Author Topic: Methylamine clean-up  (Read 728 times)

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aleph

  • Guest
Methylamine clean-up
« on: August 20, 2003, 08:34:00 AM »
I dreamed of making methylamine from formaldehyde and ammonium chloride.  Everything went according to text until the end - the crystals would supposedly form in the hot solution after volume reduction, and be somewhat brown.  My crystals formed only after I turned off the heat plate and the solution started cooling, and they are very brown.  Anyone know a simple way to clean up these crystals?  Also, is methylamine supposed to smell like a dog in heat, or did I dream a screw-up?

raffike

  • Guest
Chloroform will clear that shit up.Or if not...
« Reply #1 on: August 20, 2003, 08:38:00 AM »
Chloroform will clear that shit up.Or if not then try acetone.Smell is right.. ;D


biffman

  • Guest
Methylamine cleanup
« Reply #2 on: August 23, 2003, 02:30:00 PM »
First you should rinse with chloroform to remove any dimethylamine but then you definitely should be purifying the methylamine by re-crystalization.  If you can get it, and if you can put up with the lovely smell, n-butyl alcohol works better than ethanol. 
  Reflux your crystals in the alcohol and get as much into solution as possible then decant (or filter) and let cool.  The methylamine will come out nicely.  Filter off the crystals. Repeat as many times as necessary.  I found that to get the final smelly n-butyl alcohol out of the methylamine rinse with isopropyl alcohol then acetone.

raffike

  • Guest
wet ethanol doesn't work,it contains too much...
« Reply #3 on: August 24, 2003, 12:19:00 AM »
wet ethanol doesn't work,it contains too much water and methylamine is pretty soluble ethanol aswell,propyl/butyl alcohol should work just fine


technology

  • Guest
In order to obtain a pure product, the crude...
« Reply #4 on: August 24, 2003, 01:41:00 AM »
In order to obtain a pure product, the crude methylamine hydrochloride is recrystallized from absolute alcohol. The crude salt is placed in a flask fitted with a reflux condenser protected at the top with a calcium chloride tube. Absolute alcohol is added and the mixture heated to boiling. After about one-half hour the undissolved material is allowed to settle and the clear solution is poured off. When the alcoholic solution is cooled, methylamine hydrochloride crystallizes out. It is filtered off, and the alcohol used for another extraction. The process is repeated until the alcohol dissolves no more of the product (about five extractions are necessary). In the flask. you still end up with ammonium chloride remains. And the result being recrystallized methylamine hydrochloride.


Since ammonium chloride is not absolutely insoluble in 100 per cent ethyl alcohol (100 g. dissolve 0.6 g. at 15°), the methylamine hydrochloride purified in the manner described contains appreciable traces of it. A purer product can be prepared by recrystallizing from n-butyl alcohol, in which the solubility of ammonium chloride even at the boiling temperature is negligibly small. Methylamine hydrochloride is somewhat less soluble in this solvent than in ethyl alcohol, but as a rule three extractions carried out at 90–100° with 4–6 parts of fresh butyl alcohol for each extraction result in a substantially complete separation. Since the last traces of the solvent are not readily removed by exposure to air, a solution of the recrystallized material in a small quantity of water should be distilled until free of alcohol, and allowed to crystallize



all the best, :P  :P  :P


aleph

  • Guest
thanks, bees
« Reply #5 on: August 24, 2003, 08:47:00 AM »
Thanks for the info Bees

NeoSynthesis

  • Guest
Correct me if i'm wrong Tech
« Reply #6 on: October 11, 2003, 04:23:00 PM »
Ok.. Not sure about the part with the CaCl tube, but if i understood you correctly, what you're sayin is that the MeAm xtals are boiled/refluxed in a flask of "Absolute Alcohol" (volume?) for about half-an-hour to an hour. Whatever settles to the bottom is basically crap. The solution is allowed to cool down to r/t, at which point the MeAm xtals come out of solution, are filtered out (not sure if you mean vac-filtered?) and then the remaining absolute alcohol is good to go for your next batch?

Also, you said that n-butyl alcohol (if can be obtained) is better for this then absolute alcohol (solubility of NH4Cl, etc). Would the clean up be done the same way?

What did you mean by:

"but as a rule three extractions carried out at 90–100° with 4–6 parts of fresh butyl alcohol for each extraction result in a substantially complete separation"?

Last thing: Does either one of these clean up jobs remove foreign smell from the MeAm xtals that result from the synth? And.. do these clean ups REPLACE chloroform or acetone washing? (mind you.. if you wouldn't mind explaining how chloroform/acetone washes are carried out, I would be much obliged)

Thanks in advance - Peace out