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1.
Titus Constantinescu Petre Ionita Ion Chiorescu Gabriela Ionita 《Central European Journal of Chemistry》2003,1(4):465-476
Ten novel and stable free radicals of nitronyl-, imino-nitroxide and hydrazyl type compounds were synthesized and their physico-chemical
properties investigated. UV-Vis and ESR spectroscopic data, as well as the lipophilicities and specific hydrophobic areas
of the compounds are compiled. The reaction of these radical compounds with nitric oxide and nitrogen dioxide was also investigated.
The radicals synthesized, show selectivity in their reaction with these nitric oxides, depending on their structure (nitronyl-nitroxide
radicals react with NO, while hydrazyl radicals react with NO2). The processes are easily monitored by UV-Vis or ESR spectroscopy. 相似文献
2.
H. S. Singh V. P. Singh B. S. Arya G. R. Varma 《Monatshefte für Chemie / Chemical Monthly》1981,112(11):1253-1260
Kinetics of oxidation of xylitol and galactitol by hexacyanoferrate(III) ion in aqueous alkaline medium is reported. The reaction rate is of first order with respect to hexacyanoferrate(III) in each substrate. The reaction is first order at lower concentrations of xylitol and galactitol and tends towards zero order as the concentration increases. Similarly first order kinetics was obtained with respect to hydroxide ion at lower concentrations and tends to lower order at higher concentration in the oxidation of xylitol; in the oxidation of galactitol the reaction is first order with respect to hydroxide ion even up to manyfold variation. The course of reaction has been considered to proceed through the formation of an activated complex between [K Fe(CN)6]2– and substrate anion which decomposes slowly into radical and [K Fe(CN)6]3–. A probable reaction mechanism is proposed.
Kinetik und Mechanismus der Oxidation von Xylit und Galaktit mit Hexacyanoferrat(III) in wäßriger, alkalischer Lösung
Zusammenfassung Das Geschwindigkeitsgesetz der Titelreaktion ist in beiden Fällen erster Ordnung bezüglich Hexacyanoferrat(III). Die Oxidation ist erster Ordnung bei niedrigen Konzentrationen von Xylit und Galaktit und geht bei Erhöhung der Konzentration gegen null. In gleicher Weise wurde eine Kinetik erster Ordnung bezüglich Hydroxyl bei niedrigen Konzentrationen und eine erniedrigte Ordnung bei höheren Konzentrationen für die Oxidation von Xylit beobachtet; bei Galaktit bleibt die Oxidation auch bei höheren Hydroxyl-Konzentrationen erster Ordnung. Es wird angenommen, daß die Reaktion über einen aktivierten Komplex zwischen [KFe(CN)6]2– und dem Substrat-Anion verläuft; dieser Komplex zerfällt in [KFe(CN)6]3– und ein Substrat-Radikal. Ein möglicher Reaktionsmechanismus wird vorgeschlagen.相似文献
3.
Renate Drozdzak Nele Ledoux Bart Allaert Ileana Dragutan Valerian Dragutan Francis Verpoort 《Central European Journal of Chemistry》2005,3(3):404-416
A two step procedure for the synthesis of a novel family of homogeneous and immobilized Ru-complexes containing Schiff bases
as O,N-bidentate ligands is described. The new Ru-complexes have been structurally characterized by IR, Raman,1H-,13C-NMR spectroscopy. The Schiff bases were associated with a diversity of inorganic and organic ligands such as chloride, phosphane,
arenes, various carbenes (alkylidene, vinylidene, indenylidene and allenylidene as well as N-heterocyclic carbenes) and cyclodienes.
By choosing a selective range of substituents for the Schiff base, useful physical and chemical properties of the prepared
Rucomplexes can be induced. This synthetic approach is promising in creating a valuable and diverse selection of Ru-complexes,
valuable for future applications. 相似文献
4.
