Asparagus polysaccharides. I. Isolation and characterization of polysaccharides ofA. neglectus: Glucomannans of the roots

Water-soluble polysaccharides and pectin substances have been isolated from various organs ofA. neglectus and their quantitative amounts and monosacchardie compositions have been determined. Native acetylated glucomannans (A, B, and C) containing 13, 15, and 20% of acetyl groups and being homogeneous according to the results of gel chromatography have been isolated from the roots. On the basis of the results of periodate oxidation, methylation, and IR spectroscopy it has been established that the neutral polysaccharides of the roots ofA. neglectus is a mixture of three glucomannans consisting of -14 linear-bound D-gluco- and D-mannopyranose residues.Deceased.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 702–706, November–December, 1981.     

Plant polysaccharides VIII. Polysaccharides ofLagochilus zeravschanicus

Water-soluble polysaccharides, pectin substances, and hemicelluloses have been isolated from the epigeal part ofLagochilus zeravschanicus and characterized. The pectins isolated are characterized by a high degree of esterification of the carboxy groups, and their base consists of a fragment constructed from -14-linkedD-galacturonic acid residues.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 40 64 75. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 569–572, July–August, 1997.     

Carbohydrates ofAllium. IV. Glucofructans ofAllium longicuspis

Water-soluble polysaccharides have been isolated from the bulbs ofAllium longicuspis Rgl. By fractionating the combined water-soluble polysaccharides, homogeneous polysaccharides with molecular weights of 15,500 and 5100 have been isolated. It has been shown by spectral and chemical methods that they consist of glucofructans of a mixed type containing glycosidic bonds of the inulin (2 1) and levan (26) types in a ratio of 2.1:1.Deceased.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 703–707, November–December, 1984.     

Displacement of aqua ligands from the hydroxopentaaquarhodium(III) ion by pyridine-2-aldoxime: A kinetic and mechanistic approach

Summary The kinetics of anation of the hydroxopentaaqua-rhodium(III) ion by pyridine-2-aldoxime have been studied spectrophotometrically as a function of pH, substrate concentration, entering ligand, temperature and solvent polarity. The reaction rate increases with an increase in pH, temperature and ligand concentration, and reaches a limiting value at high ligand concentration. The activation parameters (H ^# = 87.5 kJ mol^–1 and S = –52.3 JK^–1 mol^–1) have been calculated from an Eyring plot and are compared with aqua exchanges in other systems. All the experimental facts lead to an associative interchange (I _a) mechanism with the prior formation of an outer-sphere association complex. Solvent polarity effects lead to the same conclusion.     

Spectrochemistry of solutions,part 23. Changes of enthalpy and entropy in the formation of contact ion pairs: A vibrational spectroscopic appraisal using thiocyanate and azide solutions

Summary The vibrational spectra of solutions have been analyzed to assess both qualitatively and quantitatively the changes in enthalpy and entropy for ion pair formation in solutions of LiNCS, Mg(NCS)₂, and LiN₃ in liquid ammonia, dimethylformamide, dimethylsulphoxide and acetonitrile. Contrary to predictions both the H _ass and S _ass terms are all positive in the cases examined, indicating that the driving force in the ion association process derives from solvent-solute restructuring, and not the energy of the interaction between the cation and anion. This characteristic of contact ion pair formation is likely to be found to be applicable over a wide range of solvents. The following specific values of the thermodynamic parameters at 298 K have been obtained: LiNCS/DMF, G=–1.3 (1) kJ mol^–1, H _ass =+1.8 (5) kJ mol^–, S _ass =+10 (2) J mol^–1 K^–1; LiNCS/DMSO, G=+0.9 (2) kJ mol^–1, H _ass =+0.3 (3) kJ mol^–1; Mg(NCS)₂/DMF, G _ass =–4.0 (3) kJ mol^–1, H _ass =+15 (4) kJ mol^–1, S=+64 (17) kJ mol^–1; LiN₃/DMSO, G _ass =–2.5 (3) kJ mol^–1, H _ass =+4.9 (9) kJ mol^–1, S _ass =+25 (10) J K^–1 mol^–1.Submitted to celebrate the 70th Birthday of Professor Viktor Gutmann, and in recognition of his considerable contributions towards the better understanding of Chemistry in the Solution Phase     

Mechanism of the oxidation of L-ascorbic acid by the bis(pyridine-2,6-dicarboxylate)cobaltate(III) ion in aqueous solution

