Monomere chemisch gebundene stationäre Phasen für die Gas- und Flüssigkeits-Chromatographie mit ≡Si−C≡Bindung

Zusammenfassung Die Herstellung von chemisch gebundenen monomeren station?ren Phasen mit≡Si−C≡ Bindung an der Oberfl?che von Kieselgelen ist beschrieben. In der Gas-Chromatographie ist die gute Temperaturstabilit?t (bis zu 240–270°C) hervorzuheben. Ihre Best?ndigkeit gegenüber Hydrolyse ist für die Flüssigkeits-Chromatographie wesentlich. Die chromatographischen Eigenschaften, besonders die hohen Analysengeschwindigkeiten (in der Gas-Chromatographie bis zu 80 theoretischen B?den pro Sekunde) werden mit gasf?rmigen und flüssigen mobilen Phasen demonstriert.

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Chemically bonded monomeric stationary phases with ≡Si−C≡bonds for gas and liquid chromatography

Summary The preparation of≡Si−C≡ bonded monomeric stationary phases on the surface of silica is described. In gas chromatography a principal advantage is the temperature stability up to 240–270°C. These phases are stable to hydrolysis, important in liquid chromatography. The chromatographic properties, especially the high speed of analysis (in gas chromatography up to 80 theoretical plates per second) is demonstrated with gas and liquid mobile phases.

     

Biradical with the “non-linear” diacetylene fragment

The nitronyl nitroxide biradical, 2,2′-[1,1′-(hexa-2,4-diyne-1,6-diyl)bis(1H-pyrazole-4,1-diyl)]bis(4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole 3-oxide 1-oxyl), was synthesized. The structure and magnetic properties of the biradical were studied. In the solid state, this nitroxide contains the nonlinear C^S-C≡C-C≡C-C^S fragment. The C^S-C≡C and C≡C-C≡ angles are 172.4(5) and 171.1(3)°, respectively. Dedicated to Academician G. A. Tolstikov on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 385–390, February, 2008. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 385–390, February, 2008.     

Synthesis,characterization, and non-isothermal curing kinetics of two silicon-containing arylacetylenic monomers

Vinyltri(phenylethynyl)silane ((ph–C≡C)₃–Si–C=CH₂; VTPES) and phenyltri(phenylethynyl)silane ((ph–C≡C)₃–Si–ph; PTPES) were synthesized by Grignard reaction. Their molecular structures were characterized by means of ¹H NMR, ¹³C NMR, ²⁹Si NMR, and FT-IR spectroscopy. Their nonisothermal thermal curing processes were characterized by DSC, and the corresponding kinetic data, for example activation energy (E), pre-exponential factor (A), and the order of the reaction (n), were obtained by the Kissinger method. The results showed that the melting points of VTPES and PTPES were 84 and 116 °C, respectively. Their curing reaction rates were consistent with first-order kinetic equations. VTPES monomer had a lower activation energy and curing temperature as a result of coordination between reactive groups.     

Intensity of bands of the C≡C stretching modes in the IR spectra and conjugation in silylacetylenes

A comparative study of the integrated extinction coefficients (A) of the C≡C stretching bands in the IR spectra of acetylene derivatives Me₃SiC≡CR, HC≡CR, and Me₃CC≡CR was carried out. The resonance interactions of substituents with a triple bond are the main cause of the changes in the values ofA. The total resonance effect of the Me₃Si fragment involves both acceptor (d, π-conjugation) and donor (σ, π-conjugation) components; d, π-conjugation dominates in the silylacetylenes studied. Theσ _R ⁰ resonance constant of the Me₃Si substituent in compounds Me₃SiC≡CR is 0.17±0.02. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 76–80. January 1997.     

