Effect of the degree of sulfoethylation of polyethylenimine on the selectivity of sorption of palladium(ii) from binary solutions

Poly(N-2-sulfoethylethylenimine) (SEPEI) with a degree of modification equal to 0.30, 0.58, and 0.74, cross-linked with diethylene glycol diglycidyl ether, demonstrates efficient sorption properties with respect to Pt^IV, Pd^II, and Au^III ions. The selectivity coefficient K_Pd/Au in a HCl solution with pH 0.8 decreases from 90 to 61, and the selectivity coefficient K_Pd/Pt in a HCl solution with pH 3.9 increases from 0.94 to 480 with an increasing degree of modification. A thiourea hydrochloric acid solution effectively removes metal ions; the desorption of Pt^IV, Pd^II, and Au^III from the SEPEI surface reaches 100, 96.9, and 83.8%, respectively.

     

Special features of preparation of nanosized zirconium diboride powders of various dispersity

Products of the zirconium powder reaction with amorphous boron in a Na₂B₄O₇ ionic melt at 650–850°C and those of the ZrCl₄ reaction with NaBH₄ at 300–725°C have been studied by means of X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, thermogravimetry, and elemental analysis. At temperature ≥750°C, single-phase ZrB₂ with the particle size of 60–80 nm is formed in a Na₂B₄O₇ ionic melt, whereas the ZrB₂ powder obtained via the reaction of ZrCl₄ with NaBH₄ at temperature ≥575°C consists of particles differing in the shape, some of which are close to spherical with diameter of 10–35 nm.     

Re-examination of the Kinetics of the Thermal Dehydroxylation of Goethite

The kinetics of thermal dehydroxylation of aluminuous goethites [1] synthesised from a ferrous salt has been re-examined using the general reaction order kinetic law. The utilised data processing was based on the procedures employed by dissolution kinetics. Recalculation of the activation energies E_A of the dehydroxylation yielded the values 130, 132, 128, and 123 kJ mol⁻¹ for pure goethite, goethite with 10, 20, and 30 mol% Al substitution, respectively. The values of E_A are in a good agreement with those given for goethite in literature. The E_A values are linearly related with the chemically bound excess H₂O/OH⁻ in the crystal lattice that is apparently influenced by Al substitution. This revised version was published online in August 2006 with corrections to the Cover Date.     

Study of hydration of two cements of different strengths

Main hydration products of two cement pastes, i.e. CSH-gel, portlandite (P) (and specific surface S) were studied by static heating, and by SEM, TEM and XRD, as a function of cement strength (C-33 and C-43) hydration time (th) and subsequent hydration in water vapour.Total change in mass on hydration and air drying, M_o, increased with strength of cement paste and with hydration time. Content of water escaping at 110 to 220°C, defined as water bound with low energy, mainly interlayer and hydrate water, was independent on cement strength but its content increased with (th). Content of chemically bound (zeolitic) water in CSH-gel, escaping at 220-400°C, was slightly dependent on strength and increased with (th). It was possibly derived from the dehydroxylation of CSH-gel and AFm phase. Portlandite water, escaping at 400-500°C, was independent on cement strength and was higher on longer hydration. Large P crystals were formed in the weaker cement paste C-33. Smaller crystals were formed in C-43 but they increased with (th). Carbonate formated on contact with air (calcite, vaterite and aragonite), decomposed in cement at 600-700^oC. It was high in pastes C-33(1 month) and C-43(1 month), i.e. 5.7 and 3.3%, respectively; it was less than 1% after 6 hydration months (low sensitivity to carbonation) in agreement with the XRD study showing carbonates in the air dry paste (1month), and its absence on prolonged hydration (6 months) and on acetone treatment. Water vapour treatment of (6 months) pastes or wetting-drying increased this sensitivity.Nanosized P-crystals, detected by TEM, could contribute to the cement strength; carbonate was observed on the rims of gel clusters.This revised version was published online in November 2005 with corrections to the Cover Date.     