Stanisław Zieliński Lechosław Lomozik Anna Wojciechowska 《Monatshefte für Chemie / Chemical Monthly》1981,112(11):1245-1252
The formation of the lanthanide (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Lu) complexes with proline and hydroxyproline has been investigated by potentiometric methods as well as by a turbidimetric one which has provided some additional conclusions. It has been found that 11 and a slight amount of 21 complexes are formed. The deviation from the typical course of the formation function is discussed. It is suggested that the perturbations of complex formation in the systems are caused by hydrolysis. The stability constants of the complexes are reported.
Potentiometrische Untersuchungen an Lanthanid-Komplexen von Prolin und Hydroxyprolin
Zusammenfassung Die Bildung von Lanthanid-Komplexen (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Lu) mit Prolin und Hydroxyprolin wurde potentiometrisch und mit Hilfe von Trübungsmessungen untersucht. Es wurde festgestellt, daß sich Komplexe der Zusammensetzung 11 und in kleiner Menge auch 21 bilden. Die Abweichung von typischem Verlauf der Bildungskurven wurde untersucht. Es wurde dabei festgestellt, daß für die Störungen in der Komplexbildung die Hydrolyse verantwortlich ist. Die Stabilitätskonstanten wurden bestimmt.相似文献
5.
6.
Physico-chemical properties of Chitosan films 总被引:1,自引:0,他引:1
Luminita Balau Gabriela Lisa M. I. Popa V. Tura V. Melnig 《Central European Journal of Chemistry》2004,2(4):638-647
Chitosan films obtained by dry phase inversion were prepared from an aqueous solution of chitosan in acetic acid. The films,
of thickness less than 20 μm, were transparent, very flexible and had smooth surfaces. Increasing the film thickness induced
an increase of the internal tensions and the consequent formation of a rough surface. Structural investigations by X-ray diffraction
and Fourier transform IR analysis, showed that the chitosan films, as prepared, are amorphous. Further annealing to evaporate
acetic acid and water traces, changed the amorphous phase into a more ordered phase, characterized by diffraction peaks at
2θ values of 9, 17, 20 and 23 degrees. Thermal investigations by TG, DTG, and DTA revealed that the decomposition of the chitosan
films as prepared proceeds in two stages, starting from 180°C and 540°C. 相似文献
7.
Mineralization procedures for blood and urine suitable for the determination of arsenic by Hydride Generation Atomic Absorption
Spectrometry (HGAAS) are studied on model samples, and the results are utilized in biological monitoring investigations. The
objective of this work is to obtain good total As recoveries for both matrices regardless of added As species (As(III), As(V),
DMA, MMA, AsB, or AsC). Prior to the HGAAS analyses, preparation procedures were controlled under optimised conditions by
graphite furnace atomic absorption spectrometry (GFAAS). Two preparation procedures for urine give As recoveries close to
100% by HGAAS: a) dry ashing at 420°C with Mg(NO3)2 on a hot plate, and b) microwave oven decomposition with (NH4)2S2O8. For blood samples, As recoveries by HGAAS range between 95 and 108% for all species when using dry ashing after a pretreatment
of samples with HNO3 and H2O2 in a microwave oven. Wet digestion with (NH4)2S2O8 in a microwave oven gives recoveries very near 100% for As
inorg.
and MMA. For other As species in spiked blood samples, recoveries of less than 20% As are found. Precision and detection
limits obtained by both techniques are evaluated as well. For arsenic concentrations of 20 μg dm−3 or more in blood and urine, a chemical modifier is recommended for GFAAS analysis; it may or may not be proceeded by a mineralization
step. For low As levels encountered in the unexposed population, the HGAAS technique provides reliable results only if a very
complete mineralization procedure is used. 相似文献
8.
