Reaction of nitronium fluosulfate with fluoroolefins

Conclusions We were the first to add nitronium fluosulfate to the multiple bond of fluoroolefins to give the corresponding fluorinated -nitroalkyl fluosulfates. The theory was expressed that the electrophilic mechanism applies to the given process.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1437–1441, June, 1983.     

Ductile-to-ductile transition in dispersely filled composites based on thermoplastic polymers

The fracture mechanism for rubber-filled composites based on gutta-percha, LDPE, medium-density PE, and rubber particles has been studied. An increase in the concentration of filler particles leads to a change in the stress-strain behavior of the composites from neck propagation to homogeneous plastic deformation. For the filled composites, the criterion for the ductile-to-ductile transition is the equality of yield and draw stresses. The critical concentration of rubber particles at the ductile-to-ductile transition is controlled by the ratio between the yield stress of matrix polymer and the neck propagation stress. Transition from neck propagation to homogeneous plastic flow of the material is accomplished under two conditions: the breaking strength of the polymer matrix should be higher than the yield stress, and stretching of the composite should not be accompanied by the formation of diamond cracks. The latter condition is fulfilled when the dimensions of rubber particles are below a certain critical value, which is determined by the ductility of the matrix.     

Tri-component diblock copolymers of poly(ethylene glycol)–poly(ε-caprolactone-<Emphasis Type="Italic">co</Emphasis>-lactide): synthesis,characterization and loading camptothecin

Biodegradable tri-component diblock copolymer was synthesized by bulk copolymerization of ε-caprolactone (CL) and D, L-lactide (LA) in the presence of methoxy poly(ethylene glycol) (MePEG), using stannous octoate as catalyst. Their chemical structure and physical properties were investigated by GPC, NMR, DSC, TGAand XRD. The increase of CL/LA ratio in the diblock copolymer leads to lower T _g, higher decomposition temperature and crystallinity. Nanoparticles formulated from MePEG–poly(CL-co-LA) (PCAE) possess spherical structure, which was characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The DLS results indicate that the particle size increased with the increase of CL/LA ratio and the hydrophobic fragment length in the copolymer. The drug encapsulation efficiency and the drug release behavior in vitro conditions of camptothecin were measured by high performance liquid chromatography (HPLC). The encapsulation efficiency can be achieved as high as 84.4% and the release behavior can be made well-controlled. MePEG–poly(CL-co-LA) nanoparticles might have a great potential as carriers for hydrophobic drugs.     

Five-coordinate Cobalt(II), Nickel(II) and Zinc(II) Complexes Derived from 2-pyridine-2-yl-3-(pyridine-2-carboxylideneamino)-1,2-dihydroquinazolin-4(3H)-one. The Crystal Structure of the Cobalt(II) Complex

The synthesis of cobalt(II), nickel(II) and zinc(II) complexes of 2-pyridine-2-yl-3(pyridine-2-carboxylideneamino)-1,2-dihydroquinazolin-4(3H)-one is described. The ligand and metal complexes were characterized by elemental analysis, conductivity measurements, spectral (u.v.–vis., i.r., 1D n.m.r., 2D hetcor and mass) and thermal studies. The cobalt(II) complex crystallizes as pink crystals in the monoclinic crystal system, space group P21/n with a = 10.066(6) Å, b = 15.929(9) Å, c = 12.624(7) Å, α = 90.00(9)°, β = 110.850 (8)°, γ = 90.00, V = 1891.5 (18) ų and Z = 4. The geometry around the cobalt atom is distorted trigonal bipyramidal with τ = 0.83 [structural parameter, τ = (β − α)/60; where α and β are the two basal angles in a five coordinate complex].     

AFM of adsorbed polyelectrolytes on cellulose I surfaces spin-coated on silicon wafers

Thin layers of cellulose I nanocrystals were spin-coated onto silicon wafers to give a flat model cellulose surface. A mild heat treatment was required to stabilize the cellulose layer. Interactions of this surface with polyelectrolyte layers and multilayers were probed by atomic force microscopy in water and dilute salt solutions. Deflection–distance curves for standard silicon nitride tips were measured for silicon, cellulose-coated silicon, and for polyelectrolytes adsorbed on the cellulose surface. Transfer of polymer to the tip was checked by running deflection–distance curves against clean silicon. Deflection–distance curves were relatively insensitive to adsorbed polyelectrolyte, but salt addition caused transfer of cationic polyelectrolyte to the tip, and swelling of the polyelectrolyte multilayers.     

