Phase-Transfer catalyzed alkylation of morpholine with 1,2-dichloroethane

Russian Journal of General Chemistry -     

Phase formation mechanism of the Ni?+?Zr?+?polytetrafluoroethylene reactive mixture

The combustion process in the Ni?+?Zr?+?Polytetrafluoroethylene (PTFE) system is investigated. Effect of PTFE addition on the process parameters and characteristics of products are studied. The reacting mixtures and product obtained are studied by differential thermal analysis (DTA) and thermogravimetric (TG) techniques, mass-spectroscopy, ion-chromatography, and XRD analysis. Results are discussed in terms of literature data. The mechanism of combustion process is proposed according to which at initial stages monomer formed at PTFE decomposition reacts with metals to form ZrC, ZrF₂, and NiF₂. At elevated temperatures, ZrF₂ disproportionate to form gaseous ZrF₄. Heat generated at early stages of the process stimulates the formation of Ni?CZr intermetallic phases.     

X-ray studies of magnetic phase transitions in the intermetallic compounds RMn2Ge2 (R=La, Sm, Gd, Nd, Tb, and Y)

The lattice parameters a and c of the tetragonal intermetallic compounds RMn₂Ge₂ (R=La, Sm, Gd, Nd, Tb, and Y) have been measured by x-ray diffraction in the temperature interval 10–800 K. Anomalies are observed in the temperature dependence of a and c due to phase transitions from the paramagnetic to the magnetically ordered state in the Mn subsystem, transitions between various magnetically ordered phases due to a change in the magnitude and sign of the Mn-Mn exchange interaction, and magnetic transitions caused by ordering of the rare-earth subsystem leading to a rearrangement of the magnetic structure of the Mn subsystem. It is concluded that, along with the lattice parameter a, the lattice parameter c also has an influence on the Mn-Mn exchange interaction. Fiz. Tverd. Tela (St. Petersburg) 41, 2053–2058 (November 1999)     

A base promoted cyclization of N-propargylaminopyridines. Synthesis of imidazo[1,2-a]pyridine derivatives

A base promoted cyclization of the protected N-propargylaminopyridines was shown to be an efficient method for the preparation of imidazo[1,2-a]pyridine derivatives. The reactions were carried out with a small excess of base, at room temperature or slightly above producing the heterocyclic products in moderate to good yields. The stereoelectronic properties of substituents on the pyridine ring were shown to influence the cyclization process.     

Magnetic phase diagrams of ferrimagnets having two magnetically unstable subsystems

The molecular field approximation is used to construct magnetic phase diagrams along with magnetization curves for ferrimagnets having two magnetically unstable subsystems. Diverse sequences of phase transitions of various kinds—first order (metamagnetic) and second order (via a noncollinear phase)—are realized in the course of magnetizing such ferrimagnets. Analysis reveals how the magnetization curves depend on the relative values of parameters of the two subsystems, e.g., sublattice magnetizations in weak and strong states, critical fields, and values of the exchange interaction between sublattices. Fiz. Tverd. Tela (St. Petersburg) 40, 280–284 (February 1998)     

Monte Carlo simulations of vapor–liquid–liquid equilibrium of some ternary petrochemical mixtures

The aim of this study was to determine the capability and accuracy of Monte Carlo simulations to predict ternary vapor–liquid–liquid equilibrium (VLLE) for some industrial systems. Hence, Gibbs ensemble Monte Carlo simulations in the isobaric–isothermal (NpT) and isochoric–isothermal (NVT) ensembles were performed to determine vapor–liquid–liquid equilibrium state points for three ternary petrochemical mixtures: methane/n-heptane/water (1), n-butane/1-butene/water (2) and n-hexane/ethanol/water (3). Since mixture (1) exhibits a high degree of mutual insolubility amongst its components, and hence has a large three-phase composition region, simulations in the NpT ensemble were successful in yielding three distinct and stable phases at equilibrium. The results were in very good agreement with experimental data at 120 kPa, but minor deviations were observed at 2000 kPa. Obtaining three phases for mixture (2) with the NpT ensemble is very difficult since it has an extremely narrow three-phase region at equilibrium, and hence the NVT ensemble was used to simulate this mixture. The simulated results were, once again, in excellent agreement with experimental data. We succeeded in obtaining three-phase equilibrium in the NpT ensemble only after knowing, a priori, the correct three-phase pressure (corresponding to the force fields that were implemented) from NVT simulations. The success of the NVT simulation, compared to NpT, is due to the fact that the total volume can spontaneously partition itself favorably amongst the three boxes and only one intensive variable (T) is fixed, whereas the pressure and the temperature are fixed in an NpT simulation. NpT simulations yielded three distinct phases for mixture (3), but quantitative agreement with experimental data was obtained at very low ethanol concentrations only.     

