Gas-Chromatographic Study of the Polarity and Selectivity of Nematic Liquid Crystals

The sorption properties of stationary phases based on nematic p-substituted azoxybenzenes were studied. Correlations were revealed between the structural selectivity of mesogens, chemical nature of terminal substituents, capability for dispersion interactions and polarity of the sorbents, temperature gradient of the retention indices, and thermodynamic parameters of solution of xylene isomers in the sorbents.     

Thermodynamic Properties of Tetraphenyltetrahydroxycyclotetrasiloxane,Octaphenyltetrahydroxytricyclooctasiloxane, Octaphenylpentacyclosilsesquioxane,and Polyphenylsilsesquioxane in the Range 0-300 K

The temperature dependences of the heat capacities of crystalline tetraphenyltetrahydroxycyclotetrasiloxane, octaphenyltetrahydroxytricyclooctasiloxane, and octaphenylpentacyclosilsesquioxane and of glassy polyphenylsilsesquioxane were measured in the range 6-300 K with an adiabatic vacuum calorimeter, with an accuracy of 0.3%. From these data, the thermodynamic functions C ⁰ _p (T), H ⁰(T) - H ⁰(0), S ⁰(T) - S ⁰(0), and G ⁰(T) - H ⁰(0) of these substances were calculated for the range 0-300 K. The standard entropies of their formation from elements at 298.15 K, _f S ⁰, and the entropies of mutual transformations of these substances in the range 0-298.15 K were calculated.     

Reaction of 2,2-bis(4′-hydroxy-3′-N,N-diethylaminomethylphenyl) propane with triethyl phosphite

Conclusions The reaction of 2,2-bis(4-hydroxy-3-N,N-diethylaminomethylphenyl)propane with triethyl phosphite gave 2,2-bis(4-ethoxy-3-diethylphosphonomethylphenyl)propane via the intermediate formation of a compound with a pentacovalent phosphorus atom. In the presence of acetic acid the reaction leads to 2,2-bis(4-hydroxy-3-diethylphosphonomethylphenyl)propane.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1621–1624, July, 1978.     

Asymmetric Michael reaction between aldehydes and nitroalkanes promoted by pyrrolidine-containing C2-symmetric organocatalysts

Russian Chemical Bulletin - Bifunctional C2-symmetric organocatalysts derived from chiral 1,2-diaminoethanes and (S)-2-aminomethylpyrrolidine were fi rst used for promoting the asymmetric Michael...     

Nanosized cation exchanger for the electrophoretic separation and preconcentration of catecholamines and amino acids

The first example of application of nanosized polystyrene-based cation exchanger (NSCE) with sulfo groups as a dynamic coating of capillary walls was demonstrated. The conditions of dynamic coating formation were optimized and ensured the long-term stability of the coating. Capillary-to-capillary and day-to-day repeatabilities were 4% and 3%, correspondingly. The NSCE coating stability at various pH and influence of pH on the EOF mobility were investigated. The developed NSCE-modified coated capillaries provided improved resolution (R_s = 0.9–3.2 for catecholamines and R_s = 1.7–2.8 for amino acids) and efficiencies (330–520 ×10³ t.p./m) of basic analytes, which are 1.5 times higher compared to untreated capillary. The optimized conditions were as follows: 50 mM phosphate buffer solution at pH 2.2 with 5 μM NSCE. The effect of the NSCE concentration in BGE on the electrophoretic mobilities of the analytes was investigated. The various online concentration techniques were tested in order to decrease the LODs. The simultaneous application of NSCE capillaries and field-amplified sample stacking provided the lowest LODs of catecholamines and amino acids and allowed to determine these analytes in human urine.     

Tuning the morphology and magnetic properties of single-domain SrFe8Al4O19 particles prepared by a citrate auto-combustion method

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