N,N-Dimethylformamide (DMF) (68-12-2) 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 vacuumjacketed
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 Burfield and 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.
[ Last edited by lovehappy2008 on 2009-2-23 at 20:58 ]，
返回小木虫查看更多
京公网安备 11010802022153号
一般无水的话，加点干燥剂就可以了。
绝对无水的话，加点钠等类型干燥剂，蒸馏。
N,N-Dimethylformamide (DMF) (68-12-2) 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 vacuumjacketed
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 Burfield and 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.
[ Last edited by lovehappy2008 on 2009-2-23 at 20:58 ]，
我除水一般是先用无水硫酸镁处理一个星期，然后减压蒸馏，温度不能太高，收集最中间的馏分。基本可以满足做无水反应的要求。
N，N-二甲基甲酰胺 沸点149~156℃，折光率1.430 5，相对密度0.948 7。
无色液体，与多数有机溶剂和水可任意混合，对有机和无机化合物的溶解性能较好。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。
无水硫酸镁干燥24小时，发现不结块后，用氢化钠回流4小时，减压蒸出
五氧化二磷泡上几天，再减压蒸馏，除水又除胺，很好用
上面的方法都很好，如果要求不是绝对无水的话，可以把5A分子筛在马弗炉里烘过后冷却，加入DMF里面，我曾经试过。