Six-membered cyclic semiaminal as intermediate in the synthesis of thiazoles from thiosemicarhazide and α-haloketones

Cyclization of thiosemicarbazide with methyl 3-chloro-2-oxo-3-phenylpropionate in MeCN results in 5-hydroxy-2-imino-5-methoxycarbonyl-6-phenylperhydro-1,3,4-thiadiazine. The structure of the product has been confirmed using spectral (IR,¹H,¹³C,¹³C{¹H} NMR) methods and chemical transformations.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1962–1965, November, 1993.     

Identification of structural vacancies in carbides,oxides, and sulfides by Doppler broadening of the gamma-ray line

A method has been developed to identify the sublattices of a crystal structure in which there are atomic vacancies. This method is based on determining the chemical environment of vacancies and is implemented using the method of the positron annihilation by measuring the momentum distribution of core electrons. To determine the characteristic momentum distribution of electrons, a special two-detector spectroscopy is used, which ensures measurements of Doppler broadening of the annihilation gamma-ray line with a high (up to 10⁶) signal-to-noise ratio. To test the method, vacancies in irradiated silicon carbide (6H-SiC), sintered nonstoichiometric titanium carbides (TiC _y ) and titanium monoxides (TiO _y ), and chemically deposited lead and cadmium sulfides (PbS and CdS) have been identified. Vacancies in the carbon and silicon sublattices have been identified in silicon carbide after irradiation by low- and high-energy electrons, respectively. Vacancies in the nonmetal sublattice have been identified in TiC _y . Vacancies in the metal sublattice have been identified in TiC _y , as well as in PbS and CdS.     

In situ study of the temperature stability of TiO1.05 titanium monooxide using synchrotron radiation

The temperature stability of cubic TiO_1.05 titanium monooxide is investigated. An in situ X-ray structural analysis is performed using synchrotron radiation in a high temperature vacuum chamber. It is found that under poor vacuum and at high heating rates of up to 1250°C, the structural transformations in TiO_1.05 occur at 630°C. In particular, there is a phase transition from TiO_1.05 (space group Fm-3m) to rhombohedraic Ti₂O₃ (space group R-3c) via Ti_2.5O₃ (space group Immm).     

Micellar nanocontainers based on cationic surfactants with a pyrrolidinium head group for increasing drug bioavailability

Russian Chemical Bulletin - A homologous series of cationic surfactants with a pyrrolidinium head group containing a hydroxyethyl moiety was studied for the solubilization of nonsteroidal...     

Aggregation behavior of morpholinium surfactants in the presence of organic electrolytes

It was shown that the addition of organic electrolytes to aqueous solutions of morpholinium surfactants facilitates micellization, reduces the micellar surface potential, increases the hydrodynamic diameter of micelles and favors the formation of cylindrical micelles which behave as pseudoplastic fluids. At low shear rates, the viscosity is extremely large and changes insignificantly, and it decreases sharply with increase in shear rate. Significant decrease in viscosity upon the increase in shear deformations indicates the orientation of cylindrical micelles along the direction of the flow with the increase in shear rate.     

Direct functionalization of the C—H bond in (hetero)arenes: aerobic photoinduced oxidative coupling of azines with aromatic nucleophiles (SNH-reactions) in the presence of a CdS/TiO2 photocatalyst

A highly selective coupling of azines with aromatic nucleophiles (S_N^H-reactions) in the presence of a heterogeneous oxidation system O₂/CdS/TiO₂ upon exposure to daylight was accomplished.     

Nanosized reactors based on polyethyleneimines: from microheterogeneous systems to immobilized catalysts

Effective nanoreactors based on polyethyleneimines (PEIs) for the hydrolytic cleavage of O-alkyl O-p-nitrophenyl chloromethylphosphonates (alkyl = ethyl, hexyl) and di(p-nitrophenyl)phosphate were developed in conformity with the idea of modeling the polyfunctional catalytic mechanism of enzymes. A step-by-step modification of the single PEI solution by additives with their own catalytic activities (sodium dodecyl sulfate and lanthanum salt) gave rise to a marked improvement in the reaction efficiency. A 104-106-fold acceleration of the reaction compared to the aqueous basic hydrolysis of the substrates was achieved in the sodium dodecyl sulfate-polyethyleneimine-La(III) ternary system. This system can be considered to be metallomicelles immobilized on a hydrophilic polymer matrix. When the PEI immobilized on silica gel was used as a catalyst, the full completion of the reaction was achieved for 100 min under mild conditions, while the half-life of the reaction in a comparable homogeneous regime exceeds 100 h.     

Investigation of structural vacancies in titanium monoxide by electron-positron annihilation

Local atomic environment of vacancies in nonstoichiometric titanium monoxide ranging in composition from TiO_0.74 to TiO_1.26 was studied by electron-positron annihilation. Analysis of the Doppler broadening spectra of the annihilation gamma line for titanium and liquid oxygen showed that positrons in titanium monoxide are trapped by titanium vacancies. Experiments revealed that the lifetime of positrons in ordered and disordered titanium monoxide TiO _y increases with increasing oxygen content y and varies from 184 to 210 ps. Data on the valence electron density permitted the prediction that the lifetime of free positrons in stoichiometric titanium monoxide is about 140 ps and the lifetime of positrons localized in an oxygen vacancy is about 170 ps. The method used to analyze the gamma-line Doppler broadening spectra makes it possible to determine the type and number of atoms around a vacancy and to investigate order-disorder phase transformations in nonstoichiometric compounds.     

Electrical conductivity and magnetic susceptibility of titanium monoxide

Conductivity and magnetic susceptibility of disordered cubic titanium monoxide TiO_y(0.920≤y≤1.262) are studied. Temperature dependences of the conductivity of TiO_y monoxides with y≤1.069 are described by the Bloch-Grüneisen function with Debye temperature 400–480 K, and temperature dependences of the susceptibility include Pauli paramagnetism of conduction electrons. The behavior of conductivity and susceptibility of TiO_y with y≥1.087 is typical of semiconductors with nondegenerate charge carriers obeying Boltzmann statistics. The band gap ΔE between the valence and conduction bands of TiO_y(y≥1.087) is 0.06–0.17 eV, and effective mass of charge carriers is equal to 7–14 electron masses.