共查询到20条相似文献,搜索用时 62 毫秒
1.
P. J. Masset 《Journal of Thermal Analysis and Calorimetry》2009,96(2):439-441
The dehydration of LiCl·H2O was studied under inert helium atmosphere by DTA/TG for different heating rates. The dehydration of LiCl·H2O proceeds through a two step reaction between 99–110 and 160–186°C, respectively. It leads to the formation of LiCl·0.5H2O as intermediate compound. The proposed mechanism is:
and
Based on the temperature peak of the DTA signals the activation energies of the two reactions were determined to be 240 kJ
mol−1 (step 1) and 137 kJ mol−1 (step 2), respectively. 相似文献
2.
Rupam J. Szarma Andrei S. Batsanov Ritu Kataky Jubaraj B. Baruah 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(1-2):1-9
Encapsulation of 4−[(4′-hydroxy−3′,5′-dimethylphenyl)(aryl)-methylene]−2,6−dimethyl-cyclohexa−2,5−dienones (when aryl=4−hydroxyphenyl 1, 4−methoxyphenyl 2, 2,3,4-trimethoxy phenyl 3) by β-cyclodextrin is studied. The compound 2 is selectively encapsulated by β-cyclodextrin. The result is rationalised by analysing the structural parameters from the crystal structure of 1–3. The visible spectra of the compounds 2 and 3 at pH 9.0 show red shifts on the absorption maxima upon addition of cetyltrimethylammonium bromide (CTAB). For example, addition of a solution of CTAB to aqueous ethanolic solution of 2 at pH 9 causes shift of the absorption at 578–593 nm (Δλmax=15 nm). The advantage of this observation is taken to use 2 and 3 to determine the critical micelle concentration of CTAB in basic medium.Graphical Abstract Structural investigations on quinone methides for understanding their properties in confined media Rupam J. Sarma, Andrei S. Batsanov, Ritu Kataky, Jubaraj B. Baruah
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3.
Violeta D. Mitic Snezana D. Nikolic Vesna P. Stankov-Jovanovic 《Central European Journal of Chemistry》2010,8(3):559-565
A kinetic spectrophotometric method for hydrazine determination in the range of 9.36×10−7 to 4.37×10−5 mol dm−3, based on the inhibitory effect of hydrazine on the oxidation of Victoria Blue 4- R by KBrO3, was developed and validated. Kinetic parameters are reported for both the indicating and the inhibiting reaction. The detection
limit was established as 9.98×10−8 mol dm−3. The selectivity of the proposed method was tested considering the influence of different ions that may be present in real
samples. The method was successfully applied for hydrazine determination in various samples (very pure water from the water-steam
system of a power plant and Isoniazid tablets, a pharmaceutical product).
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4.
A. Rotaru Anna Kropidłowska Anca Moanţă P. Rotaru E. Segal 《Journal of Thermal Analysis and Calorimetry》2008,92(1):233-238
Thermal analysis of three azomonoether dyes, exhibiting liquid-crystalline properties, was performed in dynamic air atmosphere.
Thermal stability studies and the evaluation of the kinetic parameters of each physical or chemical transformations are essential
for a full characterization, before attempting accurate thin films’ depositions of such materials used in non-linear optical
applications. New synthesized dyes with general formula:
where R is a nematogenic group: CN, CF3 or a highly polarizable group: NO2 were investigated using TG, DTG, DTA and DSC techniques, under non-isothermal regime. The evolved gases were analyzed by
FTIR spectroscopy. The activation energies of the first decomposition step were evaluated for each compound, the obtained
results revealing complex mechanisms. 相似文献
5.
Seied M. Pourmortazavi Iraj Kohsari Seiedeh S. Hajimirsadeghi 《Central European Journal of Chemistry》2009,7(1):74-78
The present study concerns the electrochemical synthesis of basic copper carbonate nanoparticles by oxidation of metallic
copper on the anode in an aqueous bicarbonate solution. This simple and one-step preparation can be considered as green synthesis.
The scanning electron microscopy (SEM) analysis indicates that average particle size of the product is in the range of about
70 nm. On the other hand, basic copper carbonate micro-powder has been prepared, by mixing solutions of copper(II) sulphate
and sodiu bicarbonate. The SEM analysis showed that the size of particles prepared in the same way is in the range of about
1 μm. In another part of this study, the thermal decomposition of micro and nanoparticles of copper carbonate produced by
various methods was studied in air using TG-DTA techniques. The results of thermal study show that the decomposition of both
samples occurs in single step. Also, the TG-DTA analysis of the nanoparticles indicates that the main thermal degradation
occurs in the temperature range of 245–315°C. However, microparticles of Cu(OH)2 · CuCO3 decomposed endothermally in the temperature range of 230–330°C.