Effect of the Nature of Second-Sphere Cation on the Architecture of Crystalline π-Complexes Ca[CuCl2(HOCH2C≡CCH2OH)]2.4H2O and (C7H5N2H2)[CuCl2(HOCH2C≡CCH2OH)]

In the MCl-CuCl-HOCH₂C≡CCH₂OH (M = Ca, C₇H₅N₂H₊²) system, the crystals of two anionic Ca[CuCl₂(HOCH₂C≡CCH₂OH)]₂-4H₂O (1) and (BimH)[CuCl₂(HOCH₂C≡CCH₂OH)] (2) (BimH⁺ is cation of benzimidazole-C₇H₅N₂H₊²) π-complexes are obtained and studied by single crystal X-ray diffraction Crystals of 1 are monoclinic: C2/c space group, a = 8.323(3) ?, b = 13.283(4) ?, c = 16.741(5) ?, β = 92.35(3)°, V = 1849.3(10) ?³, Z = 4; crystals of 2 are triclinic: P1 space group, a = 6.901(3) ?, b = 9.898(4)?, c = 9.987(4) ?, α = 94.91(3)°, β = 93.91(3)°, γ = 107.59(4)°, V = 644.7(5) ?³, Z = 2. Complex 1 consists of infinite bimetallic chains [Ca(H₂O)₄CuCl₂(HOCH₂C≡CCH₂OH)₂]_∞ forming a three-dimensional framework through (Ow)HCl and (C)O-HCl hydrogen bonds. Compound 2 is built from discrete anions [CuCl₂(HOCH₂C≡CCH₂OH)]^- paired by edge-to-edge packing in the [100] direction and large BimH⁺ cations with face-to-face packing. In both structures, the π-coordinated Cu(I) atom has the trigonal environment involving two Cl^- anions and C≡C 2-butyne-1,4-diol bond (Cu-(C≡C) distance is 1.918(2) ? and 1.910(4) ? for 1 and 2 respectively).     

π-complexes of copper(I) with but-2-yne-1,4-diol. Synthesis and crystal structure of the anionic π-complex (PipH2)[CuCl2(HOCH2C≡CCH2OH)]2 · H2O ((PipH2)2+ is the Piperazinium Cation)

A reaction of but-2-yne-1,4-diol with CuCl in a concentrated aqueous solution of piperazinium dichloride gave the π-complex (PipH₂)[CuCl₂(HOCH₂C≡CCH₂OH)]₂ · H₂O ((PipH₂)²⁺ is the piperazinium cation). The complex was examined by X-ray diffraction analysis (space group P , a = 7.355(1) ?, b = 10.3572(8) ?, c = 13.632(2) ?, α = 101.055(9)°, β = 95.350(1)°, γ = 101.875(9)°, Z = 2). The complex consists of two crystallographically independent anions [CuCl₂(HOCH₂C≡CCH₂OH)]⁻ and the biprotonated piperazinium cation. The trigonal environment of the Cu(I) atom in either complex anion includes is made up of two Cl atoms and the C≡C bond. Apart from the hydrogen bonds N-H⋯O that imparts a directed character to the ionic interaction Cat⁺⋯An⁻, the piperazinium cation with molecules of crystallization water with bridging function form the cross-linking hydrogen bonds N-H⋯OH₂ and OH-H⋯Cl. Original Russian Text ? Yu.I. Slyvka, V.V. Kinzhibalo, T. Lis, B.M. Mykhalichko, M.G. Mys’kiv, 2009, published in Koordinatsionnaya Khimiya, 2009, Vol. 35, No. 4, pp. 311–315.     