A detailed investigation of the oxidation of L-ascorbic acid (H₂A) by the title complex has been carried out using conventional spectrophotometry at 510 nm, over the ranges: 0.010 [ascorbate] _T 0.045 mol dm^–3, 3.62 pH 5.34, and 12.0 30.0 °C, 0.50 I 1.00 mol dm^–3, and at ionic strength 0.60 mol dm^–3 (NaClO₄). The main reaction products are the bis(pyridine-2,6-dicarboxylate)cobaltate(II) ion and l-dehydroascorbic acid. The reaction rate is dependent on pH and the total ascorbate concentration in a complex manner, i.e., k _obs = (k ₁ K ₁)[ascorbate] _T /(K ₁ + [H⁺]). The second order rate constant, k ₁ [rate constant for the reaction of the cobalt(III) complex and HA^–] at 25.0 °C is 2.31 ± 0.13 mol^–1 dm³ s^–1. H = 30 ± 4 kJ mol^–1 and S = –138 ± 13 J mol^–1 K^–1. K ₁, the dissociation constant for H₂A, was determined as 1.58 × 10^–4 mol dm^–3 at an ionic strength of 0.60 mol dm^–3, while the self exchange rate constant, k ₁₁ for the title complex, was determined as 1.28 × 10^–5 dm³ mol^–1 s^–1. An outer-sphere electron transfer mechanism has been proposed.     

Determination of traces of bismuth by quenching of solid-substrate room-temperature phosphorescence from morin-labeled silicon dioxide nano-particles

Silicon dioxide nano-particles, diameter 50 nm, containing morin (morin–SiO₂) have been synthesized by the sol–gel method. They emit strong and stable room-temperature phosphorescence (SS-RTP) on filter paper as substrate, and bismuth can quench the intensity of the SS-RTP. On this basis a new morin–SiO₂ solid-substrate room-temperature phosphorescence-quenching method has been established for determination of traces of bismuth. Reduction of phosphorescence intensity (I_p) is directly proportional to the concentration of bismuth in the working range 0.16–14.4 ag spot^–1 (sample volume 0.40 L spot^–1, corresponding to the concentration range 0.40–36.0 fg mL^–1). The regression equation of the working curve is I_p=14.86+5.279×[Bi³⁺] (ag spot^–1) (n=6, r=0.9982). The detection limit of this method is 0.026 ag spot^–1 (corresponding to a concentration of 6.5×10^–17 g mL^–1).This sensitive, reproducible and accurate method has been used for successful analysis of real samples.     

A new route to the asymmetric Schiff base ligands. The ligand exchange in [Mo(CN)<Subscript>3</Subscript>O(salhy)]<Superscript>2−</Superscript> ion. Kinetics and mechanism

The kinetics of the ligand exchange in (PPh₄)₂[Mo(CN)₃O(salhy)]. 6H₂O (Hsalhy = salicylaldehyde hydrazone) by a solvent molecule and by 2,2-bipyridine (bpy) have been studied in EtOH. For the ligand exchange by a solvent molecule the pseudo-first order rate constant equals k _obs = 3.2 (±0.2) × 10^–3 s^–1 (t=25 °C), H =67 (± 7) kJ mol^–1, S =–75 (±23) J mol^–1 K^–1, while for the exchange by a bpy molecule k _obs=3.5 (±0.2) × 10^–3 s^–1 (t=25 °C), H =56 (±7) KJ mol^–1, S = –104 (±8) J mol^–1 K^–1. It was found, that all reactions proceed via the same mechanism which involves the chelate ring opening cis to the Mo=O bond. The mechanism of the reaction was proposed and was proved by the synthesis of (PPh₄)₂[Mo(CN)₃O(N-pic)]. 2.5H₂O (N-pic denotes that the nitrogen of picolinic acid is trans to Mo=O) by ligand exchange in EtOH, while in aqueous solution the O-pic analogue is formed exclusively.     

Determination of traces of iron with the catalytic maximum wave in differential pulse polarography

Summary A differential pulse polarographic method for the determination of iron employing the catalytic maximum wave has been studied. A well-defined differential pulse polarographic peak for iron(III) in Britton-Robinson buffer solution containing 50 mol/l N-(2-hydroxyethyl) ethylenediamine N,N,N-triacetic acid (HEDTA) and 5 mmol/l KBrO₃ is observed in the potential range from +0.2 to –0.3 V vs. SCE. The peak current is very large compared to that of the Fe(III)/EDTA complex, being proportional to the concentration of iron(III) between 1.00×10^–8 and 3.58×10^–6 mol/l under optimum conditions. The relative standard deviations for 3.58×10^–7 mol/l and 1.79×10^–6 mol/l iron(III) were 1.38 and 0.54%, respectively (n=5), and the calculated detection limit was 5.2×10^–9 mol/l iron(III). The method has been applied to the determination of iron in fresh snow and rain waters.

