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.     

Alkaloids of Sophora alopecuroides tricrotonyltetramine

Summary From the fraction of strong bases ofSophora alopecuroides (flowering stage) a base C₁₂H₂₄N₄, mp 101–103°C, has been isolated which has been identified as tricrotonyltetramine. Its stereoconfiguration has been established.All-Union Scientific-Research Institute of Medicinal Plants. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 752–754, November–December, 1974.     

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.     

Adsorption studies of cesium on potassium copper nickel hexacyanoferrate(II) from aqueous solutions

Adsorption of cesium from aqueous solutions on potassium copper nickel hexacyanoferrate(II) (KCNF) has been investigated in batch experiments and optimized as a function of concentration of acids, salts and adsorbate using a radiotracer technique. The results are presented in terms of distribution coefficient, K_d (ml·g^–1). The uptake of cesium obeys a Freundlich adsorption isotherm over the concentration range of 3.7 to 37 mmol·l^–1 with b values of 0.77, 0.68 and 0.56 at temperatures of 293, 313, 333 K, respectively. The Langmuir adsorption isotherm is followed in the concentration range of 15 to 75 mmol·l^–1 in the same temperature range. The values of limiting adsorption concentration (C_m) have been found to be 2.58, 2.44 and 2.32 mmol·g^–1. The heat of adsorption was calculated as 26.43 kJ·mol^–1. The influence of a number of anions and cations on cesium retention has also been studied. Column experiments have been performed and breakthrough have been obtained under different operating conditions. The low cesium capacity of 1.1 mmol·g^–1 has been obtained under dynamic conditions as compared to batch experiments. Desorption of cesium from the column has been achieved (45.4%) by nitric acid solution of 8M concentration at a flow rate of 0.5 ml·min^–1.     

Atomic absorption spectroscopic determination of molybdenum in aqueous tetrathiomolybdate solutions

The flame atomic absorption spectroscopic determination of molybdenum, in aqueous solutions of tetrathiomolybdate (MoS ₄ ^2– , TTM) and paramolybdate species (Mo₇O ₂₄ ^2– , PM) has been investigated. A serious signal decrease occurred, if molybdenum has been present as tetrathiomolybdate species, and the sensitivity loss has been 85%. To improve the sensitivity, the solutions of TTM have been digested by wet-acid treatment, and made 0.14 mol·l^–1 ammonia. Finally, Mo has been determined by AAS using a nitrous oxide-acetylene flame. The range of the calibration was 0–100 mg·l^–1 and the relative standard deviation of the slope was less than 1%.Dedicated to Professor Dr. Dieter Klockow on the occasion of his 60th birthday     

Phospholipase A2 from the venom of the spider Eresus niger

A phospholipase A₂ with a molecular mass of 12–14 kDa has been isolated from the venom of the spiderEresus niger by three-stage column chromatography. Asparagine has been identified as the N-terminal amino acid.Institute of Physiology, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 557–560, July–August, 1991.     

Calculations of silicooxygen ring vibration frequencies

In the work model calculations of the vibrations of ideally isolated silicooxygen rings (using PM3 method) have been carried out. three-, four-, and six-membered rings have been considered. It has been found that that the three-membered silicooxygen rings are flat and practically undeformed showing D_3h symmetry. The rings of higher number of ring members (i.e. n>3) are deformed to some extent. The deformation reveals itself most significantly in the Si–O–Si bond angles distribution. In the case of all the rings the bridging Si–O–Si bonds are ca. 0.02–0.04 Å shorter than the non-bridging Si–O⁻ bonds. Hypothetical IR spectra for all the rings considered have been also calculated. Analysis of these hypothetical spectra leads to the conclusion that the whole spectrum can be divided into four wavenumbers regions, 1200–1100 cm⁻¹ stretching Si–O(Si) vibrations; 1000–800 cm⁻¹ stretching Si–O⁻ vibrations; 800–600 cm⁻¹; the region in which a band characteristic of silicooxygen rings appears, and below 600 cm⁻¹ bending ⁻O–Si–O⁻ and (Si)O–Si–O(Si). It has been also found that as the number of ring members increases the ‘ring band’ shifts to lower wavenumbers: 725 cm⁻¹ for three-membered rings, 650 cm⁻¹ for four-membered rings and 610 cm⁻¹ for six-membered rings. Calculated spectra have been compared with the experimental spectra of cyclosilicates. They showed good agreement in the 1200–600 cm⁻¹ region. In the experimental spectra as well as in the calculated ones, with increasing the number of ring members the ‘ring band’ shifts towards lower wavenumbers.     

