Ab initio Calculation of the charge distribution and the ligand field splitting in the tetrahedral halo complexes CuCl 4 2− 4 and NiCl 4 2−

The charge distribution and the ligand field splitting in the tetrachloro complexes CuCl ₄ ^2– and NiCl ₄ ^2– have been investigated by means of the restricted Hartree-Fock method. A rather large basis set of contracted Gaussian type orbitals has been employed. The charge distributions have been analysed by means of Mulliken population analyses. The ligand field splitting 10Dq has been compared with literature results known for the octahedral cluster NiF ₆ ^4– occurring in KNiF₃. A detailed analysis has been carried out for CuCl ₄ ^2– . From calculations on a selected number of states of NiCl ₄ ^2– the Racah parameters B and C have been obtained.     

Water in melts: Raman spectral investigation of the molten Ca(NO3)2·4H2O−KNO3 system

The Raman spectra of molten mixtures of Ca(NO₃)₂\4H₂O–KNO₃ have been examined, covering the concentration range of 0–70 mole% KNO₃. The frequencies in the spectra of the mixtures have been found to change slightly with concentration. Striking variations in the band shapes have been observed in the regions corresponding to the O–H stretching mode (2850–3850 cm^–1) and the v₄-NO ₃ ^– mode (700–750 cm^–). The results are discussed in terms of perturbed quasi-lattice structure for the melt, in which there could be a displacement of water molecules in the first coordination sphere around Ca²⁺ by the NO ₃ ^– ion.     

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.     

Polysaccharides of the cell walls of fungi pathogenic for the cotton plant

The dynamics of the secretion of polysaccharides by fungi pathogenic for the cotton plant — Verticillium dahliae and Fusarium oxysporum — have been studied. An alkaline hydrolysate of the fungal cell walls has been obtained. Total fractions of the polysaccharides have been separated on Sephadex G-50 and Acrilex P-4, and their monosaccharide compositions have been determined.Institute of Microbiology, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 41 71 29. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 198–201, March–April, 1995. Original article submitted October 19, 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.     

A study of the tautomerism of the N-butyl-4(2)-methoxycarbonyl-pyrrolid-3-ones and their hydrochlorides

The tautomerism of N-butyl-2-methoxycarbonyl-4-methylpyrrolid-3-one (I), N-butyl-4-methoxycarbonylpyrrolid-3-one (II), N-butyl-4-methoxycarbonyl-2-methylpyrrolid-3-one (III), N-butyl-4-methoxycarbonylpyrrolid-3-one hydrochloride (IV), and N-butyl-4-methoxy-carbonyl-2-methylpyrrolid-3-one hydrochloride (V) has been studied by UV and IR spectroscopy. It has been found that the esters I–V are highly ionized in aqueous and ethanolic solutions at concentrations of 10^–2–10^–3 M. On passing from methyl cyclopentran-1-one-2-carboxylate to the esters II and III the position of the equilibrium in heptane and CCl₄ shifts in the direction of the keto form. On passing from the esters II and III to the esters IV and V, the position of the equilibrium shifts in the direction of the enol. Meyer's relationship is not satisfied for the esters II and III, while it is satisfied for the esters IV and V. Hypotheses have been put forward on the causes of the phenomena mentioned.     

Bis(2,4–pentanedionato)vanadium(IV) aryloxides

Complexes of composition [VCl(acac)2(OAr1–4)] and [V(acac)2(OAr1–4)2] (HOAr1=HOC6H4NO2–4, HOAr2= HOC6H4OMe-4, HOAr3=HOC6H4But-4 and HOAr4= HOC6H2But-2,6–Me-4; acac=2,4–pentanedionato ion) have been synthesized by the reaction of [VCl2(acac)2] with the respective phenols or their trimethylsilyl derivatives. The complexes have been characterized by physicochemical and spectroscopic techniques. They are non-electrolytes in nitrobenzene. Room temperature magnetic moments in the 1.71–1.82B range are consistent with the VIV system. The reactions of [VCl(acac)2(OAr2)] and [VCl(acac)2(OAr3)] with chloride acceptors have been studied by conductance techniques and the formation of ionic complexes of the types [V(acac)2(OAr2,3)][MCl4] (M=Fe, Al or Sb) and [V(acac)2(OAr2,3)][MCl6] (M=P or Sb) is indicated by the conductance composition curves. Several of these complexes have been isolated and characterized.     

