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Author: Subject: Preparation of anhydrous AlCl3 in DCM - photos
peach
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[*] posted on 5-7-2010 at 07:01
Preparation of anhydrous AlCl3 in DCM - photos


[edit: if the videos say "daily download limit reached" please let me know and don't worry, they're probably trying to rape money from you, it may be a scam host]

I decided to make some anhydrous AlCl3, and I'd read that it'd work if Al were simply gassed with HCl in DCM. So I set up a salt / H2SO4, HCl(g) generator and blew it through anhydrous CaCl2 to remove any moisture from the stream. I was using approximately 20g of finely atomized Al powder with an excess of HCl(g).

The Al powder, I don't know what mesh it is, but you can see it's finely divided.


Al in DCM suspension, gripping stuff! :D


I begin gassing with HCl. I know, a sintered head is a good idea, but mine is damaged, so I'm having to make do with a normal bubble head.


After a good hour or more, the color of the suspension hasn't changed at all. I can't see any evolution of gas from the Al (H2) and the generator is pretty much off it's full evolution and is just trickling along very slowly. If I stop the stir bar, it settles and I see the DCM has turned green. The generator isn't producing much more HCl(g) and no visible bubbles are appearing in the DCM wash head. But look at the end of the wash head, there is efflorescence occuring within the volume trapped in the tube. Why would that be, but not elsewhere?


The reaction seems to have failed and, reading this forum and doing some googling, it looks like I need to heat the Al to form the salt. I sit back and watch some TV, thinking I'll wait until tomorrow to clear the HCl(g) out. Then, half an hour later, I get up and this is happening. The solution is quite violently bubbling away and there are clouds of this muck floating around. Hours and hours after I started it. Importantly, the stir bar has been sitting still in this picture for about half an hour or an hour since the last one, those clumps have lifted themselves via effervescence. It's bubbling a lot more than it appears in this picture.


Here's a video from before I took that photo. The generator is still producing a visible amount of HCl(g), but the bulk Al isn't reacting, whilst something in the wash head tube is.
Nothing much happening...

About an hour or two after it started, the clouds disappear and the effervescence stops. The DCM has cleared the green color, but is now 'salty' opaque. I've added the Keck clips to give the camera something solid to focus on. Also note... the Keck clips are entirely fucked. The small amounts of HCl leaking from the tapers (sealed with PTFE) seems to have massively degraded them, they're literally falling apart between my finger tips. These clips were made by Schott Duran, in Germany. I've owned quite a few pieces of glassware made by them. All of them have fractured. And now the clips have fallen to bits. Hmmmmmm..... quite unusual for a German manufacturer.


A loooong time after the generator stops, the reaction begins, then picks up pace until it looks like this.

I haven't tried evaporating a sample of the solution yet, to see if there's a salt there, but I'm curious about what's happened here. I didn't use any heat, at all. From me starting the HCl(g) generation, it must have been hours before this reaction started. I've read that this method of producing the salt requires a catalytic amount of AlCl3 to be present from the start (I don't know if it has to be anhydrous, or if another salt would function).

As I didn't add any preformed AlCl3, perhaps it took so long because it was very hard for the initial AlCl3 to be generated? It seems to have then sped up. If I turn the stir bar on...


There's obviously still a lot of Al powder unreacted. My guess is that only some of the HCl(g) made it into the DCM, which (eventually) reacted with the Al.

I can't think of what else would have caused the reaction hours later. I had drying agents in place, and it wasn't occurring in a way that'd seem in line with absorption through the tubing.

I've bottled the results as I want my DCM back, but what do you think what happening there?

[Edited on 5-7-2010 by peach]
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[*] posted on 5-7-2010 at 08:02


Next time add abit of activated Al using HgCl2 to avoid the runaway and allow the formation to start right away. I did this a while back on a small scale using Cl2 and small amount of activated Al and it appeared to proceed nicely so If I where to ever scale up, something which I plan on doing one day I would indeed add a small amount of Al/Hg just to get the ball rolling and that would provide you with the AlCl3 needed to initiate the rest of the reacton.


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.





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[*] posted on 5-7-2010 at 08:27


If you look carefully in the picture you can see its the cover of a book. Although the aim is to obtain AlCl3, its nice to see attempts that are simple like this, but which do not use mercury or its salts; as chemists we have the responsibility to experiment safely and in an environmentally sound manner, and safe disposal of mercury wastes (especially in solution) is not easy.

