first Al/Hg - complete error :(

[Xicori]

High Bees!

Swim needs once more the opinion of more experienced bees, to find out what he´s done wrong..

Goal was the reductive amination of P2P with Methylamine.HCl and Al/Hg. The procedure is described here:

https://www.thevespiary.org/rhodium/Rhodium/chemistry/p2p-meth.html

Here is what was done:

19,5g of thick aluminium foil was cut into ~2x2 cm and placed into a wide mouth erlenmeyer flask. The aluminium was covered with a solution of 500mg HgCl₂ in warm water.

Stirring wasnt easy with the magnetic stirrer, so the flask was swirled from time to time. After 30sec the solution turned grey and hydrogen envolved at a steady rate. After 1 more minute the HgCl₂ solution was decantet, and the aluminium was washed with 2x 500ml of cold (tap) water.

Then there was added in the following order:

32g of MeAm.HCl (prepared via ammonium chloride/paraformaldehyde an recrystallized from IPA - it was still a bit wet from IPA so more was used) in 30ml of warm tap water.

~ 75ml of Isopropanole
~70ml of 25% NaOH solution [Note 1]
and finally 20g P2P dissolved in 175ml of IPA (P2P that was prepared in

Post 473189

(Xicori: "P2P-Success! (Phenylacetic acid/AA/NaAc)", Stimulants))

Great amounts of Hydrogen envolved from the aluminium surface and temperature rose. The flask was cooled from time to time in a water bath to keep temperatures below 45°C. The most exothermic part of the reaction was over after ~ 5 hours.

At first a grey sludge settled at the bottom, but the colour changed to a brownisch/grey after some hours.

After 5 hours all aluminia foil was consumed, and tha flask was stirred for additional 10 hours at room temperature.

Then again 50ml of 25% NaOH was added what caused some (but very little) bubbling.

After everything settled to the bottom of the flask the clear orange liquid was decanted and the residue was washed 3 times with 100ml of IPA.

The washings were combined, and the solvent was removed on the rotary evaporator.

The residue was poured into 700ml of water and conc. HCl was added until the pH was 1-2. After a lot of stirring (a lot od organic material didnt dissolve in the acidic water) the solution was washed 3 times with 50ml of DCM.

The DCM extracts were orange in colour while the aqueous phase was now nearly colourless.

The aqueus phase was basified which caused a lot of solid material (i think Al-Hydroxides) to fall out of solution. (I think that souldn´t happen at that stage?!)

The basified mixture was extracted 3 times with 80ml of DCM, but extraction was very hard (Emulsions because of the salts that floated around).

The combined extracts which were very slightly brownish were washed once with water and then dried over sodium sulfate.

The solvent was removed on the rotary evaporator to leave about 2-3ml of dark brown oil ( ). This amount wasnt enough for distillation so it was suspended in acidic water, but some of the oil didnt dissolve, even with excessive shaking.

So it was washed once more with 15ml of DCM, and the (colourless) aqueous phase was evaporated under vacuum on the rotary evaporator to leave a purple(!!) amorphous solid (a very little amount)    

Does ynone has any ideas why this failed? i dont wanna perform this reaction until i know what my error was, because swims amount of ketone is a limiting factor...

Maybe the procedure isnt the best one...? - it sounds strange to add all the NaOH solution at once to the Al/Hg, etc... did anybee have success with this method?

Note 1: maybe a bit too much NaOH was added at that stage, may this have caused the error?

I´ll hope to find out the reason with your help!   

Best wishes,
xicori

Edit: I´m sorry, i think that sould belong to the Stimulants forum  

[Osmium]

That procedure sucks and produces consistently bad yields. There's too much water present.
And of course you have to remove the Al hydroxides completely by filtration, decantation isn't good enough.

[Xicori]

thanks osmium!

A comment should be added to the document on rhodiums page... i think many bees tend to try this procedure because it is the only one here that deals directly with p2p and not mdp2p... so irritating & disappointing  experiences could be limitited.

What procedure would you suggest instead? There are many Al/Hg´s out there....

best wishes
xicori

[Rhodium]

Strange, the friend of mine who submitted the writeups included in that document has always gotten consistent yields (65-70%) with that method. I wonder what the catch is...

Could it have something to do with the ketone purity? I seem to remember some inconclusive TLC pics... Have you tried purifying the ketone through its bisulfite complex?

[Xicori]

Could it have something to do with the ketone purity? I seem to remember some inconclusive TLC pics... Have you tried purifying the ketone through its bisulfite complex?

No, i didn´t purifie the ketone any further. Maybe that was a failure too. bisulfite test was positive, and the ketone was very carefully distilled over a 30cm vigreux column, so i think it should have been ok. Maybe there was some dibenzylketone impurity present but that shouldnt have influenced the yeild in that dramatic way...

What could this purple stuff be? I´ve read now some posts on the hive about bees that get purple solutions when trying to crystallize MA/MDMA after an Al/Hg.

[Rhodium]

As Osmium said, decantation from the sludge is not enough, you need to vacuum filter to recover all of your product (and use a filter aid like Celite, or it'll take forever) and don't forget to wash the filter cake with THF or an alcohol.

The purple stuff people are getting is most likely condensation products between various impurities, which react with each other (and also with perfectly fine ketone or product amine) to form colored condensates. Therefore pure starting materials is important, as is distillation of the freebase (or the impurities may goo up when acidifying the product with HCl).

Performing a bisulfite test only confirms the presence of ketone, I referred to convering all of your ketone to its bisulfite adduct, wash it with alcohol to remove soluble impurities, and then decompose the isolated adduct to the ketone again using aqueous sodium carbonate, followed by extraction, drying and solvent evaporation.

[Osmium]

> has always gotten consistent yields (65-70%) with that method.

I consider 65% to be consistently shitty yields. A correctly done Al/Hg should rather produce 90% yields.

[interested]

Couldn't the MDP2P Al/Hg reactions be used to reduce P2P to meth?  If so, here is one of the most clear and concise methods I have ever read.

https://www.thevespiary.org/rhodium/Rhodium/chemistry/alhg-meno2.html

Bee sure to read the photo essay by Dr. Gonzo.
Here's more pictures of the same method with a different setup.

https://www.thevespiary.org/rhodium/Rhodium/clandestine/bucket/index.html

[Xicori]

Couldn't the MDP2P Al/Hg reactions be used to reduce P2P to meth?  If so, here is one of the most clear and concise methods I have ever read

yep, this methods work with nearly every ketone!

...but i would prefer a reaction with Methylamine instead of Nitromethane.


@Rhodium: next time i´ll purify the ketone via the bisulfite adduct, but i dont think that impure ketone was the reason of error - at least it should have yielded at least a little bit, even with impurer ketone..

Distillation of the freebase is my prefered method of purification, but this tiny amounts (~2ml) cant be distilled without very special apparatus.

have a nice weekend!
xicori

[beez_neez]

https://www.thevespiary.org/rhodium/Rhodium/chemistry/alhg.osmium.html

Osmium states here that he has used this method with both mdp2p and p2p.
Something he should have mentioned when he answered the earlier post!