Thermodynamic Properties of NaCl Solutions at Subzero Temperatures

Heat capacities at infinite dilution of NaCl (aq) for the temperature range 0 to –25°C and apparent molar volumes at infinite dilution for 0 to –15°C have been estimated from a synthesis of experimental data collected at subzero temperatures. The parameters of the Helgeson–Kirkham–Flowers (HKF) equation for Na⁺ (aq) have been obtained, from which the Gibbs energies of Na⁺ and Cl^– have been calculated. The estimated values of Pitzer-equation parameters for thermal and activity-coefficient properties have been adjusted for subzero temperatures. The experimental phase diagram for the NaCl–H₂O system could be reproduced with these data, demonstrating the low-temperature applicability of the HKF model to extrapolate thermodynamic properties of aqueous-solution species at infinite dilution.     

Nonempirical calculations of potential-energy surfaces for nucleophilic addition of H− and F− to an acetylene molecule

The minimal energy paths for the nucleophilic addition of a hydride ion (H^–) and a fluoride ion (F^–) to a molecule of acetylene (A) have been calculated with the use of 3–21++G and 3–21+G double basis sets in the framework of the Hartree-Fock-Roothaan method. The values of the total energies of the reactants, transition states, and products have been refined by means of calculations with more complete basis sets [6–31++G// 3–21++G and 6–31++G*//3–21++G for reaction (1); 6–31+G*//3–21+G and 6–31++G**//3–21+G for reaction (2)] and by taking into account the correlation energy for reaction (1) in the framework of the SCEP/6–31++*//3–21++G method. It has been established that the activation energy of reaction (2) is 15.94 kJ/mole lower than that for reaction (1), that reaction (1) is exothermic, and that the enthalpy change accompanying reaction (2) is close to zero. The character of the distribution of the electron density along the minimal energy paths of both reactions has been analyzed, and the differences appearing as a result of the replacement of the soft nucleophile H^– by the harder nucleophile F^– have been ascertained. The results of the calculations have been compared with the results available in the literature for reaction (1).Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 149–155, March–April, 1989.     

Synthesis and structure of amino esters of menthol

The conditions for the acylation of (–)-menthol with monochloroacetyl chloride have been studied. Amino esters of (–)-menthol have been obtained by the nucleophilic replacement of the chlorine in (–)-menthol monochloroacetate by residues of secondary amines. Their properties and their mass, IR, and¹³C NMR spectra are described.Institute of Physical Organic Chemistry, Academy of Sciences of the Belorussian SSR, Minsk. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 728–733, November–December, 1981.     

Chemical synthesis and enzymatic assembly of fragments of the DNA coding immunodominant epitopes of human immunodeficiency virus

More than twenty 13- to 55-membered oligo(poly)nucleotides have been synthesized by the H-phosphonate solid-phase method in the manual variant using an original procedure. From the oligonucleotides obtained, seven DNA duplexes coding immunodominant epitopes of HIV-1 proteins have been formed: 598–609 and 737–748 gp41, 91–115 and 105–115 gag, and 940–951 pol and a number of its mutants. The ligase assembly and polymerization of the DNA duplexes obtained has been carried out. The efficiency of ligation amounted to from 60 to 90%. The possibility of their directed polymerization was determined by the flanking of the duplexes by partially completed half-sites of restrictases BamHI and XhoI.Abbreviations adopted: HIV-1 — human immunodeficiency virus, type 1; (+)-chain — the coding chain — and (–)-chain the chain complementary to the coding chain of the DNA duplex; CPG — controlled-pore glass; PAAG — polyacrylamide gel; Py — pyridine.D. I. Ivanovskii Institute of Virology, USSR Academy of Medical Sciences, Moscow. V. A. Engel'gardt Institute of Molecular Biology, USSR Academy of Sciences, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 393–399, May–June, 1990.     