[Edited on 5-7-2010 by DJF90]
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[*] posted on 5-7-2010 at 10:06


My guess is that the dissociation of HCl is far greater with AlCl3 present than not, because of the equilibrium AlCl3 + HCl <--> AlCl4(-) + H(+). Electron transfer in the net reaction Al(n) + H(+) --> Al(n-1) + H(0) would then proceed at a much higher rate.

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. It would seem that AlCl3 would adsorb strongly onto solid Al, in a kind of bi-pyramidal adduct, where the AlCl3 becomes polar and thus more electrophilic. The Al has positive net charge, and the surface region in a ring around it would have net negative charge (essentially because of Gauss's law). So I can hypothesize these reactions:
&emsp;AlCl3(solution) <--> AlCl3(adsorbed)
&emsp;AlCl3(adsorbed) + HCl(solution) <--> AlCl4(-)(adsorbed) + H(+)(adsorbed)

The adsorbed H(+) species can migrate easily, so when there are two AlCl4(-) next to each other, their corresponding H(+) will tend to migrate away from each other. When three are near each other, you have the H(+) away from the center. At that point there's the possibility of a chlorine rearrangement.
&emsp;3 AlCl4(-)(adsorbed) + Al(solid) --> 3 AlCl3(solution) + AlCl3(adsorbed) + 3e(-)(solid)
I've designated the electrons as solid because they'd be within the electron gas of the metal. I suspect that the adsorbed AlCl4(-) desorb on reaction because they only have two chlorine atoms contacting the Al surface, and that doesn't seem particularly stable.

Finally there's a standard half-reaction for hydrogen
&emsp;2 H(+)(adsorbed) + 2 e(-)(solid) --> 2 H2 (gas)

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.

I'm also idly curious as to whether there's any significant or measurable chlorination of the DCM to chloroform.
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[*] posted on 5-7-2010 at 10:13


A more efficient way to do this reaction, might be to do it in a 2 neck flask, or even a filter flask. Put a balloon over one neck and affix a hose leading to the HCl generator to the other. Fill the balloon with HCl, clamp the hose, and allow everything to stir under an atmosphere of HCl or Cl2. The solubility of HCl in DCM is fair, however I fear most of the HCl you generated did not dissolve.

P.S. Just a nit picky correction: Anhydrous AlCl3 should not be called a salt, the bonds are mostly covalent in character.

[Edited on 7-5-2010 by smuv]




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[*] posted on 5-7-2010 at 11:42


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?)

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'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.
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[*] posted on 5-7-2010 at 12:04


Quote: Originally posted by watson.fawkes  

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.





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[*] posted on 5-7-2010 at 14:31


[every post needs a photo]

Quote: Originally posted by Sedit  
Next time add abit of activated Al using HgCl2 to avoid the runaway and allow the formation to start right away. I did this a while back on a small scale using Cl2 and small amount of activated Al and it appeared to proceed nicely so If I where to ever scale up, something which I plan on doing one day I would indeed add a small amount of Al/Hg just to get the ball rolling and that would provide you with the AlCl3 needed to initiate the rest of the reacton.


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.

Quote: Originally posted by Sedit  
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  
If you look carefully in the picture you can see its the cover of a book. Although the aim is to obtain AlCl3, its nice to see attempts that are simple like this, but which do not use mercury or its salts; as chemists we have the responsibility to experiment safely and in an environmentally sound manner, and safe disposal of mercury wastes (especially in solution) is not easy.

[Edited on 5-7-2010 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. :D

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.

Quote: Originally posted by watson.fawkes  
My guess is that the dissociation of HCl is far greater with AlCl3 present than not, because of the equilibrium AlCl3 + HCl <--> AlCl4(-) + H(+). Electron transfer in the net reaction Al(n) + H(+) --> Al(n-1) + H(0) would then proceed at a much higher rate.


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

Quote: Originally posted by watson.fawkes  
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).

Quote: Originally posted by watson.fawkes  
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.

Quote: Originally posted by watson.fawkes  
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  
A more efficient way to do this reaction, might be to do it in a 2 neck flask, or even a filter flask. Put a balloon over one neck and affix a hose leading to the HCl generator to the other. Fill the balloon with HCl, clamp the hose, and allow everything to stir under an atmosphere of HCl or Cl2. The solubility of HCl in DCM is fair, however I fear most of the HCl you generated did not dissolve.

P.S. Just a nit picky correction: Anhydrous AlCl3 should not be called a salt, the bonds are mostly covalent in character.

[Edited on 7-5-2010 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.

