Doklady Chemistry最新文献

The highly alkaline multicomponent systems TiO₂–H₂SO₄–Na₂SiO₃–NaOH–H₂O and TiO₂–H₂SO₄–(NH₄)₂SO₄–Na₂SiO₃–NaOH–H₂O have been studied under conditions of hydrothermal synthesis, which gives new products with specified technical properties. It has been shown that, by a targeted selection of structure-forming components, in particular, titanium compounds, together with optimal parameters of hydrothermal treatment of the formed precursor, one can obtain compounds with given chemical composition and particle size and morphology. It has been found that the rate of structural transformations in the synthesis depends on the phase composition of titanosilicate precursors. Their hydrothermal treatment involves the alkaline and thermal hydrolysis followed by dehydration of the hydrolyzed phases of titanium(IV) and silicon. This is accompanied by the localization of free bonds ensuring the formation of Ti–O–Si–O bridges and their subsequent transformation into new structured species.

Radical copolymerization of coumarin with N-vinylamides (N‑vinylpyrrolidone, N-methyl-N-vinylacetamide, N-vinylformamide) has been used to prepare copolymers of various composition with variable molecular weights. Subsequent reactions in their polymer chains affords water-soluble copolymers of salts of hydroxycinnamic acid and its hydrazides. The synthesized copolymers of hydroxycinnamic acid salts and hydrazides with N-vinylamides have low cytotoxicity and demonstrate the pronounced antiviral activity against human respiratory syncytial virus (strain A2).

The paper presents a new low-temperature method for the synthesis of fine powders of double phosphates LiCoPO₄ and LiNiPO₄ using a low-waste technology. It has been shown that the morphology and particle size distribution of the synthesized materials are determined by the type of precursor used. The resulting compounds are characterized by chemical analysis, X-ray powder diffraction analysis, scanning electron microscopy, cyclic voltammetry, and cyclic chronopotentiometry. The new approach to the synthesis of submicron powders of lithium and transition metal (nickel or cobalt) double phosphates is more efficient than the existing conventional methods.

The phenomenon of selective sorption of a stable nitroxyl radical TEMPO on rubber particles in the powder of dried and dispersed root of kok-saghyz has been discovered. This feature of the rubber-bearing root material has contributed to the development of a new, highly sensitive method of quantitative analysis of rubber by measuring the integrated intensity of the EPR TEMPO signal. The main advantages of the proposed method are the speed and the ability to determine the content of rubber directly in the roots of the plant in microquantities (5–30 mg).

The possibility of using widely available stearin to produce fatty acid-derived ionic liquids (ILs) has been shown for the first time. New amphiphilic ILs based on imidazolium, pyridinium, and quaternary ammonium cations containing long-chain alkyl substituents have been prepared. The synthesized compounds have been shown to have biological activity comparable to known antimicrobial compounds. ILs with one alkyl substituent have higher cytotoxicity and antimicrobial activity compared to disubstituted derivatives.

In the palladium-catalyzed cross-coupling of potassium pentafluorophenyltrifluoroborate with aryl chlorides in the presence of the precursor of SIMes carbene, the yields of pentafluorobiphenyls decrease, whereas the yield of 2,3,4,5,6-pentafluoro-4'-methylbiphenyl from 4-bromotoluene under the same conditions increases. An explanation for this phenomenon and for the intensification of the side hydrodeboration reaction of the initial borate has been proposed.

The activating effect of AlCl₃ in the amount of 10 mol % in the homocoupling of alkyl-, phenyl-, and silyl-substituted acetylenes with the Mg–Cp₂ZrCl₂ reagent system was found for the first time. The unique nature of this activation is indicated by the fact that in the presence of 10 mol % of Lewis acids BF₃⋅Et₂O, Me₃SiCl, InCl₃, and SnCl₄, the reaction with 5-decyne does not occur even after 5 h, while in the presence of AlCl₃, homocoupling products are selectively formed in high yields within 10 min at room temperature.

A five-stage method for the synthesis of Y-shaped push–pull fluorophores based on 2-(4'-methoxyphenyl)-1,2,3-triazole was proposed. The resulting molecules exhibited emission in the range from 350 to 450 nm with high quantum yields (QY) of 90–99% in solvents of various polarity. The products proved to be applicable as chemosensors for both aromatic and aliphatic nitro analytes in concentrations down to 300 ppb.

The course towards active development of the Arctic zone of the Russian Federation by fuel-and-energy companies involves the development of new methods and approaches to the storage and transportation of natural gas to reduce the negative impact on the ecosystems of cold regions while maintaining the economic feasibility of their use. This work proposes a method for optimizing the technology for transporting and storing natural gas in the form of gas hydrates using soy lecithin as a promoting additive. Experimental methods showed that the addition of soy lecithin to a concentration of 0.5 wt % is on a par with the most efficient promoter of hydrate formation—the surfactant sodium dodecyl sulfate at a concentration of 0.1 wt %. However, a comparison of environmental characteristics demonstrates a clear advantage of soy lecithin. In addition, it was demonstrated that the synthesis of methane hydrate from ground frozen solutions of soy lecithin is at least three times faster than that from liquid solutions.

Methylation and amination reactions of 4Н-[1,2,3]triazolo[4,5-c][1,2,5]oxadiazole salts (K⁺, Ag⁺, Et₃NH⁺, DBUH⁺) have been studied for the first time. It has been shown that the reaction of these salts with MeI results in two methylation products: K and Et₃N salts produce 4- and 5-isomers in equal amounts, while Ag and DBU salts form mainly 4-isomer. It has been found that the main amination product of K and DBU salts of 4Н-[1,2,3]triazolo[4,5-c][1,2,5]oxadiazole with O-(p-tolylsulfonyl)hydroxylamine is 4-azido-3-amino-1,2,5-oxadiazole. A mechanism of its formation via rearrangement of 5-amino-[1,2,3]triazolo[4,5-c][1,2,5]oxadiazole has been proposed.