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51.
Russian Journal of Organic Chemistry - 相似文献
52.
The formation of negative hydrogen ions in a conventional hollow cathode discharge has been investigated. A mixture of Ne and H2 proved to be more advantageous compared to pure hydrogen. The study has been performed by solving the electron Boltzmann equation, coupled with a system of balance equations for neon and hydrogen neutral and charged particles. The vibrational distribution function of hydrogen has been calculated. Our calculations show unusually high population of vibrationally excited hydrogen molecules in a Ne–H2 mixture, which explains the high density of negative hydrogen ions under optimal conditions (total gas pressure of few Torr, hydrogen number mole fraction of 1–10% and discharge current of 10–100 mA). Line intensities originating from highly excited neon states vs. hydrogen pressure have been calculated and a comparison with existing experimental results has been made. 相似文献
53.
Svetlana V. Amosova Vladimir A. Shagun Natalia A. Makhaeva Konstantin A. Lysenko 《Journal of organometallic chemistry》2007,692(16):3307-3315
The structure of 2,4-dibromo-2-dibromomethyl-3,3-dimethyl-1-selena-3-silacyclopentene-4, formed by regioselective electrophilic addition of SeBr4 to dimethyl diethynyl silane, has been determined using X-ray analysis technique. Quantum chemistry methods were used to study elementary stages of the reaction. It was found that the first stage consisted of SeBr4 conversion into bimolecular complex Br2?SeBr2, initiated by dimethyl diethynyl silane. Possible formation of five-membered and six-membered heterocycles involves different cyclization mechanisms. The formation of only five-membered heterocycle is explained by kinetically preferable ring closure through four-center transition state. The conclusions obtained by calculations were confirmed by monitoring of the reaction using 1H NMR method. 相似文献
54.
Volodkin DV Petrov AI Prevot M Sukhorukov GB 《Langmuir : the ACS journal of surfaces and colloids》2004,20(8):3398-3406
A new approach to fabricate polyelectrolyte microcapsules is based on exploiting porous inorganic microparticles of calcium carbonate. Porous CaCO3 microparticles (4.5-5.0 microns) were synthesized and characterized by scanning electron microscopy and the Brunauer-Emmett-Teller method of nitrogen adsorption/desorption to get a surface area of 8.8 m2/g and an average pore size of 35 nm. These particles were used as templates for polyelectrolyte layer-by-layer assembly of two oppositely charged polyelectrolytes, poly(styrene sulfonate) and poly(allylamine hydrochloride). Calcium carbonate core dissolution resulted in formation ofpolyelectrolyte microcapsules with an internal matrix consisting of a polyelectrolyte complex. Microcapsules with an internal matrix were analyzed by confocal Raman spectroscopy, scanning electron microscopy, force microscopy, and confocal laser-scanning fluorescence microscopy. The structure was found to be dependent on a number of polyelectrolyte adsorption treatments. Capsules have a very high loading capacity for macromolecules, which can be incorporated into the capsules by capturing them from the surrounding medium into the capsules. In this paper, we investigated the loading by dextran and bovine serum albumin as macromolecules. The amount of entrapped macromolecules was determined by two independent methods and found to be up to 15 pg per microcapsule. 相似文献
55.
Vladimir Kovacik Janos Hirsch Detlef Thlmann Hans-Friedrich Grützmacher 《Journal of mass spectrometry : JMS》1991,26(12):1085-1088
Glycosidic oxocarbenium ions A1+ were formed by isobutane chemical ionization from methyl 2,3,4,6-tetra-O-methyl-β-D -mannopyranoside, methyl 2,3,4,6-tetra-0-methyl-β-D -galactopyranoside and methyl 2,3,4,6-tetra-O-methyl-β-D -glucopyranoside (the ring - O-being converted into ? O ? ), and then- reaction with ammonia was studied by Fourier transform ion cyclotron resonance Spectrometry. Very slow formation (reaction efficiency 0.6-1.4%) of the adduct ion [A1 + NH3]4 was observed as the main process for carefully thermalized ions A1+. Interestingly, the efficiency of the adduct ion formation depends on the sterochemistry of ions A1+. 相似文献
56.