Buffer Standards for the Physiological pH of Zwitterionic Compounds,MOBS and TABS from 5 to 55°C

The values of the second dissociation constant, pK₂, and related thermodynamic quantities of 4-(N-morpholino)butanesulfonic acid (MOBS) and N-tris(hydroxymethyl)-4-aminobutanesulfonic acid (TABS) have already been reported over the temperature range 5–55°C including 37{°}C. This paper reports the pH values of twelve equimolal buffer solutions at designated pH (s) with the following compositions: (a) mixtures of MOBS (0.05 mol-kg^–1) + NaMOBS (0.05 mol-kg^–1); (b) MOBS (0.08 mol-kg^–1) + NaMOBS (0.08 mol-kg^–1); (c) MOBS (0.08 mol-kg^–1) + NaMOBS (0.08 mol-kg^–1) + NaCl (0.08 mol-kg^–1); (d) TABS (0.05 mol-kg^–1) + NaTABS (0.05 mol-kg^–1); and (e) TABS (0.08 mol-kg^–1) + NaTABS (0.08 mol-kg^–1); and (f) TABS (0.08 mol-kg^–1) + NaTABS (0.08 mol-kg^–1) + NaCl (0.08 mol-kg^–1). Two buffer solutions have ionic strengths I= 0.05 mol-kg^–1, another two have I=0.08 mol-kg^–1, and the remaining two buffer solutions have I= 0.16 mol-kg^–1, which is close to that of the clinical fluids (blood serum). These buffers have been recommended as a useful pH standard for the measurements of physiological solutions. Conventional pH values of all six buffer solutions from 5–55°C, as well as those obtained from the liquid junction potential correction at 25 and 37{°}C have been calculated. The flowing-junction calomel cell has been utilized to measure E_j, the liquid junction potential.     

Synthetic analogs of natural flavolignans. II. A new synthesis of benzodioxepane analogs of silandrin and hydnocarpin

Benzodioxepane analogs of chalcones have been obtained from which analogs of natural flavolignans — silandrin and hydnocarpin — have been synthesized. The PMR spectra of the new substances are given and are discussed.KIEN, Karakalpak Division, Academy of Sciences of the Republic of Uzbekistan, Nukus. Taras Shevchenko Kiev University, Ukraine. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 480–483, July–August, 1994.     

Spectroscopic characterization of environmentally relevant C10-chloroterpenes from a photochemically modified toxaphene standard

Twenty-five pure environmentally relevant toxaphene components have been isolated from photochemically modified technical toxaphene by means of a combination of column chromatography on silica gel and preparative high resolution liquid chromatography. These compounds are 6 chlorinated camphenes (1–3, 5, 7, and 11) and 19 chlorinated bornanes (4, 6, 8–10, 12–16, 18–24, 26, and 27 according to Table 1). Two further chlorobornanes (17 and 25) have been isolated from a highly chlorinated mixture obtained by the excess chlorination of 2-exo,10-dichlorobornane. The structural elucidation of the isolated compounds has been carried out with spectroscopical methods.     

Bisindoles. 18. Some electrophilic substitution reactions in the 1,2-di(indol-5-yl)ethane series

A quantum-chemical calculation has been made and the laws of the electron-density distribution in the molecule of 1,2-di(indol-5-yl)ethane have been determined. The electrophilic substitution reactions most characteristic for it have been studied.For communications 15–17, see [1–3].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 73–77, January, 1984.     

Osmotic coefficients of dilute aqueous solutions of unsymmetrical cobalt-amine type salts at 0°C

The osmotic coefficients of dilute aqueous solutions of [Co(pn)₃]X₃ [pn=1,2-diaminopropane and X=Cl^–, Br^– and (NO₃)^–] and [Co(tn)₃]X₃ (tn=1,3-diaminopropane and X=Cl^– and Br^–) have been measured from 0.00 to 0.02 mol-kg^–1 at 0°C by the freezing point method. The results have been compared with those obtained from the numerical integration of the Poisson-Boltzmann equation.     