Activity coefficients of electrolytes from the emf of liquid membrane cells. IV: Revised activity coefficients of lanthanum hexacyanoferrate(III)

Lanthanum ferricyanide is so far the only 3–3 electrolyte whose activity coefficients have been studied carefully; however, the results have been acknowledged to be inconsistent below 1×10^–4 mol-kg^–1. New measurements have been made with an improved cell, proving that the wrong trend was due to chemical interference in the original cell. The new cell makes it possible to reach dilution levels of the order of 4×10^–6 mol-kg^–1. The salt behaves radically unlike Debye-Hückel's predictions, but agrees with other more refined treatments of the hard sphere models without needing any further hypotheses, such as e.g., association. The revised values of the activity coefficients are reported.     

Carbohydrates, amino acids, phytin, and macroelements of the herbage ofTrifolium pratense

Two monosaccharides have been found by paper chromatography in an aqueous extract of the herbage of red clover (Trifolium pratense). One of them has been identified as glucose. After hydrolysis of a dry water-soluble extract by paper chromatography in the presence of markers, galactose, arabinose, xylose, and mannose were detected. By paper chromatography in the presence of markers the amino acids phenylalanine, leucine (isoleucine), methionine, aspartic acid, proline, alanine, and histidine have been identified. Phytin with decomp. p 276°C has been isolated and identified, giving, after hydrolysis, inositol with mp 225–226°C, and Ca²⁺, Mg²⁺, and PO ₄ ^3– have been detected. The amount of ash in the herbage of clover is 8.4% and the amount insoluble in HC1 1.5%. The amounts of macroelements were determined by the flame photometry of a solution of the ash (mg–%): K⁺ 1620; Na⁺ 310; Ca²⁺ 1240; Mg²⁺ 1090.Pyatigorsk Pharmaceutical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 483–485, July–August, 1980.     

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.     

X-Ray structural investigation of the alkaloid speciosine

The molecular and crystalline structures of a tropolone alkaloid of the colchicine series — speciosine — have been determined by x-ray structural analysis. It has been established that the presence of an orthohydroxyphenyl group does not lead to appreciable changes of the colchicine skeleton in the speciosine molecule. In the crystals, the speciosine molecules are linked into zigzag chains through O6–HO1 intermolecular H-bonds.Translated from Khimiya Prirodnykh Soedinenii, No 4, pp. 608–612, July–August, 1997.     

Kinetics and mechanism of the oxidation of alkyl and aryl methyl ketones by permanganate ion in aqueous ethanoic acid

The kinetics of electron-transfer reactions between permanganate ion and ethyl and aryl methyl ketones have been studied in aqueous MeCO2H acid medium in the presence of HClO4 at different temperatures. For ethyl methyl ketone and XC6H4COMe (X = p-Cl, p-Br or p-NO2) the reaction obeys the rate law –d[MnO4–]/dt = (kKe[H+][MnO4–][RCO Me])/(1 + Ke[H+][RCOMe]).But the oxidations of XC6H4COMe (X = p-Me and p-OMe)follow the rate equation –d[MnO4–]/dt = k3[H+][MnO4–][RCOMe]. The reaction involves a fast pre-equilibrium with intermediate formation of a permanganate ester before the two-electron transfer, rate-determining, step. A number of thermodynamic parameters have been evaluated.     

The chemical composition of the essential oil of the larch

Summary The essential oils of various species of larch have been separated by gas-liquid chromatography under conditions of linear temperature programming.Of the 45 compounds present in each of the essential oils, 32 components have been identified, 16 of which have not previously been found in larch essential oil.The chemical compositions of the oxygen-containing and sesquiterpene hydrocarbons of four species and one variety of larch have been studied. It has been shown that there is no quantitative difference between the compositions of the individual species of larch and only their quantitative compositions differ.Voronezh Institute of Wood Technology. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 456–462, July–August, 1976.     

