Sorption of butane, propane, ethane, methane, and carbon dioxide on asphaltene

Isotherms of sorption of butane, propane, ethane, methane, and carbon dioxide on an asphaltene sample of known elemental composition were measured. The effect of the pressure and temperature on the shape the sorption isotherms for all the adsorption systems studied was examined. The values of the initial heat of sorption were determined and compared to the energies of interaction of the molecules with asphaltene. The results obtained suggest that asphaltene is a swellable amorphous sorbent.     

Organoinorganic composites based on tetraethoxysilane and nitrogen polybases

Hybrid organoinorganic composites insoluble in water and organic solvents were prepared by the hydrolysis of tetraethoxysilane in the presence of poly-1-vinylpyrazole, poly-1-vinylimidazole, and poly-4-vinylpyridine. The composition of the composites was determined by the nature of the polymeric nitrogen base and hydrolysis conditions. The composites synthesized showed high sorption activity in the extraction of the [PdCl₄]^2?, [PtCl₆]^2?, and [AuCl₄]^? ions from hydrochloric acid solutions.     

Energy barriers to carousel rearrangements of carbocations: Quantum-chemical calculations vs. experiment

By DFT method energy barriers were calculated for carousel rearrangements of bicyclo[3.1.0]hexenyl, cyclobutenyl, and homotropylium cations. A plausible agreement between calculated and experimental findings was found.     

Temperature dependence of development of slip bands and of strain hardening in AgCl crystals

The dependence of the flow stress and the slip band density on the plastic strain has been measured at 201 K, 293 K and 363 K. The growth of deformation concentrated in an average slip band has been stated. The types of obstacles acting against the rise and development of a slip band and the temperature dependence of the strain hardening in AgCl crystals are discussed. An equation stating the dependence of the flow stress on the slip band density is presented. The hardening in AgCl crystals is classified as the stage III — hardening.     

Phase equilibrium and p s-T-x diagrams of the Ln2S3-LnS2 (Ln = La, Pr, Nd, Sm-Er) systems

A new methodology is proposed and the phase equilibrium is investigated in the Ln₂S₃-LnS₂ systems, in which the low-temperature behavior of nonstoichiometric phases is controlled by the kinetics of the ordering of defects. It is shown that, under equilibrium conditions, the phase equilibrium in the systems is represented not only by a polysulfide with a wide homogeneity region, but also by several (or one) phases of constant irrational compositions combined in the homologous series Ln_nS_2n?1 (n = 3, 4, 7, 8, and 10). The formation of sulfur vacancies and isolated [S₂]^2? ions (which compensate the charge) in the anionic S^2? layer is the basic mechanism of changing the composition of the members of the series. On the basis of structural data, the possible mechanisms of the ordering of defective LnS_2?x polysulfides are examined and it is shown that the formation of stable or metastable phases is a kinetics-controlled process. The role of p _s-T-x diagrams in the interpretations of complex structures of metastable phases from the point of view of attainment of the equilibrium state is discussed.     

Reduction of Alkyl-2-amino-5,6-dialkyl-3-cyanopyridine-4-carboxylates

Reduction of alkyl-2-amino-5,6-dialkyl-3-cyanopyridine-4-carboxylates with sodium borohydride in protic solvents gave rise to 4-amino-3-imino-6,7-dialkyl-1,3-dihydrofuro[3,4-c]pyridines that at hydrolysis in acid medium afforded the corresponding lactones.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 2, 2005, pp. 288–291.Original Russian Text Copyright © 2005 by Vasil’ev, Lyshchikov, Nasakin, Kayukov, Tafeenko.     

Crystal and molecular structures of the complexes of cobalt dichloride with 1-isopropenylimidazole and 1-vinylimidazole

The crystal and molecular structures of bis(1-isopropenylimidazole)dichlorocobalt (C₁₂H₁₆Cl₂·N₄Co) [R 0.036 (R _W 0.089) for 3229 unique reflections with I > 2σ(I)] and tetra(1-vinylimidazole)dichlorocobalt (C₂₀H₂₄Cl₂N₈Co) [R 0.031 (R _W 0.072) for 1863 unique reflections with I > 2σ(I)] were determined. In these molecular complexes, the monodentate terminal 1-alkenylimidazole ligands coordinate to the metal via a “pyridine” nitrogen atom. In C₁₂H₁₆Cl₂N₄Co, the Co atom has a distorted tetrahedral 2N,2Cl coordination. The coordination polyhedron of cobalt in C₂₀H₂₄Cl₂N₈Co is a strongly elongated 4N,2Cl octahedron. The Co-N and Co-Cl bonds [Co-N 2.015(2) and 2.032(4) Å; Co-Cl 2.229(2) Å] in the tetrahedral complex C₁₂H₁₆Cl₂N₄Co are shorter than those in the octahedral complex C₂₀H₂₄Cl₂N₈Co [Co-N 2.134(2) and 2.157(2) Å; Co-Cl 2.518(1) Å]. In the structures of both complexes there are short contacts involving the Cl atoms.     

Effect of the nature of the metal oxide on selective transformation of methane under unsteady conditions in the absence of oxidant in the gaseous phase

The catalytic transformation of methane into higher hydrocarbons was studied under unsteady conditions on oxides of various metals (Pb, Fe, Nb, Ti, Cd, Mo, Mg, Zn, Zr, Bi, Mn), and also on Sr-, La-, Y-, and Mn-containing oxides of perovskite structure. It is shown that the effectiveness of the catalysts not only depends on their chemical composition, but also is determined to a considerable degree by the specific surface of the oxides. L. V. Pisarzhevskii Institute of Physical Chemistry, Academy of Sciences of Ukraine, 252039 Kiev, Prosp. Nauki, 31, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 2, pp. 91–95, March–April, 1997.     

Formation of furan derivatives in the course of the Stevens rearrangement of ammonium salts containing 4-allyloxy(phenoxy)-2-butynyl group

Ammonium salts containing phenacyl group in combination with 4-allyloxy(phehoxy)-2-butynyl group, when treated with a suspension of potassium hydroxide in benzene, undergo the 3,2-Stevens rearrangement with the formation of allenic amino ketones which under the reaction conditions give the furan derivatives.