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Spurenbestimmung von Eisen mit Hilfe der katalytischen Maximumsstufe in der Differential-Puls-Polarographie

Zusammenfassung Das Verfahren beruht auf der Tatsache, daß in Britton-Robinson-Puffer (mit 50 mol/l HEDTA und 5 mmol/l KBrO₃) im Potentialbereich von +0,2 bis –0,3 V gegen SKE ein gut definierter puls-polarographischer Peak für Eisen(III) auftritt. Der Peakstrom ist im Vergleich zu dem des Fe(III)/EDTA-Komplexes sehr groß und ist unter optimalen Bedingungen im Konzentrationsbereich von 1,00·10^–8 bis 3,58·10^–6 mol/l der Eisen(III)-Konzentration proportional. Die relative Standardabweichung beträgt 1,38% bzw. 0,54% (n=5) für 3,58·10^–7 mol/l bzw. 1,79·10^–6 mol/l Fe(III). Die berechnete Nachweisgrenze liegt bei 5,2·10^–9 mol/l Fe(III). Das Verfahren wurde zur Eisenbestimmung in Schnee- und Regenwasser eingesetzt.

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This work was supported in part by a Grant-in-Aid for Scientific Research from Hokkaido-prefecture, 1982.     

Carbohydrates ofSymphytum asperum

It has been shown that the carbohydrates ofSymphytum asperum L. — a promising fodder plant — include water-soluble polysaccharides, pectin substances, protopectin, hemicelluloses, a glucomannan, and cellulose. The quantitative amounts of the polysaccharide fractions in the raw material have been established and their characteristics are given. The protopectins of the leaves and stems ofSymphytum asperum L. have been characterized. Their macromolecules are based on a fragment constructed of D-galacturonic acid residues linked by -glycosidic bonds.M. V. Lomonosov Odessa Technological Institute of the Food Industry. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 15–20, January–February, 1984.     

Study of the catechins and proanthocyanidins ofQuercus robur

More than 20 compounds have been isolated from the bark ofQuercus robur. Monomers: (–)-epicatechin, (–)-epicatechin gallate, (+)-catechin, (+)-catechin gallate, (+)-gallocatechin, (–)-epigallocatechin, and (–)-epigallocatechin gallate; dimeric proanthocyanidins: (+)-catechin-(4-8)-(+)-catechin, 3-O-galloyl-(+)-catechin-(4-8)-3-O-galloyl-(+)-catechin, 3-O-galloyl-(+)-gallocatechin-(4-8)-(+)-gallocatechin, (–)-epicatechin-(4-8)-3-O-galloyl-(–)-epigallocatechin gallate, 3-O-galloyl-(–)-epicatechin-(4-8)-3-O-galloyl-(–)-epigallocatechin, 3-O-galloyl-(–)-epigallocatechin-(4-8)-(+)-catechin; and oligomeric proanthocyanidins: D14-D19.Materials presented at the IInd International Symposium on the Chemistry of Natural Compounds (SCNC, Eskiehir, Turkey, October, 22–24, 1996).Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 40 64 75. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 819–833, November–December, 1997.     

Binuclear complexes with uranyl ions in non-equivalent coordination environments: synthesis and electrochemistry of complexes with binucleating aroyl hydrazones and 2,2′-bipyridine

The binuclear complexes [(UO₂bipy)₂L^1–3]NO₃, (1–3), {H₃L^1–3=1-(2-hydroxybenzoyl)-2-(2-hydroxy-benzal/3-methoxybenzal/naphthal)hydrazine}, and [(UO₂bipy)₂L^4–5](AcO)₂, (4–5), [H₂L^4–5 = 1-(2-aminobenzoyl)-2-(2-hydroxy-benzal/naphthal)hydrazine], have been synthesised. Complexes (4–5) possess longer O=U=O bonds than those in the complexes (1–3) as the strong -donating phenolate is replaced by the amino group. The spectral data and electrochemical behaviour confirm the electronic nonequivalence of the coordination environments around the two uranyl ions in these complexes.     

