overunity33
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Vaccume distilling to dryness? buffer?
If one were hypothetically distilling an amine freebase oil in a solvent, you would distil the solvent etc, throw it out or reuse it and then add
pressure to distil the freebase oil. My worry is that right before the freebase oil has all come over it is gona leave a nasty residue in the
glassware. Is there a higher boiling buffer you can add to prevent this? I read somewhere sunflower oil or silicon is recommended. Can anyone chime
in and let me know your experiences? Thanks.
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turd
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In one word: bullshit.
1) This is material for the "Beginnings" sub-forum.
2) Hopefully you apply vacuum and not pressure.
3) There is no nasty residue which can't be cleaned with acetone, soap and a brush.
4) Adding sunflower or silicone oil is NOT recommended.
5) Stop that "I read somewhere..." nonsense without providing pointers. Probably you just made that up anyway.
Edit: silicone, not silicon. 
[Edited on 11-4-2010 by turd]
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unionised
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The use of "chaser" solvents is well documented
e.g.
http://www.erowid.org/archive/rhodium/chemistry/equipment/di...
(and the paper copy of the book says the same thing.)
It's not so common to see them used in vacuum distillations but they would still work.
I have also seen recommendations that you add an involatile oil when distilling things like ether. If there's any peroxide in the ether it will get
left behind. If the oil were not added you would have straight peroxide which would almost certainly explode and cause damage. With the oil present
you get a solution which decomposes slowly and harmlessly. I can't find a ref. for that at the moment.
To use these same ideas in the vacuum distillation of a product seems sensible enough to me. I'd use liquid parafin rather than silicone oil (which
can be difficult to remove fully) or sunflower oil (which is likely to react with the base).
Make sure the oil has a much lower vapour pressure than the product or it will contaminate it.
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turd
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This thread is neither about the fractional distillation with a column with large surface area (the reference that you provided) nor about the
distillation of peroxide forming ethers. It is about the distillation of high boiling freebases of (probably alpha-methyl-beta-phenylethyl)amine
compounds. I can assure you that those distill nicely to the end and that there is no mythical residue. Addition of a "chaser" will do nothing in the
best case, but most likely reduce yield or contaminate product. Not recommended.
PS: I know the Zubrick book is recommended, but the style reminds me too much of Uncle Fester, Prof. Buzz, etc...
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unionised
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I bow to your superior knowledge of the distillation of banned substances and their analogues.
However if the guy has little enough understanding of the techniques that he's asking I wonder how sure you can be that the products he's working with
are clean enough to distil without messing up the distillation flask.
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turd
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I never had to throw away a flask because of organic oligomers, did you? I alway was able to clean them by long - and in really bad cases repeated -
soaks in acetone or EtOH. One hears bad things about Reimer-Tiemann reactions, but luckily I've been sparred this ordeal. If there is a lot of
oligomers (there shouldn't be!) I found it to be advantageous to pour it away directly after distillation as long as it is still hot.
But you are right, who knows what's inside that flask and maybe he heats to 500°C, after all he was talking about applying pressure. 
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overunity33
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Quote: Originally posted by turd  | In one word: bullshit.
1) This is material for the "Beginnings" sub-forum.
2) Hopefully you apply vacuum and not pressure.
3) There is no nasty residue which can't be cleaned with acetone, soap and a brush.
4) Adding sunflower or silicone oil is NOT recommended.
5) Stop that "I read somewhere..." nonsense without providing pointers. Probably you just made that up anyway.
Edit: silicone, not silicon.
[Edited on 11-4-2010 by turd] |
Turd, my post may have been unclear but your post is just straight up worthless. Oh, man I was slightly sloppy with my writing that's my problem,
your problem is the fact that you took the time to reply to my post and criticise me. I got my point across didn't I, is that not the point of
language? Of course im applying vacuum and when I say pressure I mean negative pressure. Are you too thick to deduce that or just gota get your
rocks off nitpicking someone's post on a science message board. Maybe in school someone nitpicked you around too much? You say there is no nasty
residue that can't be easily cleaned? That sounds more ignorant then any part of my post. I would find the reference to adding a buffer oil or
silicone to prove you wrong turd but honestly I just couldn't be bothered to care enough. Some of us are here to learn and apparently others are here
to pay their aggressions forward. Just because nobody takes you serious in the real world turd, doesn't mean you have to assert yourself in such a
way on this message board. Its just not helpful.
Thank you to everyone with a legitimate response.
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unionised
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I have yet to throw out a flask because it was full of tarry stuff, but I have broken a fair few while washing them. Perhaps if I had thought of this
before I might have saved one or two.
