Leben
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Preparation of (non lithium)Alkali Superbases - Alkali + Haloalkane?
Lithium Superbases such as butyllithium are prepared by reaction of Lithium Metal with a halobutane. Is there any reason this reaction wont work with
other alkali metals? For instance, Potassium Metal + Dichloromethane?
4K + CH2Cl2 -> 2KCl + CH2K2 (Methyldipotassium / Dipotassium Methylate?)
Lithium is of course known for its ability to swap halogens, but shouldn't some of the other alkali metals be strong enough to abstract halogens? I
know that Sodium Metal can abstract halogens from Aryl Halides, so if it can do that it must be strong enough to work on haloalkanes such as DCM.
[Edited on 24-8-2014 by Leben]
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BromicAcid
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Check out the Wurtz Reaction.
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Metacelsus
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Mixing halomethanes and alkalai metals is generally a bad idea (they are on the "list of things you shouldn't mix").
A dihaloalkane such as dichloromethane would probably not work as well as a monohaloalkane. You would probably get a dangerously exothermic reaction
that produces polymerized gunk.
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FireLion3
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Quote: Originally posted by Cheddite Cheese  | Mixing halomethanes and alkalai metals is generally a bad idea (they are on the "list of things you shouldn't mix").
A dihaloalkane such as dichloromethane would probably not work as well as a monohaloalkane. You would probably get a dangerously exothermic reaction
that produces polymerized gunk. |
These reactions are very exothermic but I wouldn't go as far to say bad idea, as long as conditions are controlled.
Mixing Lithium with haloalkanes produces very strong lithium superbases, with low temperatures preventing most side reactions. No idea if it works
with potassium or sodium. These organolithium compounds also function as nucleophiles, but this is less prevalent at low temperatures.
Leben if you mix Lithium (carefully and at -78c temperatures) with dichloromethane, the reaction will most likely go forward in the manner that you
have laid out. This is typical preparation of lithium superbases. When using your base, ethane gas is generated, similar to how butane gas is
generated with butyllithium.
I don't think you will get polymerized gunk as Cheddite says, these lithium superbases are generally insoluble in solution, but will easily react with
whatever else you add to the flask.
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PHILOU Zrealone
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Alkalies metal and halogenated solvents, especially polyhalogenated solvents, are detonable mixture... by shock and probably by heat! I think the
exothermicity can make it go boom if insulated or not cooled enough.
Typically:
R-X + Na/K --> NaX/KX + R-R
CH2X2 + 2Na/K --> 2NaX/2KX + CH2=CH2 (what may eventually polymerize into PE).
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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