Sciencemadness Discussion Board - Preparation of anhydrous AlCl3 in DCM - photos

posted on 5-7-2010 at 14:31

I'm speculating, but if this inspires anybody else for alternative mechanisms, I'm happy. It does seems that getting Al out of its crystal matrix is hard with just isolated single chlorine atoms in HCl. I get the impression that a bit of Cl2 in solution might help initiate the reaction, since adsorbed Cl2 would give three chlorine atoms adsorbed in proximity far more frequently. If that works, it would certainly be more benign as an initiator than HgCl2.

The experiment I performed sometime ago(sorry most data was lost in a computer crash) was based on two test one as a control and one with HgCl2 as an activator. The DCM was saturated with Cl2 till it was yellow in both test tubes. Al foil was shreaded in a blender along time prior to this experiment. An equal amount of Al was added to both with a trace amount of HgCl2 in one of the test tubes. About 1 hour later they where observed and there was almost no reaction in the control which was still yellow with Al sitting on the bottom and some has rose to the top .

The one with HgCl2 was no longer yellow and much of the Al had turned to a grey(ish) powder/gitter. Im sure an excess of Al was used and im pretty confident that if Cl2 was feed in I would have sustained a reaction and managed to consume all the Al present.

It was all done in the absence of light at RT BTW which could have caused a different outcome due to Cl radicals attacking the Al easier.

As a result I am not very confident that Cl2 would be efficient in starting the reaction safely. Perhaps best to just try to heat some Al in a testtube while feeding in Cl2 and scrape the subliminate off the edge to get the needed AlCl3 to catalyse the reaction. Or feed only a small amount of HCl at first into your reaction and allow it to age before proceeding.

peach

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[every post needs a photo]

That's an interesting idea. Where you simply gassing it at room temperature in solvent? DCM? It's surprising Cl2 worked, since that seems to need hundreds upon hundreds of C going directly against Al, whereas HCl works quite a lot lower.

Love the pics. It that rainbow there as a color chart or just an artifact of the photo? Its a good idea either way and I think I may start adding ones to photos to give a better idea of the reaction mixtures color under the light I was under.

If you like that, you'd love my underpanties. They won me an award, $20, for a photo of them, which I believe has now been publicly circulated.

I didn't add the book on purpose, but that is an extremely good point you make. As that was actually an issue with this, the camera didn't pick the green of the DCM up at all well! Before the reaction started, it was strong limey green.

The book is "Designing the 21st Century"

I'm guessing at least some AlCl3 may have formed then, so it may pick up again if regassed. I'll give it a try once I have some more sulfuric. If that doesn't work, I'll prime it with some Hg salt as suggested.

When the reaction really started to pick up, it was very impressive. It had been doing absolutely nothing for hours as I stared at it. Then I looked back and there was a tiny, tiny stream of bubbles. Some time later, it was going like a shook up bottle of coke. I did worry it was going to run away, but it didn't significantly warm up or accelerate past there.

Using DCM as the solvent probably made it impossible for the temperature to go very high, but it didn't even reach DCMs boiling point. And everyone knows DCM can be refluxed by a warm fart.

Quote: Originally posted by DJF90

Well spotted, can I assume you've seen Blade Runner? "enhance, pan... print copy". Now if you look even more closely...
closer...
you'll see there's someone naked standing in the room.

I have some mercury chloride, but you're right, I'd prefer not to open it if I don't have to really. Whenever I'm doing something involving gases or vapors, I try to wash the exhaust of the reaction through something I know will entirely neutralize it to a salt, for instance. But it's better to avoid a risk as opposed to patch it up.

I wonder if a small amount of iron salt would be enough to start the disassociation and allow the Al to pick it up.

I have much less an idea what the intermediates are, but it seems that the important facts are that the Al is a solid and a good electronic conductor, so it's useful to look at half-reactions at the surface that involve free electrons

Exactly, it seems like a pretty basic thing to make, but there was certainly something being produced hours after the gassing had stopped. And it wasn't being produced earlier.

The only thing I could think of is that some of it had been converted to AlCl3, because I can't imagine what else it'd so readily form into along the way, involving the evolution of what I suspect was H2.

Apparently, AlCl3 it's self is a rubbish conductor. For reasons I think someone has already hinted at (covalent like ionic bonding).

