共查询到20条相似文献,搜索用时 453 毫秒
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借助手持技术通过滴定的方法探究了碳酸氢钠与氯化钙溶液的反应原理,根据相关文献知识和实验对比研究,结合相关实验数据从定量和定性的角度深度分析了碳酸氢钠溶液与氯化钙溶液反应生成沉淀和产生气体的可能性。 相似文献
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盐酸、氯化钙混合溶液中滴加碳酸钠溶液,当碳酸钙沉淀出现后,混合溶液pH是否基本不变?此时的pH是否为7?为此用数字化实验对盐酸、氯化钙混合溶液中滴加碳酸钠溶液pH的变化进行了探讨,对平台段的出现及平台段溶液pH进行了实验探究和理论分析。 相似文献
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马冬云 《理化检验(化学分册)》2002,38(7):367-367,378
煤制气的副产品氨在回收时 ,工艺上对氨溶液中二氧化碳含量要求十分严格 ,因为二氧化碳与氨水形成碳酸铵结晶堵塞管道和腐蚀管道。原设计手册中的分析方法是先将氨溶液中的二氧化碳蒸出 ,用氢氧化钡溶液吸收 ,再用硫酸标准溶液滴定。该方法不但所需时间长 ,氢氧化钡溶液易吸收二氧化碳而形成碳酸钡沉淀 ,而且误差大。本法用过量氢氧化钠溶液吸收氨溶液中二氧化碳 ,再用硫酸滴定混合碱的滴定方法。在消除氨、硫化氢及氰化氢的干扰后 ,能快速准确地测定氨溶液中的二氧化碳含量。吸收和滴定反应如下 :CO2 +2NaOH =Na2 CO3 +H2 O2N… 相似文献
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运用溶度积计算出与氢氧化镁沉淀相关的反应、与硫化铜沉淀相关的反应、与碳酸钙沉淀相关的反应的平衡常数。通过以上的计算与分析,让学生熟练掌握了运用溶度积计算化学平衡常数,从而判断反应能否发生。 相似文献
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传统实验方法较难判断干冰能否与氢氧化钠溶液反应,更无法呈现其反应的过程。通过验证生成物的实验可以判断干冰与氢氧化钠溶液反应,成功实现将无明显现象反应变成有明显现象反应。运用手持技术数字化实验将“不可见”的化学实验现象转化为“可观测”的数据与曲线图像,以及探究反应产物与氢氧化钠溶液浓度的关系,从而实现对二氧化碳化学性质的深度学习。 相似文献
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对有机胺介质中CaCl2与二氧化碳的碳酸化反应进行了研究,在二氧化碳压力为2MPa~5MPa、CaCl2浓度为1.31mol/L~2.44mol/L下考察了压力和浓度对该多相反应体系碳酸钙收率和有机胺萃取效率的影响。结果表明,碳酸化反应过程中碳酸钙收率和有机胺萃取效率随二氧化碳压力和CaCl2初始浓度的增大而增加。结合Pitzer电解质溶液模型、二氧化碳溶解模型对该多相反应进行热力学平衡分析。有机胺的萃取平衡决定了HCl在有机相和水相的分配平衡,水相中H+浓度限制H2CO3解离,制约碳酸钙沉淀反应。CaCl2浓度大小影响了HCO3-和CO32-的活度系数,对沉淀/溶解平衡也有一定影响。热力学平衡转化率与实验结果接近,表明该反应受化学反应平衡控制。 相似文献
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In this report, we try to show the importance of incorporation of name reactions in the sequential cascade reaction in which significantly decreasing the number of steps towards an ideal and practical multi-step synthesis of natural products as well showing virtually all the advantages already mentioned for “Click Chemistry”. In addition, since the chiral inductions are desired for most of these sequential name reactions, their asymmetric catalyzed reactions were also described. 相似文献
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《Green Chemistry Letters and Reviews》2013,6(4):311-320
Abstract In the second part of our paper, further recent developments of ionic liquids in selected name reactions of carbonyl chemistry such as Mannich, Reformatsky, Cannizaro, Streacker, Barbier, Pechmann, etc. are described. 相似文献
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Thermal reaction of 2-[N-(alk-2-enyl)benzylamino]-3-(2-substituted and 2,2-disubstituted)vinylpyrido[1,2-a]pyrimidin-4(4H)-ones gave azepine, the desired ene products, and/or pyran derivatives. The formation of the latter was responsible for the [4+2] cycloaddition reaction between the α,β-unsaturated ester carbonyl moiety as a diene part and the alkenylamino moiety as an ene one. The reaction features depended upon the kinds of substituents both on the vinyl and alkenyl counterparts; strongly electron-withdrawing substituents on the vinyl moiety or an electron-donating substituent on the alkenyl one changed the reaction feature from the ene reaction to the hetero Diels-Alder reaction. 相似文献
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Palladium bis(2,2,6,6-tetramethyl-3,5-heptanedionate) catalyzed Suzuki, Heck, Sonogashira, and cyanation reactions 总被引:1,自引:0,他引:1
Nitin S. Nandurkar 《Tetrahedron》2008,64(17):3655-3660
Palladium bis(2,2,6,6-tetramethyl-3,5-heptanedionate): a structurally well-defined O-containing transition metal complex is reported as an efficient catalyst for Suzuki, Heck, and Sonogashira cross-coupling reactions. The protocol was also applied successfully for cyanation of aryl halides under milder operating conditions. The system tolerated the coupling of various aryl halides with alkenes, alkynes, and organoboronic acid along with the cyanation of aryl halides providing good to excellent yields of desired products. 相似文献
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Arash Ghorbani‐Choghamarani Masoud Mohammadi Robert H.E. Hudson Taiebeh Tamoradi 《应用有机金属化学》2019,33(8)
A boehmite@tryptophan‐Pd nanoparticulate catalyst was prepared by a simple, fast and convenient route. The nanomaterial was characterized using various techniques and employed as a thermally stable catalyst for Heck, Stille and Suzuki cross‐coupling reactions. Optimized conditions for these reactions are described. The catalyst could be isolated, post‐reaction, by simple filtration and recycled for several consecutive cycles without a notable change in its activity. 相似文献
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Thomas A. Klein 《Tetrahedron letters》2005,46(27):4535-4538
Dimethylnitro alcohols are constructed in a one-pot process from benzylic halides and 2-nitropropane. The use of tetrabutylammonium fluoride (TBAF) as the promoter is essential for this tandem Hass-Bender/Henry reaction to proceed. 相似文献
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温度和时间对有机合成反应影响的探讨 总被引:1,自引:0,他引:1
根据物理化学和有机合成原理,从动力学、热力学、反应机理及溶解度等各方面详细分析了反应温度和反应时间对有机合成反应的影响。通过这些分析,可以让同学们更好地在合成反应课程的学习中掌握和分析反应温度和反应时间对反应的影响。 相似文献
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钯催化的交叉偶联反应是非常实用的合成新方法.文章给出了Heck反应、Negishi反应和Suzuki反应的概念,对其反应机理作了详细的说明,并对其在复杂化合物和天然产物全合成中的应用作了评价. 相似文献