The effect of the structure of bonded cyanoalkyl stationary phases on their selectivity in the liquid chromatographic separation of polynuclear aromatic hydrocarbons

Summary The paper discusses the effect of the length and structure of the hydrocarbon chain connecting the nitrile group to the silica gel surface on the chromatographic properties of cyanoalkyl phases.When using non-polar and polar mobile phases, the selectivity of the cyanodecyl phases toward PAHs is higher than of the cyanopropyl phase and of hydroxylated silica gel.Polar additives to the mobile phase drastically decrease the retention on silica gel and on the cyanopropyl phase while affect the properties of cyanodecyl phases only to a considerably less degree. Newly synthesized phases with different structures of the hydrocarbon chain are compared with the commerical cyano-and ODS-phases. The retention mechanism on the cyanoalkyl phases is discussed.     

Homolytic alkylation of quinaldine and quinoxaline with 18-crown-6

Homolytic alkylation of protonated quinoxaline with 18-crown-6, initiated by the system pivalic acid-iron(II) sulfate at 20–25C, gives (quinoxalin-2-yl)-18-crown-6 in 85% yield. Under analogous conditions, the reaction with quinoline affords two isomers: (quinolin-4-yl)-18-crown-6 and (quinolin-2-yl)-18-crown-6, in yields of 20 and 30% respectively.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 75–76, January, 1988.     

New reactions of sulphur dichloride with olefines

The interaction between SCl₂ and adamantylideneadamantane produces epithiocompounds $\text{2}$ and $\text{3}$ or polychloroadamantylideneadamantanes $\text{4}$–$\text{7}$ depending upon conditions. The structure of $\text{3}$ was determined by X-ray analysis.     

Some physical properties of polyorganosiloxanes. I. Linear polyorganosiloxanes

Some physical properties of linear polydimethylsiloxanes have been studied. The states and transitions in polydimethylsiloxanes have been investigated by using the method of dynamic heat capacity and a thermomechanic method in the temperature range from ?150 to +200°C. The temperature dependence of primary and secondary crystallization has been studied by optical, calorimetric, and x-ray methods.     

The hydration of hydrophobic substances

A model of the hydration of hydrophobic substances in water is suggested. The models of fluctuation formation of empty cavities in water as a stage of hydration extensively used in the literature were shown to be at variance with experiment. The fundamental role played by the interphase boundary surface was emphasized. On this surface, the successive addition of water molecules with the formation of capsules around hydrophobic molecules occurred. The physical meaning of the Ostwald equation was revealed. This equation characterized the distribution of hydrophobic volatile substances between the gas and aqueous phases. The method of optical probes (hydrophobic aromatic molecules) was used to reveal the synergistic character of autocorrelation of dispersion interactions between water and hydrophobic substance molecules. This synergism was at variance with the Lennard-Jones potential. The synergism (superadditivity) of dispersion attraction forces, which strengthened their directional character, caused the self-organization and enhanced stability of hydration capsules with encapsulated hydrophobic molecules. Computer models were used to show that the spatially directional character of dispersion interactions necessary for the self-organization of hydrated aggregates could be simulated by the molecular mechanics method on the basis of orientational correlation of water molecules and hydrophobic substances in the starting system.     

Discrimination of impact approximations for velocity and velocity sign autocorrelation functions

The velocity and velocity sign autocorrelation functions as well as the distribution of time intervals between velocity sign changes of a particle in a gas or fluid are studied within the framework of impact theory. The results of the uncorrelated successive velocity reversal model (USVRM), for which this approach provides a limiting case of infinitesimal collision time, are checked. It is shown with this simple model that the two approaches are equivalent in two special cases: either when there is no correlation between pre- and post-collision velocities, or when the only possible result of a collision is elastic back scattering. Otherwise, the USVRM leaves out the scope of its view the important correlations of velocity in course of collisions.     

Cyclization reactions of nitrils. 29. Regioselective synthesis of 6-aryl-3-cyano-2(1H)-pyridinethiones and the corresponding selenones and their characteristics

The condensation of cyanothio- and cyanoselenoacetamide with 3-aryl-3-oxo-1-piperidino-1-propene or sodium 3-aryl-3-oxo-1-propen-1-olate takes place regioselectively with the formation of the 6-aryl-3-cyano-2(1H)-pyridinethiones or the corresponding selenones. Thieno[2,3-b]pyridines, thiazolo[3,2-a]pyridinium salts, and other annellated heterocycles were obtained from the 6-aryl-3-cyano-2(1H)-pyridinethiones.For Communication 28, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 805–812, June, 1988.     

Dimeric quinoline alkaloids

The review is denoted to an analysis of the literature on the investigation of dimeric quinoline alkaloids, which are divided into four groups depending on the structures of the terpenoid moiety. The natural sources, structures, stereochemical features, possible biogenetic schemes of formation, and methods of synthesizing the alkaloids of this group are considered.Institute of the Chemistry of Plant Substances, USSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 4–18, January–February, 1989.     

Research on 1-azabicyclic compounds

1-(2-Furyl)-3-amino-4,4-dimethylpentane was used to obtain 3-tert-butyl-1,2-dihydropyrrolizine, the catalytic hydrogenation of which over Rh/Al₂O₃ at room temperature gives a mixture of cis- and trans-3,8-H-3-ter-butylpyrrolizidines with predominance of the cis isomer, whereas hydrogenation at 90–100 °C gives a mixture containing the trans isomer as the principal component. The three-dimensional structures of the isomers follow from data on the catalytic hydrogenation and isomerization and the IR, Raman, and PME spectra. A considerable percentage of the trans-fused form is characteristic for cis-3,8-H-3-tert-butylpyrrolizidine.     

Studies of dynamic properties of heterogeneous catalytic reactions in a closed isothermal gradientless system over biographically inhomogeneous catalyst surface

The dynamics of a closed isothermal system of constant volume consisting of an ideal gaseous mixture and particles adsorbed over the biographically inhomogeneous catalyst surface, has been studied. The existence, uniqueness and asymptotic stability of the point of detailed equilibrium in each positive reaction simplex has been proved.

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