converted into final reaction products with a concomitant decrease in the average molecular weight. The intermediates and final products of the oxidative transformation of 1,1-dimethylhydrazine were characterised on the basis of their elemental composition using van Krevelen diagrams and possible compounds corresponding to the most intense peaks in the mass spectra were proposed. The data obtained are indicative of the presence of the following classes of heterocyclic nitrogen-containing compounds among the oxidation products: imines, piperidines, pyrrolidines, dihydropyrazoles, dihydroimidazoles, triazoles, aminotriazines, and tetrazines. The results obtained open up possibilities for the targeted search and identification of new toxic products of the degradation of rocket fuel and, as a result, a more adequate assessment of the ecological consequences of space-rocket activity.

Studies of reaction products of hydrolytic lignin with nitric acid

The properties of the reaction products of hydrolytic lignin with nitric acid in water—dioxane medium were studied. The products are a mixture of nitrogen-containing oligomeric compounds with high degree of polydispersity.

Synthesis of a magnetoactive compound based on iron(II) sulfate

The effect of synthesis parameters on properties of a magnetoactive compound (MAC) prepared via condensation of iron(II) sulfate in the presence of sodium nitrite is investigated. It is found that nitrite ions almost completely coprecipitate with the solid phase during the formation of a magnetoactive compound and subsequently participate in the redox conversions to yield magnetite. In order to obtain a magnetoactive compound with high relative magnetic susceptibility, condensation from the initial solutions is to be carried out at least 15 min after it is prepared; sodium nitrite consumption is to be at least 0.12 mol/mol FeSO4.

The influence of the nitrosation conditions of lignosulfonates on the synthesis of magnetoactive compound

The influence of reagent consumption (sodium nitrite and nitric acid) and nitrosation time of lignosulfonic acids on their peptization activity during subsequent synthesis of a magnetoactive compound on the basis of iron(II) sulfate with the properties of a magnetic fluid was determined.

Synthesis of 2,4-dinitrophenol

New highly selective method is suggested for synthesis of 2,4-dinitrophenol by nitration of phenol with nitric acid in an aqueous-alcoholic medium at the boiling point of the reaction mixture. The yield of 2,4-dinitrophenol is as high as 80%.

Spectrophotometric determination of mercury(II) with sodium sulfite

A photometric procedure is developed for determining mercury(II) in aqueous media. It is based on the reaction of mercury(II) with sodium sulfite giving a product with an absorption maximum at 230 nm. The optimum conditions are found. The procedure allowed 0.5 to 13.0 μg/mL of mercury(II) to be determined for 1 min. The effect of some metal cations is estimated.

Synthesis of a magnetoactive compound by the interaction of iron(II) sulfate with potassium chromate

A study was made of the effect of synthesis conditions on the properties of a magnetoactive compound obtained by the interaction of iron(II) sulfate with potassium chromate. It was found that, in the formation of the magnetoactive compound, chromium is almost completely coprecipitates with the solid phase. To produce the magnetoactive compound with high relative magnetic susceptibility, it is necessary to precipitate it from the initial solution in no less than 10 min after its preparation at a K2CrO4: FeSO4 molar ratio of 0.16–0.18.

Nitration of sulfate lignin under homogeneous conditions studied by electron spectroscopy

The nitration of sulfate lignin by nitric acid in an aqueous-dioxane medium under homogeneous conditions was studied. The method proposed makes it possible to synthesize nitrated lignin with the content of one nitro group per 1.5–2 phenylpropane units. At low consumptions of nitric acid, the nitration starts after an induction period, the duration of which decreases with increasing temperature. The presence of the induction period is related to redox transformations forming nitrous acid that nitrosates lignin.

Nitration of phenol in 1,4-dioxane

The nitration of phenol with excess nitric acid in aqueous dioxane, in contrast to the nitration in aqueous ethanol, yields exclusively 2,4-dintrophenol, whereas at equimolar ratio of phenol and nitric acid the major reaction products are mononitrophenols (99%), among which the p-isomer prevails.