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6.
Unusual reaction of 3,4-bis(3-nitrofurazan-4-yl)furoxan with ammonia,primary amines and hydrazine 总被引:1,自引:0,他引:1
Alexander A. Astrat’ev Dmitry V. Dashko Andrei I. Stepanov 《Central European Journal of Chemistry》2012,10(4):1087-1094
The nucleophilic displacement of two nitro groups in 3,4-bis(3-nitrofurazan-4-yl)furoxan with ammonia, primary aliphatic amines
and hydrazine leads to formation of a novel heterocyclic system, 7H-tris[1,2,5]oxadiazolo[3,4-b:3′,4′-d:3″,4″-f]azepine. The
reaction of compound 1 with secondary aliphatic amines proceeds in a typical way for nitrofurazans when the nitro-group in
the starting compound is substituted by RR’N-group.
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7.
Oliver Staller Dietmar Holzmann Gerhard Gritzner Pavel Diko Daniel Mikolaj František Kováč 《Central European Journal of Chemistry》2008,6(2):135-139
Textured Ni tapes were fabricated from commercially available nickel pellets (98.5% Ni). Ingots produced by a melt process
were cold rolled to 150–400 μm thick tapes. Texturing was achieved by annealing in a reducing atmosphere (Ar + 6.5% v/v H2). Sharp cubic biaxial textured Ni tapes were obtained by thermal treatment at 1000°C for 2 hours in a reducing atmosphere.
The tapes were characterized by scanning electron microscopy, X-ray diffraction and by electron backscattering diffraction.
The tensile strength, the thermal expansion behavior and the Vickers hardness for the cold rolled tapes and for the heat-treated
tapes were measured.
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8.
Halil Turgut Şahin 《Central European Journal of Chemistry》2007,5(3):824-834
Attempts were made to plasma deposit an oriented π-conjugated polymer of pyrrole (Py) on paper surfaces in order to produce
electrically conductive layers. The N/C atomic ratio of 0.13–0.24 was observed for all treatment conditions. This implies
the nature of the deposition formed on the paper surface via pulsed plasma is different from that of pyrrole monomer. An increase
in conductivity of all pyrrole-plasma treated papers was observed. The 50 W RF-power with 5 min plasma exposed paper sample
shows 8.15 × 10−9 S·cm−1 conductivity. The conductivity measurements indicated a plasma-enhanced ring-opening reaction mechanism of pyrrole.
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9.
Thermal and Spectroscopic Studies on the Decomposition of Some Aminoguanidine Nitrates 总被引:1,自引:0,他引:1
S. R. Naidu K. V. Prabhakaran N. M. Bhide E. M. Kurian 《Journal of Thermal Analysis and Calorimetry》2000,61(3):861-871
Diaminoguanidine nitrate (DAGN) and triaminoguanidine nitrate (TAGN),potential energetic materials in emerging propulsion
technology with high mass impetus at low isochoric flame temperature have been studied as regards kinetics and mechanism of
thermal decomposition using thermogravimetry (TG), differential thermal analysis (DTA),infrared spectroscopy (IR) and hot
stage microscopy. Kinetics of thermolysis has been followed by isothermal TG and IR. For the initial stage of thermolysis
of DAGN the best linearity with a correlation coefficient of 0.9976 was obtained for the Avrami-Erofe'evequation, n=2, by isothermal TG. The activation energy was found to be 130 kJ mol–1 and logA=11.4. The initial stage of thermolysis of TAGN also obeyed the Avrami-Erofe'ev equation, n=2, with a correlation coefficient of 0.9975by isothermal TG and the kinetic parameters are E=160.0 kJ mol–1 and logA=16.0. High temperature IR spectra showed exquisite preferential loss in intensity of the NH2, NH, N–N stretching and CNN bending. Spectroscopic and other results favour deamination reaction involving the rupture of
the N–N bond as the primary step in the thermal decomposition.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
Abstract Using ab-initio calculation, we have explored new chemical paths for the coalescence of C60 units into higher fullerenes and novel structures. Besides the Stone–Wales paradigm used for rationalizing the fusion of
fullerenes and nanotubes, we demonstrated that an alternative path exists for the fusion of two C60 units. This path uses successive “π–π” additions and subsequent bond reorganizations to lead to a specific C120 peanut-like structure. The energies of the chemical barriers, the intermediate structures, and the final product are markedly
lower than their counterparts found in the chemical paths based on Stone–Wales bond rotations. The results rationalize the
existence of a temperature range in which peanut-like structures are obtained during thermal treatment of peapod structures.
