共查询到20条相似文献,搜索用时 15 毫秒
1.
M. A. S. Silva R. G. Kelmann T. Foppa A. P. Cruz C. D. Bertol T. Sartori A. Granada F. Carmignan F. S. Murakami 《Journal of Thermal Analysis and Calorimetry》2007,90(2):463-467
The thermal decomposition of two inclusion compounds Mn(HCOO)2·1/3C4H8O2 and Mn(HCOO)2·1/3C4H8O was studied in the inert atmosphere. The process of both dioxane, and tetrahydrofurane removal has two steps; the intermediate
phase is unstable and kinetically hindered. Manganese formate is stable up to 330°C. Thermogravimetric data (obtained at different
rates of linear heating) were processed with computer program (with ‘Model free’ approach). Kinetic parameters were calculated
for the first decomposition step, and the process is described by equation of n-order reaction with autocatalysis. 相似文献
2.
The bismuth salt of lauric (dodecanic) acidBi6O4(OH)4(C11H23COO)6 was studied earlier. This salt has layer structure (the interlaminardistance=37.50 Å), under heating this liquid-crystalline state has themesomorphic transformation, turns to the amorphous state, decomposes stepwisewith the formation of well-ordered layers of bismuth nanoparticles. DSC-curveswere used for the study of the decomposition kinetics in the area of decompositionwith small mass loss and exothermic effect (423–483 K). 相似文献
3.
V. Logvinenko O. Polunina Yu. Mikhailov K. Mikhailov B. Bokhonov 《Journal of Thermal Analysis and Calorimetry》2007,90(3):813-816
Thermal decomposition of silver acetate was studied (TG, DSC, mass-spectrometry, X-ray analysis, electron microscopy). Non-isothermal
thermogravimetric data (obtained at two different rates of linear heating) were used for kinetic studies. Kinetic parameters
were calculated only for the chosen decomposition step. 相似文献
4.
5.
The influence of molecular structure on the stability of high-energy compounds is considered. The kinetic parameters of the
decomposition of various energy-rich groups in monofunctional compounds are established. Data on decomposition of compounds
with mixed functional groups are described. The sites of primary breakdown are determined and the mutual influence of functional
groups on the stability is considered.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 231–234, February, 2000. 相似文献
6.
Paul Jara Nicolás Yutronic Guillermo González 《Journal of inclusion phenomena and macrocyclic chemistry》1995,22(3):203-210
The synthesis and structural aspects of urea host-guest inclusion compounds containing linear secondary alkylamines (dibutyl-,dipentyl-, dihexyl-, dioctyl-) at 25°C are reported. Elemental analysis,13C CP-MAS NMR and1H-NMR Spectroscopy, and Powder X-ray Diffraction Analysis confirm the inclusion process. The basic host structure of the products is similar to that of urea-hydrocarbon systems.13C MAS-NMR experiments show chemical shift differences for the confined guest molecule with respect to the liquid phase. Stoichiometry and |c
g| values for the inclusion compounds with dipentyl-and dihexylamine suggest a commensurate structure. 相似文献
7.
V. N. Grebennikov G. B. Manelis G. M. Nazin A. V. Fokin 《Russian Chemical Bulletin》1994,43(2):315-318
The kinetics of decomposition of 15 difluoroamino compounds with NF2 groups at primary, secondary, and tertiary carbon atoms in the liquid state was investigated. Activation energies (E
a) for all of the compounds were in the interval 100–120 kJ · mol–1. The reaction rate does not depend on the electronic effects of the substituents and decreases only in the case of steric shielding of the NF2 group. ForN-difluorobenzylamine it was shown that the gas-phase elimination of HF is characterized byE = 176 kJ·mole–1, while the rate of decomposition in a solution depends on the dielectric constant of the medium. Based on the results obtained, a mechanism for liquid-phase decomposition, which involves heterolysis of the N-F bonds, is suggested.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 336–338, February, 1994. 相似文献
8.