Aqueous dispersions of single-wall and multiwall carbon nanotubes with designed amphiphilic polycations 总被引:1,自引:0,他引:1
Sinani VA Gheith MK Yaroslavov AA Rakhnyanskaya AA Sun K Mamedov AA Wicksted JP Kotov NA 《Journal of the American Chemical Society》2005,127(10):3463-3472
Poor solubility of single-walled and multiwalled carbon nanotubes (NTs) in water and organic solvents presents a considerable challenge for their purification and applications. Macromolecules can be convenient solubilizing agents for NTs and a structural element of composite materials for them. Several block copolymers with different chemical functionalities of the side groups were tested for the preparation of aqueous NT dispersions. Poly(N-cetyl-4-vinylpyridinium bromide-co-N-ethyl-4-vinylpyridinium bromide-co-4-vinylpyridine) was found to form exceptionally stable NT dispersions. It is suggested that the efficiency of macromolecular dispersion agents for NT solubilization correlates with the topological and electronic similarity of polymer-NT and NT-NT interactions in the nanotube bundles. Raman spectroscopy and atomic force and transmission electron microcopies data indicate that the polycations are wrapped around NTs forming a uniform coating 1.0-1.5 nm thick. The ability to wind around the NT originates in the hydrophobic attraction of the polymer backbone to the graphene surface and topological matching. Tetraalkylammonium functional groups in the side chains of the macromolecule create a cloud of positive charge around NTs, which makes them hydrophilic. The prepared dispersions could facilitate the processing of the nanotubes into composites with high nanotube loading for electronic materials and sensing. Positive charge on their surface is particularly important for biological and biomedical applications because it strengthens interactions with negatively charged cell membranes. A high degree of spontaneous bundle separation afforded by the polymer coating can also be beneficial for NT sorting. 相似文献
57.
G. Petrov 《无机化学与普通化学杂志》1977,431(1):293-298
Some Transition Metal Complexes of Diethyl Esters of 1-Cyano-2-oxo-propane-phosphonic Acid and Ethoxycarbonylmethane-phosphonic Acid By means of metal exchange cobalt(II), nickel(II), and chromium(III) complexes of diethyl esters of 1-cyano-2-oxo-propane-phosphonic acid (1-CDEPA) and ethoxycarbonylmethanephosphonic acid (CMPD) were obtained from their corresponding potassium salts and halides of transition metals. The stable chelatic structure of these complexes was established by means of i.r. spectra and the configuration on the basis of the electron spectra and their magnetic moments. 相似文献
58.
59.
V. A. Tartakovskii A. S. Ermakov Yu. A. Strelenko D. B. Vinogradov E. Yu. Petrov 《Russian Journal of Organic Chemistry》2005,41(1):120-123
A practical procedure has been proposed for the synthesis of functionally substituted 4,5-dihydro-1,2,3-oxadiazole 2-oxides on the basis ofsulfamic acid derivatives.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 1, 2005, pp. 121–123.Original Russian Text Copyright © 2005 by Tartakovskii, Ermakov, Strelenko, Vinogradov, Petrov. 相似文献
60.
Vladimir L. Kolesnichenko Victor B. Rybakov Leonid A. Aslanov Sergei V. Volkov 《Journal of Cluster Science》1997,8(1):27-45
Thioselenohalide complexes Mo2(μ-S2)2Cl6(SeCl2)2 (I), Mo2(μ-S2)2Br6(SeBr2)2 (II), and W2(μ-S2)2Br6(SeBr2)2 (III) were synthesized by the reactions of corresponding metal halides or carbonyls or molybdenum metal with excesses of S2 X 2+Se2 X 2 mixtures. The complex W2(μ-S2)2Cl6(SeCl2)2 (IV) was obtained by an exchange reaction between (III) and excess of Se2Cl2. Coordination of the neutral SeX 2 ligands to thiohalidesM 2(μ-S2)2 X 6 results in higher thermal stability, and suggests the possibility to synthesize SeX 2 complexes of the unstable parent tungsten thiohalides. An unusual oxidative addition reaction of (I) was detected: {fx27-1} Both (I) and (IV) were characterized by X-ray crystal structure analysis. They are isostructural and form discrete molecules. Bridging S 2 2? ligands are coordinated perpendicularly to the metal-metal bond;d(M?M)=2.8066 Å and 2.793 Å for I and IV, respectively. Nonequivalence of chlorine atoms which are bound to the metal atom, relate to nonequivalence of halogen atoms in the complexesM 2(μ?S2)2 X 8 2? . Chlorine atomstrans to SeCl2 ligands form short bonds with the metal; the corresponding35Cl NQR frequency is increased. The selenium dichloride ligand is ambidentate. The selenium atom binds as a donor to the metal and as an acceptor to two chlorine atoms which are also bound covalently to the same metal atom. 相似文献