Author Topic: Easy preparation of HCl salt w/o gassing  (Read 2910 times)

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Bandil

  • Guest
Easy preparation of HCl salt w/o gassing
« on: June 16, 2004, 10:51:00 AM »
Gassing sucks, this is a axiom as certain as the second law of thermodynamics  :)

There has been various discussions on how to prepare anhydrous HCl in IPA or ether. None of these where really succesfull without gassing at some point. Sometimes its possible to crash out the salt with aq. HCl in IPA and acetone, but it often fails. Lately I have1 devised a sure fire way of making bone dry chlorides of the precious amines, without gassing. The method takes advantage of the azeotrope formed when distilling a light  non-polar mixed with water. Here is how its done.

Once the final amine has been isolated (predrying of the NP prior to the stripping is not even necessary), it is weighted. From this weight the molar amount is calculated. Add an equal molar amount of aqeous 10% HCl2 dropwise while stirring heavily.

From here, there are two ways to go depending on what equipment you have at hand. The optimal setup is using a Dean Stark trap, but a normal distillation setup will suffice.

The Dean Stark way:
Add twice the volume of the water / amine phase of toluene or xylene to the flask. Attach a Dean Stark adaptor with a condensor on top. Start refluxing, untill no more water comes over. Once the water is gone, keep distilling off the toluene or xylene (keep the temperature below 150°C at all times to avoid hurting the amine). The stop cork of the trap can simply be opened and the solvent drained directly into a new flask. Wash the NP with brine and save it for future drying runs3. The remains of the method is identical for both ways, so skip the next paragraph if using this method.

The ghetto way:
If using toluene, add 10X the volume of the amount of 10% HCl you used. i.e. if 10 mL's 10% HCl was needed for the neutralization, add 100 mL toluene. This is a healty 100% excess of what theoretically is needed to dry it, but better be sure. With xylene a little less is required; 6-7X the volume should suffice. Rig the flask for simple distillation. Stirr the mixture heavily and heat. Distill of as much of the xylene / toluene as possible, without going over the B.P. of the solvent. Save the flask with the amine in it and proceed as described in the last section. The toluene / xylene can be reused. Pour the distillate into a sep. funnel and discard the lower water layer. Wash the toluene / xylene once with brine, and its useable for drying again3.

Final work:
Once most of the solvent has been stripped (if you are very keen on getting all of the solvent of, use vacuum for the last bit), disconnect everything. Let the amine salt in its liquid form cool down and then add a bunch of acetone. Usually 5-10X the volume of the amine is fine. Place it in the freezer and within a few hours crystallization should be complete. In one run i had to scratch the inside of the flask with a glass rod to induce crystallization; but for the "normal" compounds this shouldn't be neseccary. Filter the crystals and recrystallize untill it's pure enough  :)

Summa summarium: No gas, no water causing oiling out, no problems  8)  It sounds like a lot of work, but once you get the hang of it, it's way easier than gassing etc.

Notes:
[1]
Barium has suggested the use of azeotropes for completely drying various substrates before, so alot of the credit goes to him!

[2]
I chose to use dilute acid, in order not to hurt the amine by local "over-acidification".

[3]
The toluene I reuse for this purpose is only used for drying. The purity of the isolated distillate is fine in this context - but for other purposes I am not sure. So simply keep a flask of 500 mL's "drying tolly" standing around - it will last a long time.

Regards
Bandil


Chimitant

  • Guest
Nice procedure...
« Reply #1 on: June 16, 2004, 08:02:00 PM »
and so simple! HCl gassing is/was problematic for me since I don´t like HCl gas floating around in my kitchen. I always used phosphoric acid to make phosphate salts of my amines. Next time I´ll try this procedure. It may take a while compared to my old method but the idea of having chloride salts next time sounds attractive to me. Thanks Bandil and Barium!


hest

  • Guest
Phosphates
« Reply #2 on: June 17, 2004, 04:43:00 PM »

I always used phosphoric acid to make phosphate salts of my amines



And it works nice ??, my eksp. is some gummie masses, not good. I must have done somethin wrong. (only triet it once with Amph)


Chimitant

  • Guest
It works but....
« Reply #3 on: June 17, 2004, 11:24:00 PM »
you have to be careful when adding phosphoric acid. Do it in small portions and stirr well. When overacidification occurs you will end up with a large blobs of what you call gummie masses. I always make sure to keep the pH slightly above 7, remove the fine precipitate by filtration and reuse the solvent for a second precipitation. After drying and an acetobe wash you will have a nice white powder. I did not use phosporic acid for amphetamine yet , only for MDMA, and MDA. Sulphates are my choice for amphetamine.


GC_MS

  • Guest
amfetamin
« Reply #4 on: June 18, 2004, 04:29:00 AM »
And it works nice ??, my eksp. is some gummie masses, not good. I must have done somethin wrong. (only triet it once with Amph)

I tried it twies wit good results (amfetamin). The podrukt is not gummie but curtainly not cristaline ether. You can grint the podrukt wit mortar and pestle though... It will have an estelletically acceptible look but will still suck ofr its porperties. But I am not rally a stimulant-fan  ;)


runne

  • Guest
Also for recovery of too much moisture in gassing?
« Reply #5 on: June 25, 2004, 07:03:00 PM »
Bandil,

Could SWIM also use this procedure to remove excess moisture from a gassing that brought too much moisture into the mix?

