thunderfvck
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HCl and Al, AlCl3?
Hi.
I've mentioned this subject in another thread, but that thread had nothing to do with this, so I've started one up myself. Yes, now that
I've explained my actions...
I took a piece of aluminum (from store, the kind you wrap human limbs with) and poured some HCl (31%) on it. Results? Burning death gas, looked like
smoke when concentrated. Exothermic, QUITE. Solution turns bluish, dark musky blue, very dirty looking. Gas given off turns litmus red. When HCl is
reacted completely (additional Al causes little to no reaction) litmus is red in solution.
6HCl + 2Al --> 2AlCl3 + 3H2
is what I've come up with.
Questions. Does the solution I have contain AlCl3? The gas turned litmus red, H2 is not acidic to my understanding, could it have been HCl evolved in
minute quantities as the reaction was very exothermic.
I've learned that AlCl3 is a useful catalyst in friedel-crafts reactions, I've also learned that in order to eliminate the catalyst it is
treated with cold water.
AlCl3 + 3H2O --> Al(OH)3 + 3HCl
So, as the AlCl3 is formed, isn't it converted to Al(OH)3? AND more HCl, so the reaction really isn't over until there's no more water.
That really doesn't sound right. Someone help. I need the low down.
I should also add that I've read a synthesis of AlCl3 on megalomania's site and it's pretty high-tech compared to my primitive
HCl/aluminum dunking basement experiment, so there's obviously something I'm missing here. Probably over there too.
[Edited on 16-2-2004 by thunderfvck]
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guaguanco
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Yes, you prepared a solution of AlCl3.
You undoubtedly got a bunch of gaseous HCl released by the heat of this very exothermic reaction. I would assume there is an equilibrium:
Al(OH)3 + 3 HCl <==> Al(+3) + 3 Cl(-) + 3 H2O
plus a variety of other related ionic species. This equilibrium would be dependent on the pH of the solution, but I don't have the time to find
facts and figures. Al(OH)3 is highly insoluble, so you can visually track what's going on (to some extent) by the presence or absence of a milky
greyish precipitate.
When a Friedel-Crafts reaction is quenched, it's usually with aqueous NaOH, which drives the equilibrium towards Al(OH)3, since the HCl is
neutralized by the alkali.
I've never heard of any way to convert hydrated AlCl3 to anhydrous AlCl3; it's prepared commercially by reacting the elements. But someone
else may know more.
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chemoleo
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No you can't make the catalytic AlCl3 this way. With aqueous HCl one always gets the hydrate complex. You cannot simply evaporate off the water
to be left with AlCl3, instead it will decompose, leave (ultimately) Al2O3 and HCl.
That's why you can only get AlCl3 by a direct reaction of Cl2 with Al.
It figures why the fumes that were given off were highly acidic...
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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Organikum
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If you mix 30% HCl with Al you will get
1. hydrogen and AlCl3:
3HCl + Al = AlCl3 + 3H
2. HCl gas:
AlCl3 + 6H2O = AlCl3.6H2O
as the hexahydrate of AlCl3 is formed this process dehydrates the HCL and releases lots of HCl as gas.
The addition of water shouldnt decompose the AlCl3 it will only form the hydrated form of AlCl3 which is almost inactive as Friedel-Crafts catalyst.
A base will of course destroy the ACl3.
After my best of knowledge FC-reactions are quenched with water - often followed by addition of diluted HCl, this mainly depends on the properties of
the formed compound and the following separation. A base is not needed for quenching - at least when strong Lewis-acids are employed (AlCl3, FeCl3,
SnCl4....). When working with easy to alkylate/acylate compounds which condense already by the use of H2SO4 for example or even without Lewis-acid,
neutralization/basifying may be advised in quenching the reaction.
Production of AlCl3:
Anhydrous:
1. Dry HCl gas is vented over heated Al, the AlCl3 formed sublimes and is collected in a cooled part of the reaction tube.