Quantum chemical study of 2-substituted 4-oxo-and 4-thioxospiro(benzo[h]quinazoline-5,1′-cycloalkanes) in alkylation reactions

The steric and electronic structures of 2-substituted 4-oxo- and 4-thioxospiro(benzo[h]quinazoline-5,1-cycloalkanes and their deprotonated forms have been calculated by the semiempirical PM-3 quantum chemical method. Using the conclusions of limiting orbital theory, a quantum chemical explanation has been derived, based on the calculations made, for the selectivity of alkylation of the systems investigated.A. L. Mndzhoyan Institute of Fine Organic Chemistry, Armenian Academy of Sciences, Erevan 375014, Armenia. M. V. Lomonosov Moscow State University, Moscow 119899, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1118–1124, August, 1998.     

Synthesis of triazoles and tetrazoles condensed with spiro(benzo[h]quinazoline-5,1′-cyclohexane)

Condensation of 3-R-4-oxo-2-thioxo-1,2,3,4,5,6-hexahydrospiro(benzo[h]quinazoline-5,1-cyclohexanes) with 2-ethanolamine, 3-propanolamine, and hydrazine hydrate gives the corresponding 2-ethanolamino, 2-propanolamino, and 2-hydrazino derivatives. Triazoles and tetrazoles, a- or b-condensed with benzo[h]quinazolines were obtained from 2-hydrazinobenzo[h]quinazolines depending on the presence of a substituent at position 3.A. L. Mndzhoyan Institute of Fine Organic Chemistry, Armenian Republic Academy of Sciences, Yerevan 375014. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 396–400, March, 2000.     

Investigation of the Circular Waveguide Radiating Slotted Structures Using Polarization Degeneration of the Main Mode Wave

The unusual paired slotted radiating structure of a circular waveguide is investigated when the wave of main mode H₁₁ is propagating in it. This structure is constructed in such a way that the phenomenon of the polarization degeneration of wave with this mode is taken into account. In the waveguide cross-section, the centers of the paired half-wave transverse slots are spaced by an angle γ over both sides of the waveguide diametric line along the direction of polarization of the H₁₁ mode. The radiation patterns at different spaced angles γ equal to 45°, 65°, and 72° as well as at the two-tiered location of such paired slots are investigated. The second tier is located on the distance equal to the half of the waveguide wavelength along the waveguide longitudinal axis. The pair slots of both tiers have the same γ angle but they are located at the opposite sides of the waveguide. The possibility is shown of synthesizing an omnidirectional radiation pattern by combination of the two-tiered structure with the opposite frontal slots and the two-tiered structure with the oppositely paired slots.     

Nucleation and Growth of Magnetron-Sputtered Ag Nanoparticles as Witnessed by Time-Resolved Small Angle X-Ray Scattering

Kinetic aspects of the synthesis of Ag nanoparticles (NPs) by magnetron sputtering are studied by in situ and time-resolved small angle X-ray scattering (SAXS). Part of the NPs are found to become confined within a capture zone at 1–10 mm from the surface of the target and circumscribed by the plasma ring. Three regimes of the NP growth are identified: 1) early growth at which the average NP diameter rapidly increases to 90 nm; 2) cycling instabilities at which the SAXS signal periodically fluctuates either due to expelling of large NPs from the capture zone or due to the axial rotation of the NP cloud; and 3) steady-state synthesis at which stable synthesis of the NPs is achieved. The NP confinement within the capture zone is driven by the balance of forces, the electrostatic force being dominant. On reaching the critical size, large NPs acquire an excessive charge and become expelled from the capture zone via the electrostatic interactions. As a result, significant NP deposits are formed on the inner walls of the aggregation chamber as well as in the central area of the target.