• Neuroscience & Pharmacology Discussion Welcome Guest
    Posting Rules Bluelight Rules
    Recent Journal Articles Chemistry Mega-Thread
    FREE Chemistry Databases! Self-Education Guide

  • N&PD Moderators: Skorpio | someguyontheinternet

Gamma Butyrolactone purification

Status
Not open for further replies.
Survived Abortion

Survived Abortion

Bluelighter
Joined
Jul 4, 2007
Messages
1,431
Location
England
I have some GBL, and I would like to go about purifying it in case it contains any impurities.

Would it be possible to do this with one of those Brita water filter jugs? It seems that the filter in these devices uses activated carbon, as well as some kind of ion-exchange resin which removes metals (such as lead). I could just use some normal activated charcoal in a beaker of course, but I don't have any experience doing such. Additionally, the Brita water filter should theoretically remove more impurities.

I am wondering whether there are any reasons I shouldn't do this. Could the GBL leach anything from the plastic in the filter? (The GBL is currently stored in the plastic bottle it was shipped in.) Will the ion-exchange resin remove - or have any negative effect on - the GBL?

If it is better to just use powdered activated carbon, I would appreciate some guidance in how to go about the procedure, for example how much to use per millilitre of GBL.

Please note: the GBL will not be consumed as GBL. I thought I'd add this in case anyone is thinking of preaching to me about the potential health consequences of consuming industrial solvents. Thank you.
 
I would also like a little info, I will be purchasing some non-BASF GBL due to the price and would like to clear it up a bit :)
 
The best method for purifying GBL is to distill it at ~10mmHg.

It's a pretty good solvent, I would expect it to leach plasticizers from all the plastic parts of the Brita filter.
 
In all honesty, I'm not that sure. I read that tetrahydrofuran may be one of the impurities if it is synthesized from it. I've also seen talk of heavy metals, particularly lead, in small quantities (0.05%). I have no idea if that is an acceptable amount or not.

Any other impurities, perhaps derived from synthesis routes other than THF, I would expect you guys in ADD to know about. Wikipedia says that one route to GBL "utilises bromine generated in situ from an aqueous solution of sodium bromate and potassium hydrogen sulfate", and produces a yield of 80%. Another route uses calcium hypochlorite, acetic acid, and acetonitrile. And another method converts GABA to GBL using sodium nitrile via a Sandmeyer reaction.

I don't know what synthesis was used to produce the GBL I have. The solvent looks fairly clear. If bromine was an impurity, I would expect the GBL to be coloured brown. But it could of course also contain some colourless impurities.

Are you saying that these compounds aren't toxic enough to pose a problem when ingested in such quantities, and therefore it is a waste of time to purify the GBL? I'm interested to hear your opinion about this. However, I feel a little uneasy with that considering I know nothing about how it was synthesized or it's true purity level. It is GBL, and it appears clear, but I would feel better running it through some activated charcoal all the same.

Roger&Me said:
The best method for purifying GBL is to distill it at ~10mmHg.
Click to expand...

Oops, I missed this.

Thank you. And just how do I go about this without vacuum pumps and condensers? :D

Roger&Me said:
It's a pretty good solvent, I would expect it to leach plasticizers from all the plastic parts of the Brita filter.
Click to expand...

So does this mean it already has plasticizers in it after being sat in a plastic bottle all this time? What if I put the Brita filter over a glass container - maybe the filter would remove the plastisizers from the GBL, and because the GBL will only be in contact with the Brita filter for a short period of time only a small quantity will be leached as it passes through?

Are plastisizers even toxic?

Please forgive my noob-like ignorance.
 
Last edited:
Depends on what kind of plastic its stored in, some are OK. HDPE would be fine, but I definitely wouldn't store it in a PETE bottle.

And I doubt ingesting plasticizers is a great thing for you, but I'm no doctor, and I'm also too lazy to look it up on wikipedia.

Survived Abortion said:
Thank you. And just how do I go about this without vacuum pumps and condensers? :D
Click to expand...

A still is a relatively cheap piece of glassware, and can be bought online (along with some roundbottoms and a cow). You can find something capable of pumping down to 20-30mmHg (which will do) for a couple hundred bucks if you look around (you can even pump down to ~50mmHg with just a really good brass aspirator running cold water... that would halve the boiling point of GBL, which might be low enough to distill without degradation). Anyway, you're certainly not going to separate THF from GBL with a brita filter, they're too similar in structure and polarity. The THF will come right through the filter because its miscible with the GBL. Distillation is really the only way to go if your goal is to purify a liquid.
 
