共查询到20条相似文献,搜索用时 290 毫秒
1.
Y. C. Chu J. R. Chen J. M. Tseng L. C. Tsai C. M. Shu 《Journal of Thermal Analysis and Calorimetry》2011,106(1):227-234
Di-tert-butyl peroxide (DTBP) is an organic peroxide (OP) which has widespread use in the various chemical industries. In the past,
thermal runaway reactions of OPs have been caused by their general thermal instability or by reactive incompatibility in storage
or operation, which can create potential for thermal decomposition reaction. In this study, differential scanning calorimetry
was applied to measure the heat of decomposition reactions, which can contribute to understand the reaction characteristics
of DTBP. Vent sizing package 2 was also employed to evaluate rates of increase for temperature and pressure in decomposition
reactions, and then the thermokinetic parameters of DTBP were estimated. Finally, hazard characteristics of the gassy system
containing DTBP, specifically with respect to thermal criticality, were clearly identified. 相似文献
2.
The complex bioactive natural and unnatural benzopyran congeners have been synthesized using one-/two-step approaches in very good yields from the reactions of two different dihydroxyphthalides, natural resorcyclic acid derivative, and trihydroxybenzophenone with citral and/or farnesal, via the phenol-driven intramolecular diastereoselective thermal/base-catalyzed dipolar [2+2] cycloaddition reactions and three different thermal intramolecular cyclization reactions. The effects of the nature and the position of phenolic groups in the starting materials on the course of these cycloaddition reactions have also been described. Depending upon the absence or presence of intramolecular hydrogen bonding of the phenolic group with the carbonyl moiety in the starting materials, these phenol-driven intramolecular thermal/base-catalyzed dipolar [2+2] cycloaddition reactions either furnished the kinetically controlled products or directly formed the thermodynamically controlled rearranged products, respectively. 相似文献
3.
Calorimetry combined with thermal analysis is an essential tool for the evaluation of thermal risks linked with chemical reactions at industrial scale. The energies of synthesis reactions or decomposition reactions as well as the heat capacities of reaction masses can be measured using such techniques. The capacity of the SETARAM differential reaction calorimeter (DRC) to determine essential safety data has been demonstrated with the measurement of heat capacities of cyclohexane and propanoic acid. Results of an industrial reaction are also presented. 相似文献
4.
Thermal
analysis was done to determine the temperatures of thermal reactions, phase
transformations or melting reaction during continuous heating. These reactions
are a direct response to the steel composition and to the sintering atmosphere.
Simultaneous thermal analysis TG-DTA (STA) shows up the sintering behaviour
of sintered low prealloyed chromium steels and their peculiarities. Given
the high oxygen affinity of chromium, graphite additions can modify their
thermal reactions, and hence the sintering behaviour of the steel. Evidence
is given of the effect of carbon on the sintering process and the nature of
the oxides. 相似文献
5.
Andrzej Łopusiński 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4):383-390
Abstract The stereochemical course of the thermal or by nucleophiles catalyzed extrusion reaction of thiocarbonyl fluoride from Two diastereoisomeric (6) and optically active (10) organophosphorus S-trifluoromethylthioates has been investigated. To explain the observed retention of configuration at phosphorus in fluoridates 7 formed in the thermal reactions, a four center transition state for such reactions has been proposed. The lack of the stereoselectivity in the catalyzed reactions of 6, and the observed racemization of the final product 11 are briefly discussed. 相似文献
6.
7.
M. S. Masoud T. S. Kassem M. A. Shaker A. E. Ali 《Journal of Thermal Analysis and Calorimetry》2006,84(3):549-555
Iron, cobalt, nickel,
copper, zinc, cadmium and mercury murexide complexes have been prepared and
characterized. The thermal properties of these complexes are studied deeply
by DTA technique where their thermal peaks are explained. The multi-stages
thermal decomposition mechanism is proposed. The thermodynamic parameters
of the decomposition steps are calculated. The entropy change values for all
complexes are of the same magnitude and all transition states of the thermal
reactions are more ordered than the reactants. The thermal reactions proceed
in complicated mechanisms. The fractions appeared in the calculated orders
of the thermal reactions confirmed that these reactions proceeded via complex
mechanisms. 相似文献
8.