2. Dry chlorine ngas is vented over STRONGLY heated Al to form AlCl, which sublimes like above.
3. Dry chlorine gas is vented over a strondly heated mixture of aluminium oxide and carbon (bauxit and charcoal). sublimation as above. This is
conveniantly done in retorts made from clay (pottery).
4. If you already have a small amount of anhydrous AlCl3 and would like to have more:
AlCl3 is dissolved in benzene, Al powder/filings are added and dry HCl gas is vented into the refluxing reaction mixture, strong stirring is applied,
AlCl3 is formed from the Al and the HCl. Without any AlCl3 this reaction will NOT start.
I would guess other solvents like chloroform/DCM may substitute the benzene here, but thats a guess.
Hexahydrate:
1. Toss Al-foil into water and add slowly DILUTED HCl. As soon you smell HCl fumes, add more water. After all Al is dissolved what takes some time
btw. you may concentrate the solution by boiling away excess water. Anhydrous AlCl3 can NOT be isolated by heating as the AlCl3.6H2O decomposes:
AlCl3.6H2O = Al(OH)3 + 3HCl + 3H2O
(here this equatation is right placed...)
Rather comprehensive, isnt it?
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thunderfvck
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Ah. I see. Thanks home cat, master G.
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S.C. Wack
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Not Al and HCl, rather Al2O3 and CCl4. Thought this thread was close enough. No need to tell me that you think that this is no more practical than the
alternatives. I'm throwing it up just in case someone might be able and willing to give it a try.
This was left out of the Inorganic Syntheses compilation made earlier. On second thought, if you have CCl4 and would like to heat some up in a bomb at
400C for a few hours with a metal oxide to get the anhydrous chloride in quantitative yield, check this out. If not, don't.
Attachment: alcl3_from_al2o3_and_ccl4.djvu (51kB)
This file has been downloaded 1169 times
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Organikum
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Of course Al and dry HCl.
Thats the standard method from the old days and still included in the Gattermann.
Trick: When the Al is (partly) almagamated the reaction works at lower temperatures.
Also (partly) almagamated Al reacts nicely with HCl in benzene and perchlorethylene. Only very small amounts of Hg-salt are needed, it suffices to add
a drop elemental Hg to the Al some hours before and to use this.
Dry HCl gas is favorably prepared from ammoniumchloride chunks and H2SO4.
/ORG
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CherrieBaby
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1) The prepn. is on page 812 of Bauer, vol 1. 2e. which S. C. Wack has made available, see the books thread in General Chem.
2) Durrant [General & Inorganic Chemistry, P. J. Durrant, 2e, Longmans, 1954] says that anhydrous AlCl3 is made by passing a current of Cl2 over
heated alumina (Al2O3) and charcoal. Al2O3 + 3C + 3Cl2 -> 2AlCl3 + 3CO.
3) AlCl3 is also be made by passing dry Cl2 gas over heated Al metal in a similar way to the Bauer prep. Partington gives the prepn. [Textbook of Inorganic Chemistry, 5e, J.R. Partington, MacMillan, 1939, p880]
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alchemie
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Let's not forget the bromide and iodide. These can be made in a more simple way: suspend a slight excess of aluminium foil, powder or turnings in
an organic solvent (no ethers or alcohols, use something inert: e.g. toluene, cyclohexane, acetonitrile) and, slowly, add Br2 or I2. Reflux if
necessary, to complete the reaction. Filter and evaporate the solvent. Or use the solution itself for whatever you have planned.
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Nicodem
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If I would be in a desperate need of anhydrous AlCl3 and only had OTC chemicals, I would try to make it from Al foil and trichloroethylene.
I never did this as I was never in such a need of AlCl3 to bother so much, but I see no reason why it couldn’t be done. However this reaction is not
as straightforward as the MSDS of trichloroethylene seams to imply when warning of its violent reaction with Al and some other metals [1]. Obviously
in real experience C2HCl3 is one hell of an inert solvent (personal experience).