Hydrogenation of fullerites in the presence of intermetallic compounds or metals

Fullerene hydrides containing 24–26 H atoms per fullerene molecule were obtained by hydrogenation of solid-phase mixtures of fullerenes with either intermetallic compounds LaNi₅, LaNi_4.65Mn_0.35, CeCo₃ or V and Pd metals with gaseous hydrogen at 1.0–2.5 MPa and 573–673 K. These fullerene hydrides decompose at 800 K with evolution of H₂. Upon subsequent heating to 1000 K, vanadium reacts with fullerene to yield a cubic phase of vanadium carbide. The intermetallic compounds react with fullerene with the formation of a metallic phase of the 3d-metal and destruction of fullerene. Palladium does not react with fullerene. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 679–683, April, 1997.     

Photodegradation of polyethylene in the presence of ferric chloride

Effects of ferric chloride (FeCl₃) on photodegradation of high-density polyethylene (PE) were investigated by using ESR and infrared spectrometry. In the system with irradiation at light of λ > 220 nm, PE irradiated at 77°K yielded an 8-line spectrum, the intensity of which was markedly weakened by using FeCl₃ with the sample, indicating a distinct depression of radical formation. On the other hand, PE with the use of FeCl₃ yielded radicals under irradiation only with light of λ > 300 nm, showing a singlet spectrum with a line width of 15 gauss. For photooxidized PE, almost the same effect of FeCl₃ was observed. On irradiation at room temperature, PE samples with and without FeCl₃ showed a singlet spectrum with line widths of 15 and 25 gauss, respectively. On the other hand, the unsaturated double bond contained in a small amount in PE sample was observed by infrared study to be decreased with photoirradiation; however, the decrease was sharply depressed with the addition of FeCl₃ to the sample. The degradation of carbonyl group in a photooxidized sample was markedly affected by photoirradiation, and the decay was obviously reduced for the sample on addition of FeCl₃. It is concluded that FeCl₃ works upon photodegradation of PE to enhance the Norrish type II reaction and to accelerate the formation of unsaturated double bond in the chain.     

Preparation of conjugates of peptides imitating part of the antigen-determinant section of protein VP1 of foot-and-mouth disease virus A12 with various supports

The preparation of conjugates of peptides 143–148, 153–159, 149–159, 146–159, and 143–159, imitating a section of a protein of the foot-and-mouth disease (FMD) virus of type A₁₂, with bovine serum albumin, with. a copolymer of N-vinylpyrrolidone with acrylic acid, and with a copolymer of N-vinylpyrrolidone with maleic anhydride is described. The dependence of the degree of conjugation on various factors is discussed.V. I. Lenin Tadzhik State University, Dushanbe. Institute of Immunology, Ministry of Public Health of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 516–519, July–August, 1990.     

Deconvolution of liquid scintillation alpha spectra of mixtures of uranium and radium isotopes

A method for the determination of uranium and radium isotopes in water samples is proposed. Liquid scintillation techniques were used for collecting alpha spectra, which were then analyzed by fitting the alpha peaks with overlapping Gaussians. The analysis can quantify the observed isotopes with accuracy depending on the activity of each isotope.In order to simulate the peaks with Gaussian normal distribution functions, the centroid of each peak as well as the full width at half maximum (FWHM) are required, as they depend on the quenching of the sample. For this purpose, samples with known activities of ²²⁶Ra and its decay products and also of the uranium isotopes ²³⁸U and ²³⁴U, at various quenching levels, were used to establish the correlation of the peaks’ shift with the quench effect. In addition, the correlation of the FWHM with the centroid of a peak was determined, using the same procedure.Following the above analysis technique, an average of 97 ± 2% of detection efficiency and a lower limit of detection of 8.2 mBq kg⁻¹ for alpha isotopes were achieved.     

