gbl products

Soap · Tue Apr 19, 2005 9:34 am

recently N-Methyl-2-pyrrolidone has been added to gbl based solvents. before extracting gbl from otc products could be easily done with activated charcoal and distillation. however this additive makes seperation very difficult. the boiling point of N-Methyl-2-pyrrolidone is almost the same as gbl, it has similar chemical behaviors. any ideas?the little information swim has found is believed to have never been tested. the following is from A.D.C

The boiling points of N-methyl-pyrrolidone (202°C) and
> gamma-Butyrolactone (204°C) are way too close for it to be
> possible to separate them by vacuum distillation. Also, take
> note of that the auto-ignition point of NMP is 270°C according
> to its MSDS1, so do NOT subject either pure NMP or a NMP/GBL
> mixture to excessive heat!

> Thus, for separation of the two compounds, you have to resort
> to another scheme, and my best suggestion for this follows here.
> The scheme works perfect in theory, but has not to my knowledge
> been tested in practice by anyone, so please exercise caution,
> and also report back to me if you have performed this separation
> like suggested here, or in any other fashion for that matter.

> Vigorous basic hydrolysis2 of a mixture of N-methyl-pyrrolidone
> and gamma-butyrolactone would create 4-hydroxybutyric acid and
> N-methyl-4-amino-butyric acid (N-Methyl-GABA). Mild acid
> treatment3 of this mixture would preferentially esterify the GHB
> to GBL, while still leaving the amino acid in its zwitterionic
> form - amides form much less readily than lactones, especially
> in aqueous solution. The formed GBL could then be continuously
> extracted from the reaction mixture4 with a water-immiscible
> solvent in an extraction apparatus or by allowing the mixture to
> cool and make a solvent extraction in a sepfunnel every 20-30
> minutes until no more GBL is retrieved. Yet another alternative
> method would be to steam distill the GBL from the hydrolysis
> mixture as it forms adding water at the same rate it distills off.
> Finally the distillate is extracted with a water-immiscible
> solvent from the GBL/water mixture.

> Finally, regardless of method chosen above, you now have a
> solution of crude GBL in a non-polar solvent, and pure GBL is
> isolated by drying the solution over anhydrous MgSO4 or similar,
> filtering, evaporating the solvent (preferably under vacuum,
> collect it for reuse!), followed by (fractional) vacuum
> distillation of the GBL (Important!). It is possible to do without
> vacuum, but it is a bit impractical as the bp of GBL is 204°C at
> atmospherical pressure - something really requiring a heating
> mantle. During this distillation (which is to be conducted very
> slowly, 1-2 drops a second), watch closely for any distillate
> coming over below 204°C and discard this and the first 10-15% of
> the GBL (as it likely contains/consists of NMP, bp 202°C - this
> portion is not lost however, as you can resubject it to the above
> separation again).