The reaction of trichloroethylene is, accordingly to [2] from which most of the present information is taken, something like this:
Al + CHCl=CCl2 ==> AlCl3 + [CCl2=CH]2 +[CHCl=CCl]2 + similar oligomeric vinylchlorides
Once some AlCl3 forms, it is able to cause a “self-accelerating, 'autocatalytic' dehydrochlorination of the solvent”.
In case anybody is to make such experiments here are some advices (which might be completely wrong since I never bothered to make a thorough research
on it). Also beware that trichloroethylene can produce toxic fumes like acetylenedichloride in some reactions and possibly other nasty side products
(fume hood!).
One problem is that commercial trichloroethylene contains some stabilizators that inhibit its reaction with metals [3]. In fact they are so efficient
that trichloroethylene can be safely used to clean aluminum and other metals (it is its main use in fact). Simply distilling it once might not be
enough since many inhibitors have a low boiling point. Maybe washing it with conc. sulphuric acid before distillation might help. Adding any other
solvent (toluene, DCM…) helps in further disinhibiting trichloroethylene.
Another problem is the inertness of the Al metal surface passivated by the oxide layer. The reaction is autocatalytic and starts only when some AlCl3
(or possibly other acids) forms on the metal surface. Therefore once it starts it also runs to the end (exothermally!). Hence, besides the removal of
the stabilizators, an activation of the Al foil surface is necessary. This should be possible in two ways: either by amalgamation or by etching the
surface by a reagent which would form a Lewis acid. The amalgamation should be possible by adding a drop of mercury in the Al/C2HCl3 mixture followed
by intense mixing. The other possibility would be to add some iodine crystals instead, in order to form some AlI3 on the surface. Reflux and anhydrous
conditions are a must for the reaction to start (a CaCl2 trap on the top of the condenser should be used). In order to prevent the exothermic runaway
of the reaction, only a small amount of aluminum should be added until the reaction starts and then further amounts of it added in portions. It is
best to use a considerable excess of C2HCl3 in order to minimize the formation of polymeric vinylchlorides, tar or carbon.
The formed AlCl3 probably forms a complex with the solvent (it forms a red complex with Me-CCl3, for example). Maybe it would be necessary to
precipitate it by addition of petrolether or naphta. The precipitate should be then vacuum filtered after the reaction is finished and cooled. The
polymeric side product should be washed off by some dry petrolether. If the product is a complex of AlCl3 with the solvent it might be possible to
obtain AlCl3 by heating it in order to destroy the complex. AlCl3 is extremely hygroscopic and therefore all this should be done in anhydrous
conditions.
A similar reaction should be possible with other chlorinated solvents like 1,1,1-trichloroethane, CCl4 and even methylenechloride.
[1] http://www.bocgases.ca/newsite_eng/gases/pdfengli/G217.pdf (“May react violently with aluminum, titanium, magnesium or their alloys.”)
[2] http://www.eurochlor.org/chlorsolvents/publications/digest20...
[3] patents on the inhibitors and stabilizators: GB617572, GB994167, US4368338, EP0033782, US4287003, GB940494, US2803676 and many other (there is
even a patent on how to remove stabilizators from trichloroethylene, but I can’t find it anymore)
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searat
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prepared from al and CL2 or HCL or cl2 over Al2O3 plus carbon, yellow solid.
I think ALCL produces gas with a wet atomsphere.
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IrC
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CherrieBaby, can you put this file back up somewhere, I tried the link and got the following:
File /files/786898/AlCl3.pdf.html has been deleted.
Reason: No download for a longer period. Inactivity-timeout exceeded.
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verode
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| Quote: | Originally posted by Nicodem
If I would be in a desperate need of anhydrous AlCl3 and only had OTC chemicals, I would try to make it from Al foil and trichloroethylene.
I never did this as I was never in such a need of AlCl3 to bother so much, but I see no reason why it couldn’t be done. However this reaction is not
as straightforward as the MSDS of trichloroethylene seams to imply when warning of its violent reaction with Al and some other metals [1]. Obviously
in real experience C2HCl3 is one hell of an inert solvent (personal experience).
