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All 9 posts   Subject: Post NaBH4 crystalization problems   Please login to post   Down

11-11-04 02:36
No 540953
      Post NaBH4 crystalization problems     

I just ran my first NabH4 reduction on MDP2P. I generated the 10%MeAm in MeOH solution in situ by dissolving 70g MeAm.HCl in 500ml methanol then adding 42g NaOH slowly under stirring and cooling. This took roughly 2 hours as I had to periodically put the solution into the freezer. When this step was completed I filtered off the NaCl. This was my first time working with MeAm and I was unsure if the step worked but the MeOH absolutely stunk like MeAm generated from the Nitromethane Al/Hg. To this 100g of -15C MDP2P from a performic was added and allowed to stir for 30min. Under cooling 10gms of NaBH4 was added in 2g portion over 5 hours. The solutin turned from a orange clear to a milky pink/red color. I allowed to stir for 20hrs slowly warming to room tempeature. Post reaction was basified with 4L 5% NaOH solution and freebase was seperated. It was pink/brown color. Freebase was dissolved in 500ml acetone and 100ml 50% HCl was added. I was expecting the MDMA.HCL to precipitate however nothing happened. The whole solution is in the freezer cooling right now to see if anything happens. Did I screw up? I thought you could crash the crystals out of solution this way. The solution did not warm up too much upon addition. Any ideas?
11-11-04 03:22
No 540959
      some calculation for the reaction...     

yield freebase was 78g MDMA x 1mol/192.7 g = 0.4 mol MDMA
started with 100g MDP2P x 1mol/178g = 0.56 mol MDP2P

% yield MDMA = 0.4 mol MDMA/0.56 mol M2P2P = 72.3% MDMA feebase
(Hive Bee)
11-11-04 07:09
No 540979

You have a solution of mdma hcl, acetone and h2o, distill of the acetone h2o azetrope the slow distill off the water check you ph for 6 or 7. That should work
(Hive Bee)
11-11-04 08:46
No 540991
      The solutin turned from a orange clear to a...     

The solutin turned from a orange clear to a milky pink/red color
Usually turn bit lighter during the addition of boro
Post reaction was basified with 4L 5% NaOH solution and freebase was seperated. It was pink/brown color.
You should've at least AB'd it,especially if freebase didn't seem pure and pink doesn't seem like pure to.Cub always got bright yellow or almost white freebase even before AB and after AB it looked like water,smelled kind of fishy though not overwhelming and not ketone like.It smelled bit like ammonia but smell was weak and definitely distinguishable from ammonia,it smelled like...freebasesmile
Freebase was dissolved in 500ml acetone and 100ml 50% HCl was added.
Should have gassed.Anyway just evap and see what remains.
(Hive Bee)
11-11-04 14:40
No 541025
      Hi b00ked, The method that you used looked ok...     

Hi b00ked,

The method that you used looked ok to SWIM. However, you did not indicate the temperature of the solution while adding NaBH4. As per Sir Labtop, the best is from 0-5C.

SWIM always perform an A/B extraction to pull all freebase from the methanol solution, and to seperate what is not needed.

SWIM also always try to distill his freebase to a clear color oil, this way, salt/.HCl can be obtained using any preferred method.


oops i did it again
(Hive Bee)
11-11-04 16:04
No 541035
User Picture 

First of all, in situ MeAm gas generation is normally accomplished with a solvent not miscible with saturated aequous salt solutions. MeOH is miscible with NaCl/H2O, so I would advise you to use EtOH, iPrOH or even better a nonpolar like hexane or toluene here. See Barium's "wet method" for details...

Next thing is that the MeAm solution mustn't become hotter than 15-30°C, or else the gas will escape and you'll be left with a maybe 5% solution instead of 10%...

Also, I would rather add the ketone before basifying the methylamine.HCl - the 30 minutes before NaBH4 addition are not enough time for the imine to form. And the imine formation occurs preferably when the formed water is removed - this is accomplished in situ by the generated NaCl; it dissolves in the water from imine formation, forms a very polar solution, and the amine/imine/ketone containing solvent becomes immiscible with this polar NaCL soln. Therefore my advice of using a np solvent...

And I really wonder about your crystallization: WHERE THE HELL did you get 50% HCl? smile AFAIK 37% is the highest concentration possible! Or did you mean a pregassed 50% alcoholic HCl solution?

(Hive Bee)
11-11-04 19:52
No 541066
      To increase some yield, you can try to add 3A...     

To increase some yield, you can try to add 3A mol sieves after NaOH has been dissolved. Add them bit by bit and take note of the changes. Do this while the temp is cold. You might notice some meam smell escaping from the methanol, this is when the sieves have successfully suck up the water, pushing the meam freebase into methanol.

Keeping the solution cold would mean lower solubility of NaCl, thus will not affect the solubility of NaBH4 in that methanol solution. Try to seperate all solid NaCl away from the methanol solution, none of the theory SWIM knows of, but through practical, the NaCl kills. After filtering the NaCl, add some methanol to rinse the NaCl(filter cake) and combine them to the mother methanol solution.

Adding of Ketone before meam in situ generation is good, provided that filtration of NaCl can be done easily. The filtration process must be done in shortest possible of time to reduce meam gas escaping. As SWIM used vacuum filtration and gas escaping under vacuum is fast....(SWIM assumed)tongue

oops i did it again
11-13-04 01:03
No 541311
      doubtful about procedure...     

I beleive that generating the MeAm in situ is a far inferior method and that this step caused the reaction to fail. Tempeature never exceeded 12C. So far there has been no precipitation of mdma.hcl while in the -15C freezer. 30min for imine formation was probably hasty. The reason swim is in such a hurry is because of time constraints at the place i'm working at. I will not try this reaction again...MDP2P is too valuabe. I cannot find anywhere to gas MeAm into solution and I'm not doing it inside. I will aminate with Al/Hg just to get my confidence back. Does anybody have any experience with Osmiums Al/Hg method?

I got the 50% HCL solution from a major chemical supplier most will know all too well. Hint I go to regular AA meetings. Thanks for the replys.

Where does one find the solubilities of various salts in solvents such as MeOH and EtOH etc. Tried to find solubilities of MeAm.HCl and NaCl in methanol with no luck.
(Hive Bee)
11-13-04 16:48
No 541387
User Picture 
      Al/Hg isn't better     

No, the wet NaBH4 method with in situ MeAm(g) generation works fine and gives good yields as long as

a) the NaOH isn't added all at once, but rather dissolved in a min. amnt of H2O and dripped in over 10-20 minutes

b) the miscibility of the solvent with polar aequous salt solutions should be ideally zero, or molar sieves and other inert drying agents may be used

c)the imine formation step is given at least 2 hours time

d) the borohydride isn't added too fast/all at once etc.

e) the workup is done properly

And I would guess that in your case, it was a combination of rules b) and c) that wasn't complied with...


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