Brominerain
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possible synthesis of anhydrous aluminum chloride at room temperature
Anhydrous aluminum chloride is a very useful reagent.
The most common synthesis is from the pure elements (aluminum and chlorine) at high temperatures(650-700 C).
For me at least, this method is not viable, therefore I was thinking of another process.
Theoretically, it is possible to synthesize anhydrous aluminum chloride through the single displacement reaction between copper(II)chloride and
aluminum metal. However, this reaction cannot occur in water as the hexahydrate will form instead. Thus, anhydrous ethanol or acetone can be used as
the reaction solvent.
It should be noted that both anhydrous CuCl2 and anhydrous AlCl3 are adequately soluble in these solvents.
*I am unsure if the procedure described is good enough, as I haven't executed it yet and it is utterly theoretical.
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teodor
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I had success with the metathesis reaction of an ethereal solution of (anhydrous) FeCl3 and a piece of aluminum metal. The problem is that aluminum
chloride forms etherate (as big clear crystals).
I think the same issue you will have with all water-like solvents: alcohols, ethers (all having the structure R1-O-R2). In all these cases you
probably will get the coordination of the solvent molecule to Al center through O atom which is very strong.
You can check those solvents which don't form solvates with AlCl3. The obvious choice is different covalent chlorides which are liquids at room
temperature. But I believe there are also other possibilities, just check data for various solvents.
This task could be simplified a lot because for some application you don't need AlCl3 as a solid. Sometimes it is used as a solution, let's say, in
nitrobenzene. In this case, the choice of solvent could be obvious.
[Edited on 6-9-2022 by teodor]
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Organikum
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Chlorinated hydrocarbons would be the solvent of choice. I made SnCl4 from tin metal in perchlorethylene by venting chlorine into the vessel (cooling
is advised). AlCl3 and FeCl3 can be made the same way.
I could not see why this is not possible as metathesis reaction except for a predictable separation problem. AlCl3 sublimation is a major PITA.
You should be able to do most reactions calling for AlCl3 with SnCl4 too (I used it in a Friedels Crafft with good success) and I had chosen it for it
is a liquid at RT and can be distilled without problems what makes separation and purification a walk in the park.
DCM and chloroform can be used instead of perchlorethylene, in case of solubility issues one could add a small amount of another inert solvent, I
doubt total solvation is necessary or even wanted.
PS: A very small amount of mercury salt helped a lot to get it going, I suspect this will be also true for a metathesis reaction.
[Edited on 7-9-2022 by Organikum]
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macckone
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Do not put copper (II) chloride into acetone. It produces chloroacetone and reduces the copper to copper (I) chloride.
Further acetone complexes with the produced aluminum chloride.
Aluminum chloride will react with ethanol to produce aluminum ethoxide.
Nilered has a good video on the same reaction with isopropanol.
Organikum's suggestion to use perchlorethylene seems reasonable.
1,4-Dioxane or propylene carbonate might work as a solvent but it may be slow as the solubility of the chlorides is going to be low and you may still
get some side reactions. Note that aluminum chloride is used with propylene chloride in some electrolysis reactions to obtain pure alkali metals. It
may complex but it apparently isn't as bad as acetone.
The zinc chloride aluminothermic reaction works.
Additionally for a friedel-craft reaction you can use a catalytic amount of a metal chloride and do an in situ creation with hydrogen chloride gas and
aluminum. This works with benzene and toluene, I am unsure about applicability with other targets for the reaction. HCl is not very soluble until
more aluminum chloride is present.
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