N,N-Dimethylformamide (DMF) (68-12-21 M 73.1, b 40°/10mm, 61°/30mm, 88°1100mm, 153°/760mm, d 0.948, nZ5 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 CaS04, MgS04, 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 800. The liquid remaining in the distn flask is further dried by adding MgS04 (previously ignited overnight at 300-4000) to give 25gL After shaking for one day, a further quantity of MgS04 is added, and the DMF distd at 15-20mm pressure through a 3-ft vacuum- jacketed column packed with steel helices. However, MgS04 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 (50gL; 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 1957. 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 19761. [For efficiency of desiccants in drying dimethylformamide see Burfieldand Smithers [J Org Chem 43 3966 1978, and for a review on purification, tests of purity and physical
properties, see Juillard Pure Appl Chem 49 885 1977.
It has been purified by distilling from K2CO3 under high vac and fractionated in an all-glass apparatus. The middle fraction is collected, degassed (seven or eight freeze-thaw cycles) and redistd under as high a vacuum as possible [Mohammad and Kosower JAm Chem Soc 93 2713 19711.
Rapid purification: Stir over CaH2 (5% w/v) overnight, filter, then distil at 20mmHg. Store the distd DMF over 3A or 4A molecular sieves. For solid phase synthesis, the DMF used must be of high quality and free from amines
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要求不高就分子筛干燥; 较高要求就用CaH2回流后减压蒸出
如果你的产品对温度稳定的话，可以85 度用油泵抽。
2楼的方法是常用的
N,N-Dimethylformamide (DMF) (68-12-21 M 73.1, b 40°/10mm, 61°/30mm, 88°1100mm, 153°/760mm, d 0.948, nZ5 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 CaS04, MgS04, 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 800. The liquid remaining in the distn flask is further dried by adding MgS04 (previously ignited overnight at 300-4000) to give 25gL After shaking for one day, a further quantity of MgS04 is added, and the DMF distd at 15-20mm pressure through a 3-ft vacuum- jacketed column packed with steel helices. However, MgS04 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 (50gL; 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 1957. 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 19761. [For efficiency of desiccants in drying dimethylformamide see Burfieldand Smithers [J Org Chem 43 3966 1978, and for a review on purification, tests of purity and physical
properties, see Juillard Pure Appl Chem 49 885 1977.
It has been purified by distilling from K2CO3 under high vac and fractionated in an all-glass apparatus. The middle fraction is collected, degassed (seven or eight freeze-thaw cycles) and redistd under as high a vacuum as possible [Mohammad and Kosower JAm Chem Soc 93 2713 19711.
Rapid purification: Stir over CaH2 (5% w/v) overnight, filter, then distil at 20mmHg. Store the distd DMF over 3A or 4A molecular sieves. For solid phase synthesis, the DMF used must be of high quality and free from amines
书上是这样说的，
我做硕士论文时用的就是严格无水的DMF做溶剂。首先对其进行蒸馏，常压就可以，去掉前后两部分馏分，去中间部分后放入预备容器中，然后干燥若干4A分子筛，将其在马弗炉中800度烘几个小时即可。然后将其放入DMF中静置一夜即可得到严格无水的DMF。
楼上的，常压蒸馏DMF不是部分分解了吗？
N，N-二甲基甲酰胺含有少量水分。常压蒸馏时有些分解，产生二甲胺和一氧化碳。在有酸或碱存在时，分解加快。所以加入固体氢氧化钾（钠）在室温放置数小时后，即有部分分解。因此，最常用硫酸钙、硫酸镁、氧化钡、硅胶或分子筛干燥，然后减压蒸馏，收集76℃/4800Pa(36mmHg)的馏分。其中如含水较多时，可加入其1/10体积的苯，在常压及80℃以下蒸去水和苯，然后再用无水硫酸镁或氧化钡干燥，最后进行减压蒸馏。纯化后的N，N-二甲基甲酰胺要避光贮存。N，N-二甲基甲酰胺中如有游离胺存在，可用2，4二硝基氟苯产生颜色来检查。