Synthesis and photophysical properties of luminescent mononuclear and dinuclear gold(I) complexes with ethynyl-substituted phenanthrolines

A novel asymmetric dinuclear gold(I) complex with 3,6-diethynylphenanthroline, 3,6-bis{(PPh₃)–Au–C≡C}₂-phen, has been synthesized from Au(PPh₃)Cl (PPh₃ = triphenylphosphine) and 3,6-diethynyl-1,10-phenanthroline. The asymmetrical dinuclear gold(I) complex, 3,6-bis{(PPh₃)–Au–C≡C}₂-phen, demonstrated a weak phosphorescence assignable to the metal-perturbed ³ π–π* transition in the long wavelength region compared to an intense emission of the symmetrical dinuclear complex with 3,8-diethynylphenanthroline, 3,8-bis{(PPh₃)–Au–C≡C}₂-phen. A similar tendency of phosphorescent bands for the mononuclear gold(I) complexes with 5-ethynylphenanthroline, 5-{(PPh₃)–Au–C≡C}-phen, and 3-ethynylphenanthroline, 3-{(PPh₃)–Au–C≡C}-phen was observed. The absorption bands assignable to the π–π*(C≡Cphen) transition and phosphorescent emission assignable to the metal-perturbed ³ π–π* transition for these four gold(I) complexes were reasonably consistent with the results calculated by DFT and TD-DFT.     

Acyl iodides in organic synthesis: XIII. Reaction of acyl iodides with nitrogen-containing heteroaromatic compounds

Reactions of acetyl iodide with pyridine at room temperature and with quinoline both at 20–25°C and on cooling to −50°C involve dehydrohalogenation of acetyl iodide with formation of ketene and pyridinium or quinolinium iodides. The reaction of acetyl iodide with pyridine at −5 to −50°C led to the formation of N-acetylpyridinium iodide. Benzoyl iodide reacted with both pyridine and quinoline at both −50°C and at 20–25°C to form stable N-benzoylpyridinium and N-benzoylquinolinium iodides. The reaction of pyrrole with acetyl iodide under analogous conditions was accompanied by polymerization.     

Radical addition reactions: factors determining the transition-state geometry

Interatomic distances in the reaction centers of the addition reactions of (i) H^· to the C=C, C=O, N≡C, and C≡C bonds, (ii) ^·CH₃ radical to the C=C, C=O, and C≡C bonds, and (iii) alkyl, aminyl, and alkoxyl radicals to olefin C=C bonds were determined using a new semiempirical method for calculating transition-state geometries of radical reactions. For all reactions of the type X^· + Y=Z → X— Y—Z^· the r ^# _X...Y distance in the transition state is a linear function of the enthalpy of reaction. Parameters of this dependence were determined for seventeen classes of radical addition reactions. The bond elongation, Δr ^# _X...Y, in the transition state decreases as the triplet repulsion, electronegativity difference between the atoms X and Y in the reaction center, and the force constant of the attacked multiple bond increase. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 894–902, April, 2005.     

Effect of preparative conditions on the surface characteristics of mixed zirconium and titanium oxides

The surface characteristics of mixed zirconium and titanium oxides prepared from different starting materials are investigated. One mode of preparation entailed the use of zirconium sulfate and titanium oxysulfate as starting materials and ammonium hydroxide as precipitating agent. The produced oxides were washed to different extents to obtain samples with different sulfate content. A second preparative mode used zirconium oxychloride and titanous chloride as starting materials also with ammonium hydroxide as precipitating agent. The oxidation of the titanous to the titanic form for these oxides was carried out by means of oxygen gas. Resulting samples were heat treated at 400 °C and 600 °C, and textural characteristics determined from the adsorption of N₂ at 77 K, complemented by infrared and thermal studies. The samples precipitated from the oxychloride and chloride salts of zirconium and titanium, as well as those precipitated from the sulfate and oxysulfate salts and washed free of the sulfate ions displayed quite similar textural characteristics. The unheated samples and those heat-treated at 400 °C were mesoporous, with some microporosity, and relatively large surface areas in the order of 200–300 m²/g. Heat treatment to 600 °C led to a relative decrease in surface area, in the order of 100 m²/g, and to the disappearance of microporosity. The mixed zirconium and titanium oxides with a sulfate content of ≈17% displayed significantly lower surface areas, smaller than 10 m²/g, with a prevalence of micro and mesoporosity. Infrared and thermal studies indicated the presence of differently bounded sulfato groups, which seem to have a blocking effect on the pores, resulting in the observed smaller surface areas.     

