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宋远涛铁杆木虫 (著名写手)
涛:tuzi24:
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求助乙腈的纯化工艺。。400金币
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| 主要是实验室用过的废乙腈，想重复使用。。。。 |
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leegane
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106楼2009-11-03 13:02:53
leegane
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Acetonitrile (methyl cyanide) [75-05-8] M 41.1, b 81.6°, d25 0.77683, n 1.3441, n25 1.34163. Commercial acetonitrile is a byproduct of the reaction of propylene and ammonia to acrylonitrile. The following procedure that significantly reduces the levels of acrylonitrile, allyl alcohol, acetone and *benzene was used by Kiesel [Anal Chem 52 2230 1988]. Methanol (30OmL) is added to 3L of acetonitrile fractionated at high reflux ratio until the boiling temperature rises from 64° to 80°, and the distillate becomes optically clear down to X = 240nm. Add sodium hydride (Ig) free from paraffin, to the liquid, reflux for lOmin, and then distil rapidly until about 10OmL of residue remains. Immediately pass the distillate through a column of acidic alumina, discarding the first 15OmL of percolate. Add 5g of CaH2 and distil the first 5OmL at a high reflux ratio. Discard this fraction, and collect the following main fraction. The best way of detecting impurities is by gas chromatography. Usual contaminants in commercial acetonitrile include F^O, acetamide, NH4OAc and NH3. Anhydrous CaSO4 and CaCl2 are inefficient drying agents. Preliminary treatment of acetonitrile with cold, satd aq KOH is undesirable because of base-catalysed hydrolysis and the introduction of water. Drying by shaking with silica gel or Linde 4A molecular sieves removes most of the water in acetonitrile. Subsequent stirring with CaH2 until no further hydrogen is evolved leaves only traces of water and removes acetic acid. The acetonitrile is then fractionally distd at high reflux, taking precaution to exclude moisture by refluxing over CaH2 [Coetzee Pure Appl Chem 13 429 1966]. Alternatively, 0.5-1% (w/v) P2O$ is often added to the distilling flask to remove most of the remaining water. Excess ?2O5 should be avoided because it leads to the formation of an orange polymer. Traces of ?2O5 can be removed by distilling from anhydrous ^CO3. |
107楼2009-11-03 13:03:15