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991.
Isabela P. Veronez Josiane S. P. Daniel Jerusa S. Garcia Marcello G. Trevisan 《Journal of Thermal Analysis and Calorimetry》2014,115(3):2407-2414
Desloratadine (DL) is a selective antagonist of the histamine H1 receptor, which has been widely used to treat allergic symptoms, and stands out from other drugs in this therapeutic class because it does not cause sedative effects. In the present study, the physico-chemical properties of DL were fully characterized using six analytical techniques such as Differential Scanning Calorimetry (DSC), Thermogravimetric analysis (TG/DTG), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, Powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). The DSC curve shows a sharp endothermic event at 158.4 °C, and the TG/DTG curve presents two decomposition events between 178.4 and 451.9 °C. A compatibility study involving DL and nine pharmaceutical excipients generally used in pharmaceutical formulations was performed. Physical binary mixtures of DL with each excipient were prepared in a 1:1 (w/w) ratio. After preparation, the samples were analyzed immediately and the results reveal solid-state interaction with anhydrous lactose, microcrystalline cellulose, magnesium stearate, and stearic acid. 相似文献
992.
Petr Brázda Eva Večerníková Eva Pližingrová Adriana Lančok Daniel Nižňanský 《Journal of Thermal Analysis and Calorimetry》2014,117(1):85-91
Thermal behavior of highly crystalline ε-Fe2O3 nanoparticles of different apparent crystallite sizes was characterized using thermogravimetry, differential thermal analysis, and analysis of evolved gas by mass spectrometry. Phase composition of the samples was monitored ex situ by X-ray powder diffraction. The results show that the thermal stability of this metastable iron oxide polymorph decreases with increasing particle size. For the particle diameter of 19(2) nm, the transformation temperature was equal to 794(5) °C, while for 28(2) nm only 755(10) °C. Surface of the nanoparticles contained adsorbed water and carbon dioxide. Elimination of these species proceeds in two steps. Water is removed at temperatures below 200 °C and CO2 in the temperature range between 200 and 450 °C. 相似文献
993.
Lucas Stiegler Ribeiro Layse do Prado Cordoba Tiago André Denck Colman Cristina Soltovsti de Oliveira Marina Morena Pereira Andrade Egon Schnitzler 《Journal of Thermal Analysis and Calorimetry》2014,117(2):935-942
When starch is incorporated into puddings, desserts, and other foods containing sugar as the main ingredient, it will have an effect on the gelatinisation temperature and pasting properties. Many studies have been undertaken to investigate the effect of several sugars in foods and starches, as well as their physicochemical and functional properties. These studies have verified the significant influence on these properties, which are dependent on the nature of sugar and of starch. In this study, pinhão starch was extracted in the laboratory and was added, stirring for 60 min, to solutions at 1 % of each of the following sugars: fructose, glucose, sucrose, and 0.5 % fructose and 0.5 % glucose. After this time, the slurry was filtered, washed, dried at 40 °C and kept in a desiccator over anhydrous calcium chloride until constant mass. The effects of each sugar on the surface of the pinhão starch granules were observed using the non-contact method of atomic force microscopy, whereby it was possible to verify a decrease in the average diameter and an increase in the average roughness. X-ray diffractometry made it possible to evaluate the degree of relative crystallinity, which was proportional to the roughness and inversely proportional to the gelatinisation enthalpy (ΔH), which was studied by differential scanning calorimetry. 相似文献
994.
Acylsilanes in Rhodium(III)‐Catalyzed Directed Aromatic C–H Alkenylations and Siloxycarbene Reactions with CC Double Bonds 下载免费PDF全文
Peter Becker Dr. Daniel L. Priebbenow Ramona Pirwerdjan Prof. Dr. Carsten Bolm 《Angewandte Chemie (International ed. in English)》2014,53(1):269-271
Acylsilanes are known to undergo a 1,2‐silicon‐to‐oxygen migration under thermal or photochemical conditions to form siloxycarbenes. However, there are few reports regarding the application of siloxycarbenes in organic synthesis and surprisingly, their reaction with C? C double or triple bonds remains virtually unexplored. To facilitate such a study, previously inaccessible aromatic acylsilanes containing an ortho‐tethered C? C double bond were identified as suitable substrates. To access these key intermediates, we developed a new synthetic method utilizing a rhodium‐catalyzed oxidative Heck‐type olefination involving the application of an acylsilane moiety as a directing group. When exposed to visible‐light irradiation, the ortho‐olefinated acylsilanes underwent a smooth intramolecular cyclization process to afford valuable indanone derivatives in quantitative yields. This result paves the way for the development of new transformations involving siloxycarbene intermediates. 相似文献
995.
Dehydrogenative Meyer–Schuster‐Like Rearrangement: A Gold‐Catalyzed Reaction Generating an Alkyne 下载免费PDF全文
M. Sc. Yang Yu M. Sc. Weibo Yang M. Sc. Daniel Pflästerer Prof. Dr. A. Stephen K. Hashmi 《Angewandte Chemie (International ed. in English)》2014,53(4):1144-1147
Easily accessible propargylic esters are converted to the inverted alkynyl ketones in an oxidative gold‐catalyzed reaction. Gagosz’s catalyst in combination with PhI(OAc)2 is the best system for this conversion and 18 examples with yields up to 80 % are reported. The results indicate that the triple bond in the product is formed by elimination from a vinylgold intermediate. In a formal sense the new conversion overall is a dehydrogenative Meyer–Schuster rearrangement. 相似文献
996.