Graphical abstract
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
11.
Bo?ena Bittner Ewa Janus Eugeniusz Milchert 《Central European Journal of Chemistry》2011,9(1):192-198
A comparative study of the Diels-Alder reactions between cyclopentadiene (1) and dienophiles (2 a–c) in N-hexylpyridinium
bis(trifluoromethylsulfonyl)imide in a temperature range of 20–45°C is reported. The reaction rate constants and activation
energies were calculated. Moreover, the catalytic systems based on N-hexylpyridinium bis(trifluoromethylsulfonyl)imide and
Lewis acids were tested as a reaction media to perform the Diels-Alder reaction. Yb, Y, Mg, Zn triflates and chlorides (0.005
to 0.1 mmol) were used as catalysts. The recycling of catalytic system consisted of YCl3 and ionic liquid was performed.
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12.
Carla Ferragina Romolo Di Rocco Pasquale Patrono Lucantonio Petrilli 《Central European Journal of Chemistry》2009,7(1):31-34
Layered compounds with CdS particles supported on the ion-exchanger, γ-titanium dihydrogen phosphate, were prepared by the
stepwise reaction of the ion-exchanger and cadmium solution, followed by reaction with H2S gas. The CdS content on the ion-exchanger is dependent on the timeframe of the H2S gas flow. The materials obtained were layered, as shown by the X-ray measurements that exhibit both precursor and CdS diffraction
peaks. The thermal treatment of the material obtained gives evidence of its stability (≤ 320°C) before the CdS decomposition,
which occurs in a single step.
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13.
Petar T. Todorov Rosica N. Petrova Emilia D. Naydenova Boris L. Shivachev 《Central European Journal of Chemistry》2009,7(1):14-19
The crystal structures of 3-amino-cycloheptanespiro-4′-imidazolidine-2′,5′-dione (I) {systematic name: 3-amino-1,3-diazaspiro[4.6]
undecane-2,4-dione} and 3-amino-cyclooctanespiro-4′-imidazolidine-2′,5′-dione (II) {systematic name: 3-amino-1,3-diazaspiro[4.7]
dodecane-2,4-dione}, have been determined. In both compounds the polar hydantoin groups cause molecules to aggregate via N-H...O
and N-H...N interactions, forming a layer structure, in which the cycloalkane rings project outwards from the central, more
polar, region. The observed molecular structure is compared with that calculated by density functional theory methods.
相似文献
14.
Ramin Ghorbani-Vaghei Seyedeh Mina Malaekehpour 《Central European Journal of Chemistry》2010,8(5):1086-1089
N,N,N,’N’-Tetrabromobenzene-1,3-disulfonamide [TBBDA] is found to be a reusable catalyst for efficient synthesis of various amidoalkyl
naphthols from β-naphthol, aromatic aldehydes and urea in good to high yields under solvent-free conditions.
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15.
M. Zayat R. Pardo G. Rosa R. P. del Real M. Diaz-Michelena I. Arruego H. Guerrero D. Levy 《Journal of Sol-Gel Science and Technology》2009,50(2):254-259
On December 2004, the Spanish Space Agency INTA (Instituto Nacional de Técnica Aeroespacial) launched the first nanosatellite
called NANOSAT (Fig. 1) on board an European rocket Ariane 5, from the French Guyana. The satellite consists of a hexagonal device of <19 kg of
weight with a diameter of about 50 cm, which describes a LEO orbit of 655 km of altitude. The main objective of the satellite
is to probe the operation and performance of micro- and nanotechnologies in space environment. One of the scientific experiments
implemented on board was the Sol–Gel based magnetic nanosensor.
Fig. 1 NANOSAT 01
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16.