It does seems that getting Al out of its crystal matrix is hard with just isolated single chlorine atoms in HCl. I get the impression that a bit of Cl2 in solution might help initiate the reaction, since adsorbed Cl2 would give three chlorine atoms adsorbed in proximity far more frequently. If that works, it would certainly be more benign as an initiator than HgCl2.

That's an idea as well. I'd prefer not to start using the hot processes if possible. Although, I could give them a go too. I'll have to visit the local neon sign store for some borosilicate tubing first.

I'm also idly curious as to whether there's any significant or measurable chlorination of the DCM to chloroform.

Urban Dictionary;
"Does This Smell Like Chloroform?

Jack: "Hey Dorothy, does this smell like chloroform to you?"
Dorothy: "Hmm let's see..." *smells, faints*
Jack: "Great Success!" *unzips pants*"

There is indeed an odd smell to the DCM. When I first smelt it, I thought it smelt eggy. Smelling it some more, it is somewhat ethereal and sweet smelling. It's certainly not HCl(g) or DCM it's self.

I was using neoprene tubing to direct the gas around, but that shouldn't have produced that kind of smell. I don't really like the neoprene, I'd like some Tygon or something like that.

I'll investigate when recovering the solvent. Hopefully there's enough there to show up on the thermometer, and I get a solid number out of it. It'd be fun if it was hey! UV illuminating the DCM could accelerate the process if so; perhaps explosively, so probably best tested small scale and out of the glass first. Actually, I wonder if UV would help the disassociation here. [adds deuterium lamp to shopping list]

Quote: Originally posted by smuv

I can't use the balloon trick. My gas generator is glassware, so it'll pop if I restrict the outlet. I try to gas things as slowly as I can get the gas generated. I'd much, much prefer a fritted wash head, but the frit fell off mine after some harsh cleaning. That another thing on the shopping list, which is getting longer by the minute...

I think a decent amount of the HCl(g) went into solution. As I say, the camera doesn't pick up how green the DCM was very well.

But I'm considering building a HCl generator for the ease of preparation, measurement and flow control; the generator isn't particularly convenient or study even with a pressure equalizing funnel. I googled it and found a document about "Clandestine HCl generators". A ton of people use old propane bottles, which seems extremely risky; there's no way I'd do that myself. The authorities show the correct way to do it in their own PDF, plastic pipe fittings with a pressure relief. The pressure never seems to go over 60psi (although I note, they didn't try charging it with more reactants IIRC).

Personally, I'd have the blow off valve connected to another bit of tubing full of strong base in solution, to deal with all that acid should it pop. A safety feature I also note the authorities not using.

And yes, you're correct about the bonding.

DCM = dichloro methane?

Is AlCl3 supposed to be soluble in DCM?

CaCl2 isn't the greatest drying agent, if pure anhydric, unhydrolysed AlCl3 is your goal (for organic catalysis?)

DCM = Dichloromethane. My last container of 'paint stripper' (pure DCM) arrived in this box. Dun den deeeeeeerrrr..... But is it toxic watson?

I'm only pulling your leg.

AlCl3 is supposed to be soluble in DCM yep, you'd expect it to be really soluble on first appearances. But it's not all that soluble at all. This makes me wonder why my DCM may have clouded. I doubt it's the salt, but maybe it's some of watson's chloroform?

I chose DCM because it's polar aprotic and it'd readily absorb the HCl(g) and could be easily stripped away from the AlCl3, it can even be used as the solvent for work further down the line.

Enough AlCl3 will dissolve in DCM that the solvent will fume when exposed to water, however.

CaCl2 isn't the greatest drying agent, if pure anhydric, unhydrolysed AlCl3 is your goal

I should probably use some concentrated sulfuric I suppose. AlCl3 doesn't absorb airborne moisture too rapidly. It'll certainly do it, but not at an unhandleable rate. My main concern about getting moisture on it is something I think Sauron said about using it to demethylate xylene and there needed to be a Bron.Low acid present for the F.C. I'm considering using xylene and such things as a solvent with the Lewis acid, so I don't want it stripping methyls off wherever it likes.

Quote:

I wouldn't have expected the reaction in DCM to proceed at RT without catalysis: any dissolved HCl is likely to be undissociated or very poorly dissociated.

