Unexpected Reaction of Ethyl 4-(Chloromethyl)pyrazolo- [5,1-<Emphasis Type="Italic">c</Emphasis>][1,2,4]triazine-3-carboxylates with Thiourea and Its Mechanism

The reaction of ethyl 4-(chloromethyl)pyrazolo[5,1-c][1,2,4]triazine-3-carboxylates with thiourea in dimethylformamide involves ANRORC rearrangement (Addition of the Nucleophile, Ring Opening, and Ring Closure) followed by N-formylation to give N-{5-(4-oxo-8-phenyl-1,4-dihydropyrazolo[5,1-c][1,2,4]-triazin-3-yl)-1,3-triazol-2-yl}formamides whose structure was confirmed by X-ray analysis. The reaction mechanism has been studied by HPLC/MS.     

Crystal structure and spectroscopic properties of A[VO2(SO4)(H2O)2] · H2O (A = K, Rb, Tl, NH4) compounds

The crystal structure of dioxovanadium(V) sulfate trihydrates A[VO₂(SO₄)(H₂O)₂] · H₂O, where A is K, Rb, Tl, or NH₄, has been determined based on a combination of neutron and X-ray diffraction data. The compounds are isostructural and have a monoclinic lattice (space group P2₁, Z = 2) with unit cell parameters a = 6.24535(8), 6.26016(7), 6.25817(5), and 6.2500(1) Å; b = 9.8417(1), 9.99736(8), 9.96217(9), and 9.9742(1) Å; c = 6.52113(8), 6.69303(5), 6.70379(6), and 6.70334(9) Å; β = 106.99(1)°, 107.83(1)°, and 107.83(1)°, 107.99(1)°, respectively. The SO₄ tetrahedra and VO₄(H₂O)₂ octahedra share an oxygen vertex to form infinite isolated chains. Atoms A have CN = 10. IR and Raman spectroscopy data are reported.     

Author index to volume 29

It is shown that if stationary oscillatory chemical reactions are observed in a closed homogeneous system of the Lotka, Lotka-Volterra or similar type, stationary chemical circulations must simultaneously occur there. In an open system of this type concentration oscillations may take place in the absence of stationary chemical circulations. The paper presents experimental data on temperature oscillations symbatic with concentration oscillations, for the Belousov-Zhabotinsky reaction.     

Crystal structure and spectroscopic properties of AVO2SO4 (A = K, Rb) compounds

The crystal structure of alkali-metal dioxovanadium(V) sulfates AVO₂SO₄, where A is K or Rb, has been determined based on a combination of neutron and X-ray diffraction data. The compounds are isostructural and have an orthorhombic lattice (space group P2₁2₁2₁, Z = 4) with unit cell parameters a = 11.1004(2) and 10.8193(1) Å; b = 8.2626(2) and 8.9042(1) Å; c = 5.4772(1) and 5.5722(1) Å, respectively. The structures are of the chain type. Zigzag chains are formed by vertex-sharing VO₆ octahedra. Sulfate groups SO₄ link neighboring chains and form a spatial framework with cavities accommodating alkali-metal atoms with CN = 9 (K) and 8 (Rb). IR and Raman spectroscopy data are reported.     

Infrared study of nitrogen adsorption on alumina

Good agreement of the results of numerical calculations with experimental data shows that the simple representation of a Lewis acid site of an alumina surface as a positive point charge plus van der Waals interaction can describe some characteristics of its interaction with a nitrogen molecule.     

Phosphor for the Near-IR and Short-Wave IR Ranges Based on a Garnet Structured Cubic Modification of Lithium–Lanthanum Niobate

Physics of the Solid State - Cubic garnets activated by neodymium and holmium, Li6CaLa2Nb2O12:Nd3+,Ho3+, were obtained by solid-state method. The main regularities of changes in the luminescence...     

Hydrodynamics of Intensive Self-Exited Oscillations of the Reversed Vane in a Plane Diffuser

The problem of the nonstationary flow of a viscous incompressible fluid in a flat diffuser containing a hinged partition in the form of a reverse vane directed toward the flow is considered. The mechanism of excitation and maintenance of the angular auto-oscillation regime of the vane is revealed, accompanied by shock interaction of the vane sock with the channel walls and the formation of two antiphase pulsating jets at the exit from the diffuser. This mode is reproduced in a physical experiment and in numerical simulation.     

Almost-Linear Segments of Graphs of Functions

Mathematical Notes - A general telescoping scheme is devised for evaluating the Gaussian 2F1-series. Three main theorems are proved, which contain several mysterious-looking formulas of Maier...