Kinetic studies of some substituted hexarhodium carbonyl clusters

Reactions of the halides X- (X- = chloride, bromide or iodide) with the substituted cluster Rh6(CO)15(PPh3) in oxygen-free chloroform lead to [Rh5(CO)14(PPh3)]-, Rh(CO)2(PPh3)2X and [Rh(CO)2X2]- in the molar ratios 2:1: approximately 13. Oxidation by the solvent is assumed to lead to most of the Rh(I) product, and the stoichiometry for reactions with I- can be defined as 4Rh6(CO)15(PPh3) + 27I- + 12CHCl3 --> 2[Rh5(CO)14(PPh3)]- + Rh(CO)2(PPh3)2I + 13[Rh(CO)2I2]- + 6C2H2Cl4 + 4CO + 12Cl-. This can be rationalized quite simply with the aid of a few generally justifiable assumptions. Rate constants for reactions with bromide increase to a limiting value with increasing [Br-] in a way that shows that breaking of one Rh-Rh bond, with an unusual closo to nido structural change, is rate determining. This opening of the cluster might be spontaneous or solvent induced. To complete the reaction, the bromide has to compete with the reverse nido to closo change. The same closo to nido change is also a major rate determining step for reactions with P(OPh)3 in oxygen-free solutions, and for reactions with bromide in oxygenated solutions in the presence of trifluoroacetic and some other acids. The limiting rates increase slightly with increasing basicity of the ligands P(p-XC6H4)3 along the series X = F3C, Cl, F, H and MeO. Activation parameters for these reactions are reported.     

Limiting Partial Molar Volumes of Electrolytes in 2-Methyl-2-Butanol <Emphasis Type="Bold">+</Emphasis> Water Mixtures at 298.15 K

Partial molar volumes at infinite dilution, V⁰₂, of alkali–metal halides (LiCl, NaCl KCl RbCl CsCl, NaBr, KBr, KI), tetra-n-alkylammonium bromides, R₄NBr (R=Me, Et, n-Pr, n-Bu, n-Pen), NaBPh₄, and Ph₄PCl have been determined in binary solvent mixtures of water with 2-methyl-2-butanol covering the water-rich region and the alcohol-rich region at 298.15 K. V⁰₂ for alkali–metal halides show relatively little dependence on the solvent composition. However, in the case of hydrophobic electrolytes the observed effects are more pronounced. A good linear dependence between V⁰₂(R₄NBr) and the molecular weight of the tetra-n-alkylammonium cation is found. Limiting single-ion volumes have been obtained using the assumption that V⁰(Ph₄P⁺)–V⁰(BPh^–₄)=2.0 cm³-mol^–1. The trends in the single-ion volumes are discussed in both solvent regions.     

XANES Determination of Intraatomic Potentials

A new scheme has been developed for determining the parameters of the local one-electron potential in molecules and solids. The scheme is based on interpretation of the experimental X-ray absorption near edge struucture. The scheme is an extension of the method for solving the inverse problem of XANES theory suggested by one of the authors. In this scheme, oscillator strengths and maximum heights are considered along with the energy and half-width of spectral maxima. The scheme is used for determining the intraatomic potential in the nitrogen molecule.Original Russian Text Copyright © 2004 by Yu. F. Migal and O. M. Kholodova__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 986–989, November–December, 2004.     

Reactivity of Cage-Like Amines toward p-Toluenesulfonyl Chloride and Diphenyl Chlorophosphate in Acetonitrile

The nucleophilic reactivity of amines of the norbornane, norbornene, and adamantane series toward ptoluenesulfonyl chloride and diphenyl chlorophosphate in acetonitrile at 25°C is determined mainly by the steric factor. Parameters characterizing spatial accessibility of the reaction center in the amine molecule have been determined. Cage-like substituents show no appreciable effect on the amine reactivity, as compared to common alkyl groups.     

Influence of Masking Agents on the Color Reactions of Dithizone with Pd(II), Hg(II), and Ag(I) Ions after the Sorption of Their Chloride Complexes on the Fibrous Filled Anion Exchanger AV-17

The influence of masking agents (acetate, thiosulfate, tartrate, and iodide ions; thiourea; and ethylenediaminetetraacetic acid (EDTA)) in a dithizone solution on the complexation of Hg(II), Pd(II), and Ag(I) ions on the solid phase of the fibrous anion exchanger filled with AV-17 was studied. Mercury, palladium, and silver were adsorbed as chloride complexes. The possibility of the simultaneous group determination of the three elements and the selective determination of palladium in the presence of mercury and silver by measuring the diffuse reflection coefficient at two wavelengths (580 and 680 nm, respectively) was demonstrated. A mixture of dithizone with EDTA, acetate, iodide, or thiosulfate can be used for masking concomitant elements. The reaction of palladium with dithizone on the solid phase can be used for the test determination of palladium with the detection limit 0.01 mg/L.