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GHB yield calculation

C

Chawnce

Greenlighter
Joined
Oct 24, 2016
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Hey fellas, It's been a while since I was in chemistry class and definitely need to brush up on the fundamentals. I've found on several forums that one can do the following:

1. Take an aqueous solution of unknown concentration of NaGHB (following a Sandmeyer synthesis, solvent extraction, and NaHCO3 or NaOH reflux) and evaporate the water off to form a paste.
2. Paste is then dried to completion in the oven.
3. The solid is then weighed so when it is redissolved in a calculated volume of water, one would know the g/mL concentration.

Wouldn't there be a significant amount of NaCl in the dried & weighed precipitate? How is this accounted for when yield is calculated? Is recrystallizing the NaGHB in anhydrous ethanol or methanol an option?

Thanks for your help
 
NaCl has much higher solubility in water than NaGHB so as you concentrate the solution down the GHB should precipitate and leave you with a solution of concentrated brine that you can separate off. (I'm assuming you adjust the pH with HCl as the final step - if your last step is NaOH treatment with no adjustment of pH then the impurity will be lye and not salt - which is not good to eat!)

A properly conducted synthesis shouldn't contain an amount of salt worth worrying about. Even if you ignore the salt and assume your GHB is 100% pure, you have a far more accurate way to calculate dosages than totally blind guessing. I say that because the error will always work out to taking *less* GHB - if you measure out 2 grams then you know there will be no more than 2 grams of GHB, but possibly less.
 
But GHB is very hygroscopic and rather than precipitating it is likely to solidify in hydrated form integrating that brine rather than letting you separate it off, I don't know if it matters much if you do this at elevated temperature or more reduced aqueous volume.

I think what you are suggesting would require synthing it in alcohol? Or reXting in it as per the OP.

FWIW, neutralizing to NaCl *should* be fine but you definitely wouldn't want to make certain inorganic salts like acetates which can be pretty damn disgusting for the end result.
 
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Ah you got me there, I guess I didn't consider like the salt of an organic compound like the HCl of a drug - should have said simple salt or just plain salt.
Acetates are also moiety often found in otherwise inorganic complexes, coordination compounds etc, in certain contexts a chemist might call it inorganic but technically you are right of course.
 
Sandmeyer reaction i assume you mean making naghb from gaba. You realize youd be handing fuming nitric acid, hydrochloric acid, and using extremely flammable or toxic organic solvents. No offense but it just seems dangerous to me.
 
Nobody's saying *he's* doing the reaction, that's just the route that someone must have used.

Sandmeyer doesn't use nitric acid either, it uses sodium nitrite.
 
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