joemacone
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Intro/Need help deciphering
Hey guys! New to the board, glad to be here. I have a little organic chemistry and chemistry experience from college, and I am still studying it.
I am reading this, and for the life of me, can't seem to grasp what exactly the chemist did:
"All the decantations and washes were combined, and the solution concentrated under vacuum.
The residue was taken up in 1000ml water, acidified by the addition of conc HCl, and washed with 3x50ml DCM, basified with 25% NaOH, and extracted
with 3x100ml DCM. The combined DCM extracts were dried over MgSO4, filtered and the solvent distilled off. The residue was distilled twice under
aspirator vacuum"
Could you guys give me a hand to figure out exactly what he did? Thanks guys
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blogfast25
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Welcome!
That's the work-up of some organic synthesis.
Post the rest of the procedure, actual synthesis included and I'm sure some here will enlighten you.
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Dr.Bob
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Likely the first few washes of the aqueous acidic solution is to remove some acidic or neutral organic impurities. Once the aqueous is made basic
with 25% NaOH, the basic materials in the water will become less soluble and then dissolve in the DCM, so the water is extracted with DCM and all of
those extracts (after the basificiation) are combined, and the total DCM soln is dried with MgSO4, filtered to remove the MgSO4, and then the DCM is
removed to leave the basic organic residue.
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macckone
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That is from erowid and this should go in the trash pile.
It is cookery.
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Crowfjord
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Howdy, and welcome to the board. For future reference, things like this, where there is no literature reference and you just need help understanding
basics, should be posted in Beginnings.
I'm surprised you did not learn this stuff in your organic chemistry course, but here is a detailed explanation.
It sounds like something was rinsed with a solvent, which was poured off the top (decanted), and this was done more than once. The solvent from each
decantation and washing was combined (mixed together), then the solvent was evaporated either in a rotary evaporator or a distillation apparatus whose
internal pressure had been lowered by use of a vacuum pump of some sort. This increases the concentration of whatever was dissolved in the solvent.
He residue is what is left over after evaporating the solvent. The put the residue in 1000 mL of water - I will assume it dissolved - then added
concentrated hydrochloric acid until he solution was acidic (pH below 7). Washing means to shake with a liquid/solvent not soluble with the liquid
being washed, in this case dichloromethane (DCM). This is usually done in a separatory funnel. So, three times they shook the acidic water (aqueous)
solution with 50 mL of DCM, let the two separate into layers, and drained off the DCM.
Then they made the aqueous solution basic (pH above 7) with a solution that is 25% sodium hydroxide and 75% water by mass. Then they washed with DCM
exactly like before, but this time it's called an extraction because the thing you want is now going into the DCM. The DCM is drained off and
anhydrous (no water) magnesium sulfate is added to absorb the small amount of water dissolved in it. I'm sure you know what it means to filter and
distill something. What's left over after distilling the solvent is then itself distilled, by lowering the pressure in the apparatus with an aspirator
(this is a device that makes a vacuum by using running water).
This sounds like a typical amine purification procedure.
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joemacone
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Hi guys! Thanks a lot.
Noted, Crowford.
The thing is, I did learn these things, but in french. I am mainly french and have a pretty hard time with my english, ha!
Thanks again guys. I will try to contribute to the board as I can, and post other questions if they arise. 
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Bert
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Thread Moved
1-7-2015 at 06:35 |
Darkstar
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It is. As suspected, a quick Google search confirmed what macckone said, pointing to a procedure hosted on Erowid that describes a reductive amination
reaction between phenylacetone and methylamine. The distillate in the OP's procedure is methamphetamine freebase, which is then further converted to
its hydrochloride salt by gassing an ethereal solution of it with dry HCl.
Now, whether or not this thread actually belongs in Detritus, I don't know. If the OP is simply asking about that particular step in order to better
understand the chemistry involved, I suppose it's not technically cookery. He hasn't explicitly stated what his intentions are or asked obvious
spoon-feeding/"how-to" questions.
[Edited on 7-2-2015 by Darkstar]
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joemacone
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Hey guys, to clarify, I am not interested in actually doing this experiment. I just like to understand the different ways of synthesis and had trouble
figuring this paragraph out.
I hope this is fine, this is illegal where I live, anyways. There would be no interest for me to make this.
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