Synthetic and modified isoflavonoids. XIII. Synthesis of analogues of fujikinin

Analogues of a natural isoflavone glycoside — fujikinin — have been synthesized. Their structures have been confirmed by their PMR spectra.Taras Shevenko Kiev University: KIEN, Karakalpak Division, Academy of Sciences of the Republic of Uzbekistan, Nukus. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 347–351, May–June, 1994.     

Hysteresis effect and autooscillation phenomena in the oxidation of 1-hexene on palladium

The gas-phase oxidation of 1-hexene on a palladium film has been investigated in a gradient-free reactor at atmospheric pressure and temperatures of 293–693 K, at flow rates of 0.3–0.15 liter/min and an initial concentration of hexene in air of 15.5·10^–4 M. Autooscillation phenomena have been observed and a hysteresis effect in the reaction rate as function of temperature, caused by the branched-chain heterogeneous-homogeneous reaction mechanism.Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 24, No. 1, pp. 107–110, January–February, 1988.     

Tetrakisisopropoxy tantalum(V)O,O′-alkylene dithiophosphate complexes

Summary Tetrakisisopropoxytantalum(V) alkylene dithiophosphato complexes, (G=–CMe₂CMe₂–, –CHMeCHMe–, –CH₂CMe₂CH₂– and –CH₂CEt₂CH₂–) have been prepared from equimolar ratios of tantalum(V) isopropoxide and alkylene dithiophosphoric acids in benzene. These moisture-sensitive compounds, which are soluble in common organic solvents and are monomeric, have been characterized by elemental analysis, molecular weight determinations and by their i.r. and n.m.r. spectra. An octahedral geometry is suggested in which the ligand is bidentate.     

The speed of sound in mixtures of the major sea salts. A test of Young's rule for adiabatic PVT properties

The relative sound speed of mixtures of aqueous solutions of NaCl–MgSO₄ and MgCl₂–Na₂SO₄ at I=0.1 and 0.5m have been determined at 5, 15, and 25°C and pressures to 1000 bars. The resulting sound speeds, adiabatic and apparent molal compressibilities have been compared to results estimated from binary solutions using an additivity principle — Young's rule. The estimated sound speeds agree with the measured values for the NaCl–MgSO₄ system to ±0.15 m-sec^–1 and for the Na₂SO₄–MgCL₂ system to ±0.20 m-sec^–1. The deviations increase with increasing ionic strength (±0.08 m-sec^–1 at I=0.1 and ±0.25 m-sec^–1 at I=0.5 m).The sound speed of seawater have also been estimated from 0 to 40°C, 0.1 to 0.7 ionic strength and 0 to 1000 bars. The estimates were found to be in good agreement (±0.4 m-sec^–1) with the measured values.These results indicate that reasonable estimates of the adiabatic PVT properties of dilute mixtures of electrolyte solutions can be made using the additivity principle, without excess mixing terms.     

New sesquiterpene quinones from marine sponges of the order dictyoceratida

Isospongiaquinone and a new sesquiterpene quinone — dictyoceratidaquinone — have been isolated from a dictyoceratidan marine sponge. Ilimaquinone and the new aminoquinone, a sesquiterpenylamylaminohydroxyquinone, have been isolated from a spongeSpongia sp. Synthetic analogs of natural aminoquinones have been obtained by replacing the methoxy group in ilimaquinone and isospongiaquinone by an amine group.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Branch, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 47–51, January–February, 1990.     

