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Gamma Butyrolactone purification

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I attempted to saponify a small batch of the GBL using Sodium Bicarbonate. This is how:

I weighed ~0.286 moles of NaHCO3 and put it in to a flask with 100ml of tap water. I brought it to a light boil (more like a simmer) whilst continuously stirring, at which point carbon dioxide was seen bubbling out of the solution. About five minutes after it started boiling, I added ~0.286 moles of GBL to the solution over the course of about five minutes, stirring fairly vigorously. I allowed this solution to continue boiling/simmering for roughly 40 minutes, all the while stirring 75% of the time.

Almost immediately after adding the lactone to the basic solution, there were large chunks forming in the bottom of the flask. Vigorous stirring broke most of them up, but there remained many smaller chunks. On top of that, it seemed that there remained a considerable portion of unreacted sodium bicarbonate/sodium carbonate, and a notable amount of unreacted lactone detectable through smell.

By the 25 minute mark, there was only half the water I had started with, so I topped it up. Chunks kept forming. After 45 minutes and not getting anywhere, I gave up and threw it down the drain.

What did I do wrong?
 
Personally I have only ever done this using NaOH, and method using NaOH is quite a bit easier than NaHCO3
 
Sodium bicarbonate isn't a strong enough base to saponify very effectivvely, I don't think. Most GHB syntheses use lye (hydroxide)

I bet the "chunks" were Na-GHB.
 
Couldn't the chunks be just NaHCO3? It's solubility isn't that great and the addition of something less polar but water-miscible (namely GBL) would force it out of solution.
Plus I don't believe bicarbonate is strong enough to get this reaction going.

Definitely use hydroxide.
 
sekio said:
What are the expected impurities? Purifying technical GBL is probably a waste of your time and money.
Click to expand...

He's purifying from the slurry resulting from the one-pot synth from GABA; I know what you're up to, OP. ;)

ebola
 
I was under the impression that recrystallization from alcohol would be effective?
 
Survived Abortion said:
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.
Click to expand...

You might find this interesting: http://pubs.acs.org/doi/abs/10.1021/je100803e
 
It depends what the impurities are. If you do a distillation and monitor the temperature then you can collect the GBL vapour only and discard what comes at higher or lower temperatures.
 
You'd want to do it with a vacuum pump and a fractionating column, if you attempt a "simple" distillation of GBL, you'd better have a glass retort that can handle being heated to ~300C ... and deal with the resultant charring/blackening/loss of product....
 
Bp of over 200°C... This is surprising to me. Why is the bp of GBL so high?
 
It's polar as fuck? Hydrogen bonding?

Generally the more heteroatoms you throw in a molecule, the more polar it gets, so lots of O atoms proportional to C = high b.p.
 
Yeah sure, but at the same time, aliphatic esters like ethyl acetate or ethyl propionat have bps under 100C. Maybe the ring structure allowes the lactones to pack more densly within the condensed phase?

Also no hydrogen bonding, if the GBL is dry, no?
 
Dry gbl has no active H for hydrogen bonding...
And cyclic esters generally have higher bp than acyclic ones
 
Note that cyclohexanone also has kind of high BP already, and delta-valerolactone has a higher BP than GBL. They are hygroscopic so the 'dry' wouldn't apply I think. So it seems that the H-bonding is a good explanation and that the cyclic nature also helps packing more efficiently than aliphatic counterparts? Aliphatic vs cyclic non-polar alkanes are not significantly different in this respect so that also implies the interactions like the H-bonding present with the polar analogues.

Oh oops the BP is determined as the dry compound?
 
I would think that even with water hydrogen bonding wouldn't be happening in GBL its not going to hydrolize and open up the ring under just neutral water conditions, and even if you have base or acid catalyzed hydrolysis, the intramolecular nature of the lactonization of the hydrolized species would keep the equilibrium towards the lactone.

and water hydrogen bonding to the gbl wouldn't make this distillation of gbl require higher temp than pure gbl, and if anything distilling it with water present would lower the temp you would see lactone distilling at ala steam distillation. assuming you had a huge amount of water. and if it was a small amount you would just distill off the water then the gbl under vaccuum.
 
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