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Author: Subject: AlCl3 from HCl and foil
Texium (zts16)
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[*] posted on 5-3-2018 at 18:33


I ran a quick qualitative experiment to test out the possibility of making AlCl3 in methanol. Freshly dried anhydrous CuCl2 was dissolved in dry methanol (dried over anhydrous MgSO4). A crumpled piece of aluminum foil was added to the solution (left). To compare, some of the same CuCl2 was added to another beaker containing water (right), and a piece of aluminum foil was added to it as well. Effervescence was observed in the methanol solution. After a few minutes without much happening, a small grain of iodine was added to each beaker. This did not appear to change anything- a slight increase in the rate of effervescence at best.

Displaced copper metal was observed in both solutions, but was evolved more rapidly in the aqueous solution. Effervescence was observed in both solutions but occurred at a much faster rate in the methanolic solution.

Methanol-CuCl2.JPG - 1.1MB

I don't think that these conditions will work for producing AlCl3, but it is difficult to determine what is actually happening here. Aluminum methoxide forming in situ?




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clearly_not_atara
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[*] posted on 5-3-2018 at 20:32


Copper is known to activate aluminium (usually CuSO4) so the methoxide seems like a strong possibility.

Iodine reacts rapidly with methanol and cannot be used to activate aluminium in methanol. Formaldehyde is produced. Solvents compatible with I2 include acetonitrile, propylene carbonate, tert-butanol (maybe) and DMF. Acetone will surely be oxidized; DMSO might be oxidized.




[Edited on 04-20-1969 by clearly_not_atara]
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[*] posted on 5-3-2018 at 20:45


Iodine reacts rapidly with methanol? I don't think so- I've run labs where the students react iodine with zinc in dry methanol to determine the product of the reaction.



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[*] posted on 5-3-2018 at 21:22


Really? I suppose I was wrong. I2 has come up for alcohol oxidations before, can't remember why.



[Edited on 04-20-1969 by clearly_not_atara]
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[*] posted on 5-3-2018 at 21:31


In basic solution, iodine will oxidize things like isopropanol to give acetone, and then follow up with the iodoform reaction, but we've boiled zinc and iodine in methanol for extended periods without the methanol obviously reacting.



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Texium (zts16)
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[*] posted on 6-3-2018 at 06:52


Not to mention using iodine and phosphorus (or aluminum!) in methanol or ethanol to make the corresponding iodides. It's pretty well accepted that iodine does not oxidize methanol to formaldehyde.

[Edited on 3-6-2018 by Texium (zts16)]




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[*] posted on 6-3-2018 at 08:52


Oh, and last night after about an hour, the aluminum fully reacted with the methanolic CuCl2 (solution was colorless, copper metal and excess aluminum was present). The aqueous solution took much less time to react.

I decided to test the methanolic solution by adding a few drops to a test tube with some water. It didn't visibly react, but the mixing was noticeably exothermic. It seems most likely that there is dissolved aluminum methoxide present, as there wasn't any HCl gas formed as far as I could tell. In retrospect I suppose I should have checked the pH, but I wasn't really thinking.




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[*] posted on 6-3-2018 at 08:59


Why would you even consider the formation of methoxide? The expected product would be aluminum chloride, solvated with methanol.



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[*] posted on 6-3-2018 at 09:11


Do you know for a fact that aluminum chloride doesn't react with methanol? I couldn't find anything saying explicitly that it does or doesn't, but I also saw that aluminum chloride generally reacts with alcohols to give alkoxides: https://www.masterorganicchemistry.com/2011/07/22/reagent-fr... (Yeah, I know it's a homework-helping site so take it for what it's worth)

And while looking around I also saw this patent: https://patents.google.com/patent/US3083218




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[*] posted on 6-3-2018 at 11:21


I would expect the equilibrium of AlCl3 + 3 ROH = Al(OR)3 + 3 HCl to lie to the left, because methoxide is a really strong base (even when coordinated to aluminum) and HCl is a really strong acid. If you were to boil off the HCl, you might get the methoxide, but I'd guess you'd be more likely to get a crappy mix of oxide, hydroxide, methoxide and basic chloride.



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