Structure of diptocarpilidine

Diptocarpilidine (bp 193–194° (4 mm)) has been isolated from the epigeal part and seeds ofDiptychocarpus strictus (Fisch) Trautv., and its structure has been established as 1-cyano-6-methylsulfinylhexane.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 84–86, January–February, 1984.     

An application of the DFT-based scaled quantum mechanical force field method to a weakly bonded system: N2O4

The adequacy of the density functional derived scaled quantum mechanical force field method of Rauhut and Pulay has been tested for a weakly bound dimer, N₂O₄. The Becke3–Lee–Yang–Parr/6-31G^* harmonic force field has been scaled with the transferable scale factors of Rauhut and Pulay (developed originally for `common' organic compounds without any reference to the N–O bond) resulting in 20.7 and 38 cm⁻¹ for the mean and the maximal individual deviations, respectively, as compared with experimental spectra. Consequently, the force field method of Rauhut and Pulay may give reliable results for non-common compounds as well.     

Rapid determination of telmisartan in pharmaceuticals and serum by the parallel catalytic hydrogen wave method

The polarographic characteristics of telmisartan have been investigated in 0.8 mol L^–1 NH₃.H₂O–NH₄Cl (pH 8.9)–0.01 mol L^–1 H₂O₂ as supporting electrolyte. The results demonstrate that the polarographic reduction wave at ca. –1.30 V in the absence of H₂O₂ is a catalytic hydrogen wave, and the reduction wave enhanced by H₂O₂ is a so-called parallel catalytic hydrogen wave. The analytical sensitivity of the parallel catalytic hydrogen wave is ca. 60 times higher than that of the corresponding catalytic hydrogen wave. Based on the parallel catalytic hydrogen wave a novel method has been developed for determination of telmisartan by linear sweep polarography. The calibration curve is linear in the range 2.0×10^–8–2.0×10^–6 mol L^–1 and the detection limit is 1.0×10^–8 mol L^–1. The precision is excellent with relative standard deviations of 2.6% at a concentration of 1.0×10^–7 mol L^–1 telmisartan. The proposed method has been applied to the direct determination of the telmisartan in capsule forms and biological samples. The proposed method has been proved to be advantageous over existing CZE and MEKC methods in simplicity, rapidity, and reproducibility.     

Kinetics of reduction of hydroxycuprate(III) in KOH solution

The solution of an unstable copper(III) complex, hydroxycuprate(III) i.e. Cu(OH)^– ₄, has been obtained by oxidising a copper anode in 0.5–3 M KOH solution. The kinetics of the copper(III) reduction in KOH solution has been studied spectrophotometrically and is first order with respect to copper(III), and the pseudo-first order rate constant increases as the KOH concentration increases. The kinetic data is explained by a scheme according to which a Cu^III intermediate, in equilibrium with Cu(OH)^– ₄, reacts with OH^–. On the basis of the kinetic data, the molar absorptivity of the Cu(OH)^– ₄ solution has been determined.     

The question of the production of Plantaglyutsid

The stage of extracting Plantaglyutsid from the leaves of rippleseed platain has been optimized by the methods of mathematical statistics. Information has been obtained on the optimum parameters of performing the process, as a result of which the yield of desired product has been increased and the amount of energy used and the consumption of extractant have been decreased.Tahskent Pharmaceutical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 735–737, November–December, 1985.     

Preparation and Characterization of Ultrafine Rare Earth Molybdenum Complex Oxide Particles

Ultrafine rare earth molybdenum (La–Mo and Ce–Mo) complex oxide particles have been synthesized by the sol–gel process using citric acid as complexing agent. The influence of preparation conditions such as thermal treatment temperature (T), molar ratio of citric acid to metallic ions (L/M), and pH value of the starting solution on the oxide particle size has been studied. The formation of La₂Mo₂O₉and Ce₂Mo₃O₁₂has been investigated using XRD, DTA–TG, FT-IR, TEM, and BET surface area measurements. It is shown that the morphology and structure of the oxide particles are significantly dependent on the preparation conditions. The influence of different preparation methods on the particle size of La–Mo and Ce–Mo oxides is also discussed.     

Adsorption of low level51Cr(VI) from aqueous solution by bismuth trioxide: Kinetic and IR study

Radiotracer technique has been used for the investigation of adsorption of chromium (VI) traces on bismuth trioxide from aqueous solution. The effect of pH (2–10), concentration of chromate solution (10^–6–10^–2M) and temperature (303–323 K) has been thoroughly investigated. The influence of certain foreign ions has also been studied. The calculated kinetic and thermodynamic parameters indicate the first order rate law, spontaneity and exothermic nature of the adsorption process. Further, IR studies have established the chemical interaction between the sorbate and sorbent and a possible mechanism of the sorption process based on ligand exchange has been proposed.     

