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请问如何精制DMF
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| 我的样品主要是怕水,请问如何精制DMF,麻烦大哥们教教小弟,把具体怎么操作,以及条件什么等的参数稍微写详细一点告诉一下... |
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4楼2007-12-13 17:22:06
2楼2007-12-13 17:12:22
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sinevil(金币+2,VIP+0):谢谢
sinevil(金币+2,VIP+0):谢谢
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，DMF和P2O5回流（每次P2O5蒸的时候里面都是黑乎乎的，不过还比较好洗干净），体系往往呈红棕色，而且有难闻气味。你可在DMF中加入固体氢氧化钠，回流后将DMF减压蒸出就是。 2，DMF常含有水 ，乙醇，伯胺，仲胺等杂质，并能与2分子水形成HCON（CH3）2。H2O。要得到高纯度的产品，可使用干燥剂与蒸馏并用的方法。首先加入1/10体积的苯，常压下共沸以除水。再按下列方法精制：a加入无水硫酸镁（25g/L）干燥，减压2-2.67kPa蒸馏；b加入粉状氧化钡，搅动后倾出液体，减压蒸馏；c加入氧化铝粉末（50g/L，500-600）度烧成，混合摇动，减压（0.67kPa-1.33kPa) 蒸馏；d加入三苯基氯硅烷（5-10g/L），120-140度加热24小时后减压（0.67kPa) 蒸馏。四种方法任选一 3，最简单最简单的方法是用氢化钙在5， 60度左右搅拌4， 5个小时，或者过夜，然后减压蒸馏，收集是去头去尾。如果你循环水泵好的情况下，大概在50-60度就可以出来。保存时可以用分子筛，最好不要用碱，密闭保存。 4，如果不是要求很苛刻的话, 只需减压蒸馏, 蒸出的前部分液体可不要, 蒸出大部分的液体做一般性的反应足以.原因: DMF与水为共沸物 |
3楼2007-12-13 17:16:23
xiqizhizi
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sinevil(金币+1,VIP+0):谢谢
sinevil(金币+1,VIP+0):谢谢
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提纯手册是这样介绍的：Dimethylformamide (DMF) [68-12-2] M 73.1, b 40°/10mm, 61°/30mm, 88°/100mm, 153°/760mm, d 0.948, n25 1.4269, pK -0.3. Decomposes slightly at its normal boiling point to give small amounts of dimethylamine and carbon monoxide. The decomposition is catalysed by acidic or basic materials, so that even at room temperature DMF is appreciably decomposed if allowed to stand for several hours with solid KOH, NaOH or CaH2. If these reagents are used as dehydrating agents, therefore, they should not be refluxed with the DMF. Use of CaSO4, MgSO4, silica gel or Linde type 4A molecular sieves is preferable, followed by distn under reduced pressure. This procedure is adequate for most laboratory purposes. Larger amounts of water can be removed by azeotropic distn with *benzene (10% v/v, previously dried over CaH2>, at atmospheric pressure: water and *benzene distil below 80°. The liquid remaining in the distn flask is further dried by adding MgSO4 (previously ignited overnight at 300-400°) to give 25g/L. After shaking for one day, a further quantity of MgSO4 is added, and the DMF distd at 15-20mm pressure through a 3-ft vacuumjacketed column packed with steel helices. However, MgSO4 is an inefficient drying agent, leaving about 0.01M water in the final DMF. More efficient drying (to around 0.001-0.007M water) is achieved by standing with powdered BaO, followed by decanting before distn, with alumina powder (50g/L; previously heated overnight to 500-600°), and distilling from more of the alumina; or by refluxing at 120-140° for 24h with triphenylchlorosilane (5-10g/L), then distilling at ca 5mm pressure [Thomas and Rochow J Am Chem Soc 79 1843 /957]. Free amine in DMF can be detected by colour reaction with l-fluoro-2,4-dinitrobenzene. It has also been purified by drying overnight over KOH pellets and then distd from BaO through a 10 cm Vigreux column [Exp Cell Res 100 213 7976]. [For efficiency of desiccants in drying dimethylformamide see Burfield and Smithers [/ Org Chem 43 3966 1978, and for a review on purification, tests of purity and physical properties, see Juillard Pure Appl Chem 49 885 7977]. |
5楼2007-12-13 18:47:03