Cyclopropane ring opening in the reaction of methylenecyclopropane with silyl radicals stabilized on an activated Aerosil surface

Alkyl type radicals stable at room temperature and incorporating a double bond not conjugated with the free valence, ≡Si−C(=CH₂)−CH₂−CH₂, are formed in the reaction of methylenecyclopropane with silyl radicals (≡SiO)₃Si on an activated Aerosil surface. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1065–1066, May, 1997.     

Oxidation of aromatic compounds: XVII. Oxidative cross-dimerization of diarylacetylenes in the system CF3CO2H-CH2Cl2-PbO2. Characteristic of cation-radicals of diarylacetylenes by cyclic voltammetry and ESR spectroscopy

The oxidation of mixtures of diarylacetylene ArC≡CAr and Ar′C≡CAr′ in a system CF₃CO₂H-CH₂Cl₂-PbO₂ (0°C, 1.5 h) results in products of cross-dimerization, (Z)-1,2,3,4-tetraarylbut-2-ene-1,4-diones Ar(ArCO) C=C(COAr′)Ar′. The routes of transformation of intermediate cation-radicals of diarylacetylenes [ArC≡CAr]^+· into the final products of oxidative dimerization are elucidated. By cyclic voltammetry and ESR spectroscopy the high reactivity of the diarylacetylene cation-radicals is demonstrated, the character of their singly occupied molecular orbitals (a₂ or b₁) has been revealed by ESR method.     

Carbon in silica

The structure of paramagnetic centers (PMC) in carbon-doped silica is studied by the EPR and quantum chemistry methods. Three types of radicals, ≡Si-^·CH₂, (≡Si-)₂ ^·CH and (≡Si-)₃C^·, are identified in which the free valence is localized on the impurity carbon atom. Their structure is determined by using samples enriched by isotopes ²D, ²⁹Si, and ¹³C. The assignment of the obtained radiospectroscopic parameters of radicals is confirmed by quantum-chemical calculations of model systems. Based on the obtained data, a conclusion is made that paramagnetic centers (the so-called EX-centers) discovered earlier by the EPR method in silicon oxidation products have the structure (≡Si-)₃C^·, i.e. are not the intrinsic defects of the material but are related to impurity carbon atoms. Differences in the spectral characteristics of the (≡Si-)₃C^· groups observed in experiments are caused by the amorphous structure of silica. The kinetic nonequivalence of the (≡Si-)₃C^· radicals in the reaction of the hydrogen atom detachment from the H₂ molecule is established (the activation energies for different PMC fractions lie in the range from 10 to 17 kcal/mol). The quantum-chemical calculations of model systems performed in the paper suggest that the differences observed in the reactivity of radicals are related to their spatial structure. It is found that the high-temperature pyrolysis of the (≡Si-)₃C-H and (≡Si-O-)₃Si-H groups is accompanied by the quantitative regeneration of free radicals (≡Si-)₃C^· and (≡Si-O-)₃Si^·. The probable mechanism of carbon atom embedding from. (≡Si-O-)₃Si-O-CH₃ groups to silica accompanied by the formation of (≡Si-)₄C groups is analyzed.     

Effect of a thin spreading solvent film on the efficiency of the hexadecan-1-ol monolayer deposited for water evaporation retardation

