Author Topic: Yet another OTC GBL extraction  (Read 4639 times)

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raybeez

  • Guest
Following it all up
« Reply #20 on: October 25, 2004, 07:51:00 PM »
Due to some PM requests, Swim wants to post where he is now with this procedure for this given OTC product.

Recall that Swim was obtaining roughly 190mL of GBL per 500mL of remover, however GHB resulting from this was an odd paste like consistency, off colour, and funny tasting.

Swim observed that the tan colour in his product was forming only with the addition of 10M NaOH to the remover. It seemed as though the NaOH was hydrolysing another compound in the remover, which in turn was moving into the aqueous layer with the GBL, and ending up in the final product.

To summarize the remainder of the post for those beez who only have a slight interest, and don't want full experimental details:

a) Swim was able to simply use dh2o washes to remove GBL from the remover, and leave behind a huge chunk impurity was reacting with NaOH and showing up in the final NaGHB product. Technique results in 50mL loss of GBL being recovered (per 500mL)

b) Swim was able to further tweak his washing to obtain a highly pure product subjectively identical to one made with pure GBL. Technique results in an additional 30mL loss of GBL per 500mL (ie 110ishmL being recovered instead of 190).

Technique 1:

1) 500mL of product placed into a seperatory funny, and washed 3 times with distilled water (250mL, 250mL, 125mL). Water layer stays on top, garbage stays on the bottom.

2) The three washes are collected, and reacted with 10M NaOH  to pH 7 and excess water boiled off to collect NaGHB (s) according to standard procedure

It's as simple as that!

Observations: The product is whiter, a much harder consistency, and no longer has an odd aftertaste, so obviously the impurity is not pulled into the water washes, and the water washes can be safely reacted with NaOH. Yield calculations show roughly 140-145mL of GBL being obtained per 500mL of product (so around a 50mL loss of GBL). However, product _still_ has a touch of yellow colouration when a quantity of it (50-100g) is dissolved in distilled water (!)

Swim however has observed that the first 250mL water wash is cloudly, while the second and third washes are clear. So swim decided to try the following:
- Washing 500mL of remover with 3x250mL of distilled water. As per usual, first wash is cloudy, while 2nd and 3rd are clear. The first wash is put aside while the second/third washes are combined and reacted with NaOH.
- Results: Product is the picture of perfection, however calculations show that only 110mL of GBL now being recovered. Obviously, a) some GBL is in the first wash, and b) none or trace impurity is in the 2nd/3rd washes.

Swim has now been trying to stepwise determine the minimum amount of dh2o needed in the 1st wash to prevent any impurities from showing up in the second/third washes. So far swim has tried using 125mL and 150mL for the first wash.  In both cases, yield of GBL only goes down by around 5mL, (ie 130-135mL recovered) while bulk impurity is removed. Impurity still shows up in the final product, so Swim (when time permits) will try and gradually increase the water used in the first washes, to try and establish the amount of water to use to maximize impurity removal while minimizing GBL loss.

Hope that helps those out there who have been PMing Swim. If   anyone out there has any suggestions for how to optimize the H2O washings, please post your suggestions!

redeemer

  • Guest
Water solubility increase with decreasing temp
« Reply #21 on: October 25, 2004, 11:32:00 PM »
SWIM has read on a page (link at the bottom) that "...water solubility [of alcohol ethoxylates (AEO)] decrease with increasing temperature as the molecular heat movements obstruct hydrogen bonding"
So SWIM was thinking if decreasing the temperature of the dH20 used for the first wash would make more of the AEO (and maybe less of the GBL) go over in the polar layer.
SWIM is assuming that the impurity in the final product is AEO because of its ability to dissolve in the polar and non-polar solvents.

http://www.kemi.se/kemamne_eng/alkohol(C6-18)etoxilater_eng.htm

raybeez

  • Guest
Good Find
« Reply #22 on: October 26, 2004, 12:59:00 AM »
Good find, Swim will have to play around with that one and let you know how it goes. Pretty sure that the AEOs are the main impurity, as the addition of NaOH causes the appearance of discolouration of the product (yellow/tan), and the Benzyl Alcohol and Orange sweet don't seem likely to react with OH.

It should be noted that Benzyl Alc. is somewhat h2o soluble itself (I recall reading in the gram/100mL range, but I don't have my Merck handy right now) and could potentially be in the final product as well.

redeemer

  • Guest
Benzyl alcohol's boiling point
« Reply #23 on: October 26, 2004, 03:33:00 PM »
On a couple of sites, benzylalcohol solubility in water was said to be 42.9 g/L (

http://www.evol.nw.ru/labs/lab38/spirov/hazard/benzyl_alcohol.html

) but it should boil away after reacting the GBL with NaOH. It has a bp around 200C, so letting the reacted GBL+BA simmer at about 150C should get that away... Shouldn't it?

raybeez

  • Guest
4g/100mL was the figure I was thinking of, so...
« Reply #24 on: October 26, 2004, 10:33:00 PM »
4g/100mL was the figure I was thinking of, so that sounds right. Its possible that the BA steam distills out with the H2O..

The problem with the NaG made from this product is that it seems to auto-solidify. Swim remembers a time when 99.9% GBL was on hand, and NaGHB made from it would stay liquid at 140-150degC where it was held to remove excess water/gbl. Solidification only occured as the liquid began to cool.

This G however starts to turn solid at 130-140degC, and any attempt to keep the temp going up only burns the final product.