I wasn't expecting it to either, given the heating that's usually needed. I was sure it was a complete flop, until it sprang it's self into life and started evolving it's own gas. It's also curious, as I say next to one of those pictures, that the bulk of the Al isn't reacting at first, yet something in the wash head is fizzing away. Maybe that's moisture? Hmmm. A conundrummer.

I'm guessing that anyone who can set up a HCl generator and lead the HCl through a suspension of Al in DCM without poisoning himself is also capable of leading said HCl over hot Al filings or powder, collecting the subliming AlCl3 and safely dispose of the H2.

Thanks for the vote of confidence. You're right, in terms of a proven method, that's pretty much unbeatable and yields a sublime result!

I'm a huge advocate of wash heads and actually neutralizing things before they escape over relying on a fume hoods to catch and absorb things that get airborne. So for this example, I was blowing the exhaust through strong KOH solution, there was absolutely no sign of HCl at the output.

And it's not poisoning! It's burning! That's something of a special joke which watson alone will get.

I'm avoiding using the hot methods because I need to sort out my glassware to sublime in a dry atmosphere. Also, a cold method would be easier just in terms of handling the glass and so on.

I want to make my own firstly for the fun of doing it, but also because this is the state the last batch I ordered turned up in. This is straight out of their sealed bottle. I suspect that's iron contamination, which is common with commercial AlCl3 apparently. I don't know how iron gets in there, maybe it's sludge graded Al they use from scraping out ladles or something. But iron trichloride is not brown, and this stuff is only sitting on the surface of the grains.

I'd had it sitting in a puddle of DCM for weeks, changing it whenever it went brown again. I must have had it in DCM for three weeks or more, and no visible quantity of it dissolved. Look at the state of the solvent! Incidentally, in it's time in the Hotel de Flask, it chemically etched the taper shut. I had it in there for weeks because I was trying everything I could to get the stopper back off. I had to smash it in the end. Yes, some idiot forgot to grease / tape the taper before it jammed. I'd like some PTFE keck clips, bottle caps and tapers.

Because it seizes glass, and does this to rubber... Silicon or some other plastic would probably work, but virgin PTFE bar is cheap, turning a taper is easy and it's great stuff.

This is after weeks of being repeatedly shaken. Letting it sit and soak is the best way to clean it up if you have some like this. The yellow color is either water or iron trichloride. I would vote for iron contamination, as all the grains would be greeny yellow if it was moisture.

Something moderately more clean. If it's iron trichloride, it shouldn't be too much of a problem for what I'm using it for. But it makes determining colors difficult, because it's horrendously dark brown whatever it is. The bottle claims to be 99% Al, CP grade. It's still extremely reactive, it's not over exposed; it violently fumed when exposed to water at a later date. I don't understand why the brown only appears to be on on the surface though. Also note that there are white grains in there, which'd be yellow if they were damp. In fact, it looks like multicolor popping candy. Consistency does not appear to be a factor for the manufacturer. Although, some of those grains still look brown. A mixed batch? There's three different colors in there.

posted on 5-7-2010 at 16:51

(for organic catalysis?)

Indeed sir, indubitably.

I've been investigating the use of various Lewis acid for Hard Acid demethylations.

AlCl3 has been a weapon of choice, but I haven't been getting very promising results in the past.

BF3... jeez... too expensive... too nasty... too aggressive, even AlCl3 seems too aggressive.

I may try FeCl3, I was drying some today under HCl. The hexahydrate melts at tens of degrees and boils at around 280. The anhydrous salt melts over 300 and boils tens of degrees later. I managed to obtain something that stayed dry and solid at 280C, but I didn't see any of it melt as it went on to 320C. I did see some vapors coming from it. I may have managed to reduce it to iron (II) chloride, which melts over 600. Or iron oxychloride. There was an ominous leafy green tint to the flask after it cooled (indicating the (II) chloride), but it's now disappeard. Haven't tested it with some water yet, I only made about 10g so there's not a whole lot to test. I have pictures, but this is getting off topic...

I've also used AlI3. I doubt something could make more mess if it tried! And it consumes expensive I2 at quite a rate. At least it's super simple to prepare.