Solvent extraction of thorium from nitric acid solutions using di-N-butyl sulfoxide (DBSO) in xylene

The extraction of thorium(IV) from nitric acid solutions by di-n-butyl sulfoxide (DBSO) in xylene has been investigated as a function of acid, extractant and the metal concentration. The effect of contact time and diverse ions on the extraction has been examined. Phosphate, fluoride, oxalate and perchlorate reduce the extraction to some extent. The extraction of other metal ions, especially impurities associated with thorium in ores, has been measured under optimised conditions selected for thorium extraction. Na(I), K(I), Ca(II), Sr(II), Mn(II), Fe(II), Ni(II), Zn(II), Pb(II), Al(III), Ti(IV) and Hf(IV) are not extracted. Among the stripping solutions employed for back-extraction, deionized water is found to be the best and more than 99% thorium can be back-extracted in three stages. The extracted species is supposed to be Th(NO₃)₄·2DBSO. The extraction is found to be almost independent of the thorium concentration in the range between 4.3·10^–4–4.3·10^–2M and inversely dependent upon the temperature. The values of thermodynamic functions H, G and S for extraction equilibrium have been evaluated to be –19.6±2.9 kJ·mole^–1, –18.1±2.0 kJ·mole^–1 and –5.0±2.9 J·mole^–1·K^–1, respectively.     

Equilibrium constants of some protonated,nonprotonated and hydroxo complexes of uranium(VI) with xylenol orange

Summary The species, UO₂H₃L^–, UO₂H₂L^2–, UO₂HL^3–, UO₂L^4–, UO₂(OH)L^5– and UO₂(OH)₂L^6– are found in the equilibria between uranyl ions and 3,3-bis[N,N-di(carboxymethyl)-aminomethyl]-o-cresolsulphonphthalein (H₆L; xylenol orange; dcac) in aqueous solution. The equilibria have been studied by the potentiometric method at 25° and at an ionic strength of 0.1M (KNO₃). New algebraic equations have been employed to evaluate the equilibrium constants.     

New alkaloids ofDipthychocarpus strictus

New alkaloids with mp 57–59°C and diptamine have been isolated from the seeds and epigeal part ofDipthychocarpus strictus collected in Chimkent Province (KazSSR). It has been established that the base with mp 57–59°C has the structure of N,N-di(6-methylthiohexyl)urea, while diptamine is N-isopropyl-N-(7-methylsulfonylheptyl)urea.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedeninii, No. 3, pp. 363–365, May–June, 1980.     

Application of symmetry coupling coefficients in the evaluation of the electronic spectra of d 7 ions

The optical absorption spectrum of cobalt chloride thiourea has been studied at room and liquid air temperatures. The results have been interpreted using group theoretical methods taking into account all the quartet states and several doublet states. Crystal field, electrostatic, and spin-orbit coupling interactions were included to yield the allowed transitions with the relative transition probabilities. The experimental results were interpreted for the following set of parameters: B = 750cm^–1, C = 3100cm^–1, = 7370cm^–1, = -200 cm^–1, = 500cm^–1, and = 450 cm^–1.     

An equilibrium and calorimetric investigation of the hydrolysis of L-tryptophan to (indole + pyruvate + ammonia)

Apparent equilibrium constants and calorimetric enthalpies of reaction have been measured for the reaction L-tryptophan(aq) + H₂O(l) = indole(aq) + pyruvate(aq) + ammonia(aq) which is catalyzed by L-tryptophanase. High-pressure liquid-chromatography and microcalorimetery were used to perform these measurements. The equilibrium measurements were performed as a function of pH, temperature, and ionic strength. The results have been interpreted with a chemical equilibrium model to obtain thermodynamic quantities for the reference reaction: L-tryptophan(aq) + H₂O(l) = indole(aq) + pyruvate^–(aq) + NH ₄ ⁺ (aq). At T=25°C and I_m=O the results for this reaction are: K^o=(1.05±0.13)×10^–4, G°=(22.71±0.33) kJ-mol^–1, H°=(62.0±2.3) kJ-mol^–1, and S°=(132±8) J-K^–1-mol^–1. These results have been used together with thermodynamic results from the literature to calculate standard Gibbs energies of formation, standard enthalpies of formation, standard molar entropies, standard molar heat capacities, and standard transformed formation properties for the substances participating in this reaction.Presented at the Symposium, 76^th CSC Congress, Sherbrooke, Quebec, May 30–June 3, 1993, honoring Professor Donald Patterson on the occasion of his 65^th birthday.     

