Failed 4mmc synthesis

[dnBQByvHb8Zkawbjpx]

My attempts at 4mmc synthesis have been plagued with a similar problem - during acidification, after adding just few drops of HCl, the mixture turns black. Well, black is not precise, it's either green or blue. But so dark that it appears black. Only after diluting the liquid by a large factor you can see the actual color. After adding more HCl the mixture reaches pH 5 (approximately) and the 4-MMC.HCl precipitates. Some product can be usually salvaged but it takes a lot of time and acetone to wash as much color from the precipitate as possible, and then repeatedly recrystallize and wash the crystals with more acetone to purify the product. I attach two photos from two batches to show what the problem looks like.

I always pay close attention during the flushing of free base and the resulting organic layer is free of any smell of methylamine. In my last attempt I tried to super-cool everything entering the acidification step: the HCl, the free base, the acetone, everything was freezer-cold at -18 °C, but the free base diluted by acetone turned black with about the fifth drop of HCl.

My suspicion that there is unreacted bk4 in the free base and I will focus on fixing this in my next attempt. I welcome any advice in what I can try and focus on that would explain my past problems.

 

[Dr. MMX]

here we do see impuirities that are the result of improper technique earlier, it shouldnt be blacjk when acidified and left out of freezer

probably its some of reaction problems, bad acetone quality, or not proper quality of 2b4m

simply test at least melting point of of 2b4m.

 

[dnBQByvHb8Zkawbjpx]

My acetone is top notch, I stand by it. However, these photos come from batches cooked with very improvised equipment - no external heat and only a very weak magnetic stirrer. It is quite likely that I ended the reaction too early given its temperature and there was unreacted bk4 left in the RM.

The bk4 itself was not of the highest quality possible but it was not terrible to be the cause of the colored mess shown above. With some upgraded equipment I was able to run a full reaction (in EA, heated to 50-55 °C, total 30 min) and the acidification finally worked as expected - I got nice white precipitate and no change of color of the RM. Below photo is filtration after acidification. The color of the separated liquid is clear and bright (previously it was all black) and the paste is almost snow-white.

Sadly, the last batch used all my remaining bk4 so I'm unable to test it anymore. But the success of the last batch confirms to me that the problem was not in my bk4.

 

[PersonVPN]

Forget about EA!!!
Very unstable method of synthesis!!!
Very difficult to isolate the final product!
A lot of losses with EA!!!
Use Xylene, Benzene or DСM.!!!
In all other respects, stick to the same recipe as described here!!
If you are just a student, do not dilute HCL acid with acetone!
It will take some time before you understand this whole process.


For 100 g of BK4, add 500 g of the solvents I indicated.
For 100 g of BK4, add all the methylamine at once. (140 ml of 40% solution in water) With large volumes, 500 g or more, add in portions and cool!


Carry out the acidification very slowly!!! up to pH 5.5-6.
Filter, dry, ( After this, rub the dry powder through a metal sieve) and only then wash the dry powder first with xylene or Benzene!! ( NO DCM !!!) and then with chemically pure acetone.

Well, when you already know all your mistakes and gain experience, you can change the synthesis conditions as you wish!

I wish you all good luck in your studies.!!!

 

[Dr. MMX]

PersonVPN
I honestly do not agree, this solvent is suitable and has some of pros - it can be recycled during sysntheiss and even its required to distill it under negative pressure
in my opinion it provides less impurities than DCM

 

[abis777]

I did a new synthesis today with way better results but I made mistakes with acidification. All things went well except at the acidification I got ph 1 and got a white solution (last picture) then I put it in the freezer. Should I continue to extract the meph tomorrow or the synth is dead?

 

[Dr. MMX]

it shows ph1 becasue it may not have water to provide tesst result

 

[TheVacuumGuy]

I've managed to have 2 batches that were completely water free when starting acidification.
In that case you can't read PH !!
The meter jumps from 10 to 2 to 6 andsoforth.

To measure PH, your mixture needs to contain some water.

 

[Dr. MMX]

If your caculations are correct, yoou dont need to measure ph... juist calculate molar mass of anything you do.

 

[NeoTolls]

About 110ml to 130ml acid HCl 37%if use 100g 2b4m

 

[dnBQByvHb8Zkawbjpx]

That does not sound right. It's too much, in fact it's more than three times the required amount per my calculation. Double check your work.

I calculated I'd need 52 g of HCl 31 % for 100 g 2b4m. The density of HCl 31 % is slightly higher than that of water (1.15), so 52 g is 45 ml. Your HCl is higher concentration and so you are going to need to use less of it. Roughly 38 ml, if my calculation is correct. A quick look at The simplest recipe for crystal Mephedrone suggests that I am right. The reference recipe for 100 g 2b4m uses 40 ml of hydrochloric acid (presumably maximum concentration 37 %).

 

[abis777]

how much water to add in order to be able to measure ph and not dissolve the mephedrone?

 

[Dr. MMX]

just to make it wet

 

[abis777]

wet got it