ExothermicReaction
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GBL Distillation - Vacuum or no?
I know GBL distills at around 200C and I've seen some reports of successful simple distillations, but also some reports that a vacuum is highly
desirable since 200C is also close to the point at which it burns or otherwise decomposes in a manner that hurts the final product. Anyone have any
wisdom on this? Should a careful simple distillation using a precise heating source be sufficient or should I go straight for a vacuum and pull down
the temp to 150C or so?
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Eclectic
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Since one of the purification methods is distillation after refluxing with some H2SO4 added, I'd think it would be fairly stable to distillation at
atmospheric pressure. Just a guess though.
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chemrox
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I've been changing my plumbing around so I can run a water pump and condenser from the same lines and I recommend the same. I don't like the idea of
taking lactones up to near the decomposition temperatures but I don't have experience with this one. We have a bottle for processing old vinyl
flooring to get the absestos fibers out and it was reagent when we bought it.
"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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Sauron
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When in doubt, distill at reduced pressure.
A decent aspirator will get to 25 torr or less. There are applets around for free that will let you estimate the bp at any given pressure if you know
the bp at 760 torr. Also Aldrich has a nomograph in catalog for same purpose.
Sic gorgeamus a los subjectatus nunc.
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DrP
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I agree - what's the problem with lowering the pressure? It will be much easier.
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ExothermicReaction
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Ok. Vacuum it is. Looks like I've got to do the same thing you are doing, chemrox. The difficulty is that my lab location doesn't presently have a
good system for drainage. Looking at building something like this Aspirater Vacuum Station.
In a pinch, can a hand-operated vacuum pump, like the kind used for filtration be used to provide a moderate vacuum?
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Methyl.Magic
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You don't need vacuum !!!
GBL is very stable to heat and easily distilled at atmospheric pressure -
How did you get it ? Synthetised ?
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ExothermicReaction
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Well I picked up a decent vacuum pump. Its rated for 27 torr. Even if i don't 'need' it, I'd much rather get the temp down to 150 or so.
Methyl : The reason I started looking at vacuum here is that I've read more than one report that warns that GBL breaks down right around its 200C bp.
Are you saying I don't need to worry about this? At this stage, I am need to separate the GBL from the DCM which I used to extract it, so I plan to
distill of the DCM (at 40C or so) and then distill off the GBL.
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Methyl.Magic
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At frist distil sour DCM at standard pressure. Then, if you have a vacuum pump why not use it ??? You dont need it but using it, you can distill your
GBL with and oil bath.
Did you make it from GABA via Sandmeyer reaction ?
bye !!
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Counter_Culture
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Can anybody see a problem with fractionally distilling gbl directly from the sandmeyer reaction fluid.? Trying to avoid dealing with DCM.
NaHCo3 was added to the post reaction mix until slightly basic to covert gbl to ghb. Excess water was then boiled off until half the original volume.
Plan is to add H2So4 untill slightly acidic, then disill off gbl/water azeotrope. Then add column and vacuum to disill gbl.
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maxidastier
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I`ve found a bottle of "Paint stripper". After checking the MSDS , I found out, it consists of 50-65% gamma-butyrolactone. However, it also contains
up to 15% butyl glycol ((b.p. 171°C) ) as well as up to 15% butyl diglycol (b.p. 231°C). Now butyrolactone has a b.p. of 205°C.
So I set up for vacuum distillation at around 10 torr to try to get rid at least of the lower boiling butyl glcyol.
It didn't really work out well, but now the density has risen from 1,04 g/cm³ to 1,1 g/cm³. Ass both glycols have a density around 0,95g/cm³ and
the butyrolactone having 1,13g/cm³, it has at least now a way better purity. However, there still exists the higher boiling diglycol and I'm not
sure, if I'll get rid of that by means of simple distillation because the boiling points are too close (even with the butyl glycol they were very
close).
What would you suggest to further purify the gamma-butyrolactone? I would like to have it around 98/99% to be pure enough for using it as a solvent.
Should I use a vigreux column and distill again or are there other ways? Do there exist any azeotropes? I couldn`t find much information on the
butyrolactone and those glycols (apart from drug consuming and toxicity...)
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maxidastier
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OK, I see, nobody likes to talk about that stuff.
After distilling the lower boiling butyl glycol, I decided to turn the GBL which was contaminated with butyl diglycol into Na-GHB. Now I've got some
white powder which actually isn't real powder. I thought it might contain too much water and dried it at around 100°C. But oddly enough the powder
became creamy. The reason must be that there still is diglycol in it of which I can't get rid of, because it has a b.p. of 231°C. Could someone
please give me some advice? I surely don't want to eat that stuff and would like to turn it immediately back into it's legal precursor.
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sigma742
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You have an azeotrope, sucks.
You have access to a vacuum, you can get an air pump. Buy a fritted column and some alumina and perform chromatography, will take a while  .
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