Metabolites of the pathogenic fungus Verticillium dahliae VII. The phytotoxic pigment PKZh-1 from the culture liquid

Summary The phytotoxic pigment PKZh-1 that causes the characteristic symptoms of wilt in tests on cotton-plant shoots in a concentration of 100–150 µg/ml, has been isolated from the culture liquid of the fungusVerticillium dahliae Kleb.On the basis of qualitative reaction, spectral characteristics, and a study of hydrolysis products, PKZh-1 has been assigned to the peptide group. A red substance identified as 3,6,8-trihydroxy-1,4-naphthaquinone has been isolated from an acid hydrolyzate of PKZh-1.V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 690–693, September–October, 1977.     

Chemical and immunochemical investigation of the lipopolysaccharides ofVibrio alginolyticus

A chemical and immunochemical study of the LPSs of the microorganismsVibrio alginolyticus (strains 1385–80, 945–80, and 2076–80) has been made. A difference in the monosaccharide composition of the LPSs of the strains studied has been shown. It had been established that the LPSs of strains 945–80 and 2076–80 possess a high serological specificity, while the LPS of strain 1385–80 differ serologically from them. A suggestion is made of the role of different monosaccharides in the formation of the immunochemical determinants of the LPSs of the strains studied.Pacific Ocean Institute of Bioorganic Chemistry of the Far-Eastern Scientific Center of the USSR Academy of Sciences, Vladivostok. Translated from Khimiya Priorodnykh Soedinenii, No. 5, pp. 652–657, September–October, 1987.     

Theoretical study of isomerization by a 1,2-hydrogen shift in HAB molecules and HAB+ ions with 10 valence electrons

The potential-energy surfaces (PES's) of HAB molecules and HAB⁺ ions with the diatomic cores AB=CN^–, BO^–, BeF^–, N₂, CO, BF, CP^–, BS^–, NP, CS, BCl, SiN^–, AlO^–, SiO, AlF, SiP^–, AlS^–, P₂, SiS, and AlCl, which contain 10 valence electrons, have been calculated by the nonempirical MO-LCAO-SCF method with subsequent consideration of electron correlation in the framework of the third-order Møller—Plesset (MP3) method, and the isomerization realized by a 1,2-hydrogen shift in them has been studied. The similarities and differences in the form of the PES's corresponding to the migration of Li⁺ (which was previously investigated) and the migration of H⁺ around AB have been traced, and the geometric characteristics and relative energies of the isomers, as well as the heights of the activation barriers between them, have been compared. An attempt has been made to relate the differences in the properties to differences in the electronic structure of HAB and LiAB.Institute of New Chemical Problems, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 2, pp. 3–11, March–April, 1991.     

Physicochemical analysis of a protein with nerve growth activity from the muscle tissue of Rana ridibunda

A protein nerve growth factor has been isolated in the pure form from the muscles of the lake frogRana ridibunda. The individuality of the substance obtained has been shown, its molecular mass (106.0–110.0 kDa) and pI value (9.2–9.4) have been determined, and lysine and valine have been found as the N- and C-terminal amino acid residues of its polypeptide chain. In view of the detection of the presence of sugars (about 1%), the substance has been identified as a glycoprotein. Its absorption spectra in the UV region has been obtained and the amino acid composition of the isolated protein has been determined. Information on the amino acid composition of various proteins with nerve growth activity has been subjected to comparative analysis with the aid of computer programs, and on this base their phylogenetic tree has been constructed.Institute of Biochemistry, Uzbekistan Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 251–257, March–April, 1992.     

Principles of modeling in the study of conformations of histones

A study has been made by the CD method of the conformational potentialities of the polypeptides (Gly-Lys-Gly)_n and (Ala-Lys-Ala)_n and fragments of the terminal sections of histones H4 (the sequence 1–16), H2B (1–21), and H1 (152–184), and they have been used as models of histones in complex formation with DNA under various conditions of the medium.V. I. Nikitin Institute of Chemistry, Tadzhik SSR Academy of Sciences, Dushanbe. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 391–398, May–June, 1989.     

Kinetics of the formation of a complex of the palladium ion with 1,8-dihydroxy-2-(2-pyrazoline-5-azo) naphthalene-3,6-disulfonic acid

The kinetics of the complex-formation of the palladium ion with 1,8-dihydroxy-2-(2-pyrazolin-5-azo)naphthalene-3,6-disulfonic acid has been studied in aqueous solution (pH 0–5). It has been shown that the rate of the reaction is a maximum at pH 2.8 and falls at pH > 2.9 because of the hydrolysis of the palladium ions and at pH < 2.9 as a consequence of the protonation of the reagent molecule.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 5, pp. 611–613, September–October, 1985.