Author Topic: crystallizing, over acidification  (Read 1449 times)

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bruja

  • Guest
crystallizing, over acidification
« on: August 01, 2002, 02:14:00 AM »
What is the best way to readjust your PH when you over gass your product + solvent.  I know I can add NaOH aq till its basic, extract with solvent, and dry, then re-gass.  Is there another way?  Can I add super concentrated NaOH, till neutral, than dry the solvent/water/product with dry epsom salt?  Or just add dry epsom salt to my over gassed solvent, I'm afraid if I do this my product will crystallize as the water is removed making it hard to seperate product from epsom salt.  Thanks for any replys.  I've been away for a while it's good to see the Hive still rules.

Flip

  • Guest
MaDMAx is just talking big shit
« Reply #1 on: August 01, 2002, 06:40:00 PM »
He's just taking the opportunity to brag about his yeilds.
Chances are he has not been that lucky.

If you were getting a decent amount of product bruja you wouldn't have a huge problem.  But this is a very common.  I don't see how if you over-gas you would want to gas any further or try to start from the beginning.  Personally I wouldn't want to see all that NaCl forming around my crystals.   The best thing you could do is recrystallize repeatedly until clean.  You might want to try titration as an alternative method to gassing. 

Here's a good post on recovering crystals from that sticky red tar you get from evapping an over-acidification:

Post 335157 (missing)

(Chromic: "I agree", Newbee Forum)



Conclusion /nm./: the place where you got tired of thinking.

Rhodium

  • Guest
overgassing theory
« Reply #2 on: August 01, 2002, 08:21:00 PM »
Flip, don't critisize when you don't know what you are talking about.

"Over-gassing" does exist, and that is when you continue to gas well after all your product has precipitated, causing sticky polymerization of reaction by-products all over the crystals.

If you follow the procedure outlined by MadMax, filtering off your product from time to time, and also use DISTILLED freebase when gassing, there are less byproducts which can polymerize to form tars.

Flip

  • Guest
Huh?
« Reply #3 on: August 01, 2002, 09:04:00 PM »
I did not state that overgassing did not exist.  I have experienced this phenomenon myself several times before.  Dunno how you came upon that. 

Beyond filtering of your crystals, it remains true that the potential for "over-gassing" is directly proportional to the amount of freebase in solution, distilled freebase of course is an an exception.  Sure, you could filter, regass, filter, regass, etc, but if you don't have enough product in there initially you are going to overgas.

I wouldn't classify my post as a criticism as it is highly unlikely that a single chemist on this board has never experienced failure in this procedure and thus be made to overgas.  It is by these failures that one eventually comes upon success.

And so I respectfully maintain that MaDMAx is talking big shit. ;)

Flip

Conclusion /nm./: the place where you got tired of thinking.

Rhodium

  • Guest
I would believe that a chemist like MadMax always ...
« Reply #4 on: August 01, 2002, 09:37:00 PM »
I would believe that a chemist like MadMax always distills his freebases before gassing, and with the careful gassing he describes, I find it unlikely that he has encountered the symptoms of overgassing. I have encountered it only once, and that was when experimenting to see what would happen if I gassed for five more minutes after no more crystals fell out of the solution (as in not doing things the proper way). Do I talk shit too?

My statement that overgassing did indeed exist was directed towards MadMax, and not you (I wasn't clear enough on that point). However, I maintain that overgassing can easily be avoided by using proper lab technique like vacuum distillation of the freebase beforehand, and using the gas/filter technique outlined above by MadMax.

Flip

  • Guest
-officially bowing down-
« Reply #5 on: August 02, 2002, 02:42:00 AM »
I quite humbly stand corrected.

Conclusion /nm./: the place where you got tired of thinking.

noj

  • Guest
If one reserved a 10% portion of the freebase you ...
« Reply #6 on: August 02, 2002, 07:34:00 AM »
If one reserved a 10% portion of the freebase you could add that in the event of overgassing. Just keep some stored away for emergency.

there's a big difference between criticizing your government and criticizing your country

endo1

  • Guest
Correct me if I am wrong but I think if one were ...
« Reply #7 on: August 02, 2002, 09:43:00 AM »
Correct me if I am wrong but I think if one were using a solvent which can absorb a significant amount of dry HCl such as IPA then one could overgas much easier than if one were using toluene or ether which does not hold much gas.

