11-15-03 22:35
No 471110
Does NaGHB have a "boiling point"? I've never seen one listed, even in the MSDS I've found, and I'm just curious. Under enough heat, will the molecule eventually break down into simpler components? If I was able to simply heat up pure NaGHB to 250C or so, can anyone shed some light on what would happen?
Some GBL to GHB synths will have "purification" stages (like the chems-r-us synth) which has you keeping your finished product at somewhere around 160C or so if memory serves me in order to "boil off" the unreacted lactone. Why not a higher temp?
Thanks for indulging me.
(Chief Bee)
11-16-03 02:46
No 471133
NaGHB will begin to decompose somewhere above 150°C (measured with an immersed thermometer), causing the molten salt to darken and give off a foul odor as the decomposition progresses. At even higher temperature (when the distillate temp exceeds ~130°C), a foaming exothermic reaction will suddenly set in (I assume this is the point where all water has been removed from the salt) creating a yellow plastic material which does not consist of NaGHB.
(Hive Bee)
11-16-03 02:57
No 471137
On the other hand SWIM has repeatedly seen NaGHB in amount of ca. 250g heated up to 200°C, measured with an immersed thermometer that is reliable, with no signs of discoloration nor odor, and then solidifying on cooling to very hygroscopic soap-like substance of with a pearl-like snow-white shininess. This limit of 150°C is, in SWIM's opinion, exaggeration. But if both observations are correct how can such a difference be explained?
fear fear hate hate
(Stranger)
11-16-03 08:58
No 471161
swim fell asleep during a synth and reaction reached 180 c for over 3 hours with a 30-40 % loss of product but leftover was still ok slightly yellow
(Hive Bee)
11-16-03 15:46
No 471204
Ok, it might be that above 150°C decomposition occurs given enough time, but SWIM says that it was still possible to heat the NaGHB to 200°C in an open erlenmeyer and then pour it in a pan and let it cool down without problems. He also says that going past 220°C started giving troubles.
fear fear hate hate
(Stranger)
11-17-03 06:24
No 471311
Yes, thanks for the replies. SWIM has accidentally heated NaGHB a bit beyond 175C with no apparent ill effects (although the melted NaGHB only remained at this temp for a few minutes).
So this brings me to ask a followup question... the "purification" of NaGHB in some GBL->GHB synths involves (as I posted earlier) heating the NaGHB to a bit over 150C for as much time as it takes for bubbling to stop. This is done to "boil" off unreacted GBL. But the boiling point of GBL is just above 200C. So...
Is it correct to say that (a) a greater temp is not recommended in purification due to what has been posted earlier in this thread (i.e. destruction of the product) and (b) the heating of the unreacted GBL + GHB to 150C or so causes enough molecule collision that even though the mixture does not reach the boiling point of GBL, some GBL molecules gain enough energy to become vapor and escape. So eventually, at that temp, most of the GBL will be gone?
(Chief Bee)
11-17-03 12:02
No 471350
By heating the solution to boil off water, any excess GBL is carried away with the water vapor through steam distillation, every 10g water carrying about 1g GBL (according to Chromics experiments on GBL). It is not necessary to exceed the boiling point of water for steam distillation to occur.
(Stranger)
11-17-03 18:21
No 471394
Why isn't some of the NaGHB carried off with the water via steam disillation like the GBL is?
green bee
(Chief Bee)
11-17-03 19:01
No 471401
As NaGHB is a salt (in contrast to GBL), it is not volatile.
(Stranger)
11-17-03 21:49
No 471422
So since GBL is miscible with water, and is volatile, the boiling point of the GBL/water solution is a function of the molar fractions of both substances and their respective vapor pressures, correct? This is what allows the GBL to be carried off with the water, at a temp lower than the boiling point of GBL?
(Synaptic Self-Mutilator)
11-18-03 22:57
No 471622
Yep, and for concentrated solutions of GBL/water you get the 1g/10g mix that Rhodium quoted me on. The vapor pressure of GBL at 100C is about 14 torr (water, is of course, 760 torr at 100C). (remember to use mole fractions if you want to do the math, not mass fractions) This is more emperical knowledge than physical chemistry... but the #s should work out about the same.
(Stranger)
11-20-03 04:15
No 471871
Thanks for spoonfeeding me, Rhodium and Chromic, it makes sense now. I have only one question left I hope someone has a minute to answer.
I posted a thread about a month ago in Methods in which I asked a question where SWIM had a bottle of GBL/Ethoxidiglycol mix which SWIM believed to be almost purely GBL. SWIM says he may have a lot of this. SWIM wanted to use this to make NaGHB, and (briefly) Rhodium suggested using another solvent to purify, Chromic suggested using NaOH to make NaGHB and then vacuum distill off the ethoxydiglycol.
Since the ethoxydiglycol is organic, miscible with water, has a boling point very very close to GBL - why can't SWIM use the same process to make NaGHB with this and then simply boil away the water/ethoxydiglycol that remains like what can be done with excess GBL/water? Why is low pressure distillation necessary? Since SWIM only has simple distillation apparatus, this potentially simpler method interests him.
(Synaptic Self-Mutilator)
11-20-03 06:53
No 471890
You sure can use the same principle... although, I wouldn't _recommend_ it. Vacuum distillation is always the way to go when you can.