The reaction of trichloroethylene is, accordingly to [2] from which most of the present information is taken, something like this:
Al + CHCl=CCl2 ==> AlCl3 + [CCl2=CH]2 +[CHCl=CCl]2 + similar oligomeric vinylchlorides
Once some AlCl3 forms, it is able to cause a “self-accelerating, 'autocatalytic' dehydrochlorination of the solvent”.
In case anybody is to make such experiments here are some advices (which might be completely wrong since I never bothered to make a thorough research
on it). Also beware that trichloroethylene can produce toxic fumes like acetylenedichloride in some reactions and possibly other nasty side products
(fume hood!).
One problem is that commercial trichloroethylene contains some stabilizators that inhibit its reaction with metals [3]. In fact they are so efficient
that trichloroethylene can be safely used to clean aluminum and other metals (it is its main use in fact). Simply distilling it once might not be
enough since many inhibitors have a low boiling point. Maybe washing it with conc. sulphuric acid before distillation might help. Adding any other
solvent (toluene, DCM…) helps in further disinhibiting trichloroethylene.
Another problem is the inertness of the Al metal surface passivated by the oxide layer. The reaction is autocatalytic and starts only when some AlCl3
(or possibly other acids) forms on the metal surface. Therefore once it starts it also runs to the end (exothermally!). Hence, besides the removal of
the stabilizators, an activation of the Al foil surface is necessary. This should be possible in two ways: either by amalgamation or by etching the
surface by a reagent which would form a Lewis acid. The amalgamation should be possible by adding a drop of mercury in the Al/C2HCl3 mixture followed
by intense mixing. The other possibility would be to add some iodine crystals instead, in order to form some AlI3 on the surface. Reflux and anhydrous
conditions are a must for the reaction to start (a CaCl2 trap on the top of the condenser should be used). In order to prevent the exothermic runaway
of the reaction, only a small amount of aluminum should be added until the reaction starts and then further amounts of it added in portions. It is
best to use a considerable excess of C2HCl3 in order to minimize the formation of polymeric vinylchlorides, tar or carbon.
The formed AlCl3 probably forms a complex with the solvent (it forms a red complex with Me-CCl3, for example). Maybe it would be necessary to
precipitate it by addition of petrolether or naphta. The precipitate should be then vacuum filtered after the reaction is finished and cooled. The
polymeric side product should be washed off by some dry petrolether. If the product is a complex of AlCl3 with the solvent it might be possible to
obtain AlCl3 by heating it in order to destroy the complex. AlCl3 is extremely hygroscopic and therefore all this should be done in anhydrous
conditions.
A similar reaction should be possible with other chlorinated solvents like 1,1,1-trichloroethane, CCl4 and even methylenechloride.
[1] http://www.bocgases.ca/newsite_eng/gases/pdfengli/G217.pdf (“May react violently with aluminum, titanium, magnesium or their alloys.”)
[2] http://www.eurochlor.org/chlorsolvents/publications/digest20...
[3] patents on the inhibitors and stabilizators: GB617572, GB994167, US4368338, EP0033782, US4287003, GB940494, US2803676 and many other (there is
even a patent on how to remove stabilizators from trichloroethylene, but I can’t find it anymore) |
try with dry NH4Cl + Al you will get AlCl3 not adition with NH3 I Think
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praseodym
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| Quote: | Originally posted by verode
try with dry NH4Cl + Al you will get AlCl3 not adition with NH3 I Think |
Will there be any reaction between NH4Cl and Al? How do you get AlCl3 from NH4Cl + Al?
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kazaa81
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I've mixed the AlCl3 solution obtained from above experiment (HCl + Al) with acqueous ammonia (NH4OH) and obtained a gel.....is it Al(OH)3?
Drying it will get something like a hard powder....
Thanks at all for help!
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neutrino
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Probably, I don't see what else it would be.
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kazaa81
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What about using the solution obtained from the experiment to get Al soaps (making Na soaps, dissolving them in water and the mixing with AlCl3
solution to get precipitate Al soap)?