有机铝杂环化合物作为金属杂环化合物中的重要一员,在有机合成中表现出一些独特的性质。有机铝杂环化合物主要包括铝杂环戊二烯、铝杂环戊烯,以及铝杂环戊烷。本文介绍近年来有机铝杂环化合物的合成方法学、反应化学及其在有机合成中的应用研究进展。 相似文献
9.
Andrew K. Galwey 《Journal of Thermal Analysis and Calorimetry》2007,87(2):601-615
This analysis of interface
phenomena considers the alternative processes that may result from heating
a crystal, particularly including thermal decomposition, involving chemical
reactions, and melting, involving loss of long-range structural order. Such
comparisons are expected to provide insights into the factors that determine
and control the different types of thermal changes of solids. The survey also
critically reviews some theoretical concepts that are currently used to describe
solid-state thermal reactions and which provides relevant background information
to models used in a recently proposed theory of melting. Probable reasons
for the current lack of progress in characterizing the factors that control
chemical changes and mechanisms of thermal reactions in solids are also discussed.
It is concluded that some aspects of the macro properties of reaction
interfaces in crystal reactions have been adequately described, including
geometric representations of interface advance during nucleation and growth
processes. In contrast, relatively very little is known about the detailed
(micro) processes occurring within these active, advancing interfacial zones:
reactant/product contacts during chemical reactions and crystal/melt contacts
during fusion. From the patterns of behaviour distinguished, a correlation
scheme, based on relative stabilities of crystal structures and components
therein, is proposed, which accounts for the four principal types of thermal
changes that occur on heating solids: sublimation, decomposition, crystallographic
transformation or melting. Identifications of the reasons for these different
consequences of heating are expected to contribute towards increasing our
understanding of each of the individual processes mentioned and to advance
theory of the thermal chemistry of solids, currently enjoying a prolonged
quiescent phase. 相似文献
10.
Treatment of N-benzyl benzamides with a strong base (LDA or t-BuLi) followed by irradiation with a 500 W tungsten lamp provides, according to the substitution pattern of the starting amides, either norcaradienes or cycloheptadienones by overall insertion of the N-benzyl group into the benzamide's aromatic ring system. Chiral benzamides undergo the ring expansion with high (sometimes complete) stereospecificity. The reaction appears to occur via a series of pericyclic reactions (photochemical or thermal sigmatropic rearrangements and thermal electrocyclic reactions) following an initial dearomatizing cyclization. 相似文献
11.
A theoretical study based on B3LYP/6-31G calculations has been applied to the mechanisms and regiochemistry of reactions of 5-alkoxyoxazole with thioaldehydes, nitroso compounds, and aldehydes. All three reactions adopt similar mechanisms, which start with Diels-Alder (DA) reactions, followed by either a novel, concerted ring-opening-ring-closing (RORC) step to transfer the DA adduct to 2-alkoxycarbonyl-3-thiazoline and 2-alkoxycarbonyl-3-oxazoline for thioaldehydes and aldehydes, respectively, or stepwise ring-opening and ring-closing steps to generate 1,2,4-oxadiazoline for nitroso compounds. The reactions of 5-alkoxyoxazole with thioaldehydes and nitroso compounds can be conducted under thermal reaction conditions due to the 10 kcal/mol activation barriers for their rate-determining DA reactions. By contrast, the reaction of 5-alkoxyoxazole with aldehydes cannot take place under thermal conditions, since this bimolecular reaction has the rate-determining RORC transition state higher than the reactants by 30.5 kcal/mol. 相似文献
12.
This paper presents an application of the reaction class transition state theory (RC-TST) to predict thermal rate constants for hydrogen abstraction reactions of the type OH + alkane --> HOH + alkyl. We have derived all parameters for the RC-TST method for this reaction class from rate constants of 19 representative reactions, coupling with linear energy relationships (LERs), so that rate constants for any reaction in this class can be predicted from its reaction energy calculated at either the AM1 semiempirical or BH&HLYP/cc-pVDZ level of theory. The RC-TST/LER thermal rate constants for selected reactions are in good agreement with those available in the literature. Detailed analyses of the results show that the RC-TST/LER method is an efficient method for accurately estimating rate constants for a large number of reactions in this class. Analysis of the LERs leads to the discovery of the beta-carbon radical stabilization effect that stabilizes the transition state of any reaction in this class that yields products having one or more beta-carbons, and thus leads to the lower barrier for such a reaction. 相似文献
13.
