Volumetric Parameters of Interaction of Monosaccharides (D-xylose,D-arabinose,D-glucose,D-galactose) with NaI in Water at 298.15 K

Densities for monosaccharide (D-xylose, D-arabinose, D-glucose, D-galactose)–NaI–water solutions were measured at 298.15 K and were used to calculate the apparent molar volumes of these saccharides and NaI. Infinite dilution apparent molar volumes for the saccharides (V_,S) in aqueous NaI and those for NaI (V_,E) in aqueous saccharide solutions and partial molar volumes of the saccharides (V_S) and NaI (V_E) at each composition have been evaluated, together with the standard transfer volumes of the saccharides (_tr V_S) from water to aqueous NaI and those of NaI (_trV_E) from water to aqueous saccharide solutions. It was shown that the _tr V_S and _trV_E values are positive and increase with increasing co-solute molalities. Volumetric parameters indicating the interactions of NaI with saccharides in water were also obtained and applied to explore the interactions between saccharides and NaI in water. A comparison of the _ES value for NaI with those for NaCl and NaBr showed that for a given saccharide, except for glucose, the _ES value for NaBr is the largest of three sodium halides (NaCl, NaBr and NaI). These were interpreted in terms of the apparent molar electrostriction volumes ( V_e) and the structure interaction model.     

Interactions of Some Amino Acids with Aqueous Tetraethylammonium Bromide at 298.15 K: A Volumetric Approach

The apparent molar volumes, V_,2, of glycine, L-alanine, DL--amino-n-butyric acid, L-valine, and L-leucine have been determined in aqueous 0.25, 0.75, 1.0, and 1.5 mol-dm^–3 tetraethylammonium bromide (TEAB) solutions by density measurements at 298.15 K. These data have been used to calculate the infinite dilution apparent molar volumes, V_2,m, for the amino acids in aqueous tetraethylammonium bromide and the standard partial molar volumes of transfer (_tr V_2,m) of the amino acids from water to the aqueous salt solutions. The linear correlation of V_2,m for a homologous series of amino acids has been utilized to calculate the contribution of the charged end groups (NH₃⁺, COO^–), CH₂ group, and other alkyl chains of the amino acids to V_2,m. The results of the standard partial molar volumes of transfer from water to aqueous tetraethylammonium bromide have been interpreted in terms of ion–ion, ion–polar, and hydrophobic–hydrophobic group interactions. The volume of transfer data suggest that ion–ion or ion–hydrophilic interactions are predominant in the case of glycine and alanine, and hydrophobic–hydrophobic group interactions are predominant in the case of DL--amino butyric acid, L-valine, and L-leucine.     

Amiloride Conformation: The Effect of Different Crystalline Environments

The crystal structure of (3,5-diamino-6-chloro-pyrazine-2-carbonyl)-guanidine picrate has been determined with the use of X-ray diffraction method. The crystals are triclinic, space group PI with a = 10.2980(4) Å, b = 12.4322(4) Å, c = 14.4310(5) Å, = 66.317(2), = 70.077(2), = 72.462(2), Z = 2. The asymmetric unit consists of one amiloride cation, picrate anion, and three DMSO molecules from the solvent, two of which are disordered. The molecules of amiloride and picrate are almost planar. The guanidine group of amiloride is protonated and makes a kind of a salt bridge with phenolate and forms hydrogen bonds with ortho-nitro oxygen atoms of picrate. The pairs of amiloride cation–picrate anion, transformed by the inversion center and translated by 2 a and c, are mutually parallel and are connected by molecules of DMSO. The conformation of amiloride picrate is compared with those in other crystal structures.     

Thermodynamics of 2,2′,2′'-terpyridinecopper(II) complexes in aqueous solution

Summary The thermodynamic quantities relative to the protonation and the complexation of 2,2,2'-terpyridine with copper(II) ion have been determined at 25° and I=0.1 mol dm^–3 (NaNO₃). The G data was obtained by potentiometric measurements; a copper selective electrode was employed for the study of the complexation equilibria. The H values have been determined by direct calorimetry.The hydrolytic species, existing at pH>6 and their relative G and H values have also been obtained.From the thermodynamic data the importance of enthalpy and entropy terms in stabilizing the complexes is assessed.Moreover some considerations on the chelating effect are reported.Presented in part at 2 Congresso Nazionale di Chimica Analitica, Catania (1977).     