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turd
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My answer was not aggressive, just very terse and to the point. Points 3) and 4) are of course only valid for the kind of reaction I'm quite sure you
have in mind and were to coward to mention. But please go ahead and put more impurities in the mixture you want to purify.
PS: To be nit-picky: you might ponder on the concept of "negative pressure" and how to achieve such a thing with a vacuum pump.
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Nicodem
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Actually he answered all the issues quite well. It is after all a typical beginner's question, it is not pressure that you should apply, there never
was any issue with nasty residues described, it is not rational to use a chaser for a simple vacuum distillation, and you did not provide any
references.
| Quote: | | Oh, man I was slightly sloppy with my writing that's my problem, your problem is the fact that you took the time to reply to my post and criticise me.
I got my point across didn't I, is that not the point of language? |
Just because you live in the illusion that you are able to communicate with others, it does not mean you actually are able to use language. As for
every human, it is the language that uses you and not vice versa. For example, if you say "pressure", we will think exactly of "pressure" because "to
press" means to apply force on an area (and not remove force from it!). Therefore, if what you really want is to be understood, you should first of
all abandon the belief that others are able to understand you.
| Quote: | | You say there is no nasty residue that can't be easily cleaned? That sounds more ignorant then any part of my post. |
What you failed to communicate is the problem you are having, thus making any type of reply, including a sobering one, completely legitimate. If you
carefully reread your opening post, you will note that you are asking a solution for a non existing problem. You "worry" but have no arguments to
transmute your "worry" into real-world consistence. This makes your questions lack a certain reflection and your temperamental reaction to a useful
answer makes you appear like you care much more about protecting your fragile ego rather than being one of those who "are here to learn". If you
really want to learn, you should get a harder skin, listen to others and do your best in understanding them, even though knowing that you can not
really understand. I hope you understand, because if you do it will help you a lot.
Anyway, think about the operation you want to perform. It appears you are just trying to remove nonvolatiles by doing a vacuum distillation without a
column (a simple distillation), so by adding a chaser you will allow it to contaminate your distillate (droplets and aerosol coming over). Is that
fine to you? Adding a chaser will lower your recovery of the distillate according to Rault's law. Do you care about that? Is it rational at all to use
a chaser just for a hypothetically easier cleaning up of the flask, when you can just add some high boiling oil after the distillation, heat it up and
pour it out, and you would get more or less the same cleaning effect? Then ask yourself if you need a chaser for its function to prevent charring of
thermally labile side products when what you want to do is a vacuum distillation, hence a distillation at a lowered boiling point. Is it really
necessary to use double protection just because you worry? These and others such are the questions you should have been asking yourself if you really
understood the answers you already got (rather than worrying about the fragility of your ego).
PS: Moving to Beginnings section.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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Nicodem
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Thread Moved
11-4-2010 at 12:46 |
chemrox
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Turd was exactly right. Was this posted in org chem? I fo it should have mentioned the compound in question or at least some of it's structure and
properties. There are times when I try to avoid having people get sidetracked by irrelevant concerns by not posting the compounds I'm asking about.
In general this isn't a good practice. After all these are forums and if people want to comment adversely on my interests so be it. The real
transgression for an org-chem post was the "I've heard.." stuff. I have to ask myself, "where?" and "from whom?" The post should have contained at
least one reference even if it was an erowid or "Clandestine Chemist's Notebook" link. I don't mind people experimenting with amphetamines &
phenylethylamines manufacture as long as they're not planning to sell it. However, I believe we have a policy against methamphetamine discussions
because of all the detritus that they seem to inspire. The tone here is a lot higher than I first realized when I joined. I'd like to advise
something I didn't do; play dumb for awhile. Read and enjoy the site. Get familiar with the posting styles. Above all observe this simple rule:
If you can't be transparent with what you're doing this is probably not the place to ask your questions. When methamphetamine was being made by
reductive amination of phenyl-2-propanone (a long time ago), the procedures called for distilling the free base at reduced pressure. Nobody used a
'chaser' because they were working in large enough amounts that column hold up wasn't a big issue. I have to mention one other thing- I have a 500
ml equalizing funnel I used for adding propionyl chloride & GAA to a reaction mixture. I have tried 4M NaOH, chromic acid, MeOH, acetone, DCM,
hexanes and piranha solution. It still clouds when I rinse it with water. FYI- I used long soaks when I treated it with solvents. I also baked it
at 400F for a few hours. 450 F is the maximum temperature I can get out of that oven and still control the temperature. If anyone has ideas about
what to try next I'd love to hear.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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Satan
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Certainly if some chaser would be necessary for "amine oil", sunflower oil is not good choice as it`s probably going to react with your amine, forming
amides and glycerol. Chaser should be inert and not forming azeotropes with sustance being distilled as I understand this issiue.
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