Infrared and raman spectra,vibrational assignments,normal coordinate analysis,and ab initio calculations of methyltrifluoromethyldisulfide and bis(trifluoromethyl)disulfide

The infrared and Raman (3500-35 cm^–1) spectra of gaseous and solid methyltrifluoromethyldisulfide, CF₃SSCH₃, and bis(trifluoromethyl)disulfide, CF₃SSCF₃, have been recorded. Additionally, the Raman spectra of the neat liquids have been obtained and qualitative depolarization values have been measured. These vibrational data have been interpreted, for both molecules, on the basis that the C-S-S-C dihedral angle is approximately 90°. Vibrational assignments are given for both molecules and are supported by normal coordinate calculations utilizing ab initio Hartree-Fock gradient calculations with the 3-21G^* basis set to obtain the frequencies for the normal modes and potential energy distributions. The CH₃ and CF₃ torsional modes have been observed at 140 and 48 cm^–1, respectively, for CF₃SSCH₃, from which periodic barriers of 485 cm^–1 (1.39 kcal mol^–1) and 853 cm^–1 (2.44 kcal mol^–1), respectively, have been calculated. Complete equilibrium geometries have been determined for both molecules by ab initio calculations employing both 3–21G and 6–31G basis sets. The structural parameters for bis(trifluoromethyl)disulfide are compared to those suggested from electron diffraction studies. The results are compared to corresponding quantities obtained for some similar molecules.Taken in part from the thesis of M. M. Bergana which will be submitted to the Department of Chemistry in partial fulfillment of the Ph.D. degree.     

Protein content,activity, and electrophoretic composition of the inhibitor-containing fraction of pea seeds

The amounts of protein and the activities of the proteinase (trypsin) inhibitors of 16 varieties of pea have been studied. The amount of protein ranged from 19.3 to 25.2% and the amidase activities of the trypsin inhibitors from 18 to 40.8 IU. It was found that the electrophoretic spectrum of the inhibitor-containing fraction of the pea seed protein consisted of 12–16 components with molecular masses of 14–89 kDa. Features of the electrophoretic spectrum of some varieties of pea have been established.V. F. Kuprevich Institute of Experimental Botany, Belorussian SSR Academy of Sciences, Minsk. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 243–247, March–April, 1989.     

Oxomolybdenum(VI) and (V) complexes with 6–methyl-4–hydroxypyrimidinyl hydrazones

Dioxomolybdenum(VI) complexes [MoO2(L)H2O] and oxomolybdenum(V) complexes [Mo2O3(LH)2Cl2] (where LH2=hydrazones derived from 6–methyl-4–hydroxy-2–hydrazinopyrimidine with salicylaldehyde, 5–methyl-, 5–chloro-, 5–bromo-, 3–methoxy-salilcylaldehyde, or 2–hydroxy-1–naphthaldehyde) have been prepared and characterised by spectroscopic and physico-chemical methods. The MoVI complexes are diamagnetic octahedral structures, whilst the MoV complexes are paramagnetic and probably dimeric, via oxobridging.     

Triterpene and steroid glycosides of the genusMelilotus and their genins III. Funkioside B and protodioscin from the seeds ofMelilotus tauricus

Two steroid glycosides belonging to the furostan series — funkioside B and protodioscin — have been isolated from the seeds of the plantMelilotus tauricus (Bieb.).Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 766–770, November–December, 1994.     

Labdanoids ofMarrubium anisodon

The first chemical investigation has been made of Marrubium anisodon (fam. Lamiaceae). Two diterpenoids of the labdane type — vulgarol and manubiin — have been isolated. An x-ray analysis has been performed for the latter and its crystal amd molecular structures have been determined.Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 54–58, January–February, 1996. Original article submitted December 11, 1995.     

Phytoglycolipids of the grape

The qualitative and quantitative compositions of the grape and its component parts — flesh, skin, seeds — have been studied. Ten fractions have been identified, the main ones being cerebrosides and monogalactosyldiglycerides. The compositions of the fatty acids, of the sphingosine bases, of the sterols, and of the carbohydrates of the individual fraction of phytoglycolipids have been determined.Physicochemical Institute of the Academy of Sciences of the Ukrainian SSR, Odessa. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 296–300, May–June, 1984.