Quote: Originally posted by blogfast25  
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? :D ;)

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.

Quote: Originally posted by blogfast25  

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.

Quote: Originally posted by blogfast25  

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.


Quote: Originally posted by blogfast25  
(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]
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[*] posted on 5-7-2010 at 16:51


AlI3:D 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.





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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).
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[*] posted on 6-7-2010 at 10:56


Quote: Originally posted by blogfast25  
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.

Quote: Originally posted by Sedit  
AlI3:D


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.

Quote: Originally posted by Sedit  
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 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!).

Quote: Originally posted by Sedit  

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.

Quote: Originally posted by Sedit  

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.

Quote: Originally posted by Sedit  
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.


I would love for you to do so. I've been working away with these acids for half a decade +, but they so often yield tar against multi-functional group substrates.

I post a lot on other forums, but have been avoiding this one for a while as it's so intolerant of stupidity. But I've come to appreciate why it's so and that there are some far more knowledgeable people here. I am very happy to be chatting with such intelligent people for a change. I've spent so many years being the only person trying this, it's really annoyed me.

This method is CONSTANTLY ranted on about on forums, yet no one seems to ever actually see if it works. I can tell you, having spent over half a decade messing around with it, that the majority of journal entries don't seem to function when strong lewis acids are transplanted onto delicate substrates. They work for single functional group substrates, not multi. On multi-group substrates, the Lewis acids seem to go after anything that'll give them electrons. I was called modest peach and a doormat at school, but I have never seen someone actually running these reactions for themselves.

There seems to be some odd things occuring with the more powerful hard acids (I think they're interacting with the phenol / tail double bond). I expect the balance of hard / mild is important and that a soft base pusher is not all that essential. A soft acid also doesn't seem to work, as it won't attack the hard base site of the ether linkage without microwave irradiation; which shifts the charges around in the substrate provided there is an electron withdrawing group on the tail (perhaps, like a double chloride, which can be transformed to a ketone with a base).

I have a sample of material that I suspect to be the demethylation product. This sample is strongly oxygen / light sensitive from my initial impressions. It reacts, strongly, with a FeCl3(aq) test for phenols.

Alone, it'll turn from beige to dark brown in hours. In it's raw, fresh state, it looks exactly like sand or mild curry. As it's exposed to light / atmospheric oxygen, it turns dark brown. I say, 'seems to yield tar' as previous tests yielded something like intractable tar. Yet I'm fairly sure, now I have the suspect product, that it can be easily mistaken for tar once it touches the ambient atmosphere or UV for any significant period (catechols are often used for photosensitive chemistry). I'm not sure which is most important at present. I'll try vacuum distilling it as soon as I have some B14 available, which will hopefully yield a white result.

The sample stinks of coal tar, and it'll easily solidified in the freezer and flows at room temperature. I suspect some of the substrate has passed over and that the sample needs cleaning up. I washed with cyclohexane during filtration, then extracted with ethyl acetate. Again, a vacuum filtration should clear this up; I'd rather vacuum distill than recrystallize, given how little seems to be known as fact regarding this material.

However this is, again, off topic. This is about lewis acid not demethylation.

Also, you don't need a fume hood for this kind of work. You can accomplish a better effect by sealing your joints well and scrubbing the exhaust through a strongly basic solution. I have done this in person. It works perfectly. Absorption is not the same as neutralization via a strong reaction. Wash heads are incredible, better than fume hoods for a lot of work; you can reduce things like nerve agent to toothpaste with a wash head, a fume hood won't do that (wash heads are also faaaaaaar cheaper, can be stored away easily and can be used for other reactions).

I would recommend storing AlCl3 (or any other similar, hard Lewis acid) in a glass bottle and wrapping the threads with PTFE tape. My CP bottle had strongly discolored it's own label over year, indicating that the CP seal had failed to some extent. Gas PTFE on the threads and a PTFE cap liner would almost certainly fix that.

PM me with an email address anyway. I've already gone far enough off topic, I'm not going any further in this thread.

I want to try distilling this DCM to see if watson's chloroform idea is right. SEDIT, please PM me and buy some fritted wash heads.