Kerkápoly Anikó Vajda Nóra Pintér Tamás Csordás Pintér 《Central European Journal of Chemistry》2005,3(1):106-117
The increase of activities of fission products and transmutation products in the primary coolant of a nuclear power plant
indicates the presence of fuel rod failures. The measurement of the activity concentration of the primary coolant was able
to detect fuel failures in the reactor core. Microanalytical methods for examining individual hot particles have been developed
and applied to fuel failure detection under normal operation conditions as well as during the severe fuel damage that occurred
in the cleaning tank incident at Unit 2 of NPP Paks in April 2003. Several faulty fuel rods can be detected simultaneously
by the characterization of individual hot particles originating from the primary water. The analysis of particles originating
from the damaged fuels provides information relating to the dissolution process of the fuel debris. 相似文献
9.
Daniela Apreutesei Gabriela Lisa Natalia Hurduc Dan Scutaru 《Central European Journal of Chemistry》2004,2(4):553-562
The goal of this paper is to study thermal stability of some ferrocenes with acidic functional groups. Some other kinetic
characteristics such as critical temperature and the rate constant corresponding to maximal degradation speed have been also
evaluated. The type of functional units adjacent to the ferrocenyl unit determines thermal stability of ferrocene compounds.
Groups with a powerful withdrawing effect determine a decreasing of the temperatures at which the material starts to lose
weight. If a very long alkyl chain is connected to the ferrocene unit, a shielding effect in respect to the other carboxylic
groups was observed, with an increase of the thermal stability. 相似文献
10.
Jerzy L. Gębicki 《Central European Journal of Chemistry》2004,2(2):371-387
The recombination of thiocyanate anion radicals, (SCN)
2
−
, formed pulse radiolytically within the water pools of reverse micelles stabilized with anionic AOT and nonionic Igepal surfactants,
was proved as an indicator reaction to study intermicellar exchange. It was found that the exchange process is slower inIgepal
than in AOT reverse micelles with the same water to surfactant ratio. The apparent activation enthalpy and entropy of the
exchange process were determined in different alkanes. For the AOT and Igepal reverse micelles the activation parameters increase
with the droplet size, but for the AOT systems they do not significantly change with the increase of droplet concentration.
For non-percolated systems the activation parameters for Igepal reverse micelles approach those for AOT reverse micelles.
This result supports existing suggestions that the mechanism of intermicellar exchange does not differ in principle between
reverse micelles stabilized with ionic and nonionic surfactants. 相似文献
11.
12.
Physico-chemical characteristics and sorption activity of carbon, organosilica sorbents and their modified forms towards proteins,
possessing specific activity, and cholerae vibrio have been studied. It was found, that carbon materials modified by copper
(II) effectively extracts cholerae vibrio (100%) and may be recommended for disinfection of drinking water. Sorption capacity
of organosilica sorbents and their modified by copper (II) forms towards pathogenic microflora (E.coli, St.aureus, Ps.aeruginosa)
depending on the composition of the sorbents, concentration of the modified reagent, pH of medium have been evaluated. The
rows of the increase of sorption of pathogenic microorganisms by synthetic sorbents in water-salt solutions were established:
Al(III)<Zn(II)<Cu (II). It was shown that inhibiting effect of modified synthetic organosilica and natural sorbents towards
such pathogenic microorganisms as E-coli, St.aureus Ps.aeruginosa and fungus Bacillus pyocyaneus accordingly is equal 80–98%. 相似文献
13.
Applications of the CSB (Common-Sense Builder) system for the logic-oriented and knowledge-assisted simulation of chemical
reaction courses are described. We present the possibility of using the CSB for two ways of reaction simulation, i.e., as
a multi-step process or as single step procedure. Results of the first simulation type are given to predict the course, and
to model reaction mechanism. The second one is capable of complex chemical transformations such as multi-component and cascade
reactions to generate structurally diverse products for combinatorial chemistry. In several experiments performed, we analyze
the capabilities and limitations of the CSB modules and controlling tools for the examination and selective generation of
solutions. 相似文献
14.