V. Logvinenko V. Fedorov Yu. Mironov V. Drebushchak 《Journal of Thermal Analysis and Calorimetry》2007,88(3):687-692
A new polymorphic form of Norfloxacin has been identified and fully characterized by a variety of methods including powder
X-ray diffraction, vibrational spectroscopy (IR and Raman), thermal analysis (DSC and TG), SEM and solid-state NMR spectroscopy.
The relationship between the new form C and the previously known forms A and B have been studied. Moreover, the crystal structure
of the known form A has been solved by single-crystal methods. 相似文献
9.
M. Badea R. Olar E. Cristurean D. Marinescu M. Brezeanu C. Calina-Soradi E. Segal 《Journal of Thermal Analysis and Calorimetry》2000,59(3):977-984
Data concerning the thermal behaviour of four heteropolynuclear compounds with the general formula [CuML(CH3COO)3] whereM=Ni(II), Zn(II), Mn(II) and Co(II); LH=2-amino-5-mercapto-1,2,3-thiadiazole were obtained. For the kinetically workable decomposition steps the values of the kinetic
parameters were estimated.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
Elena Lizarraga C. Zabaleta J. A. Palop 《Journal of Thermal Analysis and Calorimetry》2007,89(3):783-792
Thermal analysis of fusion and decomposition processes were carried out on recently synthetized pharmaceutical compounds in
order to establish thermal stability criteria. This study was carried out using thermogravimetry, TG, and differential scanning
calorimetry, DSC. Degradation and fusion temperatures have been produced as thermal data with the aim of to study the thermal
stability of the compounds.
Relationship is found among stability and a series of effects of structure of the compounds. The compounds which present an
amide functional group in the central molecule are more stable because they have a comparatively higher fusion and degradation
temperature. In addition, the stability of this type of compounds depends on the position of the electrophilic substitution
(in ortho, meta or para). Likewise, the groups linked to the aromatic ring with high electronic density give stability, and therefore are able to
delocalize the charge in a greater spacial interval.
Therefore, criteria for the selection of substituents have established that improve the stability of compounds 相似文献
11.
Mihaela Badea Rodica Olar Dana Marinescu E. Segal A. Rotaru 《Journal of Thermal Analysis and Calorimetry》2007,88(2):317-321
A series of new complexes with mixed ligands
of the type M(4,4’-dipy)(C3H3O2)2(H2O)y ((1) M=Mn, y=2; (2) M=Ni, y=2; 4,4’-dipy: 4,4’-dipyridyl and C3H3O2 is acrylate anion) and respectively M2(4,4’-dipy)(C3H3O2)4(H2O)y
((3) M=Cu, y=0; (4) M=Zn, y=1). The
modification evidenced in IR spectra was correlated with the presence of acrylate
ion as unidentate in the case of complex (1)
and as bidentate for others complexes. The electronic reflectance spectra
showed the d–d
transition for complex (1) and (2) characteristic for the octahedral surrounding while
the spectrum for complex (3) have the characteristic
pattern for square-pyramidal stereochemistry. The thermal behaviour steps
were investigated. The thermal transformations are complex processes according
to TG and DTG curves including dehydration, acrylate ion oxidative degradation
and thermolysis process of aromatic amine. The final products of decomposition
are the most stable metal oxides. 相似文献
12.
