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Post NaBH4 crystalization problems

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indole_amine:
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?  :)  AFAIK 37% is the highest concentration possible! Or did you mean a pregassed 50% alcoholic HCl solution?


indole_amine

XrLeap:
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) :P

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