[Edited on 6-7-2010 by peach]
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[*] posted on 6-7-2010 at 12:16


"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"

Sorry don't hve much time to fully read whats typed but this caught my eye. Yes it does take AlCl3 a whil to start forming and once it does it acts like a catalyst hence the reason people say that the solvent method is ineffective unless you already have AlCl3 to initiate it. However AlI3 should serve the same catalytical use and I found last night that when I2 is added to Al grain in dry DCM almost right away there was evolution of bubble(don't really know what these are just yet more then likely an artifact of trace H2O reacting somehow) and the Deep purple color of the DCM started to fade to a more redish color. Sadly I broke mylast test tube (damn this batch was cheep) just crackin the corner so I quickly sealed it with tape and am going to feed HCl into it later tonight to see if it indeed consumed the Al in a reasonable manner.

[Edited on 6-7-2010 by Sedit]





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[*] posted on 7-7-2010 at 02:47


I recommend you buy some metal glassware clips. I bought mine on expediglass.com. I use them for all synthesis which involve acid vapors. Kech clips LOVE to fall apart from HNO3.



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[*] posted on 10-7-2010 at 09:16


I found some PTFE clips, but they're £7. EACH

Having left this reaction to stand in an amber, PTFE liner bottle, I discovered the following



The unreacted aluminium has sunk to the base, but there is very clearly a white precipitate. Which I am virtually certain will be the anhydrous AlCl3. The camera doesn't show the definition between the two colours well.

Once I have some more sulphuric, I'll regas this and get the rest of the elemental aluminium done.

It's prooving more and more difficult to find. It used to be on sale at B&Q at 96% for drain clearing. Then, last year, some woman poured it down her plughole (probably with her face over it) and received a large amount of it back. Hot.

She was severely burned and B&Q have pulled all of it off the shelves. I had a scout round in there last night and they're getting rid of any of the more pure, useful chemicals. The brick cleaner now proudly state 'Does not contain hydrochloric acid' and the only one that does is full of detergents. Sodium Chlorate greenery killer seems to have also gone. I still have a few bags of that, however.

The acid had it directly stated on the pack that it shouldn't be added directly to water, that'd it get hot and react. I doubt she bothered to read that.

Some google searching of sulphuric based drain cleaners reveals a worryingly large number of posts that are unsure about how to use it. Perhaps it was worth taking off the shelves. Doesn't make my life much easier though! :D

[Edited on 10-7-2010 by peach]
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[*] posted on 10-7-2010 at 12:42


To remove that nasty brown stuff from the AlCl3, you could always try to use a soxhlet with DCM, you wouldn't need much heat, but you'd need a really good condenser.
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[*] posted on 10-7-2010 at 21:41


That's an idea.

It may take a while. DCM boils not a lot above room temperature, as you undoubtedly know. I tried flushing that sample with very large amounts of DCM, around 500ml's worth for 25g of it, with vigorous shaking between rinses (at around 25C) and the brown would simply stain the solvent, but remain thickly in place on the grains.

When the stopper jammed, I was forced to let it sit in the DCM for a while. And that seemed to be the best option in terms of effort, solvent use and removal of the muck, to literally let it soak in just enough to cover it with a shake whenever I walked past over the next three weeks.

Sublimation may work. If it's some iron compound, the aluminium will sublime at much lower temperatures.

I don't have anymore of that CP grade acid left, and I won't be buying anymore. The convenience of having it turn up premade is outweighed by the number of variables it induces in the kind of things I'm using it for, which is experimental work.

Quote: Originally posted by entropy51  
:D Or as we used to say "It's pure, whatever it is!"


That reminds me of the Simpsons episode where the Mafia are selling milk to the schools, sucked out of rats, and Chief Wiggum busts the place then licks one...

"It's pure!"

[Edited on 11-7-2010 by peach]
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[*] posted on 15-7-2010 at 15:14


I regassed the material above today.

It did start reacting again very quickly but, after putting a significant amount of gas through it, I still don't see the acid.

I'll filter and clean it up tomorrow, but I'm not all that hopeful.

I have already used far more gas than is theoretically needed. A fritted wash head would be a good thing to have, but I have used molar excesses so far, adding it at the slowest rate my funnel will drip the conc. H2SO4 onto the salt, and don't have the result.

I had to extend my wash head's down tube with a little neoprene tubing. After a while, the solvent began turning brown. I'm not sure if that's contaminants in the Al source or if the neoprene has been chemically attacked. It does seem remarkably similar to the brown of the commercial acid, just not as dark. The tubing doesn't seem to have degraded, but I'll inspect it closer tomorrow.

I'm sick to death of running this cold solvent method. I should easily have a catalytic amount of the acid by now. I don't think it's particularly viable. I think a well thought out hot method is the way to go.

[Edited on 15-7-2010 by peach]
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[*] posted on 15-7-2010 at 16:25


Why does the solvent have to be cold?