The influence of a thin spreading solvent film (ethanol, diethyl ether, and three fractions of petroleum ether boiling at 30–60 °C, 60–90 °C, and 90–120 °C) on the properties of hexadecan-1-ol (C₁₆H₃₃OH) monolayers at the air—water interface was studied. The specific evaporation resistance and the surface pressure were determined to describe the spreading behavior of the C₁₆H₃₃OH monolayers. The physical properties of the solvents and the images obtained in an atomic force microscope were examined. The time of establishing the equilibrium spreading surface pressure of monolayers can be reduced using a more volatile solvent with a lower boiling point and a lower relative density. The influence of the monolayer nature on water evaporation corresponds to the order of changing the solvent spreading rate: petroleum ether (30–60 °C) > diethyl ether > ethanol > petroleum ether (60–90 °C) > petroleum ether (90–120 °C). The monolayers formed upon petroleum ether (30–60 °C) spreading form a film with a less deficient and relatively planar surface. When ethanol is used as a spreading solvent, water evaporation is accelerated rather than retarded, while petroleum ether (30–60 °C) is more appropriate for this purpose.     

Micellar properties of alkyldimethylphenylammonium bromides in water

The synthesis and methods applied for the purification of dodecyl-, tetradecyl-, and hexadecyldimethylphenylammonium bromides are described. The results of surface tension measurements of aqueous solutions of these surfactants show that slight amounts of strongly surface-active nonionic impurities are persistent in the crystalline materials presumably due to their low thermal stability. The Critical micelle concentration (cmc) and the degree of ionization (β) of the micelles of the salts studied in aqueous solutions were determined at 25 °C from specific conductivity versus molality plots. The temperature dependence of the cmc and of β of the tetradecyl homologue was measured in the range 4–34 °C. A minimum cmc amounting to 1.20 mmol/kg was determined at about 14 °C. The values of β were found to grow linearly with temperature. From these results, the standard Gibbs energy, the enthalpy and the entropy of the process of micellization were obtained by application of the pseudo-phase-separation model. Enthalpy and entropy show a compensation effect in their contribution to the Gibbs energy. At low temperatures the process of micellization is driven mainly by the entropic term, whereas with increasing temperature the enthalpic term becomes predominant. At the temperature of the minimum cmc, the value of the enthalpy is far from being zero because of the important contribution of the (β/T)R ln X _cmc term. Received: 27 July 1998 Accepted in revised form: 15 December 1998     

A study of the interaction of diethylzinc with the Aerosil surface

The interaction of diethylzinc with Aerosil has been examined by IR spectroscopy and mass spectrometry. The reaction involves both free hydroxyl groups and siloxane groups of the surface resulting in the formation of Si-O-Zn-Et and Si-Et fragments. At temperatures above 300 °C, these structures undergo decomposition with the recovery of Si-OH groups on the Aerosil surface and liberation of metallic zinc.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1666–1668, September, 1994.The authors are grateful to M. B. Molotovshchikova for continuous help in performing the experiment.     

Evaluation of <Superscript>99m</Superscript>TcN–moxifloxacin dithiocarbamate,as a potential radiopharmaceutical for scintigraphic localization of infectious foci

^99mTc ≡ N-Pazufloxacin dithiocarbamate (^99mTc ≡ N-PZN) complex was synthesized through the [^99mTc ≡ N]²⁺ core and its aptness was radiochemically and biologically evaluated in terms of radiochemical purity (RCP) in saline, in vitro stability in serum, in vitro bacterial uptake and percent in vivo uptake in male Wister rats (MWR) artificially infected with alive and heat killed Escherichia coli (E. coli). The ^99mTc ≡ N-PZN complex showed more than 90% RCP up to 4 h after reconstitution in normal saline at room temperature with a maximum RCP value of 98.40 ± 0.28% (at 30 min). At 37 °C in serum the complex showed stable behaviour up to 4 h with the appearance of 15.95% undesirable by products within 16 h of the incubation. The complex showed saturated in vitro binding with E. coli with a maximum uptake of 74.25 ± 0.50% (at 90 min). Normal biodistribution behaviour was noted with a sixfold higher accumulation in the muscle of the MWR, artificially infected with live E. coli as compared to the MWR infected with heat killed E. coli, inflamed and normal muscle. The high RCP in saline, elevated in vitro stability in serum, saturated in vitro binding with E. coli and the sixfold higher accumulation in the infected (live) muscle of the MWR as compared to the inflamed and normal muscle, recognized the aptness of the ^99mTc ≡ N-PZND complex as a prospective E. coli in vivo infection radiotracer.     

