Vol 480, No 2 (2018)

Reactions of catechin and dihydroquercetin flavonoids with amino acids containing primary amino groups have been conducted. Amino acids can be used in both electrophilic substitution (Mannich aminomethylation) and electrophilic substitution (acylation) reactions.

The N-acylation of partially deacetylated chitin nanofibers with succinic anhydride gave N-succinyl-chitin. The introduction of succinyl groups into chitin nanofibers followed by sonication of the aqueous dispersion of N-succinyl-chitin gives rise to a stable aqueous dispersion (with particle hydrodynamic radius of 350 nm and ζ-potential of –22 mV). The particle morphology simultaneously changes from rod-like with (100–500) × (6–15) nm size to spherical with 160–400 nm size, whereas the chitin crystal structure barely changes.

Photochromic indoline spiropyrans with carbohydrazide substituents in the pyrano[2,3-f]chromene moiety of the molecule have been synthesized. These compounds exhibit inochromic properties and are chromogenic (“naked-eye”) and fluorogenic chemosensors for lanthanide cations.

It was determined that the system LaPO₄–SiO₂–NaF–Nb₂O₅ within the temperature range 850–1200°C has regions of immiscibility of liquid phases (silicate and phosphate–salt melts). The coexisting melts have contrast chemical and phase compositions and structural-textural features, because of which the methods for extracting rare-earth elements and niobium from these melts differ. The silicate melts form glass, whereas the phosphate–salt melts have high crystallization ability. The mutual solubility of the liquid phases does not exceed 5%. The components of the system are contrastively distributed between the silicate and phosphate–salt melts. A fraction of 95–97% of niobium is extracted into the silicate melt, and 93–95% of La and P is extracted into the phosphate–salt melt.

Free SHS compaction was tested as a method for producing large compact plates more than 100 mm in size from powders of high-melting inorganic compounds based on titanium diboride. Materials science studies of the obtained plates were performed, and their physicochemical properties were investigated. The synthesized material was heat-resistant at temperatures to 1100°C.