From a failed gassing that basically "oiled out" one could just setup for distillation and distill until suitably dry? (determined by boiling point or the mdma.hcl precipitating?)

Bandil

  • Guest
Yes, it can be used to salvage many oiled out...
« Reply #6 on: June 26, 2004, 01:34:00 AM »
Yes, it can be used to salvage many oiled out gassings. Obvisouly it requires that the MDMA is pure enough to crystallize in the first place. If its not pure enough, all the dryness in the world wont make it crystallize  ;)

Simply distill, untill no more droplets comes over with the toluene distillate. Then your remaining toluene will be dry. Distill this off and crystallize in a suitable solvent!

Regards
Bandil


FlaskGenie

  • Guest
Failure
« Reply #7 on: August 04, 2004, 06:26:00 AM »
Swim tried this method w/ acetone as his starting solvent.  Swim liked to gas his goodies in acetone.  Switched brands of sulfuric at the last min. and had a foaming problem that shut things down.  The goddies were in acetone already so... Threw in the molar amt of 10% hcl.  Now swim has this brown goo.  Swim knows now  this was a mistake and he is trying to find out if there is a way of saveing his goddies.  They are very clean, A/b then distilled after amination. Some crystals fell out of acetone before the foam overtook everything. Swim is depressed!


hest

  • Guest
Yak
« Reply #8 on: August 04, 2004, 07:40:00 AM »
A/B once more Iff still black destilate and then make salt 'as usual'

r2e3

  • Guest
gas
« Reply #9 on: August 05, 2004, 02:24:00 AM »
to approx 7 ph and freeze (-20C )- wait.... crystal formation - filter crystals - check ph afterwards
start from square 1
minimise loss due to resolvation (ie to much acid)_
sulphate - why???

FlaskGenie

  • Guest
You are a bit over my head r2e3. Swim is new.
« Reply #10 on: August 05, 2004, 06:18:00 AM »
You are a bit over my head r2e3.  Swim is new. I have acidified acetone w 10% hcl and stripped off most of the acetone, I have thick solvent w goo and  brown drops clinging to the sides.  I need more info to try what you suggest.  Was hoping some bee could suggest a np to use w/ acetone for an A/b.  Thanks to all who have replied.  I humbly wait for your next instruction.


endo1

  • Guest
Flood with 4x volume of water, double check...
« Reply #11 on: August 05, 2004, 07:31:00 AM »
Flood with 4x volume of water, double check that the ph is acidic and extract with toluene (or ether etc.) Keep the water layer. Basify and extract your frebase with toluene. Distill frebase and crystalize.

placebo

  • Guest
Barium, can you explain to me what exactly is...
« Reply #12 on: August 05, 2004, 10:26:00 AM »
Barium, can you explain to me what exactly is so difficult about gassing for product? Maybe there is easier ways around your problems.
Please explain.


Bandil

  • Guest
?
« Reply #13 on: August 05, 2004, 11:05:00 AM »
Placebo>

Barium has not made a single reply in this thread - are you referring to me?

It's not difficult per se to gas. It's just so much work with HCl flying around the ears. If you have a good habit with gassing please continue to do so. Myself, im just to lazy to rig for gassing a gazillion times in a row... So thats the simple reason i prefer this method...

Regards
Bandil


placebo

  • Guest
Sorry Bandil I meant you.
« Reply #14 on: August 06, 2004, 10:57:00 AM »
Sorry Bandil I meant you.
No offence, your method is probably great, I just can't see how it's easier. But it is another option.


r2e3

  • Guest
i mean
« Reply #15 on: August 06, 2004, 08:16:00 PM »
when you hydrolize your reduced product - do add the required amount of 'muriatic acid', 33-37% HCl to neutralise NaBH4 and the acidified product also migrates more readily into the non-polar phase. (this assumes your using borohydride naturally...)

dont pre-gas your acetone or add a 10% HCl aq solution. the aq solution is particularly less effective than dry (almost) HCL gas. The less water in your acetone the better or you get brown goo.

:)  suspend your free base in -20C acetone.

then - the way I do it - react HCl/H2SO4 and introduce to the cooled mixture. Check the pH. if foaming occurs as you suggest (do you mean of this mixture) than you probably switched to the wrong brand. Look for something that says '98% sulphuric acid' - will destroy the environment etc..)

At first it takes a while to go from pH 11 to 7 - so  what may seem quite a bit of gassing. When you get as close as possible to pH 7 - don't get clever and try go over, place in the freezer again and wait... be patient.

1st you'll see nice little seeds and then the whole process accelerates. Give it a good hour more more. There will be shed loads of precipitate.

Filter and then check the pH of the filtrate. If pH slightly over 7 - cool, and gas again. Bear in mind you have much less 'base' in your mixture and MUCH less gassing is required.

As far as basifying the aqueous fraction, when spearating your base from the reduction mixture - if your gonna do it -make sure that you dont basify the lot - ie including your free base. It will screw things up.

I prefer to extract any FB from the Aq phase using solvent extraction. I also prefer to use dcm rather than toluene. Bp is 40C, and it just makes life a lot simpler/quicker.

hope this is of some help.