Amphetamine purification by acid-base extraction

[ACAB]

The following observation, which synthesis route to amphetamine does not matter.
After the A-freebase is released with the addition of NaOH and collects oilily on the surface, I perform an extraction with petroleum ether.
First I transfer the solution to a cylinder and wait for the layers to form. With a syringe I collect the upper layer in an Erlenmeyer flask. Then the solution comes into the separating funnel and is shaken with 10% of the volume of the solution 3 times with petrol ether and also collected in the Erlenmeyer.

Here it is noticed that the amphetamine base does not mix completely with the petroleum ether and two layers are formed here as well.
The Erlenmeyer is dried with 1-2 teaspoons of MgSO₄ and now something strange happens.
The solution becomes thicker and thicker even shaking does not help, it becomes a mush. Two hours in the freezer and then vacuum filtered and I now have much more salt than I added.

What happens here?
Does the A-freebase react with the SO₄ from the MgSO₄ and form amphetamine sulfate?

When I partially dissolve the salt in a beaker with water, an oily layer forms again. After adding NaOH, the upper layer can be extracted and placed together with the petroleum ether on a dish to evaporate the ether.

Who can tell me what happens there with the MgSO₄ during drying, is another desiccant to choose?
Use something else like petroleum ether?
Am grateful for any help. thanks

 

[diogenes]

ACAB, I have re-read your post and I think the key to the problem is in this sentence:
`Here it is noticed that the amphetamine base does not mix completely with the petroleum ether and two layers are formed here as well.` This means that the layer what you extract as `oily base` is not pure oily base. Why don`t you use some petroleum ether (or other non-polar solvent) here too? I mean from the point your solutions reaches pH12 and a layer forms, it is ok, to separate the oily layer, but put this in the separating funnel and add equal amount of petroleum ether, then save the petroleum ether layer in the Ehrlenmeyer if two layers are formed. The not petroleum ether layer (if it forms) you can add to the original water and then extract with the rest of the water. Using only 10% of the water volume 3 times is probably too little, use 30% then 20% then 20%.

I know it is quite a lot of ether, you can use the water as indicator: the water becomes almost clear when most of the oil has been extracted.

Combine the petrol ether fractions add them to the separating funnel and wash at least 2-3X with distilled water, then 1X with brine (saturated NaCl solution). Then start drying it, but only add `enough` MgSO4, not `more is better`. When the MgSO4 is showing snowball effect after 15-20 minutes, then you are good. If you have mol sieve then you can use that too instead of MgSO4/Na2SO4. GRAVITY filter the MgSO4. I don`t really like it as it has quite small molecular size and might come through some filters and need filtering more than one time.

When you have your clear and dry petrol ether then distill it, so that using more before won`t matter, you get it back. You should do this anyway with most of your solvents.

Also, as a general rule, when cooling or just leaving outside any dry solutions, never forget to cover it with kitchen kling film and a rubber band so that it is airtight.

Let us know if the problem still persists if you follow this way.

 

[ACAB]

I assume that the formed layer can be separated (for me this is A-oil, because something else cannot be in there, except impurities, after I have released the freebase) and I only have to extract the rest of the solution with petroleum ether. Is this assumption not correct?
Because if I try to extract the two layers with petroleum ether, I always have 3 layers and I do not get everything extracted, or I would have to make many extractions until the middle layer is completely dissolved. If that is possible at all.

 

[G.Patton]

Hi, amph base reacts with Mg2+ ions after a long exposition. I think it is a reason of your mash formation. It isn't best desiccant for amines. Na2SO4 is better for this procedure.

 

[ACAB]

Ok, but what you mean with long exposition? The reaction starts immediately after putting the salt into the solution.
And MgSO4 is also recommended here in the article as a desiccant, I was not familiar with anything else before, but what else do we extract other than amines?
I will try that first, because that also matches with my observation that A-freebase must have reacted with the salt, because the filtered salt released the base again after dissolving in water.

 

[G.Patton]

I carried out amphetamine A/B extraction with MgSO4 without problems. Probably, your problem reason is different.

 

[ACAB]

Yes me too, but sometimes i have this result that something is reacting while drying. I thought that I am not the only one who happens

 

[Mr Good Cat]

Thanks for the interesting method. I'm trying to purify quite dirty MDMA HCL. The product itself has'nt been purified at all. PH at the beginning was 7.


So the crystals after first crystallization are almost black. I tried to finish some small quantity around 18 gr + 20 ml of water.