The solvent eluotropic strength on carbon adsorbents

Summary Two theoretical approaches are discussed to calculate the solvent strength () on carbon materials. One is based on the adsorbate-adsorbent interfacial tension and the other uses the theory of solubility parameters. It is shown that there is good agreement between these approaches. Experimental values are compared with theoretical ones and there is again a good agreement. Solvents having small and highly polar molecules have small values. Solvents having large and aromatic molecules have high values. Binary solvent mixtures can be classified in two groups depending on the rate of change of with the mole fraction of the strongest solvent in the mixture.Dedicated to Professor Dr. István Halász for his 60th birthday.     

Conductance of iron(III) laurate solutions in binary liquid mixtures

Summary The specific conductivity of iron(III) laurate solutions in binary liquid mixtures shows that the soap aggregates into micelles and CMC is found to be independent of temperature and concentration of benzene, acetone and tetrachloromethane in 1-butanol. The variation of molecular conductance,, with soap concentration, C, is expressed by the equation: = 10^AC^B. Both constants A and B vary with solvent composition but B remains constant with increase in temperature. Several parameters such as molecular conductance at infinite dilution, , dissociation constant, K, heat of dissociation, H, entropy, S and free energy, G of dissociation of soap have been evaluated and the effect of the nature of solvents has been discussed.     

Oxidation Behavior of Si–Nb–C–O Ceramics Prepared by the Pyrolysis of Methyltriethoxysilane Based Organic-Inorganic Hybrid Gel

The oxidative structural characterization of Si–Nb–C–O ceramic prepared by the heat-treatment of transition metal containing polymethylsilsesquioxane hybrid was investigated. The heating temperature for the pyrolysis of precursor hybrid gels strongly affected the oxidation behavior of the resultant ceramics. The hybrid gel pyrolyzed at 600C was rapidly oxidized, while the hybrid gel pyrolyzed at 1000C showed the higher resistance to oxidation. In the hybrid pyrolyzed at 600C, new Si–O–Nb oxygen-bridged heterometal bonds were formed after oxidation, which was confirmed by FT-IR spectra. On the other hand, silica and oxycarbide protective layer was formed on the oxidized surface of the hybrid heated at 1000C, as suggested by X-ray photoelectron spectroscopy (XPS). Raman spectra showed a large luminescence background, G and D bands before oxidation. After oxidation, however, the luminescence background disappeared and G band was more symmetric than that of non-oxidative product. This strongly suggested the predominant oxidation of radical and related unstable carbon species in the ceramics.     

Physicochemical Properties of Ampicillin and Amoxicillin as Biologically Active Ligands with Some Alkali Earth,Transition Metal,and Lanthanide Ions in Aqueous and Mixed Solvents at 20, 30, and 40<Superscript>∘</Superscript>C

The acid-base equilibria of ampicillin and amoxicillin were investigated in pure water and different solvent + water mixtures (solvent = methanol, ethanol, acetone, dimethylformamide, and dimethyl sulfoxide) at a constant ionic strength (I = 0.1 mol-dm^–3 KNO₃) and organic solvent volume fractions of 10, 20, and 30%. The effect of temperature on these equilibria was studied at 20, 30, and 40C. Thermodynamic functions of these ligands were calculated and discussed in terms of G, H, and S. The number of ionizable protons was determined using conductometric titrations. The formation constant of the complexes, which form by reaction of the ligands with Mg(II), Ca(II), Zn(II), Cu(II), Ni(II), Co(II), Ce(III), Pr(III), Eu(III), Gd(III), Ho(III), Er(III), and Yb(III), are determined. The relative stability of the alkali earth, transition, and lanthanide elements are compared with each other and discussed in terms of the ionic radius and the electronic structure of the outer shell of that ion. The results obtained are discussed in terms of macroscopic properties of the mixed solvents and the possible variation in microheterogenity of the solvation shells around the solute.     

Kinetics of Fe3+ and Cu2+ sorption by fibrous polyampholite

The kinetics of Fe³⁺ and Cu²⁺ sorption from sulfate salt solutions by fibrous polyampholite have been studied.

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Fe³⁺ Cu²⁺ , .

     

Equilibrium and non-equilibrium melting of branched polyethylene relating to defect incorporation within crystals

New equilibrium melting point data, for polyethylene containing chain defects, are tested in the light of random copolymer predictions. A simplified expression for the melting point depression of random copolymers containing small amounts of non-crystallizable units is derived. Non-equilibrium melting data for rapidly quenched polyethylene samples are also reported. The fusion enthalpyH(X), and the surface free energy _e for crystals containing defects are evaluated using crystallinity, equilibrium meltingtemperatures and X-ray long period data. It is shown that increasing defect penetration within crystals induces a decrease ofH(X) withX in accordance with theoretical predictions. Finally _e is, similarly, shown to decrease with increasing number of chain defects attached to the crystal surface.     

