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zed
International Hazard
Posts: 2283
Registered: 6-9-2008
Location: Great State of Jefferson, City of Portland
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Mood: Semi-repentant Sith Lord
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I've prepared Benzyl Magnesium Chloride on several occasions. Never had a problem.
Used the I2 method however. Put the Magnesium in my reaction vessel, then I fitted the vessel with a dropping funnel and a reflux condenser.
Thereafter, I warmed the Magnesium in the flask, turned off the heat, dropped a crystal of Iodine down from the top of the condenser, dripped in a
few drops of Benzyl Chloride mixed with Ether.....And Shazzam! The reaction always started immediately.
If you are not familiar with Benzyl Chloride, it is a lacrimator. And, while you CAN run a Benzyl Chloride Grignard reaction outside of a fume hood,
you will probably find it very unpleasant.
As for drying wet Ether.....in the past, I found that Sodium wire alone, was inadequate for drying cold, wet, recycled Ether. At least, for Ether
destined for LiAlH4 reductions. Drying by some other method, or pre-drying by some other method, is a good idea.
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S.C. Wack
bibliomaster
Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
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Well I didn't think that there were any more drying articles by Burfield and Smithers to find, but I found another one. Now this does not use NaOH,
nor are they "Drying ethers over P2O5", but I mention this here because MgSO4, sieves, and CaCl2 are mentioned in this thread.
Here various things were tried drying wet (14.7 mg/g) ether, with a maximum drying time of 6 hours. MgSO4 (like everything else listed here, this was
heated to 350C overnight, loading at 10% wt/vol with intermittent shaking) gave residual water content 1.8 mg/g.
CaCl2 powder, 0.24 mg/g. 0.39 mg/g in pellet form.
4A bead: 0.29 mg/g.
4A powder: 0.095 mg/g. Inexplicably, this is a higher number than the amount of water at 15 minutes (0.092), 30 minutes (0.076), and 1 hour (0.027,
the lowest figure in the article, JCE 703, 1982)
5% loading = more water in all cases, especially with the sieve powder.
[Edited on 19-7-2009 by S.C. Wack]
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peach
Bon Vivant
Posts: 1428
Registered: 14-11-2008
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Curly arrow has an excellent blog entry on anhydrous solvents. Also have a read of the comments.
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