I recently had some luck with AlI3 though, swapping round solvents, and it made me wonder if the same would apply for AlCl3 or other Lewis acids, like FeCl3. I may try running these with the addition of some dry ice if tar production continues with different solvents. Ice / salt baths don't seem to work for AlCl3.

I expect someone is about to ask, so I'll say now that the substrate I'm talking about is primarily 4-Allyl-2-methoxyphenol. I'm sure you're all bored out of your minds seeing posts about ideas on that. I'm specifically not using the common name so the thread doesn't go down 'that route'. Also, I'm genuinely not interested in this for any profitable reasons, it's simply something of a curiosity to me. Again, that's a different topic though, this is about Lewis acids.

[Edited on 6-7-2010 by peach]

Sedit

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AlI3

That could be your safe alternative to using HgCl2 I would suspect. Add Iodine until its consumed and that should give you the catalytical amount of Alx3 compound needed to start the reaction when the solution is gassed.

I would assume more then likely incorrectly so that trace iodine could also speed the reaction up somewhat and allow it to proceed easier.

I thank you peach you are inspiring me by filling my head with so many "what ifs" that I may start experimenting with this again since it is a very useful reagent for a number of things yet as I understand its a bitch to store and somewhat of a bitch to prepair so if a quick an simple cold lab prep could be worked out it could indeed open alot of doors. I remember attempting my HgCl2 experiment in the past because someone told me that you could not generate AlCl3 by gassing withou AlCl3 being present to act as a catalyst so I had to prove that a catalyst of somesort could be generated in situ and I do believe my testtube results confirmed some reaction took place.

Keep going man before you know it I maybe working riht along side of you to tackle these various means but first I have to finish my new lab bench which I making a fume hood for to YEHHHHHH I feel so excited for the first time in years.

blogfast25

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posted on 6-7-2010 at 06:05

You should be able to leach out any FeCl3 with dry acetone in which it is readily soluble (but I'm not sure whether AlCl3 is acetone soluble or not).

peach

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posted on 6-7-2010 at 10:56

You should be able to leach out any FeCl3 with dry acetone in which it is readily soluble (but I'm not sure whether AlCl3 is acetone soluble or not).

I genuinely have no real idea what's going on with the brown coating. It seems to permeate some of the grains in that last photo, but I seriously shook the shit out of that 25g worth over three weeks. I'd walk past it and shake away. The DCM would turn brown almost immediately. It took weeks worth of shaking to get rid of most of it, and some still remained in the valleys of the grains.

At first I tried washing it with an excess of DCM, but it just wouldn't move. It kept staining but not moving. When the taper sealed, I couldn't replace the solvent anymore and I had to let it sit whilst I awaited an order of something other things (which took a month to arrive). I ended up using half a liter of CP grade DCM to try and clean that, and repeated, quick rinses do not work.

I tried SO many things to open the taper. Heating it, cooling it, dropping solvent onto it and covering it with film. Cooling it to draw the solvent in. Tapping, force. KOH to dissolve the glass in the taper. Absolutely nothing budged it. It was 100% jammed. I eventually had a 25mm wrench on it, with the flask wrapped in a towel to avoid cuts. It just didn't move AT ALL. So I had to put a screw driver through it in the end.

I tried to save the flask but, even with the stopper smashed to pieces, the remaining glass wasn't going anywhere. I seriously doubt that's a mechanical bond, I think the acid has actually etched the taper shut somehow.

I should have wrapped the glass taoer in PTFE, I do so for most work. Instead, I just stoppered it and went to bed. The next day, it was jammed forever. PTFE, win!

I do think that commercial sample is contaminated with iron. As I say, if it was water, all the grains would have gone greeny yellow.

What I don't understand is why the surface is so brown. The only thing I can think of is oxygen, but chlorine should displace that. Maybe it was removed from the forming process whilst still hot. But then, why would oxygen displace the chloride?

I began to suspect I'd been sold some form of counterfeit product, as it's from a big branded supplier. AlCl3 is white, not filthy brown.

I would seriously like an answer as to what that is, I can't stand not knowing.

If you get some AlCl3 like that, do this...