I. Capek 《Central European Journal of Chemistry》2003,1(3):291-304
The kinetics of free-radical copolymerization and terpolymerization of acrylamide (AAm), N, N′-methylenebis(acrylamide) (MBA) and methacrylic acid (MA) in the inverse water/monomer/cyclohexane/Tween 85 miniemulsion was
investigated. Polymerizable sterically-stable miniemulsions were formulated in cyclohexane as a continuous medium. Polymerizations
are very fast and reach the final conversion within several minutes. The dependence of the polymerization rate vs. conversion
is described by a curve with two nonstationary rate intervals. The maximum rate of polymerization slightly increases with
increasing concentration of crosslinking monomer (MBA) and strongly decreases by the addition of MA. The rate of polymerization
is inversely proportional to the 0.9
th
and 1.8
th
power of the particle concentration without and with MA, respectively. The number of polymer particles is inversely proportional
to the 0.18
th
and 0.13
th
power of MBA concentration. The kinetic and colloidal parameters of the miniemulsion polymerization are discussed in terms
of microemulsion polymerization model. 相似文献
15.
Krishna C. Joshi Vijai N. Pathak Raj Pal Singh 《Monatshefte für Chemie / Chemical Monthly》1980,111(6):1343-1350
Several new 2-(fluoroaryl)-3-dialkylaminomethylindoles, 3-acetyl-2-(fluoroaryl)-indoles, 2-(fluoroaryl)-3-indolylglyoxamides and corresponding tryptamines have been prepared as possible psychopharmacological agents. 2-(Fluoroaryl)-indoles have been synthesized by theFischer indole synthesis. 2-(Fluoroaryl)-indoles on treatment with oxalyl chloride and subsequent reaction with amines, gave 2-(fluoroaryl)-3-indolylglyoxamides. Some of these indolylglyoxamides were reducted with lithium aluminium hydride, to the corresponding tryptamines. 2-(Fluoroaryl)-indoles when subjected toMannich reaction afforded 3-dialkylaminomethyl-2-(fluoroaryl)-indoles. All these new compounds have been characterized by IR spectral studies.Possible Psychopharmacological Agents, Part XII, Part XI, J. Indian. Chem. Soc.57, 423 (1980). 相似文献
16.
Synthesis and Surface Properties of N-Alkyl-N-methylgluconamides and N-Alkyl-N-methyllactobionamides
Burczyk B Wilk KA Sokolowski A Syper L 《Journal of colloid and interface science》2001,240(2):552-558
Three series of nonionic N-alkylaldonamides, N-alkyl-N-methylgluconamides (Cn-MGA, Cn: n-C(10)H(21), n-C(12)H(25), n-C(14)H(29), n-C(16)H(33), and n-C(18)H(37)), N-alkyl-N-methyllactobionamides (Cn-MLA, alkyl as above-mentioned), and N-oleyl-N-methylglucon/lactobionamide, were synthesized in the reaction of an appropriate N-alkyl-N-methylamine with delta-D-glucolactone and lactobionic acid, respectively. Krafft temperatures of aqueous solutions and surface properties of these surfactants at 20 degrees C, i.e., surface excess concentration, Gamma(cmc), surface area demand per molecule, A(min), efficiency in surface tension reduction, pC(20), effectiveness in surface tension reduction, Pi(cmc), critical micelle concentration, CMC, and CMC/C(20) parameter as well as standard free energies of adsorption, DeltaG degrees (ads), and of micellization, DeltaG degrees (mic), were determined. It was shown that introduction of the methyl group to the amide nitrogen increased the solubility of the surfactants, which was confirmed by their Krafft temperatures. Lactobionamides are more water soluble than gluconamides. On the other hand, the Cn-MGA surfactants are more surface active than the respective Cn-MLA ones. This observation is based on the determined adsorption and micellization parameters. The presence of one double bond in a hydrocarbon chain as in oleyl-amides increases their hydrophilic character compared with that of saturated C18 derivatives. No distinct differences were observed between the A(min) values obtained for both series studied, although they differ markedly in the size of the hydrophilic groups. Copyright 2001 Academic Press. 相似文献
17.