Spectra and structure of small ring compounds. Part L VIII: Structural parameters for chlorocyclobutane from combined microwave data and ab initio calculations

The structural parameters of chlorocyclobutane,c-C₄H₇Cl, have been obtained fromab initio Hartree-Fock calculations employing the 6–31G^* basis set for both the more stable equatorial and the high energy axial conformers. The determined carbonhydrogen distances were adjusted by 0.010 Å and held fixed while a weighted least-squares adjust was used to obtain all of the heavy atom parameters for the equatorial conformer by fitting the rotational constants of nine isotopic species. The determinedr ₀ parameters are:r(C - C) = 1.535(8) År(C - C) = 1.548(3) År(C - Cl) = 1.788(9) Å CCC, - CL = 132.0(2)°; CCC, = 89.7(6)°; CCC, = 87.1(2)°, and CCC, = 88.7(2)°. These results are compared to the calculated values as well as those obtained earlier from electron diffraction and microwave studies.For Part LVII, seeJ. Raman Spectrosc.,1990,21, 591.Taken in part from the thesis of M. J. Lee which will be submitted to the Department of Chemistry in partial fulfillment of the Ph.D. degree.     

Thorough study of bromide control in bromate oscillators, III. Simulation by the oregonator model of the behavior of reacting BZ systems perrturber by mercury (II) ions

The behavior of the bromate-maloni acid-cerium (III) oscillator in the presence of mercury (II)-a bromide-removing ion-can be simulated by the Oregonator model if the dynamics of bromocomplex-formation and dissociation reactions is taken into account.

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- - (III) (II)- - , .

     

Study of the Surface Tensions of Cyclohexane or Methylcyclohexane with Some Cyclic Ethers

Experimental surface tensions, measured with a drop volume tensiometer and the corresponding surface tension deviations for the binary mixtures of cyclohexane or methylcyclohexane with a cyclic ether (tetrahydrofuran, tetrahydropyran, 2-methyltetrahydrofuran or 2,5-dimethyltetrahydrofuran) are given at 25 and 40 C. The results have been discussed in terms of lyophobicity and molecular interactions using the extended Langmuir isotherm. The model proposed by Patterson and Rastogi has been used to calculate the surface tensions of the pure components and of their mixtures at 25C; these calculations have been compared with the experimental results.     

Steroid saponins X. Glycosides of Allium narcissiflorum the structure of glycosides A and B

Summary FromAllium narcissiflorum Wells have been isolated for the first time trillin and a glycoside B, which proved to be 3-O-[-O-D-glucopyranosyl-(1 3)-O--D-glucopyranosyl-(1 6)-O--D-glucopyranosyl-(1 ]-26-O-[-D-glucopyranosyl-(1 ]-25R-furost-5-ene-3,22 , 26-triol.Institute of Chemistry, Academy of Sciences of the Moldavian SSR, Kishinev. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 55–58, January–February, 1976.     

Influence of sodium salt addition on the morphological and catalytic properties (ethane hydrogenolysis) of aluminasupported cobalt

NaNO₃ addition to Co/Al₂O₃ results in an increase in the reducibility, in a smaller dispersity of the metal and in a decrease in the ethane hydrogenolysis rate due to a decorative effect.

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NaNO₃ Co/Al₂O₃ ,

     

Effects of tempering time and tempering temperature of caustic mercerization on the spectral and electrical properties of Egyptian cotton fibres

Several samples of Egyptian cotton fabric strips were subjected to various caustic mercerization conditions, varying in temperature and time. On these samples extensive measurements were undertaken, comprising X-ray diffraction, IR absorption spectra and the temperature-dependence of DC-electric conductivity.The phase constitution, % crystallinity, IR band assignment, activation energies for conduction and energy gap were evaluated as a function of caustic mercerization. The results obtained were correlated and discussed in detail, leading to valuable information of use in the cotton fabric strip industries.

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Zusammenfassung Verschiedene Proben von ägyptischen Baumwollstreifen wurden unter verschiedenen Bedingungen (Temperatur, Zeit) einer Laugung unterworfen. Die gelaugten Proben wurden eingehend durch Röntgendiffraktometrie, IR-Absorptionsspektroskopie und Messungen der Temperaturabhängigkeit der elektrischen Gleichstromleitfähigkeit untersucht. Phasenstruktur, Kristallinität, Zuordnung der Banden, Aktivierungsenergien für die Leitfähigkeit und verbotene Bänder wurden in Abhängigkeit von der Laugung ermittelt. Die erhaltenen Ergebnisse wurden miteinander verglichen und in Einzelheiten diskutiert, wobei für die Baumwollverarbeitungsindustrie wertvolle und empfehlenswerte Informationen erhalten wurden.