Kinetics of the Dissolution of Silver in Thiocarbamide Solutions

The dependence of the rate of solution of silver on the pH of the solution, the ratio of the iron(III) and thiocarbamide concentrations, and the temperature has been determined. The rate constants for the solution of silver (k _i = 2.3·10^–4 to 9.6·10^–4s^–1) at temperatures from 283-298 K have been calculated and from the temperature dependence of the rate constant the activation energies have been calculated: 68.84 kJ/mol for kinetic control of the rate of solution and 26.06 kJ/mol in the adsorption inhibition region.     

Kinetic study of the reaction betweentrans-tetracyanodioxomolybdate(IV) and fluoride ions

Summary The kinetics of the reaction between [MoO₂(CN)₄]^4– and F^– have been studied in the pH range 8 to 11. The results indicated that the diprotonated form, [MoO(OH₂)(CN)₄]^2–, is the only reactive species and that the aqua-ligand is substituted by the F^– ion according to the following reaction. The k₁ and k_–1 values are 8.8(2) M^–1 s^–1 and 0.6(1)s^–1, respectively, at 15°C. A dissociative substitution process is proposed.     

Chemical investigation of the polysaccharides of the leaves ofPlantago major L.

Summary 1. Pectic acid contains galacturonic acid (78–83%) and, chemically linked with it, the monosaccharides D-galactose, L-arabinose, L-rhamnose, and substance (VIII) and (IX).2. By fractionating the polysaccharide complex of the leavesof Plantago major L. on a DEAE-cellulose column it has been shown that it consists of pectic acid (80–82%), and free galactoraban (5–6%) and galactan (4–5%).Khimiya Prirodnykh Soedinenii, Vol. 1, No. 6, pp. 369–372, 1965.We have used Kertesz's nomenclature of pectic compounds [4].     

Unsymmetrical bis-Schiff bases derived from ethylenediamine,dehydroacetic acid and another aldehyde/ketone and the preparation and characterisation of their copper(II) and nickel(II) complexes

Summary Partial displacement of the symmetrical bis-Schiff bases (1)–(4) of ethylenediamine and salicyladehyde, o-hydroxyacetophenone, acetylacetone or benzoylacetone by dehydroacetic acid have led to the formation and isolation of the unsymmetrical bis-Schiff base ligands (6)–(9). Attempted partial displacements of the symmetrical bis-Schiff base (5) of dehydroacetic acid or (1)–(4) by each of the other four carbonyl compounds have been unsuccessful. The Ni^(II) and Cu^(II) complexes of (6)–(9) have been prepared and characterized.     

Pulse radiolysis studies on the reactions of 3-pyridinol with oxidizing radicals

Reaction rate constants for the reactions of 3-pyridinol with oxidizing radicals viz. OH, N₃, Br ₂ ^– , Cl ₂ ^– , SO ₄ ^– and O^– have been determined in aqueous solutions at different, pH's. Absorption spectra of the product transient species have been recorded in the 320–600 nm region. In the alkaline region (pH 13) the N₃ reaction product decays in two steps and O^– does not bring about one-electron oxidation. Similarly, at neutral pH, SO ₄ ^– does not cause selective one-electron oxidation of 3-pyridinol.     

Optimization of the elimination of lipids from the microalgaChlorella vulgaris

Summary Using the microalgaChlorella vulgaris as an example, the possibility has been shown of eliminating the lipids and pigments by oxidizing it with hydrogen peroxide without changing the compositions of the protein-carbohydrate complex. The influence of the conditions of performing the oxidation of theChlorella biomass have been studied and it has been described mathematically. The optimum conditions for eliminating the lipids and pigments have been found and the general chemical properties of the protein product isolated have been determined.N. D. Barabash took part in the work.Siberian Technological Institute, Krasnoyarsk. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 426–430, July–August, 1976.     

Characteristics of the mass spectra of ecdysteroids with different numbers of -OR groups

The mass spectra of 15 phytoecdysteroids and acetyl derivatives have been compared. With a decrease in the number of -OR groups, the contribution of cleavages of the bonds of the steroid skeleton increases. 20,22-Diols are characterized by the greatest significance of fragmentation at the C-20–C-22 bond. In all the spectra, clear indications of fragmentation of the side chain at the C-22–C-23, C-23–C-24, and C-24–C-25 bonds are observed.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 518–528, July–August, 1980.