1H NMR studies on intermolecular association of amphiphilic cationic polyelectrolyte micelles induced by hydrophobic counteranions in water

Interactions of a series of amphiphilic cationic polyelectrolytes with various kinds of organic counteranions have been investigated in water by one- and two-dimensional ¹H NMR spectroscopy at 20 °C. The cationic polyelectrolytes were prepared by micellar homopolymerization of tail-type cationic surface-active monomers with a cationic charge with -end, (ST–C_m–AB, m=5, 7, and 9, where ST is a styrenic group, C_m, an alkylene chain at the 4-position of styrene, and AB, alkyltrimethylammonium bromide). Aliphatic monosodium salt of maleic acid (MAS) and its stereoisomer, fumaric acid (FAS), sodium benzoate (NaB), potassium hydrogen phthalate (PHK), and sodium salicylate (NaSal) were added to a salt-free aqueous solution of the polyelectrolytes and ¹H NMR measurements were carried out. Amphiphilic P(ST–C_m–AB) polyelectrolytes act as efficient hosts to strongly capture the hydrophobic counteranions B^–, PH^–, and Sal^–, but not MA^– and FA^–. The ¹H NMR signals of these hydrophobic counteranions remarkably shift upfield and broaden in water in the presence of the amphiphilic polyelectrolytes. The nuclear Overhauser effect (NOE) signals between the cationic group of the polymer and aromatic benzoate counteranion protons are clearly observed to imply cation– interaction. The capturing of hydrophobic counterions by the polyelectrolytes is likely due to electrostatic, hydrophobic, and cation– interactions between them. The reduced viscosity, _sp/C_p, for the solution at [PHK]/[P(ST–C₇–AB)]=1.0 steeply increases with increasing polymer concentration (C_p) above ca. 0.9 g/dL to show pronounced viscoelasticity.     

Theoretical studies of the benzene oxide—oxepin valence tautomerism

We have calculated the geometry and energy of the valence tautomers benzene oxide and oxepin using the semiempirical AM1 model and the 6–31G and 6–31G^* basis sets utilizing full geometry optimization. In the oxide the folding angle, the angle between the epoxide ring and the adjacent plane containing four carbon atoms, is about 106°. The carbon skeleton is almost planar, the folding angle, the angle between the two four-carbon atom planes being about 175°. In contrast, oxepin is found to have a marked boat-shaped structure with the corresponding and angles about 137° and 159°, respectively. The AM1, 6–31G, and 6–31G^* calculations give –11.4, –10.8, and –2.9 kcal mol^–1 for the energy change that accompanies the valence tautomerism, oxide-oxepin, compared to an experimental value of about +0.3 kcal mol^–1. Single point calculations of the energies at the 6–31 G^* geometry using Møller-Plesset perturbation theory to second order (MP2/6–31 G^*) and third order (MP3/6–31G^*) give E _T =+3.3 and +0.8 kcal mol^–1. The values for the energy change in the transfer of epoxide oxygen from ethylene oxide to benzene using AM1, 6–31G, and 6–31G^* are in good agreement, viz., +31.1, +34.5, and +33.6 kcal mol^–1, respectively. A large positive energy change is to be expected in view of the loss of benzene aromaticity.     

Rhodium(1) carbonyl complexes with alkyl sulphoxides and sulphides

Summary Rhodium(I) carbonyl complexes, namely Rh(CO)X(R₂SO)₂ (R = Me, n-Pr or n-Bu) and Rh(CO)X(R₂S)₂ (R = Me, Et or i-Pr) and X = CI or Br, have been prepared and characterized. The compounds Rh(CO)X[P(OPh)₃]₂ X = Cl or Br, have also been isolated. In the R₂SO and R₂S complexes, the carbonyl stretching frequencies occur atca. 2020–2025 cm^–1 andca. 1950–1980 cm^–1 respectively. In the R₂SO ligand containing complexes v(S-O) occurs atca. 1100–1125 cm^–1 indicative of metal-sulphur coordination. In presence of HBF₄, the addition of an excess of Me₂SO to (OC)₂Rh(-Cl)₂Rh(CO)₂ gives [Rh(Me₂SO)₆]³⁺ in which the central metal atom undergoes spontaneous oxidation from Rh¹(d⁸) to Rh^III(d⁶). The complexes have been characterized additionally by u.v.vis. spectra, conductivity measurements and by elemental analyses.