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[*] posted on 16-7-2010 at 01:23


It's not actually cold (this time anyway). By the time it'd started running again it was gently refluxing with it's own heat.

I suppose I could use something like cyclohexane, which has about double the BP and would probably be the solvent I'd be using later anyway, but... I don't think such a none polar solvent is going to pick the HCl(g) up very well. And there already seems to be an issue with wasting gas and a solvent method.

When I store up the energy to do it again, I might try it with a sprinkle of mercury chloride in there from the start. But I think it's going to have the same issues. I suspect there is already enough salt to catalyze, as I'm reasonably sure that's what I can see in the bottle photo. Also, if you can get mercury chloride, I doubt you need to make your own AlCl3.

I have a question for the guys who've tried blowing it over hot Al alone. Does it tend to cake up and stick to the glass where it solidifies again? And am I going to have problems piping it around if I insulate the tubing? I'm not doing anything extreme, I'd just like to simultaneously sublime it out of my test tube and to somewhere easier to get at it. I'd like advice from someone who's done this first hand, because it's a major pain in the ass when things clog up when it involves gases and concentrations of acid like this.

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[*] posted on 16-7-2010 at 10:08


Your posts are too complicated for me, too much reading about unimportant and off-topic details (sorry).
If you ask about reaction of hot Al with HCl - I did this many years ago. Condensed AlCl3 does not stick to glass and can be removed from glass pipe with aid of curved steel wire (as I did).
With pipe with not too samall diamater and on laboratory scale there should not be any problems
Besides it is very nice reaction. You can read a little more about it in Brauer.


BTW.
I would not try to do this in DCM at all. I would be affraid of CH2Cl2 reaction with Al. It is known that CH2Cl2 is using as solvent in organometallic chemistry but many halo-methanes react with Al, Zn or Mg. CH2Br2 gives violent reaction with Al.
Your coloured solution may be just result of such reactions (but not violent) giving some polymeric shit (especially during prolongated time of contact Al with DCM).
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[*] posted on 16-7-2010 at 11:10


The far too ghetto setup for my liking. The glass is all off for repairs and modifications next week, this isn't what I'd usually be happy with and it doesn't work all that well. Note the ACS grade HB pencil. This is a lazy setup, don't copy it verbatim. There should be drying tubes and siphon traps on there, not just because health and safety madness says so, but because it doesn't work so well like this


The wash on the vent is full of strong KOH solution to neutralize any HCl(g) trying to wander off. It works perfectly well. Where HCl(g) escapes, is the seals. They need fully greasing, and preferably with that chemically resistant Molykote (I think it's called)


Peach finally has RBFs


Fizzz.... this method isn't so bad, but it's not perfect either. I would certainly prefer a known, bottled quantity. I'm considering either making my own liquid storage vessel from 316 or renting a cylinder.


Death acid. I thought it was pretty the way there were tentacles falling from the down tube.


This is why wash heads with long stems are utter balls. They also seem to encourage siphoning. If anyone can explain the angles on QuickFits heads like this, please elucidate. I note they've stopped doing this. I'll be having the glassblower rip them off, straighten them and fit barbs or screw threads, probably barbs.


That's neoprene. I've used it before with HCl(g) and it's been absolutely fine. I checked for compatibility. Cole Parmer don't have any information on it, and other sources say it'll be fine with HCl. It's chlorinated and the poor mans PTFE. It's also annoying to work with for a number of reasons. I can't see what's inside it, so I can't stop a problem until it's about to drop through a wash head. I can't tell if it's clean when I wash it out. It doesn't 'flow' very nicely in terms of flexibility and it tends to stick to the glass when it gets warm. It also has quite a 'rubbery' , 'grainy' surface, which encourages things to gather up in it. I'll be going with tygon or similar PTFE like tubing in the future I think. The neoprene swells up in DCM, but that's fairly normal and not chemical attack; PTFE will do it. But, as you'll see, things don't go quite so to plan, and this tubing may be to blame


DCM attemping to escape. It's yellow because there's FeCl3 muck in the tubing. I surrounded the tube with ice when I noticed white fumes coming from it, which was the DCM escaping. It's possible some of that is Watson's chloroform, I still have to distill the solvent. But I'm not entirely sure if I want to be bothered with this one. And I've thrown out the contents of that wash tube


Either the Al or the neoprene is fizzing a lot more than it appears here. The flask is about as warm as luke warm tea, and I can see DCM refluxing off the wash head. So something is reacting


