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51.
52.
Zhou WANG Rong LAI Min PENG Saili ZHENG Lianyun LI Kejia ZHU Xianfang XU Liuping CHEN Jianxin SHI 《大学化学》2018,33(10):39-44
A survey about students' laboratory safety and environmental protection consciousness was performed in the freshmen majored in chemistry at Sun Yat-Sen University. Results showed that laboratory safety and environmental protection consciousness of most students' are weak. After analyzing the reasons, we put forward some suggestions. Cultivating students' laboratory safety and environmental protection consciousness should be carried out from several aspects such as emphasizing and regulating from school level, training in laboratory teaching, maintaining good cultural atmosphere of laboratory, as well as providing perfect laboratory safety and environmental protection facilities. We should guide students to actively learn knowledge and skills of laboratory safety and environmental protection in order to develop their good behavior and raise their consciousness. 相似文献
53.
Hou Chien Chang Ching Hsuan Lin Hung Tse Lin Shenghong A. Dai 《Journal of polymer science. Part A, Polymer chemistry》2012,50(5):1008-1017
Generally, protection and deprotection procedures of amino groups are required in preparing propargyl ether‐containing benzoxazines. In this study, we report a facile, deprotection‐free preparation of a propargyl ether‐containing phosphinated benzoxazine (2) from the nucleophilic substitution of a phenolic OH‐containing phosphinated benzoxazine (1) and propargyl bromide in the catalysis of potassium carbonate. The structure of (2) was characterized and confirmed by a high‐resolution mass spectrum, 1H, 13C, 1H‐1H, 1H‐13C nuclear magnetic resonance (NMR) spectra, and X‐ray single crystal diffractogram. infrared (IR) and differential scanning calorimetry were used to monitor the ring‐opening of benzoxazine and crosslinking of propargyl ether. The microstructure and the structure–property relationship of the resulting homopolymers and copolymers are discussed. The Tg of homopolymer of (2) is 208 °C by dynamic mechanical analysis, the coefficient of thermal expansion is 43 ppm/°C, and Td 5% (N2) is 393 °C, respectively, which are higher than those of the homopolymer of (1) . Similar trends were observed in the copolymerization system. The results demonstrate the beneficial effect of crosslinking afforded by the propargyl ether group is higher than that by the phenolic OH group. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
54.
Structures of Highly Twisted Amides Relevant to Amide N−C Cross‐Coupling: Evidence for Ground‐State Amide Destabilization
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Dr. Vittorio Pace Prof. Dr. Wolfgang Holzer Guangrong Meng Shicheng Shi Prof. Dr. Roger Lalancette D.Sc. Roman Szostak Prof. Dr. Michal Szostak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(41):14494-14498
Herein, we show that acyclic amides that have recently enabled a series of elusive transition‐metal‐catalyzed N?C activation/cross‐coupling reactions are highly twisted around the N?C(O) axis by a new destabilization mechanism of the amide bond. A unique effect of the N‐glutarimide substituent, leading to uniformly high twist (ca. 90°) irrespective of the steric effect at the carbon side of the amide bond has been found. This represents the first example of a twisted amide that does not bear significant steric hindrance at the α‐carbon atom. The 15N NMR data show linear correlations between electron density at nitrogen and amide bond twist. This study strongly supports the concept of amide bond ground‐state twist as a blueprint for activation of amides toward N?C bond cleavage. The new mechanism offers considerable opportunities for organic synthesis and biological processes involving non‐planar amide bonds. 相似文献
55.
Prof. Juliusz Pernak Michał Niemczak Prof. Łukasz Chrzanowski Łukasz Ławniczak Przemysław Fochtman Katarzyna Marcinkowska Prof. Tadeusz Praczyk 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(34):12012-12021
This study focused on the synthesis and subsequent characterization of herbicidal ionic liquids based on betaine and carnitine, two derivatives of amino acids, which were used as cations. Four commonly used herbicides (2,4‐D, MCPA, MCPP and Dicamba) were used as anions in simple (single anion) and oligomeric (two anions) salts. The obtained salts were subjected to analyzes regarding physicochemical properties (density, viscosity, refractive index, thermal decomposition profiles and solubility) as well as evaluation of their herbicidal activity under greenhouse and field conditions, toxicity towards rats and biodegradability. The obtained results suggest that the synthesized herbicidal ionic liquids displayed low toxicity (classified as category 4 compounds) and showed similar or improved efficacy against weed compared to reference herbicides. The highest increase was observed during field trials for salts containing 2,4‐D as the anion, which also exhibited the highest biodegradability (>75 %). 相似文献
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57.
M. Veiderma T. Kaljuvee R. Knubovets M. Pôldme K. Tônsuaadu 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):125-128
Abstract The mechanisms of thermal transformations in different types of natural phosphates and their mixtures with H3PO4 and Na2CO3 are discussed. 相似文献
58.
K. Uhlig 《Isotopes in environmental and health studies》2013,49(2):37-42
0. Einleitwng 1. Reaktorwissenschaft und -technik und Kernenergetik 2. Kerntechnischer Gerätebau 3. Produktion von Isotopenerzeugnissen 4. Strahlenschulz und Schutztechnik 5. Isotopenanwendung 6. Strahlentechnik 7. Zur weiteren Tätigkeit der Ständigen Kommission Atomenergie des RGW 相似文献
59.
实验研究了基于以钢丝绳为基本元件的新型柔性防撞装置的防护性能.利用DEWETRON数据采集仪及多通道同步采集传感器的信号,分析得到防撞装置在碰撞中受到的撞击力曲线.实验结果显示:靠近船舶撞击侧最近的非撞击侧位置受到的撞击力最大,属防护重点部位;在承受多次撞击后,防撞装置基本完好,且船舶在碰撞中的损伤也有所减低. 相似文献
60.
Nobuhiro Takeda Norihiro Tokitoh Renji Okazaki 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):633-636
The first rotational isomers of stable selenoaldehydes are synthesized by deselenation of cyclic polyselenides having an efficient steric protection group, 2, 4, 6-tris[bis(trimetylsilyl)methyl]phenyl (Tbt). Reactions of these selenoaldehydes with W(CO)5.THF gives the corresponding η1-selenoaldehyde tungsten complexes, the structures of which are established by X-ray crystallography. 相似文献