Oleksiy V. Grygorovych Oleksiy V. Nevskii Sofia M. Moskalenko Vasyl G. Pivovarenko Andrey O. Doroshenko 《Central European Journal of Chemistry》2010,8(4):766-782
Protolytic interactions in the series of prospective fluorescent ratiometric wide-range pH indicators — structurally rigid
analogs of 2,6-distyrylpyridine — (3E,5E)-3,5-dibenzylidene-8-phenyl-1,2,3,5,6,7-hexahydrodicyclopentano[b,e]pyridine — were
investigated. The pyridine nitrogen atom basicity in these compounds is significantly lower in comparison with that of unsubstituted
heterocycle and 2,6-distyrylpyridine. The photochemical E→Z photoisomerization and the side benzene rings substituents influence
on the acid-base equilibria were studied. The complex multi-stage mechanism of the acid-base interactions of the polysubstituted
compounds was elucidated. The most significant spectral effects were typical to the N,N-dialkylamino substituted compounds
of the investigated series. The widest pH sensitivity interval covering nearly the full range of 0–14 units was demonstrated
for compounds with both proton donor and proton acceptor substituents.
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17.
K. M. Ibrahim I. M. Gabr G. M. Abu El-Reash R. R. Zaky 《Monatshefte für Chemie / Chemical Monthly》2009,140(6):625-632
Abstract Acetone [N-(3-hydroxy-2-naphthoyl)] hydrazone (H2AHNH) has been prepared and its structure confirmed by elemental analysis and 1H NMR spectroscopy. It has been used to produce diverse complexes with Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and U(VI)O2 ions. The complexes obtained have been investigated by thermal analysis, spectral studies (1H NMR, IR, UV–visible, ESR), and magnetic measurements. IR spectra suggest that H2AHNH acts as a bidentate ligand. The electronic spectra of the complexes and their magnetic moments provide information about
geometries. The ESR spectra give evidence for the proposed structure and the bonding for some Cu(II) complexes. Thermal decomposition
of the Ni(II) and Cu(II) complexes afforded metal oxides as final products. Kinetic data were obtained for each stage of thermal
degradation of some of the complexes using the Coats–Redfern method. The formation of complexes in solution was studied pH-metrically
and the order of their stability constants (log K) was found to be U(VI)O2 > Cu(II) > Zn(II) > Ni(II) > Cd(II) > Co(II). Antimicrobial and eukaryotic DNA studies were carried out.
Graphical abstract
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18.
Tevhide Özkaya Abdulhadi Baykal Muhammet Sadaka Toprak 《Central European Journal of Chemistry》2008,6(3):465-469
Water-soluble Mn3O4 nanocrystals have been prepared through thermal decomposition in a high temperature boiling solvent, 2-pyrrolidone. The final
product was characterized with XRD, SEM, TEM, FTIR and Zeta Potential measurements. Average crystallite size was calculated
as ∼15 nm using XRD peak broadening. TEM analysis revealed spherical nanoparticles with an average diameter of 14±0.4 nm.
FTIR analysis indicated that 2-pyrrolidone coordinates with the Mn3O4 nanocrystals only via O from the carbonyl group, thus confining their growth and protecting their surfaces from interaction
with neighboring particles.
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19.
Ibuprofen membrane electrodes based on different plasticizers: diisobutyl phthalate (DIBP), o-nitrophenyloctyl ether (o-NPOE),
dioctyl sebacate (DOS) and tetraoctylammonium 2-(4-isobutylphenyl)propionate were prepared. All electrodes show: a near Nernstian
slope of characteristic (58.3–60.9 mV decade−1) in the measurement range (10−4–10−1 mol L−1), limit of detection (5.0×10−5 mol L−1), really long lifetime (12 months), dependence of the electrode potential on pH (5.5–9.0), reproducibility of potential (0.6–1.2
mV) and selectivity coefficients in relation to some organic and inorganic anions. The electrodes were applied for the determination
of ibuprofen in tablets by the calibration curve method and the standard addition method.
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20.
Hydrophilic interaction chromatography (HILIC) is an increasingly popular alternative to conventional HPLC for drug analysis.
It offers increased selectivity and sensitivity, and improved efficiency when quantifying drugs and related compounds in complex
matrices such as biological and environmental samples, pharmaceutical formulations, food, and animal feed. In this review
we summarize HILIC methods recently developed for drug analysis (2006–2011). In addition, a list of important applications
is provided, including experimental conditions and a brief summary of results. The references provide a comprehensive overview
of current HILIC applications in drug analysis.
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