共查询到20条相似文献,搜索用时 156 毫秒
1.
2.
3.
4.
本文报道了七个新的2,4,5-三氧-1,3,2,4-二氮二磷杂环戊烷衍生物的制备, 产物的结构经IR, ^1H和^31P NMR, MS以及元素分析证实, 并利用^31P NMR和GC-MS区分了化合物的顺式和反式异构体。 相似文献
5.
3,6-双(1氢-1,2,3,4-四唑-5-氨基)-1,2,4,5-四嗪的合成与表征 总被引:13,自引:2,他引:11
研究了低感度高氮化合物3,6-双(1氢-1,2,3,4-四唑-5-氨基)-1,2,4,5-四嗪的合成,其结构经元素分析,IR,^1H NMR和^13C NMR表征。 相似文献
6.
7.
3,3’-偶氮-(6-氨基-1,2,4,5-四嗪)的合成与表征 总被引:1,自引:0,他引:1
以硝酸胍和水合肼为原料,经7步反应合成了高氮含能化合物3,3'-偶氮-(6-氨基-1,2,4,5-四嗪),其结构经^1H NMR,^13C NMR,IR及元素分析表征。 相似文献
8.
9.
10.
11.
12.
Christelle Herman Tom Leyssens Valérie Vermylen Véronique Halloin Benoît Haut 《The Journal of chemical thermodynamics》2011,43(5):677-682
This paper presents two distinct methods for the determination of the solid–solid transition temperature (Ttr) separating the temperature ranges of stability of two crystallographic forms, hereafter called morphs, of a same substance. The first method, based on thermodynamic calculations, consists in determining Ttr as the temperature at which the Gibbs free energies of the two morphs are equal to each other. For this purpose, some thermodynamic characteristics of both morphs are required, such as the specific heat capacities, the melting temperatures and the melting enthalpies. These are obtained using the Differential Scanning Calorimetry (DSC). In the second method, Ttr is determined directly by an experimental study of the temperature ranges of stability of each morph. The three main originalities of the method developed are (i) to prepare samples composed by an isomassic mixture of crystals of both morphs, (ii) to set them in a thermostated and agitated suspension, and (iii) to use an in situ Raman spectroscopic probe for the determination of the crystallographic form of the crystals in suspension at equilibrium. Both methods are applied to determine the solid–solid transition temperature of the enantiotropic system of Etiracetam, and both of its two crystallographic forms so far identified, named morph I and morph II. The first method is shown to be very sensitive to the experimental data obtained by DSC while the second experimental method is a more accurate, precise, time- and effort-friendly method for the determination of Ttr. The solid–solid transition temperature of the Etiracetam system, determined with the second method, using three different solvents, is found to be equal to 303.65 K ± 0.5 K. 相似文献
13.
Christelle Herman Tom Leyssens Valérie Vermylen Véronique Halloin Benoît Haut 《Journal of Thermal Analysis and Calorimetry》2012,107(2):777-788
This article focuses on the development of an innovative method, based on thermodynamic considerations and with the use of
Differential Scanning Calorimetry (DSC), for the estimation of the melting enthalpy of crystalline compounds which are metastable
near their melting temperature. The curves obtained, at various heating rates, are analysed in two steps. In the first step,
the area of a zone generated by the melting endothermic peak is calculated following a specific method. In the second step,
the melting enthalpy is extracted from this area through an enthalpy balance. This method is applied to both identified crystallographic
forms, named form I and form II, respectively, of Etiracetam (UCB Pharma). The results show that the melting enthalpy of the
stable form II compare well with the ones obtained using conventional methods. The curves of the metastable form I present
thermal instabilities (partial solid–solid polymorphic transition and beta-recrystallization) near the form I melting peak
leading to difficulties for a direct determination of the melting enthalpy by conventional methods. The proposed method is
therefore very useful for the estimation of the form I melting enthalpy. 相似文献
14.
15.
16.
17.
18.
H2SO4-SiO2固体酸的结构及酸性研究 总被引:2,自引:0,他引:2
以溶胶-凝胶法制备了H2SO4-SiO2固体酸催化剂,并对其结构和酸性进行了系统表征.FT—IR和^29Si—NMR结果表明H2SO4和SiO2间存在相互作用,因此硫酸与硅胶形成稳定的固体、XRD、SEM和TEM结果表明,H2SO4-SiO2固体酸是一多孔无定型材料;BET法测定的H2SO4-SiO2固体酸的比表面积和孔体积结果表明,随着H2SO4与SiO2质量比增加,其比表面减少,孔体积增大;H2SO4-SiO2固体酸的酸强度和液体浓硫酸相当,酸强度与干燥温度和H2SO4加入量有关,固体酸的这一性质以^1H—MAS NMR进行了系统的表征. 相似文献
19.
20.
The solution structure of the Pd(II) complex of mn-12-S4 was studied in detail by NMR spectroscopy. The stoichiometry of the complex was determined by 1H NMR titration experiments. 3J(H,H) coupling constants were extracted from the 2D J-resolved NMR spectrum of the complex providing information concerning the S-C-C-S torsional angles. Further conclusions about the conformation of [Pd(mn-12-S4)](BF4)2 were drawn from experimental NOEs. The results of the NMR study were corroborated by molecular modelling. 相似文献