Polymerization of vinyl monomers with salts of bronsted acids

The polymerization of vinyl monomers (N-phenylmaleimide, acrylamide, acrylonitrile, methyl vinyl ketone, methyl methacrylate, vinyl chloride, and styrene) with sodium salts of Brønsted acids (sodium cyanide, sodium nitrite, sodium hydroxide, etc.) were investigated at 0°C in dimethylformamide. N-Phenylmaleimide, acrylonitrile, and methyl vinyl ketone were found to undergo polymerization with sodium cyanide, however the other monomers were not polymerized with this salt. In the polymerizations of acrylonitrile and N-phenylmaleimide with sodium cyanide, the rates of the polymerizations were found to be proportinal to the initiator concentration and to the square of the monomer concentration. The activation energy of acrylonitrile polymerization was 3.7 kcal/mole, and that of N-phenylmaleimide ws 3.0 kcal/mole. The results of the copolymerization of acrylonitrile with methyl methacrylate at 0°C in dimethyl-formamide with sodium cyanide confirm that these polymerizations proceeded by an anionic mechanism initiated by the Michael addition reaction of the monomers with the salts. In these polymerizations, the monomer reactivity increased with increase in the e values. The initiation ability of sodium salts increased with increasing pK_a of the conjugate acids and with decreasing electronegativity of metal ion in the series of lithium, sodium, and potassium cyanide. The polymerizations took place only in aprotic polar solvents, and did not occur in weak polar solvents and in protonic solvents.     

Investigation of the reaction of quinoline with bromine in nitrobenzene

The reaction of quinoline with bromine in nitrobenzene solvent is investigated using the properties of isomolar series. These properties, viscosity, conductivity, density, depression of the freezing point, are determined using a constant molar concentration of C₉H₇N +Br₂, 0.05 per mole of C₆H₅NO₂. It is shown that the nitrobenzene solution of quinoline forms with bromine a complex with the composition C₉H₇N · Br₂. The molecular conductivity of this complex in nitrobenzene solvent increases with dilution.     

Ionometric Study of the Kinetics of Acid Decomposition of Fluorapatite

A procedure is proposed for studying acid decomposition of solid materials with the use of ion-selective electrodes, with the experimental data recorded and processed with a personal computer. Variation of the H₃O⁺, F^-, and Ca^{2 +} concentrations in reaction of fluorapatite concentrate with nitric, sulfuric, and orthophosphoric acids and also the effect of particle size on the rate of solid phase decomposition were studied.     

Kinetics of reactions of 2,2′-bipyridyltetracarbonylmolybdenum(0)

Summary Kinetic results are presented for reaction of Mo(CO)₄(bipy) with cyanide in several nonaqueous solvents and in DMSO-H₂O mixtures, with methoxide, and with azide; for reaction of Mo(CO)₄(5-NO₂phen) with cyanide and with methoxide; and for reaction of Mo(CO)₄(phen) and of W(CO)₄(bipy) with cyanide. Solvent effects on the reaction of Mo(CO)₄(bipy) with cyanide are dissected into their initial state and transition state components. Here, and in the dependence of the activation volume for this and related reactions on solvent, the important role played by cyanide solvation is apparent. Preliminary investigations on reactions of compounds of this M(CO)₄(diimine) type with tertiary phosphines, diethyldithiocarbamate, and ether peroxides are described.     

Freezing temperatures of aqueous solutions of mixtures of amides and polyols. Gibbs energy of interaction of the amide group with the hydroxyl group in aqueous solution

Freezing temperatures of dilute aqueous mixtures of: formamide with myo-inositol, d-mannitol, and cyclohexanol; N,N-dimethylformamide with inositol, mannitol, and cyclohexanol; and acetamide with inositol and mannitol have been measured. These data have been analyzed to yield the pairwise molecular Gibbs energies of interaction between the molecules in an aqueous solution. Using the group additivity principle, the results yield the pairwise functional group Gibbs energies of interaction of the amide group with the hydroxyl group, G _OH,CONH =–31 J-kg-mol^–2.     

Syntheses of Thiocarbamates

The methods suitable for the preparation of thiocarbamates are described and illustrated by examples and procedures. They are grouped under the following headings:

• 1 Addition of Alcohols and Thiols to Isothiocyanates
• 2 Thioacylation of Amines
  • (a) with chlorothioformates
  • (b) with O,S-diesters of dithiocarbonic acid
  • (c) with trithiocarbonates
• 3 Thioacylation of Alcohols, Phenols, and Thiols
  • (a) with thiocarbamoyl chlorides
  • (b) with N,N-dialkylmercaptochloroformimidium chlorides
  • (c) with N,N′-thiocarbonyldiimidazole
• 4 Reaction of Thiocyanates and Cyanates with Hydrogen Sulfide
• 5 Alkylation of Metal Dithiocarbamates
• 6 Additions to Thiocyanic Acid

     

