Lysine-containing calcium hydroxylapatite: Synthesis and physicochemical characterization

The CaCl₂-(NH₄)₂HPO₄-NH₂(CH₂)₄NH₂CHCOOH-NH₃-H₂O system at 25°C is studied using Tananaev’s solubility (residual concentrations) method and pH measurements. Lysine-containing calcium hydroxylapatite Ca₁₀(PO₄)₆(OH)_1.9[NH₂(CH₂)₄NH₂CHCOO]_0.1 · 6H₂O is identified using chemical analysis, thermogravimetry, powder X-ray diffraction, and IR spectroscopy.     

The effect of the counterion composition on the chain restriction in the cationic polymerization of isobutylene

The effects of the nature of halogens in the initiatingtert-butyl halide-aluminum-containing Lewis acid system on the number average molecular weightM _n and the structure of end groups of polyisobutylene macromolecules obtained in the cationic polymerization of isobutylene in hexane at -78 °C were studied. An increase inM _n is observed in the transition from chlorine to bromine and iodine, accompanied by a decrease in the fraction of end C=C groups and an increase in the relative content of C-Hal groups (Hal = Cl, Br, and I). When atoms of different halogens are present in the counterion, more bulky atoms preferentially participate in the formation of the end groups. The results are interpreted within the framework of the principle of hard and soft acids and bases.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1184–1187, May, 1996.     

Cationic polymerization of hydrocarbon monomers induced by complexes of acyl halides with Lewis acids 5. Polymerization of isobutylene in the presence of the complexes of benzoyl chloride with aluminum bromide

Polymerization of isobutylene inn-hexane at -78 °C in the presence of the complex of benzoyl chloride with AIBr₃ (1 : 2) was investigated. The results were compared to those obtained previously for the polymerization of this monomer induced by the complex of acetyl bromide with AlBr₃. Both complexes initiate the polymerization only by acyl cations. The number average molecular weight (M _n ) of the polymer linearly increases as the degree of isobutylene conversion increases. The polymerization restarts after repeated addition of the monomer, andM _n continues to increase linearly. The efficiency of the initiaton by the benzoyl chloride complex does not exceed 6.2 %; the reaction has the second order with respect to the initiator in the case of PhCOCI · A1₂Br₆; and the chain-propagation rate constant is 13.9 L mol^–1 s t. The use of PhCOCI Al₂Br₆ as the initator of the polymerization of isobutylene allows one to prepare macromolecules with very low contents of the terminal C=C double bonds and with narrow molecular weight distributions. Unlike the MeCOBr·AlBr₃ complex, PhCOCl · AlBr₃ does not initiate polymerization of isobutylene.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1175–1179, May, 1996.     

Reaction of formaldehyde with the Wilkinson complex in the presence of carboxylic acid amides

N,N-Dimethylacetamide and N, N-dimethyformamide react with RhCl(PPh₃)₃ with displacement of PPh₃ and the formation of a complex with the amide. Formamide and N-propylacetamide do not form similar complexes under similar conditions. In contrast to the reaction of RhCl(PPh₃)₃, which leads to the formation of RhCl(CO)(PPh₃)₂ due to decarbonylation of CH₂O, stabilization of the ₂-CH₂O form of the CH₂O coordinated with rhodium is likely in the reaction of formaldehyde with a rhodium complex containing an N-bonded amide. Under the conditions of hydroformylation of CH₂O in a solution of the Wilkinson complex in an unsubstituted amide the dominating pathway of the transformation of formaldehyde is its reaction with the solvent or the ammonia formed via decarbonylation of the unsubstituted amide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2670–2673, December, 1989.     

Electret-thermal and dielectric analyses of electrically active colloids

The nature and mechanism of interfacial electrical interaction in organic colloids containing an active solid phase and a polar liquid phase are studied. Such systems are shown to offer specific properties. Specifically, high electrical forces producing gradients of the potential of the self-electric internal field arise at the liquid-solid interface. In the presence of free charges and ionic conductivity channels, this field can induce currents in such systems. When investigating the colloid system of the human venous blood, it is found that the internal field causes mesoscopic inhomogeneity in the structure of the aqueous components of the plasma and cytoplasm. It is shown that the concentration of free water molecules in the liquid phase of the system is maximal in group I blood and the physically nonuniform properties of combined water show up to the greatest extent in group IV blood. This finding is corroborated by the dispersion of the dielectric polarization in blood of different groups.     

Optimization of experimental conditions for the preparative displacement chromatography of antitumor anthracycline antibiotics on carboxylic sorbents

The physico-chemical conditions and the limits of the rates of mobile phases are determined when effective regimes of preparative chromatography in the conditions of sharpening the boundaries of chromatographic zones of anthracycline antibiotics are realized. The influence of pH on the equilibrium, kinetics and dynamics of sorption of anthracycline antibiotics (rubomycin, doxorubicin and carminomycin) on the carboxylic sorbents has been studied.     

Coprecipitation of calcium hydroxyapatite,graphene oxide,and chitosan from aqueous solutions

We determined the character of interactions between calcium hydroxyapatite Са₁₀(РO₄)₆(ОН)₂ (HA), graphene oxide (GO), and chitosan (С₆Н₁₁NO₄) _n (CHT) to yield HA/CHT/GO nanocomposites (NCs) in the СаС1₂–(NH₄)₂НРО₄–NH₃–Н₂О–(С₆Н₁₁NO₄) _n –GO system (25°С). A set of physicochemical methods helped us to elucidate composition–synthesis parameters–structure–particle size–properties correlations for the prepared NCs and to prove the feasibility to manufacture NCs with tailored HA, CHT, and GO contents, described by the bulk formula Са₁₀(РО₄)₆(ОН)₂ · х(С₆Н₁₁NO₄) _n · yGO · zН₂О, where х = 0.1, 0.2, 0.3; y = 0.6, 1.2, 2.4; and z = 6.0–7.4.     

Anomalous properties of absorbed water films in layered silicates

The electrical properties of water films in residual electric fields on the surface of crystals and in slitlike capillaries of layered silicates are investigated. The results obtained indicate a substantial change in the water structure, degradation of the dipole-orientation polarization of molecules, and a decrease in the crystallization temperature.