Magnetic force microscopy study of domain structures in magnetic films

Magnetic force microscopy is used to investigate two different types of samples: thin metal films and ferrite garnet films. It is pointed out for garnet films that magnetic force microscopy allows us only to judge the domain structure of surface layers. Problems associated with conducting measurements in external magnetic fields, the effect of the magnetic field of the probe on the investigated domain structure, and using magneto-polarized optics in combination with magnetic force microscopy are considered.     

Nitro derivatives of 1,3-dihydrobenzimidazol-2-one: I. Synthesis of <Emphasis Type="Italic">N</Emphasis>-nitrobenzimidazol-2-ones

1,3,5,6-Tetranitro-2,3-dihydro-1H-benzimidazol-2-one, 1,5,6-trinitro-2,3-dihydro-1H-benzimidazol-2-one, and 1,4,5,6-tetranitro-2,3-dihydro-1H-benzimidazol-2-one were synthesized for the first time by nitration of 5,6-di- and 4,5,6-trinitro-2,3-dihydro-1H-benzimidazol-2-ones with concentrated nitric acid in acetic anhydride.     

Reactions of 1,3,3,3-tetrafluoro-2-methoxycarbonylpropenesulfenyl chloride with enamines

1,3,3,3-Tetrafluoro-2-methoxycarbonylpropenesulfenyl chloride readily reacts with enamines (derivatives of -oxo acids) to give sulfenylation products. The reactions with N-aryl-substituted enamines are accompanied by cyclization to form N-aryl-2-(2,2,2-trifluoro-1-methoxycarbonylethylidene)-2,3-dihydrothiazoles.     

A new method for the synthesis of levulinic acid

A two- step method is described for the synthesis of levulinic acid from ethyl acetoacetate and ethyl chloroacetate in 70% yield.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 474–475, February, 1990.     

Isomerization of olefins on hydride-halide compounds of titanium and aluminium of composition LmTiH2AlXX′. The role of the cocatalyst and the geometry of the ligand environment of the titanium atom in catalytic hydrogen transfer

Using bimetallic complexes of the compositions (C₅H₅)₂TiH₂MXX′ and (CH₂)_n(C₅H₄)₂TiH₂AlXX′ (M = B, Al; X,X′ = H,Hal, Alk, n = 1–3) as examples, the rate of homogeneous catalytic isomerization of α-olefins has been studied under the influence of the ligand environment, the nature of the transition metal, and the substituent at M. Only titanium and aluminium complexes with non-rigid ligand environments and involving terminal AlH bonds show catalytic activity in the reaction. An alkyl isomerization mechanism at the heterobinuclear centre is suggested. The first reaction step involves coordination of an olefin at the six-coordinate Al atom followed by the insertion of the olefin molecule in the terminal AlH bond.     

Molecular Mechanisms of the Effect of Water on CO<Subscript>2</Subscript>/CH<Subscript>4</Subscript> Mixture Adsorption in Slitlike Carbon Pores

The grand canonical ensemble Monte Carlo method has been used to study adsorption of carbon dioxide, methane, and their mixtures with different compositions in slitlike carbon pores at a temperature of 318 K and pressures below 60 atm. The data obtained have been used to show the effect of fixed amounts of pre-adsorbed water (19, 37, and 70 vol %) on the adsorption capacity and selectivity of carbon micro- and mesopores. The presence of water reduces the adsorption capacity throughout the studied pressure range upon adsorption of gaseous mixtures containing less than 50% CO₂, as well as in narrow micropores (with widths of 8?12 Å). Upon adsorption of mixtures with CO₂ contents higher than 50%, the adsorption capacity of pores with low water contents appears, in some region of the isotherm, to be higher than that in dry pores. In the case of wide pores (16 and 20 Å), this region is located at low and moderate pressures, while for mesopores it is located at high pressures. The analysis of the calculated data has shown that the molecular mechanism of the influence of preadsorbed water on the adsorption capacity is based on the competition between the volume accessible for adsorption (decreases the capacity) and the strength of the interaction between carbon dioxide molecules and water molecules (increases the capacity). Therewith, the larger the surface area of the water–gas contact, the stronger the H₂O–CO₂ interactions.     

2-Polyfluoroalkylchromones. 10. Synthesis of regioisomeric 3-(2-hydroxyaryl)-5-polyfluoroalkyl- and 5-(2-hydroxyaryl)-3-polyfluoroalkylisoxazoles and determination of their structures by 1H, 19F, and 13C NMR spectroscopy

The reactions of 2-hydroxy-2-polyfluoroalkylchroman-4-ones with hydroxylamine yield, through ²-isoxazolines as intermediate products, 3-(2-hydroxyaryl)-5-polyfluoroalkylisoxazoles. Analogous reactions with 2-polyfluoroalkylchromones afford -diketone monooximes, which in an acidic medium undergo cyclodehydration into 5-(2-hydroxyaryl)-3-polyfluoroalkylisoxazoles. The structures of regioisomeric 3- and 5-polyfluoroalkylisoxazoles were determined using ¹H, ¹⁹F, and ¹³C NMR spectroscopy.     

Adsorption of gas-water binary systems in carbon micropores: Computer simulation

The adsorption of gas-water mixture in micropores of carbon materials at 298 K has been studied using computer simulation. Methane, nitrogen, ammonia, carbon dioxide, and hydrogen sulfide were considered as gas components. In the grand canonical ensemble Monte-Carlo simulation of adsorption, the displacement of a gas component from a pore as a result of the formation of water microclusters was observed for all systems studied. Cluster growth conditions on graphite-like and activated surfaces differ significantly. The comparative stability of adsorbed gas-water mixtures has been determined for all gases.