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Author: Subject: ZnCl2 + Al -> AlCl3 troubles... again
Opylation
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[*] posted on 9-7-2020 at 21:20
ZnCl2 + Al -> AlCl3 troubles... again


Hey all. I’m feeling pretty deflated after this last run trying to make aluminum chloride. The first time I ran it indoors which was a huge mistake and I ended up cutting it short because of the huge plumes of aluminum chloride smoke pouring out. Also the Al powder I was using seemed to have pretty bad iron contamination. That ended up netting ~a gram of powder.

Anyways, this run I switched some things out. First, I ran the reaction outside. My setup was a 500ml RBF with a claisen adapter above. The straight section of my Claisen adapter was stoppered off and the branching section was connected to a 100mm U pipe that fed straight into a hdpe bottle. Also, in an attempt to contain the AlCl3 I used parafilm to seal the bottle and the U pipe.

This time around I used an excess of 50 mol% like chemplayer said of pelleted aluminum, about the size of sesame seeds and the same ZnCl2. Now my zinc chloride was purchased off of Etsy and says that it 99.97% by HPLC. Now the only other time I’ve used this was my first attempt and when I first opened the bottle the whole thing was a damn brick. Like solid. The bottle doesn’t look like it’s hermetically sealed. Just a regular screw on. The thing came with black electrical tape around the seal but I’m not so sure how well that kept everything. Anyways, this time around the ZnCl2 looks pretty much the same, came out in huge balls stuck together and I had to used a spatula to try to break it up as much as possible.

Now, the reaction pretty much proceeded the same as before except it took a little bit longer to start. I kept the heat 3/4+ of the way to max on my heating mantle and just like before my ZnCl2 started to melt a tiny bit, not completely, which means that it’s not fully dry. But before the reaction Kicked off the zinc chloride started turning brown and then pretty much all at once it started producing aluminum chloride. Now to make sure I got all of the aluminum chloride out of the glassware I used a propane torch from the top of the RBF up to just before it went into my container. It seemed to produce a little bit more alcl3 but not much. And no matter how much I blasted the glass, until it started glowing a little bit, the white material on the glass shrunk a little bit mostly turned gray.

Anyways, I ended up calling it and I re-weighed my receiver container and I only gained 2 grams out of a theoretical yield of 50 grams so at this point I’m just waisting reagents. On top of that when I went to wash out my RBF it seemed like all my alcl3 was in there because I had to use several cups of water over 10 minutes before it stopped fuming. It was really hard for me to tell what was in the flask because the whole thing turned and opaque black and I couldn’t see anything inside of it. I’m starting to think it’s my zinc chloride because of the way it turned brown before the reaction kicked off.

I guess what I’m really trying to get at is has anybody else had success with this? I’m thinking it might just be easier to make AlI3 since everything is self contained inside an organic solvent no need to sublime it.

[Edited on 10-7-2020 by Opylation]
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draculic acid69
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[*] posted on 9-7-2020 at 22:12


Can u dry the ingredients first? It's a definite requirement for forming water sensitive compounds.dry both in a dessicator before commencing.and AlI3 & AlBr3 will both be easier to make .
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[*] posted on 9-7-2020 at 22:47


I’m wondering if the ZnCl2 I got isn’t of the best quality. I have made anhydrous CuCl2 for the preparation of AlCl3 before I realized that reaction would be more of a thermite-like reaction. I have about 100 grams of it. I have been thinking maybe stepping up from CuCl2 to ZnCl2 and then to AlCl3 would be more preferable. CuCl2 is easily dried and the enthalpy of formation between CuCl2 to ZnCl2 is about the same as ZnCl2 to AlCl3. I’m wondering preparing my own reagents may provide a better outcome. I do have some wide mouth glass reagent jars with ground glass stoppers coming in the mail. I’ve found that a thin strip of ptfe tape on the stopper and twisted tight provides a nice air tight seal. I have a 500ml RBF with that CuCl2 that’s been sitting for over a month with no signs of hydrating, still chocolate brown. I’m also unsure if maybe my reaction flask is not getting hot enough? I’m still not sure if what I’m seeing refluxing is entirely water or if it is melted ZnCl2. Regardless there is for sure some water contamination within the zinc chloride

[Edited on 10-7-2020 by Opylation]
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[*] posted on 11-7-2020 at 14:27


For anybody who’s curious or may be searching for a solution to the AlCl3 synthesis I believe I have stumbled upon a keeper. So if you look on the dibromomethane wiki page, there is a link to an article that has a synthesis on, you guessed it, dibromomethane. Anyways the synthesis of DBM uses DCM, Br2 and Al producing DBM and AlCl3 as a byproduct. The reaction runs at “a gentle reflux” under careful addition. I do not see why one can’t run the reaction to completion, distill the liquids, and sublime the left over product. That’s all she wrote!
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draculic acid69
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[*] posted on 12-7-2020 at 01:23


Maybe.try it and get back to us
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