New zinc acetate based complex compounds (of general formula Zn(CH3COO)2·1?2L·nH2O) containing one or two molecules of urea, thiourea, coffeine and phenazone were prepared namely: Zn(CH3COO)2·2.5H2O, Zn(CH3COO)2·2u·0.5H2O, Zn(CH3COO)2·tu·0.5H2O, Zn(CH3COO)2·2tu, Zn(CH3COO)2·cof·2.5H2O, Zn(CH3COO)2·2cof·3.5H2O, Zn(CH3COO)2·2phen·1.5H2O. The compounds were characterized by IR spectroscopy, chemical analysis and thermal analysis. Thermal analysis showed that no changes in crystallographic modifications of the compounds take place during (heating in nitrogen before) the thermal decompositions. The temperature interval of the stability of the prepared compounds were determined. It was found that the thermal decomposition of hydrated compounds starts by the release of water molecules. During the thermal decomposition of anhydrous compounds in nitrogen the release of organic ligands take place followed by the decomposition of the acetate anion. Zinc oxide and metallic zinc were found as final products of the thermal decomposition of the zinc acetate based complex compounds studied. Carbon dioxide and acetone were detected in the gaseous products of the decomposition of the compounds if ZnO is formed. Carbon monoxide and acetaldehyde were detected in the gaseous products of the decomposition, if metallic Zn is formed. It is supposed that ZnO and Zn resulting from Zn acetate complex compounds here studied, possess different degree of structural disorder. Annealing takes place by further heating above 600°C. 相似文献
13.
Dana Bogdan J. P. Aycard Mohamed Hnach Elena Volanschi Mihaela Hillebrand V. Badescu N. Dragoe E. Segal 《Journal of Thermal Analysis and Calorimetry》1996,46(6):1729-1740
The thermal behaviour of some compounds derived from 5-phenylfuran-2,3-dione was studied. The thermoanalytical data relating to the decomposition steps and intermediates were completed with mass spectrometric analysis and infrared spectroscopy results. For some of the investigated reactions, the kinetic and structural data correlated satisfactorily. 相似文献
14.
Y. Hadef J. Kaloustian A. Nicolay H. Portugal 《Journal of Thermal Analysis and Calorimetry》2008,93(2):553-560
The Medical Commission of the International Olympic Committee forbids the use of anabolic androgenic steroids, β-agonists,
stimulant and narcotic compounds to improve athletic performance. In this work, we evaluated the thermal stability of 17 compounds
by the use of the DSC for their potential GC-MS analysis either under free form or under TMS derivative form. In DSC, esterified
and unesterified anabolic steroids were characterized by a true melting peak, followed by a large exothermic peak at about
251–316°C due to oxidative degradation. They could be analysed by GC-MS mainly under TMS derivatives. Hydroxylated and unhydroxylated
stimulant compounds (xanthines) seemed to be more stable at high temperature. As unhydroxylated xanthines were not silylated
with BSTFA - TMCS, their GC analysis would be done under their free forms. TMS derivatisation of albuterol hemisulfate and
codeine phosphate is preferable. In our conditions, to analyse by GC-MS all 17 doping compounds in the same GC-MS run, the
optimal silylation temperature and best column initial temperature were determined at both 60°C. 相似文献
15.
Anna Sopková P. Mondík Mária Reháková 《Journal of Thermal Analysis and Calorimetry》1996,47(2):365-378
Inclusion compounds do not belong to the group of simple compounds. They consist of molecules of the host and guest components. Some of them form supermolecules and exhibit super-molecular properties.Combinations of inclusion compounds as even more complicated systems need more methods to be used for their identification. Thermoanalytical study enables to study the sorption during their formation and the progressive liberation of their individual components and parts. Many layered silicates, phosphates and other similar synthetic and natural compounds enclosing or adsorbing cyclodextrins, pharmaceuticals, aromatics, various agrochemicals and inorganics are analysed from the view of their formation and properties. 相似文献
16.
A. Książczak T. Książczak T. Zielenkiewicz 《Journal of Thermal Analysis and Calorimetry》2004,77(1):233-242
DSC method was used to study thermal stability of nitrocompounds. It was assumed the model to estimate stability of solid
phase in which perfect solid phase is totally stable and amorphous-liquid domains connected with impurities decompose according
to the kinetic model determined for the liquid phase above the melting point. The influence of sample purity on relative stability,
which is k
l/k
s — ratio of decomposition rate constants in liquid and solid phase, at temperature 20 K below the melting point was predicted.