Flip

  • Guest
Damnit-all he's telling the truth
« Reply #8 on: August 02, 2002, 09:58:00 AM »
A search of MaDMaX's posts referencing 'over*gas*' actually did not turn up but a single post waaay back in '00 where he asked whether or not it was possible.

I can't believe it, but MaDMaX is telling the truth.  Damnit.  What are the odds?  C'mon, really?

noj- that's a great idea but I don't think that I would be able to hold on to that much, or any amount, of freebase for a single day after I dispose of the other 90%.  It's all a matter of willpower, and that's something I most definitately lack when it comes to drugs.


Just so there is no lingering misunderstanding here..... Most if not all of my criticisms are playful nothingness.  The original criticism in itself was not a negative one at all, simply factoring in the likelyhood of never over-gassing a freebase solution due to low yeilds.  This is a part of the normal trial and error that is inherent to this feild that virtually no one is above.  And, it proved to be correct that MaDMaX has done an overgassing, which I have done no doubt tenfold.  I simply could not have imagined that such an avid and knowledgeable reader of this forum would be unaware of the definition of a topic which is covered many times over here.  Perhaps I misread MaDMaX's tone when I interpreted his post as more of a joke, and perhaps the tone of my own post was obscured by this misunderstanding so readers might interpret it as a negative comment.  I apologize for any misunderstanding.   One can easily see the logic behind the assumption which caused the error,i.e- factoring out such unlikely occurences as MaDMAx actually not knowing something.  If anything one should recognize this overestimation and how it reflects my statements as more of an indirect compliment than a criticism.  I normally would not go in to such depth over such technical somantic nothingness, but I am relatively certain that I read the tone of the posts following mine quite clearly and would like to prevent any further misunderstanding of that regard.



WARNING - DO NOT TAKE THIS PERSON SERIOUSLY.  NO, SERIOUSLY THOUGH.

hellman

  • Guest
Hey, stick to topic!!!
« Reply #9 on: August 05, 2002, 05:16:00 AM »
Come on guys, stop this bickering now, you all know better, ;)

IQ is the rate of logic, as Wisdom increases logic, fear & compromise decrease to reveal objectivity

foxy2

  • Guest
Re: Beyond filtering of your crystals, it remains ...
« Reply #10 on: August 09, 2002, 08:59:00 AM »

Beyond filtering of your crystals, it remains true that the potential for "over-gassing" is directly proportional to the amount of freebase in solution,




I would have to agree.  This problem seems most apparent when newbee's are doing a nano synth and they extract 5 grams with 300mL of wet nonpolar. ;D   Then blame it on overgassing.  I think what may actually occur is that when a small amount of excess HCl dissolves in the nonpolar it increases the solubility of the amine and bang the few crystals you had are gone.

Just a feeling I get from reading past posts.
Not really sure myself.


Those who give up essential liberties for temporary safety deserve neither liberty nor safety

Osmium

  • Guest
I've precipitated amines with IPA/Et2O and excess ...
« Reply #11 on: August 09, 2002, 03:50:00 PM »
I've precipitated amines with IPA/Et2O and excess aq. HCl. This could be considered 'overgassing' since the pH often was very acidic(pH paper deep red, pH 1), but the stuff never failed to crystallize.

I think foxy hit the nail on its head, that sounds like the most probable explanation.

I'm not fat just horizontally disproportionate.

Flip

  • Guest
The Wonderful Properties of Organic Peracids
« Reply #12 on: August 11, 2002, 11:11:00 AM »
To which I attribute the most common reasons for shitty yeilds.

Hmmmmm.......what to do, what to do?

Ooohh,ooh,ooohhh, I know!

It's time for something new!

"Holy shit, would you look at that?"  - Flip (8/4/2002)

El_Zorro

  • Guest
Yeah, I'm with foxy on this one.
« Reply #13 on: August 11, 2002, 10:43:00 PM »
Yeah, I'm with foxy on this one. 

My suspicion is that most "overgassing" experiences can be attributed to non-anhydrous conditions.  If the NP isn't dry, then the freebase crystallizes, but when more HCl is added, it dissolves in the wet NP, and increases the solubility of the crystals just enough to redissolve them.  I would think that drying the solvent and addition of another NP(like Et2O)/chilling the solution would fix that.  The same thing would happen if the HCl gas used wasn't dry.  When it hits the NP, the water in it lets the HCl into the solution, and dissolves the crystals.  Treat as before.

Any other problems would be, as MaDMAx said, probably be due to a failed reaction.

Who is that masked man?