Unless you have analytical equipment, trying to purify GBL is really a losers game. Going from unknown purity to unknown-but-better purity isnt very much of an improvement...

If the solvent is clear, leaves minimal residue upon ignition, & matches the density and other physical propertiesd of GBL, I would br fine using it as-is. If theres significant impurities/residue a distillaation is best.

Most GBL is going to be produced industrially from catalytic oxidation of THF, I would expect THF as an impurity (volatile but otherwise harmless in the concntrations most people are exposed to). There should not be "leftover solvents" in your peoduct.
 
Fascinating. Thanks for the very informative responses.

The only thing I would be slightly concerned about is the plasticizers Roger&Me was talking about, but I really don't have a choice since that is how it was shipped. In any case, it seems I'm in luck because these bottles are made of HDPE. Through a bit of research, it seems that Brita filters and their pitchers are made of polypropylene, NAS, and SAN, and are purported to contain no Bisphenol-A, although they don't say anything about other possible plasticizers. Nevertheless, I'm slightly unsure now if this is a good idea.

What I'm going to do is go and see if the pharmacist stocks activated carbon. If so, I'll get some in to filter out any potential heavy metals in the GBL. Then I'll transfer the GBL to a glass bottle for long-term storage. I won't be able to afford the distillation equipment for now, so I'll have to make do. I will definitely keep that in mind for the future though.

Thanks again.
 
Last edited:
Activated carbon is not going to "filter out heavy metals". There shouldn't even be any heavy metals in your GBL in the first place. Metal salts are insoluble in orgaic compounds 99.9% of the time. It will adsorb trace impurities of organic compounds but don't expect it to do much.

Whatever you do don't be pouring GBL into plastic containers unless they're HDPE because it will soften almost all plastics.
 
I worked with this a while back. there is information in the b&d thread in EADD.

There is a patent which details the use of concentrated acid to catalyse the polymerisation of impurities, and the subsequent vacuum distillation. Since I did not have any vac kit, I decided to add c.HCl and leave it. Neutralising with NaOH then precipitates any water, and the two layers can be easily separated. Salt must be added to prevent the water and GBL mixing.

I felt that the taste was not as bad, but it still wasn't great. Since I rarely use G and typically swallow it in gelcaps, I have not been bothering recently.



Activated carbon does not work because G is highly affinate for it.
 
well converting it to GHB should also remove a lot impurities and you can wash it with acetone after the conversion!
 
Well it seems I've been barking up the wrong tree with regards to activated carbon then. It's just that in the Rhodium GHB synth it mentions to clean up your GHB solution with activated carbon if it looks impure. I just though that would apply to GBL too. Obviously there's some kind of misunderstanding there.

martin33 said:
distillation, or turn it into GHB and re-crystallize that for purification
Click to expand...

Torabora said:
well converting it to GHB should also remove a lot impurities and you can wash it with acetone after the conversion!
Click to expand...

I wasn't gonna mention it because I thought it construed synthesis discussion, but yes, GHB is the intended final product. If converting it makes it easier to purify, then it looks like I'm on the right track. What are the preferred methods for purification?
 
If you have technical grade GBL, its suitable for using as feedstock for the lactone saponification as-is. only the GBL will react to water-soluble NaGHB. THF won't, other impurities should not.

You can recrystallize sodium GHB by concentrating an aqueous solution down and cooling it. Pure xtals of NaGHB will fall out but yields will be shitty if you have no experience.
 
Some notes...

g0to said:
As others have said, best method would be saponification to Na+GHB- and acetone wash + recrystallization.
Click to expand...
I think this would be not a very good method to purify it, since you take care of misc organic substances, but not of heavy metals and similar substances,
which are not unlikely to occur in GBL for industrial purposes. Depending on how much/what exactly and what are you able/equipped to do, testing for the major (toxic)
impurities and precipitating (in case of metals etc.) might make sense, since you can use methods with a high grade of selectivity (more end product...).
Picric acid with activated charcoal is an example of a nice method to get rid of most heavy metals.

...
But if you are equipped to distill it under a good vacuum, the quoted method is sufficient as final stage and you will have a very pure product.
 
I made a complete mess of it. I'm not really sure what I did wrong, but I just ended up with a big mess of crystallized chunks in a mixture of unreacted butyrolactone and water.
 
Status
Not open for further replies.
Top