Sciencemadness Discussion Board

Converting Amine Sulfate into Amine Hydrochloride ?

LuckyWinner - 4-7-2020 at 04:11

the following needs to be done:

1g of an amine sulfate needs to be converted into its hydrochloride form.

1) find proper solvent that is able to dissolve the freebase and is not dissolving the hydrochloride form. (isopropyl alcohol, in this case)
2) find proper chemical that is able to break the sulfate bond (NaOh, in this case)

Add amine sulfate (1g) to solvent under stirring and slowly add 1:1 mol weight of NaOh.
Stirr till bond is broken and freebase dissolves into solution.

One further 1/3 mol of NaOh is added to convert the
sodium hydrogen sulfate to sodium sulfate and H2O.
this will form a white precipitate at the bottom.
H2O should be absorbed by formed sodium sulfate and can be buchner filtered out from the
amine freebase infused isopropyl alcohol solution.

The amine freebase infused isopropyl alcohol solution can then be gassed by dry HCL
and buchner funneled to yield the HCL form.

or 37% HCL solution can be added and liquid (iso+water) is evaporated.


any errors with this or imporvements to get a cleaner product?


[Edited on 5-7-2020 by LuckyWinner]

draculic acid69 - 4-7-2020 at 04:52

Might be better off dissolving in water first then using naoh then using toluene or whatever then dry/gas.

Sigmatropic - 4-7-2020 at 13:30

Dissolve in water pass over a strong basic ion exchange resin Cl- form (amberlite IRA-400 for instance), evaporate or lyophillize. Regenerate resin by flushing with brine, followed by water. Can't get much cleaner than that.

draculic acid69 - 4-7-2020 at 18:30

No but you can get a lot simpler.sounds a little complicated and expensive for such a trivial task

Tsjerk - 4-7-2020 at 18:46

It is a homework question right? And the question implies a clean product, in that case it doesn't have to be practical.

If practical was the question the OP's solution would be far more practical than your solution as you don't need a to do liquid/liquid extraction, just a filtration.

karlos³ - 4-7-2020 at 19:05

I would be tempted to do it differently, in case the amine freebase is volatile with steam.
Simply freebasing in aq. solution, followed by some more water, and then without any fuss directly distilling the amine freebase out with internally generated steam(should do the trick well for most of the rather simple structured amines).
The distillate is neutralised with HCl and evaporated, the obtained HCl salt should be already pretty clean then.
If not, recrystallise, but I doubt this will be needed in practice.

The advantages compared to the solvent extraction of the freebase are obvious: less time-consuming steps to do, while providing a product having an equal or likely even a higher purity, less mechanical losses, and the time actively spent working on it is also reduced.
The distillation itself, and the evaporation of the neutralised distillate probably require more time overall than the solvent extraction would take, but all in all those two steps don't require to work actively for it, only moderate attention is needed.

LuckyWinner - 5-7-2020 at 01:00

Quote: Originally posted by karlos³  
I would be tempted to do it differently, in case the amine freebase is volatile with steam.
Simply freebasing in aq. solution, followed by some more water, and then without any fuss directly distilling the amine freebase out with internally generated steam(should do the trick well for most of the rather simple structured amines).
The distillate is neutralised with HCl and evaporated, the obtained HCl salt should be already pretty clean then.
If not, recrystallise, but I doubt this will be needed in practice.

The advantages compared to the solvent extraction of the freebase are obvious: less time-consuming steps to do, while providing a product having an equal or likely even a higher purity, less mechanical losses, and the time actively spent working on it is also reduced.
The distillation itself, and the evaporation of the neutralised distillate probably require more time overall than the solvent extraction would take, but all in all those two steps don't require to work actively for it, only moderate attention is needed.


nice but lets assume the freebase is not efficiently steam distilled, and is reacting with air.

I guess... OP's solution seems to be the easiest?
doing a couple recrystallizations afterwards to increase purity.

DavidJR - 5-7-2020 at 02:29

Another option would be using barium chloride solution.