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. , . , , , . , .

     

Structural and Microstructural Evolution During Pyrolysis of Hybrid Polydimethylsiloxane-Titania Nanocomposites

The evolution during pyrolysis of hybrid polydimethylsiloxane-titania nanocomposites has been studied as a function of the ratio between polysiloxane and titania phases. The xerogels, prepared by the sol–gel process starting from diethoxydimethylsilane and titanium isopropoxide, have been heated under argon atmosphere and the evolution with temperature has been followed by infrared and ²⁹Si solid state nuclear magnetic resonance spectroscopies, thermal analyses, X-ray diffraction, N₂ sorption measurements and scanning electron microscopy. Below 800C, the polymer-to-ceramic conversion takes place at different temperatures with changing the titania content. The stability of Si–C bonds in polydimethylsiloxane networks depends on the metal oxide amount. The high reactivity of titanium atoms towards the Si–C bonds produces Si–C bond cleavage with mild thermal treatments and in the case of 30 mol% TiO₂, leads to the ceramization of the hybrid nanocomposite at 500C. Decreasing the titania load, a shift towards higher temperatures to complete the polymer-to-ceramic conversion is observed. The structural rearrangement of the siloxane moiety produces mesoporous and microporous materials, depending on the composition; in the case of 10 and 20 mol% TiO₂ content, the samples present high specific surface area up to 1200C.The crystallization process begins at 1000C and the phase evolution depends on the composition. The phase analysis obtained from XRD spectra shows that different crystalline oxide and oxycarbide phases develop during the thermal process, as a function of the amount of available carbon, ultimately leading to the preferential crystallization of titanium carbide. Between 1000 and 1600C the amorphous silicon oxycarbide phase undergoes a continuous structural evolution caused by the decrease of carbon content in the phase, leading to almost pure silica at 1600C.     

Investigation of thermooxidative stability of oils by thermal analysis methods

Two base oils, obtained on a laboratory scale, were investigated with a derivatograph and by means of DSC. The sensitivities of the oils to some antioxidants were also examined. The high thermooxidative stability of the oil obtained from a preoxidized atmospheric crude residue was confirmed.

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Zusammenfassung Zwei im Labormaßstab hergestellte Rohöle wurden mit einem Derivatographen und mittels DSC untersucht. Die Empfindlichkeit der Öle gegenüber Antioxidanten wurde ebenfalls geprüft. Es wurde eine hohe thermooxidative Stabilität des aus einem präoxidierten atmosphärischen Rohstoffrestes erhaltenen Öls nachgewiesen.

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, . . , .

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The authors are grateful to the Institute of Petroleum Technology for the DSC measurements.     

Synthesis and Crystal Structure of the (batre)[CuBr4] Complex, where Batre is bis‐1,1′‐(4‐amino‐1,2,4‐triazolio)ethane

The (batre)[CuBr₄] complex is produced by the reaction of CuBr₂ and (batre)Br₂ in concentrated HBr; its crystal structure is determined. The acentric unit cell (Pn space group) has the following parameters: a = 7.626(2), b = 8.945(2), c = 11.702(2), = 96.69(3)°, V = 792.8(3)³, and Z=1 ((batre)[CuBr₄] composition). The structure of the complex is built up of [CuBr₄]^2- tetrahedral anions and (batre)²⁺ uncoordinated cations. The Cu—Br distances are 2.362–2.385 and the BrCuBr angles are 99.73–129.79°.     

Transformed steroids. 121. Synthesis of the δ-lactone of 3β-acetoxy-16α-hydroxy-6-oxo-24-nor-5α-chol-17(20)-en-23-oic acid

The synthesis of the ¹⁷⁽²⁰⁾-16 analog of natural chiogralactone is described. Attempts to introduce a 6-oxo group directly into the -lactone proved unsuccessful, since the first stage — saponification — took place with the formation of three products: the 3-hydroxy--lactone, the 3-hydroxy-²⁰⁽²²⁾-lactone, and the 15,17(20)-dienoic acid. The synthesis of the desired compound was effected from the ethyl ester of the 5,16-dienoic acid by the scheme 3-acetate3-tosylate6-hydroxy-3,5-cyclosteroid6-oxo-3,5-cyclosteroid6-oxo-5H--lactone. It has been shown that the cyclopropane ring in the 3,5-cyclosteroid -lactone is extremely stable under the conditions of acid treatments.N. D. Zelinskii Institute of Organic Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 184–187, March–April, 1981.