The increase of liquid domains in solid phase causes decrease of k
l/k
s ratio (relative stability) at chosen temperature.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
Ingeborg Csöregh Mátyás Czugler Edwin Weber Jochen Ahrendt 《Journal of inclusion phenomena and macrocyclic chemistry》1990,8(3):309-322
The crystal structures of the inclusion compounds oftrans-9,10-dihydro-9,10-ethano-anthracene-11,12-dicarboxylic acid host (1) with formic acid (1a), acetic acid (1b), and propionic acid (1c) as guests, and of the coordinatoclathrate of the 1,1-binaphthyl-2,2-dicarboxylic acid host (2) with acetic acid as guest (2b) have been studied by single crystal X-ray diffraction. These studies show that inclusion of small carboxylic acids by carboxylic acid hosts like1 and2 results in formation of isolated, hydrogen-bonded guest dimers. Additional H-bond contacts between host and guest carboxylic groups are only formed in cases1a and2b. The dimeric acidic guest units are sitting in the cavities of the host or host-guest framework and have no other interactions than those of a weak Van der Waals' type with the neighbouring molecules. Crystal data:1·formic acid (1:2): triclinic (P),a = 11.6769(6),b = 9.4067(4),c = 9.0020(4) Å,a = 81.522(4), = 100.310(6), = 104.208(6)°,Z = 2,R = 0.048 for 2392 reflections;1·acetic acid (1:1): monoclinic (P21/n),a = 9.717(2),b = 14.462(2),c = 13.038(3)Å, = 104.27(1)°,Z=4,R=0.046 for 3042 observations;1·propionic acid (1:1): monoclinic (P21/n),a = 9.897(4),b = 14.671(7),c = 13.284(7) Å, = 105.92(6)°,Z = 4,R = 0.056 for 2302 reflections;2·acetic acid (2:3): triclinic (P),a = 12.746(1),b = 17.781(2),c = 11.010(1) Å, = 105.606(4), = 112.992(8), = 81.175(6)°,Z = 2,R = 0.067 for 4375 observations. 相似文献
18.
19.
E. L. M. Krabbendam-LaHaye W. P. C. de Klerk R. E. Krämer 《Journal of Thermal Analysis and Calorimetry》2005,80(2):495-501
Summary Manufactures of commercially available explosives guarantee a certain lifetime of their products. In the commercial field this lifetime is usually large enough. The explosive is normally used long before the end of its lifetime. It may happen that these explosives are stored for a long time in a bunker where they sometimes exceed their lifetime. A large set of commercial explosives is characterized with a TG by heating small samples in aluminium sample cups from room temperature to 550°C, under a nitrogen atmosphere, with three different heating rates (2, 5 and 10 K min-1). The activation energy of the decomposition step is determined in several different ways. After this characterization, a selection of the samples (based on economical value) is artificially aged for periods of 2, 4 and 6 weeks. After these ageing profiles the samples are re-investigated with the TG under the same conditions (heating rates and atmosphere) followed by the calculation of the kinetic parameters of the artificially aged materials. According to the TG measurements almost all tested explosives appear to have a much longer lifetime than the values given by the manufacturer. From kinetic point of view, the different methods for calculating the activation energy result in approximately the same parameters. It may conclude that TG seems to be a reliable and quick method for the determination of the lifetime of commercial explosives. 相似文献
20.
The dynamic behavior of a reaction–diffusion model of solid-phase combustion is investigated by using the linear stability
analysis method. The diffusion coefficients of the oxygen gas and the vapor of the combustible solid (Mg) are taken as two
controlling parameters in the analysis. The bifurcation map obtained shows three dynamic regions. Region I only shows stable
combustion. Regions II and III both show stable combustion and oscillatory combustion depending on the ratio of the two diffusion
coefficients. Interestingly region II also shows a small range of a bistable state consisting of a stable focus and an oscillating
state, which is like the critical phenomena in phase transitions. The results indicate that the occurrence of oscillating
combustion requires that the value of the diffusion coefficient of the Mg vapor should be comparable to or less than that
of the oxygen gas at the same temperature.
Received: 6 November 2001 / Accepted: 25 March 2002 / Published online: 13 June 2002 相似文献