I did step 2 and reached PH=12. It took approximately 6 ml of 50% NaOH solution. But instead of forming on the top, the freebase forms on the bottom. There is also third layer, very thin barely visible, on the top. I'm pretty sure the freebase is on the bottom, as this part has specific smell of pussy.

Is it normal and I can begin step 3, or I did something wrong?

 

[diogenes]

I think MDMA-HCl should be purified by recrystallisation in hot alcohol, then the crystals washed with Acetone. I haven`t done it, so I might be wrong. I am sure general Patton has addressed this in one of his purification topics.

 

[UWe9o12jkied91d]

you need more water for impurities to have somewhere to go, I bet if you add some all that dark crap will move to the bottom water layer

 

[Mr Good Cat]

Already put 1:5. Waiting for the result.

 

[Mr Good Cat]

After the night in the separating funnel the layers changed their positions.
Here are three layers - water, freebase, ether.
It looks this black layer is the freebase. Separate it and checked weight - it fits.

 

[G.Patton]

Hello, as @UWe9o12jkied91d said, more water (or NaOH sln) will help to separate layers. You will not spoil your free base by alkaline excess. On the last picture it looks like free base layer is on the top. Middle layer is part of bottom layer with pollutants. You can separate them and add more NaOH aq sln to the bottom layer and left for several hours in case you want to collect a little bit more free base.

P.S. it is a funny comparison "has specific smell of pussy." =)

 

[UWe9o12jkied91d]

it's only 2 layers, dark stuff is crap, imo you need more water still

 

[Mr Good Cat]

The layer on the top is the ether. I added it in 20% of Rm volume yesterday and left it for the night. So it looks, all the freebase with all this black crap ascended to the middle layer.

 

[Mr Good Cat]

Well, I added some water approximately as 1:5 in total and left it in the funnel for 3 hours. The result is here. Looks all the water is on the top now, and the freebase with pollutants is on the bottom. Probably, I will be lucky if I get even a half of the beginning weight)))))

 

[G.Patton]

Is there on the picture same funnel with same content and + additional water? Have you separated layers from previous picture with funnel?

 

[Mr Good Cat]

1st picture is the first moment as step 2 finished. I put it on the funnel, separated immediately, and checked the weight and smell of both layers.

2nd picture is the funnel after I added 10ml of ether and left it overnight.

Then I separated all the three layers, put more water (1:5) to the middle layer and left it for a few hours. As the result I got 3rd picture.

Could it be the volume of pollutants is so huge, so the freebase + pollutants are more heavy than water + NaOH?

 

[G.Patton]

Your free base in the ether layer. Add about same volume of ether to the funnel right now and shake it. Let layers separates. You'll extract amph free base leftovers from this solution.
Then, separate layers and combine with previous ether extract. Continue acidification procedures.

 

[Mr Good Cat]

I did further steps:
1. Separated the solution of Pic.3 into 2 parts. Upper part (A) was considered as the freebase, lower part (B) as water.
2. The volume of (A) was estimated as 20ml approx, so I added around 100 ml of water and some NaOH, thrown it to the funnel. Then added 25 ml of ether to the funnel and left for a couple of hours.
3. Then, I simply added some NaOH to the part (B) and left it in the glass.

Now, after a while, the situation as below.
4. The solution from the funnel (former part (A)) separated into three layers. And the middle layer became much thinner, probably around 10 ml in comparison with upper layer, that is approx 25 ml - Pic.4

5. But, what is more interesting, the solution from the glass (former part (B)) is dividing into two part, upper and lower, and it looks upper part could be my extracted freebase - Pic. 5. And, if I'm right, and this upper part is the freebase, so the water from the funnel (Pic.4) could be separated by the same way.

I will try and update.

 

[G.Patton]

I think you misunderstand us.
There are just two layers. Your free base is dissolved in ether, not in water. Do you understand me? Please, read our answers you carefully and try to understand.

 

[G.Patton]

 

[Mr Good Cat]

Sorry, mate!! I got where I was wrong. But, I was confused with the volume of Ether + freebase extract as this volume was the same as the ether volume at the beginning. This is why I decided the freebase was insoluble or something.

 

[G.Patton]

pH in your mucous membranes is 7, it is good pH.

 

[diogenes]

Actually, a higher pH increases the absorption rate and amount of amphetamines. I once licked some freshly made base off my fingertip, it burnt, but then I got an almost psychedelic rush from a tiny amount.