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Crowfjord
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Here is another good read on Grignard reagents, their formation and use. It contains info on alternative solvents/solvent mixtures.
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Loptr
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Quote: Originally posted by Dr.Bob  | If you use a bucket of ice water and a fish tank pump, you can cool any condenser cool enough to condense ether fine. The key is to have at least
some ventilation, either doing it outside, in a hood, or at least in front of an open window with a fan blowing air into the building somewhere away
from the reaction. (Don't want fan blow air out the window by the ether, that sucks fumes through a sparky motor...) Ethers are best for
Grignard, some aromatics might work, but DCM I have never seen used; I suspect it is very bad, but don't have proof.
BTW, ether's flash point is -40C (or F), which is the temp. at which there are fumes enough to ignite from a spark. It has an autoignition point of
160C, which is the point at which it will catch fire without a spark present. So it is very easy to ignite ether with a spark from a motor, static,
whatever, or even without a spark, if it's fumes gets near a hot light bulb, warm hotplate or oven, it can ignite even without a spark at those
temperatures. That is why it is put into engine starting fluid, as it will burn with almost any excuse.
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I think what needs to be differentiated here is the solvent used to form the Grignard reagent, or other organometalic, and the solvent used to perform
the reaction with a substrate.
I know I keep saying "I have read", but here goes another; I have read about usage of diethyl ether/dichloromethane to help solvate particularly
insoluble Grignard reagents (Acetylides ring a bell for some reason)
I actually have that document open in one of my browser tabs when you posted. lol.
[Edited on 27-3-2015 by Loptr]
EDIT: Now that I have been thinking about it, the usage of DCM was a solvent switch after formation of the Grignard reagent, so for misleading
about the formation of a Grignard reagent in DCM, I apologize.
[Edited on 27-3-2015 by Loptr]
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karlos³
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Well, yeah, that what Loptr said, Grignard reagents need to be formed in some ether, but then can be transferred in an another, often aromatic
solvent.
But for their formation an ethereal solvent is needed as far as I know. Ive also never used another method than the standard methods.
I guess DCM can be used as a starter for a grignard reaction similiarly to ethyl-halides, but that gives probably of flammable methane as gas,
similarly to the bubbles of ethane that forms in the preparation of an indole grignard reagent, and THAT i would consider as flammable, Et2O being
harmless instead...
That was what ive meant when I said, a disastrous runaway reaction would occur.
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The Volatile Chemist
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Vogel has a few drawings for stacking, doesn't look weird to me. Seems like a natural tendency if something volatile is going to be boiling at all.
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