问题：请教二氧六环的纯化
类型：求助 (悬赏分:3分)
提问：rms
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版块：有机化学问题(jimuwei,fpcwin1211,netpanda,yjgzfl,Ftian,)
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回复：6
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时间：2006-02-09 11:12:45 编辑加入/取消收藏订制/取消短消息举报该贴

我现在的实验需要无水二氧六环。不知到二氧六环需要纯化吗。我的实验中有原剂氢化钠存在。如果需要纯化应该怎么操作呢。谢谢

回复人：flychem,★ () 时间：2006-02-09 12:33:55 编辑	1楼
发到你的注册邮箱一篇关于溶剂纯化方面的资料，请查收。

回复人：Ftian,★★ (资料请发到我的邮箱里，这里封纳米盘。) 时间：2006-02-09 13:21:27 编辑	2楼
和乙醚的纯化基本相同。

回复人：linyu,▲ (好多的时候我都在努力创造.) 时间：2006-02-09 16:33:37 编辑	3楼
有机实验书上一般都会列出写溶剂的提纯方法的介绍．你可以很容易看到的

回复人：moon,▲▲ () 时间：2006-02-09 17:49:40 编辑	4楼
500ml二氧六环中加入8ml浓盐酸和50ml水,回流6-10h,在回流过程中慢慢通入氮气除去生成的乙醛.冷却,加固体氢氧化钾,直到不能溶解为止.分去水层,再用固体氢氧化钾干燥24 h.过滤,在金属钠存在下回流8-12h,最后在金属钠存在下蒸馏.

回复人：zhangquee,▲▲▲▲ (药物合成) 时间：2006-02-09 20:14:21 编辑

5楼

1,4-Dioxane [123-91-1] M 88.1, f 11.8°, b 101.3°, d25 1.0292, n15 1.4236, n25 1.42025.
Prepared commercially either by dehydration of ethylene glycol with H2SO4 and heating ethylene oxide or bis(6-
chloroethyl)ether with NaOH. Usual impurities are acetaldehyde, ethylene acetal, acetic acid, water and
peroxides. Peroxides can be removed (and the aldehyde content decreased) by percolation through a column of
activated alumina (8Og per 100-20OmL solvent), by refluxing with NaBH4 or anhydrous stannous chloride and
distilling, or by acidification with cone HCl, shaking with ferrous sulfate and leaving in contact with it for 24h
before filtering and purifying further.
Hess and Frahm [Chem Ber 71 2627 1938] refluxed 2L of dioxane with 27mL cone HCl amd 20OmL water for
12h with slow passage of nitrogen to remove acetaldehyde. After cooling the soln KOH pellets were added
slowly and with shaking until no more would dissolve and a second layer had separated. The dioxane was
decanted, treated with fresh KOH pellets to remove any aq phase, then transferred to a clean flask where it was
refluxed for 6-12h with sodium, then distd from it. Alternatively, Kraus and Vingee [J Am Chem Soc 56 511
1934] heated on a steam bath with solid KOH until fresh addition of KOH gave no more resin (due to
acetaldehyde). After filtering through paper, the dioxane was refluxed over sodium until the surface of the metal
was not further discoloured during several hours. It was then distd from sodium.
The acetal (b 82.5°) is removed during fractional distn. Traces of *benzene, if present, can be removed as the
*benzene/MeOH azeotrope by distn in the presence of MeOH. Distn from LiAlH4 removes aldehydes, peroxides
and water. Dioxane can be dried using Linde type 4X molecular sieves. Other purification procedures include
distn from excess C2H5MgBr, refluxing with PbO2 to remove peroxides, fractional crystn by partial freezing and
the addition of KI to dioxane acidified with aq HCl. Dioxane should be stored out of contact with air, preferably
under N2.
A detailed purification procedure is as follows: Dioxane was stood over ferrous sulfate for at least 2 days, under
nitrogen. Then water (10OmL) and cone HCl (14mL) / litre of dioxane were added (giving a pale yellow colour).
After refluxing for 8-12h with vigorous N2 bubbling, pellets of KOH were added to the warm soln to form two
layers and to discharge the colour. The soln was cooled rapidly with more KOH pellets being added (magnetic
stirring) until no more dissolved in the cooled soln. After 4-12h, if the lower phase was not black, the upper
phase was decanted rapidly into a clean flask containing sodium, and refluxed over sodium (until freshly added
sodium remained bright) for Ih. The middle fraction was collected (and checked for minimum absorbency below
250nm). The distillate was fractionally frozen three times by cooling in a refrigerator, with occasional shaking
or stirring. This material was stored in a refrigerator. For use it was thawed, refluxed over sodium for 48h, and
distilled into a container for use. All joints were clad with Teflon tape.
Coetzee and Chang [Pure Appl Chem 57 633 1985] dried the solvent by passing it slowly through a column
(20g/L) of 3A molecular sieves activated by heating at 250° for 24h. Impurities (including peroxides) were
removed by passing the effluent slowly through a column packed with type NaX zeolite (pellets ground to
O.lmm size) activated by heating at 400° for 24h or chromatographic grade basic A^Oa activated by heating at
250° for 24h. After removal of peroxides the effluent was refluxed several hours over sodium wire, excluding
moisture, distilled under nitrogen or argon and stored in the dark.
One of the best tests of purity of dioxane is the formation of the purple disodium benzophenone complex during
reflux and its persistence on cooling. (Benzophenone is better than fluorenone for this purpose, and for the
storing of the solvent.) [Carter, McClelland and Warhurst Trans Faraday Soc 56 343 I960]. TOXIC.
Rapid purification: Check for peroxides (see Chapter 1 and Chapter 2 for test under ethers). Pre-dry with
CaCl2 or better over Na wire. Then reflux the pre-dried solvent over Na (1% w/v) and benzophenone (0.2% w/v)
under an inert atmosphere until the blue colour of the benzophenone ketyl radical anion persists. Distil, and
store over 4A molecular sieves in the dark.

回复人：rms,▲ () 时间：2006-03-01 19:50:19 编辑	6楼
已经打分了。

得分人：flychem-1,zhangquee-1,

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