The next day, I put more excess HCl(g) through it. There is a distinct, scary, 'burnt rubber' or 'rotting egg' smell abount the exhaust, which is certainly not the solvent or HCl(g). I am concerned


I'm not gassing it anymore, it's had it's chance. Note the discolouration of the solvent. Impurities in the Al (unlikely) or the neoprene reacting (more likely)


The particulate has gone from stirrable to caking the walls. It's the wrong colour and it's the wrong smell


But it does fume like crazy when I open it to the atmosphere; far worse than AlCl3. But the fumes are incorrect. It's not HCl(g), which it should be if it was AlCl3. The fumes stink of burning rubber or egg. I am now concerned and wish I had a fume hood, as I have no idea what that is or how carcinogenic it is



The neoprene. Despite being covered in something crystalline looking and the odd smell, the polymer seems unaffected. It's swollen, but that's the solvent. It's not rotted away, degraded or brittle. The coating on it does aggresively fume on exposure to water but, again, the smell is entirely wrong


Trying to get a clear picture of the insides is very difficult. In this picture, I'm blowing through one of the necks. AlCl3 fumes on exposure to moisture, but this is doing it far worse. It's possible the yellow is from traces of FeCl3 in the tubing, but there's more there than I'd expect from traces on the inside of the tubing. That wasn't there when I was using pure glass. What could the neoprene be producing that'd steal chlorides from the Aluminium and fume more aggressively than AlCl3? With such an odd, clearly not HCl(g), smell and behavior?


The only thing I can do is hit it with the hose. Again, this is where I'd like a fume hood, this is an unexpected and uncontrollable result. The photo does this no justice at all, it was much worse than it looks here. There were clouds of white, persistent, burnt rubber, sulphur, egg smelling fumes pouring out of the flask for an hour or two. It was so bad I thought someone was going to call the fire engines out. Worse, I tried 'misting' the fumes out of the air. If it was HCl(g), I would certainly recognize it and the water would knock it down. This definitely isn't. I'm worried about what that was, and I'm not sure if I want to know! :mad:


FAIL! NO WHITE PRECIPITATE, NO HCl(g) FUMES ON EXPOSURE TO THE ATMOSPHERE, MASSIVE EXCESSES OF HCl(g) TO REACH THIS STAGE. IF THIS WORKS, I DOUBT IT'S MUCH EASIER THAN COOKING THE AL. AND I SEVERELY DOUBT IT'S ANYWHERE NEAR AS EFFICIENT IN TERMS OF HCl(g). NEOPRENE APPEARS TO BE INCOMPATIBLE WITH HCl(g) WHEN IN DCM. MAKES ME WONDER HOW THIS WOULD HAVE WORKED WITH PURE GLASS. BUT I'M DONE MESSING AROUND. GO HOT METHOD!

[Edited on 16-7-2010 by peach]
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[*] posted on 16-7-2010 at 11:39


Sulfur crosslinking holds vulcanized neoprene together. Even though there's no sulfur in the chloroprene monomer, sulfur is added to the polymer for vulcanization in order to stiffen or harden it. If you're smelling sulfur compounds like H2S, it's coming from degradation of your tubing. Given that you had a piece of it sitting in close contact with a Lewis acid, it's hardly surprising there may have been some depolymerization or other attack. If you knew the smell of chloroprene, it would help diagnose what happened.
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[*] posted on 16-7-2010 at 13:04


See, at this point I'd quit while you're ahead, if I was you.

This whole experiment reminds me of another thread in which a serious and knowledgeable experimenter wasted hours trying to follow a patent that... wait for it... called for the reduction of KCl with Mg at RT in organic solvent media. It too sounded about as plausible as Cold Fusion, it too didn't work. I'm all for thinking outside the box but it doesn't always lead to satisfaction.

Diligent effort though... :cool:

[Edited on 16-7-2010 by blogfast25]
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[*] posted on 16-7-2010 at 17:17


Given the simplicity of the 120 year old methods for successfully making AlCl3 in the lab, this thread is well, inconclusive. Gassing Al with dry HCl works, every time.

[Edited on 17-7-2010 by entropy51]
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[*] posted on 16-7-2010 at 17:21


Entropy there are a gazzlion writeups spaking of the solent method and many claim success. I myself have had limited success as well but I think his down fall here is the use of DCM bar non.

Th solvent method has a quaint charm about it that you dont get with the ho method and I would love to see this synthesis become fruitful.

Ill share a bt of stuff monday, nothing important really just a few notes that seem strange with DCM as the solvent.





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