Modeling and simulation of free radical polymerization of styrene under semibatch reactor conditions
The first part of this approach is concerned with the elaboration of a radical polymerization model of styrenne, based on
a kinetic diagram that includes chemical and thermal initiation, propagation, termination by recombination and chain transfer
to the monomer. Furthermore, volume contraction during polymerization is considered, as well as the gel and glass effects.
The mathematical formalism that describes the model in terms of moments is explored in detail. The model was then used to
predict the changes in monomer conversion and molecular weight after intermediate addition of initiator and monomer. The results
of this operation are dependent on the conditions of the reaction mass, quantity, and moment of substance addition. Therefore,
the simulations were performed at different times with respect to the gel effect; before, during and after this phenomenon,
and also with respect to different temperatures and initiators. Increasing the initiator concentration before the gel effect
leads to an earlier appearance of the phenomenon and to a decrease in molecular weight. The ratio
reveals a polydispersity index smaller for the intermediate addition of initiator. No significant changes take place during
or after the gel effect. If along with the initiator, unreacted monomver (used to dissolve the initiator) enters the reactor,
a small dip in conversion is observed. The general conclusion of this paper reveals the intermediate addition of initiator
as a method to control polymer properties and to prevent the “dead-end” polymerization of styrene. 相似文献
18.
麝香草的新单萜配糖物的分离与合成 总被引:1,自引:0,他引:1
从麝香草(Thymus vulgaris L)的甲醇萃取物中分离出三个单萜配糖物. 用核磁共振光谱确定了它们的结构为对伞花-9-基-β-D-葡糖苷(1), 5-β-D-葡糖苷百里氢醌(2)和2-β-D-葡糖苷百里氢醌(3). 其中1是新化合物, 用以对伞花-9-醇为原料的对映体选择性合成方法确定了化合物1的8位的立体化学为R型. 相似文献
19.
The behavior of p-methoxybenzoyldiphenylphosphine oxide, previously synthesized, as a photoinitiator for the polymerization of diacrylate monomer,
in the presence of 3% (w/w) tertiary amine (triethyl amine) as synergist additive, was studied. The influence of temperature
in the range 30–90°C at 3% (w/w) photoinitiator concentration and the influence of the photoinitiator concentration in the
range 0.5–3.5% (w/w) at 30°C was investigated by differential scanning photocalorimetry (photo-DSC). In all experiments the
photopolymerization was performed at constant light intensity (3 mW cm−2). The maximum conversion was obtained at temperature of 90°C at 3% (w/w) photoinitiator concentration and 3% (w/w) triethyl
amine. The optimal concentration of photoinitiator to obtain maximum conversion was 3% (w/w), at 30°C. No thermal polymerization
occurred at higher temperature. 相似文献
20.
Dimitris Raptis John K. Kouinis Dionysios Kaminaris Andreas G. Galinos 《Monatshefte für Chemie / Chemical Monthly》1981,112(6-7):713-719
The preparationof etherates and pyridinium compounds of mixed complex iodoacids of Ga(III) is reported together with some physical and chemical properties, as well as conductometric measurements and the ultraviolet and infrared spectra of the new compounds. From the analytical, conductometric, stability and spectral data, some information is gained about the probable structure of the complexes.
Etherate und Pyridin-Verbindungen von gemischtkomplexen Jodosäuren von Gallium(III)
Zusammenfassung Es wird über die Darstellung von Ether- und Pyridiniumverbindungen gemischter komplexer Jodosäuren von Ga(III), sowie über einige physikalische und chemische Eigenschaften, konduktometrische Daten und die UV- und IR-Spektren dieser neuen Verbindungen berichtet. Auf Grund von analytischen, konduktometrischen, spektroskopischen und Stabilitätsbefunden wurden Informationen über die wahrscheinliche Struktur dieser Komplexe gewonnen.相似文献