Electrochemical methylation of a chelate anionic NiI complex with methylcobaloxime. Partial modeling of the action mechanism of the active center of acetyl-CoA synthase

Electrochemically generated anions of Co and Ni chelate complexes can be alkylated with BuⁿBr, BuⁿI, and (dmgH)₂CoMe (dmgH is the dimethylglyoximate anion). Unlike the anionic Co complexes, the anionic Ni complex cannot be alkylated with BuⁿBr; however, it reacts with stronger alkylating agents (BuⁿI and (dmgH)₂CoMe). It is assumed that the electrochemical alkylation of the Ni complex with (dmgH)₂CoMe can serve as a model for alkylation occurring in biological synthesis of acetyl coenzyme A. Reactions of some Co chelate anions with BuⁿI can proceedvia the reduction of the latter. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 55–58, January, 2000.     

Laser flash photolysis study of the decay kinetics of carbocations of 1,2,2,4-tetramethyl-1,2-dihydroquinoline in the porous glass in the presence of methanol

The efficiency of formation and the decay kinetics of carbocations formed under the photolysis of 1,2,2,4-tetramethyl-1,2-dihydroquinoline in methanol and in a porous glass filled with methanol or dried in air or in vacuo were studied by the laser flash photolysis techniques. In MeOH, the carbocations recombine via the second-order law in the reaction with the MeO⁻ anion formed in an equimolar amount and decay via the first-order law in the reaction with the solvent with rate constants of 3·10⁸ L mol⁻¹ s^{− 1} and 1.4·10³ s⁻¹, respectively. When the solution is placed into the porous glass, no recombination of the carbocations with MeO⁻ is observed, and the reaction with the solvent is somewhat inhibited (rate constant 8·10² s⁻¹). More than tenfold inhibition of the reaction of the carbocations with methanol is observed on going to a monolayer of MeOH on the surface. The main route of carbocation decay in the porous glass dried in vacuo is the geminate recombination with the SiO groups. The corresponding kinetics is described in terms of the model of freely diffusing reactants. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2239–2243, October, 2005.     

Enthalpies of transfer of amino acids from water to aqueous solutions of formamide

Enthalpies of solution of glycine, l-alanine, l-serine in water and aqueous solutions of formamide were measured at 298.15 K. Transfer enthalpies of amino acids from water to aqueous solutions of formamide were derived and interpreted qualitatively with hydration co-sphere overlap model. The results show that the structure interaction between formamide and zwitterionic head-group and hydrophilic side chain of amino acids make a negative contribution to transfer enthalpy, while that with the hydrophobic side chain is positive. In the solvent composition range studied, transfer enthalpies decrease overall with the increasing concentration of formamide, with the relative order of l-serine < glycine < l-alanine.     

Synthesis and properties of fused tetracyclic derivatives of 1,4-naphthoquinone thioglycosides

A series of 1,4-naphthoquinone O-acetylthioglycosides have been synthesized by the condensation of fully O-acetylated derivatives of 1-thio-d-xylose, 1-thio-L-arabinose, 1-thio-d-galactose, 1-thio-d-mannose, and 1-thiomaltose with 3-chloro-2-methoxy-1,4-naphtho-quinone. Their deacetylation with MeONa/MeOH proceeded with simultaneous heterocyclization to yield linear carbohydrate-containing tetracyclic quinones. Tetracycles with trans junction of the carbohydrate and quinone rings are poorly soluble in water and organic solvents.     

Electrochemical methylation of a chelate anionic NiI complex with methylcobaloxime. Partial modeling of the action mechanism of the active center of acetyl-CoA synthase

Electrochemically generated anions of Co and Ni chelate complexes can be alkylated with BuⁿBr, BuⁿI, and (dmgH)₂CoMe (dmgH is the dimethylglyoximate anion). Unlike the anionic Co complexes, the anionic Ni complex cannot be alkylated with BuⁿBr; however, it reacts with stronger alkylating agents (BuⁿI and (dmgH)₂CoMe). It is assumed that the electrochemical alkylation of the Ni complex with (dmgH)₂CoMe can serve as a model for alkylation occurring in biological synthesis of acetyl coenzyme A. Reactions of some Co chelate anions with BuⁿI can proceedvia the reduction of the latter. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 55–58, January, 2000.