Evan Walter Clark Spotte-Smith Peiyuan Yu Samuel M. Blau Ravi S. Prasher Anubhav Jain 《Journal of computational chemistry》2020,41(24):2137-2150
Thermal storage and transfer fluids have important applications in industrial, transportation, and domestic settings. Current thermal fluids have relatively low specific heats, often significantly below that of water. However, by introducing a thermochemical reaction to a base fluid, it is possible to enhance the fluid's thermal properties. In this work, density functional theory (DFT) is used to screen Diels–Alder reactions for use in aqueous thermal fluids. From an initial set of 52 reactions, four are identified with moderate aqueous solubility and predicted turning temperature near the liquid region of water. These reactions are selectively modified through 60 total functional group substitutions to produce novel reactions with improved solubility and thermal properties. Among the reactions generated by functional group substitution, seven have promising predicted thermal properties, significantly improving specific heat (by as much as 30.5%) and energy storage density (by as much as 4.9%) compared to pure water. 相似文献
14.
Alberto Ballistreri Domenico Garozzo Mario Giuffrida Pietro Maravigna Giorgio Montaudo 《Journal of polymer science. Part A, Polymer chemistry》1986,24(2):331-346
The thermal fragmentation processes in poly-Schiff bases have been investigated by direct pyrolysis–mass spectrometry. The mass spectral data show that the thermal fragmentation occurring in the polymers under investigation is characterized by hydrogen transfer reactions. In the case of a totally aromatic poly-Schiff base (polymer I ), the thermal fragmentation process involves hydrogen transfer irom the methyne group with formation of fragments bearing nitrile and/or phenyl end groups. In the case of aromatic-aliphatic poly-Schiff bases (polymers II–IV ), the hydrogen transfer process occurs from the aliphatic methylene groups. The latter process involves a lower energy and therefore occurs at lower temperatures with respect to the totally aromatic polymer I , with formation of thermal fragments bearing olefin and/or imine end groups. Beside these fragments, several thermal fragmentation compounds are also evolved by multiple hydrogen transfer reactions. 相似文献
15.
16.
Gu¨nter Gauglitz 《Trends in analytical chemistry : TRAC》1983,2(10):230-236
Microprocessor controlled spectrometers greatly extend the possibilities for kinetic analysis of complex thermal or photochemical reactions. As a result, more sophisticated evaluation procedures, such as derivative spectroscopy or dynamic multi-component analysis become possible. 相似文献
17.
M. H. Back 《国际化学动力学杂志》1970,2(5):409-418
Rate constants for the bimolecular reactions of ethylene and propylene to form radicals and to form cyclobutane or its derivatives have been calculated using thermodynamic and kinetic data. Comparison of these rates with the kinetics of the thermal reactions of ethylene and propylene show that cyclobutane and its derivatives are probably not important intermediates in the processes forming radicals. 相似文献
18.
Oxadisilole-fused acridines, dioxatrisilole-fused acridines and benzo[b]acridines were synthesized through nucleophilic additions and aromatization reactions of arynes with 2-aminoaryl ketones or 2-aminoaryl aldehydes in good yields at room temperature. The photophysical, redox and thermal properties of these compounds were characterized. These compounds show potential applications as strong deep-blue or green emitters for OLED because of high fluorescence quantum yields and good thermal stabilities. 相似文献
19.
Baiyuan Yang 《Tetrahedron letters》2009,50(43):5879-10253
Retro iminonitroso Diels-Alder reactions were investigated in both solution and solid phase. In thermal or Cu(I)-mediated reactions, interconversion of various nitroso cycloadducts occurred in the presence of separate dienes. Up to 99% of conversion was observed. Use of chiral ligands in the Cu(I)-mediated reactions gave new cycloadducts enantioselectively. 相似文献
20.
The thermal decomposition of malonic acid was investigated with a derivatograph. Values of activation energy, frequency factor and reaction order were determined from thermal decomposition curves employing different calculation methods. Equations derived for the calculation of kinetic data of inorganic thermal reactions were also found to be suitable in the case of organic reactions. Convenient methods were developed for the calculation of the activation energy, using the DTG curve. 相似文献