Put it in a flask and just about cover it with DCM. Stopper the flask with something wrapped in PTFE or perhaps use a silicon / HDPE / polyprop stopper. I don't think polyacetate will work, as HCl(g) ripped my polyacetate clips to bits in no time. PTFE plumbing tape works well if you don't have PTFE stoppers / cap liners. The gas rated kind (in yellow packs) is thicker and doesn't tear so easily.

Don't add excess DCM. Let it sit in the DCM until the solvent is filthy brown / black. Then decant the solvent (it can be poured off without loosing a grain of the lewis acid) replace and repeat. Once the solvent isn't staining filthy brown anymore, boil the remains off under vacuum.

AlI3

Yeah, you know it. It's brutally dirty stuff. I'd buy a fume hood if only to keep the damn staining to a minimum, I need some of that lab bench paper. I2 smells really nice, and water with it in tastes really nice, but damn... get it ANYWHERE and you'll need to buy some sand paper to shift the stains. I was working as carefully as I could, to 0.01g and using grade A's, and it still ruined things around it.

But it performs really nicely for this kind of work. If I use AlCl3, I usually end up with a lot of what looks like tar and I don't see any Al elemental returned. If I use AlI3, I get a nice sandy / beige colored result and a mountain of Al returned. I have tried AlCl3 at salt / ice temperatures, but it seems to yield tar. Dry ice is an option, as that seems to help with BF3, which I don't want to get involved with.

I have a ton of photos from a recent work up, I'll send you a copy. PM me your email; since it's off topic.

I can't think of anything that has formed during this DCM based method that isn't AlCl3, in terms of the bubbling and reaction I saw occur. Can you see the videos? That took hours to start, but you can see it's running. It may be that the initial AlCl3 simply takes a while to start forming. I need to try regassing that sample really and see if it picks up where it left off. I think a decent amount of my HCl(g) made it into the DCM, but at least some of it will have escaped. Especially as I'm not using a frit.

I think I reached the solubility limit of DCM fairly soon after I started gassing, as it was lime green from early on and didn't get a whole lot darker as the generator ran over night. Indicating it has reached the limit and was going to waste.

I don't like using iodine. It's just far, far, far too messy. It's the only thing that stained my school's chemically resistant lab benches. It's even stained my PTFE bar. Messy stuff. Shame it smells and tastes so nice, and is such an amazing antiseptic (You know iodine is effectively the cyanide of bacteria? Great stuff!).

I would assume more then likely incorrectly so that trace iodine could also speed the reaction up somewhat and allow it to proceed easier.

Depends which reaction you're talking about. If you mean the 'salt' formation, then probably. If you mean the demethylation, I'm less sure. And I can promise you, that latter reaction DOES NOT need speeding up when AlCl3 is concerned; including via a soft base pusher.

I thank you peach you are inspiring me by filling my head with so many "what ifs" that I may start experimenting with this again since it is a very useful reagent for a number of things yet as I understand its a bitch to store and somewhat of a bitch to prepair so if a quick an simple cold lab prep could be worked out it could indeed open alot of doors. I remember attempting my HgCl2 experiment in the past because someone told me that you could not generate AlCl3 by gassing withou AlCl3 being present to act as a catalyst so I had to prove that a catalyst of somesort could be generated in situ and I do believe my testtube results confirmed some reaction took place.

I don't think the sublimation method is prohibitive at all to some of the hundred post + members on this board. They could undoubtedly run it with their eyes closed and one hand behind their back, literally.

I just thought I'd try the DCM method because it'd been discussed on other forums.

Additionally, generating a catalytic amount of AlCl3 is NOT hard at all. If you can't do that, you certainly shouldn't be messing with HCl(g) in the first place, or any of the downstream options. I've only chosen a cold DCM method to see if it'd work, not because I don't know about the hot methods. I'll probably use the hot methods to get clean AlCl3 if further gassing doesn't work.

One thing that concerns me is that switching the stir bar back on produces a suspension similar to the original Al suspension. There won't be any intermediate Cl 'salt' there, so that indicates that a potentially large amount of HCl(g) went to the scrubber, as a large amount of Al elemental remains. Not an issue once you have some catalytic quantity of AlCl3 I know, but it just itches at me is all; that gas isn't free. I have a few grains of AlCl3 left from the CP sample, but thought I'd try this without it first.

I wonder about heating and UV however.