Pyrolysis characteristics and kinetics of sewage sludge for different sizes and heating rates

The pyrolysis characteristics and kinetics of sewage sludge for different sizes (d < 0.25 mm, 0.25 mm < d < 0.83 mm, and d > 0.83 mm) and heating rates (5, 20, and 35 °C/min) were investigated in this article. The STA 409 was utilized for the sewage sludge thermogravimetric analysis. FTIR analysis was employed to study the functional groups and intermediates during the process of pyrolysis. Meanwhile, a new method was developed to calculate pyrolysis kinetic parameters (activated energy E, the frequency factor A, and reaction order n) with surface fitting tool in software MATLAB. The results show that all the TG curves are divided into three stages: evaporation temperature range (180–220 °C), main decomposition temperature range (220–650 °C), and final decomposition temperature range (650–780 °C). The sewage sludge of d < 0.25 mm obtains the largest total mass loss, especially at the heating rate of 5 °C/min. By FTIR analysis, the functional groups including NH, C–H, C=C, etc., are all found in the sewage sludge. There is a comparison between the FTIR spectra of sludge heated to 350 °C (temperature associated to maximum devolatilization rate in the second stage) and the FTIR spectra of sludge heated to 730 °C (temperature associated to maximum devolatilization rate in the third stage). In the second stage, the alcohols, ammonia, and carboxylic acid in the sludge have been mostly decomposed into gases, and only a little bit of compounds containing CH and OH of COOH exist. The pyrolysis kinetic parameters of second stage are as follows: the reaction orders are in the range of 1.6–1.8 and the activation energy is about 45 kJ/mol. The frequency factor increases with the increase of heating rate and sewage sludge size.     

Reactions of spirocyclopropane-containing 1- and 2-pyrazolines with electrophilic reagents

Hydrochlorination of spiro(1-pyrazoline-3,1′-cyclopropanes) proceeds regioselectively at the azocyclopropane group to form 3-(2-haloethyl)pyrazoline derivatives. If the latter contain a halogen atom in the heterocycle, they are readily converted into (2-haloethyl)pyrazole hydrohalides. Bromination of 3-cyanospiro(2-pyrazoline-5,1′-cyclopropane) withN-bromosuccinimide at 20°C proceeds with retention of the cyclopropane ring to form 3-bromo-3-cyanospiro(1-pyrazoline-5,1′-cyclopropane), which is converted into (2-bromoethyl)cyanopyrazole in ∼60% yield at ∼20°C after 3–4 days.     

Experimental and Theoretical Constraints on pH Measurements with an Iridium Oxide Electrode in Aqueous Fluids from 25 to 175 °C and 25 MPa

In-situ measurement of pH at elevated temperatures and pressures is of major importance for investigating chemical and biochemical systems in extreme environments. Based on the performance of the newly developed IrO _x electrode at 25 °C, we initiated a series of experiments to test the electrode at elevated temperatures (100 to 175 °C) and high pressure (25 MPa). The experiment was carried out in a titanium flow-through reactor. Our results revealed good pH response at 100, 150 and 175 °C, with good Nernstian slopes at 100 and 150 °C. Although a greater-than-Nernstian response was observed at 175 °C, the factors that cause this difference are attributed to the accuracy of calculations of the distribution of aqueous species rather than alteration of the IrO _x surface. A key problem that may limit applications of the IrO _x electrode at elevated temperatures and pressures is the noticeable shift in E° during the 175 °C (25 MPa) experiments and between experiments with similar conditions at 150 °C. The results of tests from 25 °C to elevated temperatures provide highly useful information on the reversibility and functionality of the IrO _x -pH sensor with implications for the suitability of its use under challenging chemical and physical conditions.