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greenimp
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So I really hate to resurrect a old thread, but its this or start a new one, and something I am currently working on is exactly what is being
described in this thread.
I have been trying to make 500g of crystalline anhydrous AlCl3 for a couple of weeks. I have read the related threads on this board and others, and
have been experimenting with variations on the HCl(g) + Al -> AlCl3 in a non reactive solvent, with a small catalytic amount of AlCl3 added method.
So far I have tried xylene, tetrachloroethane, and DCM as solvents. My aluminum source has been finely cut aluminum foil.
I have had 2 problems, obtaining a solid product and obtaining a reactive product. In short here is what has been tried so far.
The experiment with xylene as a solvent ran as described in the 1960's Renylods patent. I reacted 100g of foil in 3.5L of xylene. After distilling
off the xylene, I was left with about 1.5L of red liquid product that would not yield anymore xylene. After a certain point during the distillation,
it started to sublime ALCl3. However, this liquid has the characteristics of anhydrous ALCl3, it reacts violently with h20, and gives off the proper
gas. The reaction I want to run with the ALCl3 is carried out in DCM, so the AlCL3 needs to be in a solid form.
In the tetrachloroethane experiment, I used commercially available TCE that had not been treat in any way, Al foil was used again. The reaction
produced a black grainy solid. (AlCl3 is not soluble in TCE) The problem is it was very slow reaction, no where near quantiative, and the product was
not very reactive.
The DCM experiment was somewhat more interesting. It was self sustaining, while recharging the HCL generator, the reaction continued for about 3
hours without HCL being added to the reaction. I believe this is an example of Nicoderm's trichloroethane reaction. However, again a very black
product was obtained, and it proved to have very low reactivity.
So I'm coming to you all for some suggestions. Obviously, Al powder is the first variable to change right? I'm just surprised the product was so
black, given the small amount of impurities in the Al foil, or is the black color carbon? If anyone can give me some pointers, maybe a way to purify
the product from the xylene, without having to sublime it, that would be great
Green Imp
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chemkid
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You need pure aluminum. Aluminum foil is extremely impure and leaves a large amount of residue in any reaction. That is from personal experience. I
don't know much about the rest of the procedure.
Chemkid
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UnintentionalChaos
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Xylene is a terrible choice, since you have alkyl groups and are making anhydrous AlCl3 with acid around. Heating this is just going to drive the
FC-dealkylation reaction and leave you with an odd assortment of toluene, xylene, and mesitylene.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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greenimp
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The original patent I read listed xylene as one of the possible solvents. I should have mentioned all the reaction where carried out at 70C, or
reflux in the case of DCM. Distillation of xylene was done under vacuum.
If anyone can suggest improvements I'll investigate them. Especially Nicoderm's idea. It is my belief that tetrachloroethalene and DCM should both
be usable in this reaction. The NH4Cl idea also intrigues me, but would this be a solid state reaction?
I am more then will to test ideas and report back findings.
Green Imp
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sylla
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Hi everyone.
I'm currently planning to build a homebrew fluidized bed reactor to produce anhydrous AlCl3 from very thin pyro aluminium powder and dry chlorine gas.
Heat regulation will be achieved through PID controller. I have read the discussion above on the synthesis of AlCl3 from these reactants and I have
seen that several of you quotes that the reaction only process at "high" or "quite high" temperatures. Unfortunately, it is quite hard for me to
quantify how much hot "quite high" is. I have read on the MSDS that its bp is of about 260°C so I guess the reactor should be run around these
temperatures...
Could someone point me the exact temperatures required to perform the operation ? Also, does anybody have kinetic informations on that reaction ? Is
it fast, selective (any side reactions?)... ?
Thx a lot :-) looking forward for your replies!
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chief
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If the hydrous AlCl3 from Al + HCl decomposes to Al2O3 + HCl on heating: Is all the HCl regained (no HCl-loss) ?
Then it would be a method to oxidize Al to Al2O3-powder ; might be useful some day ...
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