Ortal Haik Francis Susai Amalraj Daniel Hirshberg Luba Burlaka Michael Talianker Boris Markovsky Ella Zinigrad Doron Aurbach Jordan K. Lampert Ji-Yong Shin Martin Schulz-Dobrick Arnd Garsuch 《Journal of Solid State Electrochemistry》2014,18(8):2333-2342
Thermodynamic instability of positive electrodes (cathodes) in Li-ion batteries in humid air and battery solutions results in capacity fading and batteries degradation, especially at elevated temperatures. In this work, we studied thermal interactions between cathode materials Li2MnO3, xLi2MnO3 .(1???x)Li(MnNiCo)O2,LiNi0.33Mn0.33Co0.33O2, LiNi0.4Mn0.4Co0.2O2, LiNi0.8Co0.15Al0.05O2 LiMn1.5Ni0.5O4, LiMn(or Fe)PO4, and battery solutions containing ethylene carbonate (EC) or propylene carbonate (PC), dimethyl carbonate (DMC) or ethylmethyl carbonate (EMC) and LiPF6 salt in the temperature range of 40–400 °C. It was found that these materials are stable chemically and well performing in LiPF6-based solutions up to 60 °C. The thermal decomposition of the electrolyte solutions starts >180 °C. The macro-structural transformations of cathode materials upon exothermic reactions were studied by transmission electron microscopy (TEM), X-ray difraction (XRD) and Raman spectroscopy. Differential scanning calorimetry (DSC) studies have shown that the exothermic reactions in the temperature range of 60–140 °C lead to partial decomposition of both the cathode material and electrolyte solution. The systems thus formed consisted of partially decomposed solutions and partially chemically delithiated cathode materials covered by reactions products. Thermal reactions terminate and this system reaches equilibrium at about 120 °C. It remains stable up to the beginning of the solution decomposition at about 180 °C. The increased content of surface Li2CO3 is found to significantly affect the thermal processes at high temperature range due to extensive exothermic decomposition at low temperatures. 相似文献
997.
Probing the CH⋅⋅⋅π Weak Hydrogen Bond in Anesthetic Binding: The Sevoflurane–Benzene Cluster 下载免费PDF全文
Nathan A. Seifert Dr. Daniel P. Zaleski Dr. Cristóbal Pérez Dr. Justin L. Neill Prof. Brooks H. Pate Montserrat Vallejo‐López Prof. Alberto Lesarri Dr. Emilio J. Cocinero Prof. Fernando Castaño Prof. Isabelle Kleiner 《Angewandte Chemie (International ed. in English)》2014,53(12):3210-3213
Cooperativity between weak hydrogen bonds can be revealed in molecular clusters isolated in the gas phase. Here we examine the structure, internal dynamics, and origin of the weak intermolecular forces between sevoflurane and a benzene molecule, using multi‐isotopic broadband rotational spectra. This heterodimer is held together by a primary C? H???π hydrogen bond, assisted by multiple weak C? H???F interactions. The multiple nonbonding forces hinder the internal rotation of benzene around the isopropyl C? H bond in sevoflurane, producing detectable quantum tunneling effects in the rotational spectrum. 相似文献
998.
Weijie Chen Dr. YoungKu Kang Dr. Richard G. Wilde Prof. Dr. Daniel Seidel 《Angewandte Chemie (International ed. in English)》2014,53(20):5179-5182
In contrast to the continuously growing number of methods that allow for the efficient α‐functionalization of amines, few strategies exist that enable the direct functionalization of amines in the β‐position. A general redox‐neutral strategy is outlined for amine β‐functionalization and α,β‐difunctionalization that utilizes enamines generated in situ. This concept is demonstrated in the context of preparing polycyclic N,O‐acetals from simple 1‐(aminomethyl)‐β‐naphthols and 2‐(aminomethyl)‐phenols. 相似文献
999.
Beatriz B. Caravieri Pollyanna F. de Oliveira Ricardo A. Furtado Denise C. Tavares Eduardo J. Nassar Katia J. Ciuffi Eduardo F. Molina 《Journal of Sol-Gel Science and Technology》2014,72(3):627-636
Herein, we used tri-ureasil organic–inorganic hybrid material (tU5000) in order to enhance the solubility of nonsteroidal anti-inflammatory drugs and fine tuning the drug delivery profile. For the first time, we used tU5000 as a film-forming agent in order to provide an alternative vehicle for transdermal drug delivery systems which the cell viability of practically 100 % for the highest and the lowest tested concentrations of pure tU5000 indicated that the material was not cytotoxic. The physicochemical properties of the tU5000 drug carrier and drug-loaded hybrids were systematically studied using powder X-ray diffraction, differential scanning calorimetry, small-angle X-ray scattering, and Fourier-transform infrared spectroscopy. The structural changes of tU5000 as well as the relationships between the drug content and in vitro drug release behaviors were investigated. The results showed that the ibu molecules were homogeneously distributed in the tU5000 xerogels contributing to fine-tuning the drug delivery profile. Considering the ability to incorporated high drug content, simple and mild preparation procedure by one-pot sol–gel route, high stability of the materials, sustained-release property, this class of hybrid based on polymers and inorganic compounds may have potential applications in the design of pharmaceutical formulation as ophthalmic (contact lenses), transdermal (patches) and implantable (soft tissue) drug delivery systems. 相似文献
1000.
Frontispiece: A Multicomponent Conjugation Strategy to Unique N‐Steroidal Peptides: First Evidence of the Steroidal Nucleus as a β‐Turn Inducer in Acyclic Peptides 下载免费PDF全文