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Author: Subject: Issues with Soxhlet set up
A.Fleming
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[*] posted on 12-1-2018 at 12:11
Issues with Soxhlet set up


I've never used Soxhlet apparatus before and I have troubles understanding how to properly perform the following step from my protocol:

To a gently refluxing suspension of 1 g Lithium aluminium hydride in 100 mL of diethyl ether, there was added 1.2 g of compound as a saturated diethyl ether solution with use of a Soxhlet extraction condenser which is modified allowing the continuous return of condensed solvent (through the thimble). After the addition was complete, the refluxing conditions were maintained."

Soo... How do I do it? I run RBF with condenser on top until reflux stabilizes and then I open it, add Soxhlet with compound and continue refluxing or I set up everything cold (RBF with LAH+ether + Soxlet with compound in ether + condenser) and then start refluxing?

Thanks
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[*] posted on 12-1-2018 at 13:43


I'm sure you would get more help if you specified what "compound" is... Because the answer depends on what "compound" is. This doesn't seem like a typical soxhlet extraction, and this seems like you are running a reaction with a soxhlet to help with the reaction, but unless you specify what "compound" is, you are not likely to any help, because nobody know's what "compound" could be if you don't say.
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[*] posted on 12-1-2018 at 13:49


It sounds like they suspended 1 g of LiAlH4 in 100 mL of ether in a flask (250 mL probably) and then placed 1.2 g of the compound in a thimble and put it in a Soxhlet and then attached the Soxhlet to the top of the flask and a reflux condenser to the top of the Soxhlet then started refluxing. LiAlH4 and ether are dangerous substances to play around with, even in such small quantities, unless you know what you're doing.

[Edited on 13-1-2018 by JJay]




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[*] posted on 12-1-2018 at 14:03


Quote: Originally posted by JJay  
It sounds like they suspected 1 g of LiAlH4 in 100 mL of ether in a flask (250 mL probably) and then placed 1.2 g of the compound in a thimble and put it in a Soxhlet and then attached the Soxhlet to the top of the flask and a reflux condenser to the top of the Soxhlet then started refluxing. LiAlH4 and ether are dangerous substances to play around with, even in such small quantities, unless you know what you're doing.

Would this be used so the solvent was colder when it reached the compound?

I ask because i got two types, one has a very thing bottom, its supposed to help warm the solvent in the soxhlet while it fills up. The other has a thicker bottom and dosnt get the solvent in the soxhlet warm.

I dont know but from what you just said, it dosnt sound like something to mess with unless you know the ins and outs of it first.

Ether is a funny thing, i used it alot with no problems. I kind of treated it alot like DCM in the end, then one day about 100ml went up and to this day i have no idea what made it burn.
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[*] posted on 12-1-2018 at 14:16


Quote: Originally posted by JJay  
It sounds like they suspected 1 g of LiAlH4 in 100 mL of ether in a flask (250 mL probably) and then placed 1.2 g of the compound in a thimble and put it in a Soxhlet and then attached the Soxhlet to the top of the flask and a reflux condenser to the top of the Soxhlet then started refluxing. LiAlH4 and ether are dangerous substances to play around with, even in such small quantities, unless you know what you're doing.


But it doesn't say that, it says 1.2g of "compound" in a saturated ether sol... It sounds not like an extraction but a synthesis...
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[*] posted on 12-1-2018 at 14:17


Sounds like more of a Practical question.

Stick the stuff in the soxhlet part, surrounded by filter paper.
Bung the condenser on top, hook up the coolant pipes.

Add X amount of solvent to the flask that will be boiling the solvent - remember there has to be more than enough to fill the upper part.

Add some solvent to the upper part to avoid airlocks - basically enough to get some solvent into the syphon tube.

Turn on the juice and see what shakes loose.




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[*] posted on 12-1-2018 at 15:02


I dont understand the modified part, if you modify a soxhlet so it returns constantly, then its.......

Unless
The 1.2g is in the soxhlet as stated in a solution, the soxhlet dosnt empty fully (thats the mod), so the solvent drips into thimble and a small amount returns to the flask.

I guess you could get funky with glass and sort something, i dont know how you would mod a soxhelt to just drip back a little everytime some solvent drips into it.

Maybe try and rig something with a dean stark?

I smell fried onions ;)

[Edited on 12-1-2018 by NEMO-Chemistry]
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[*] posted on 12-1-2018 at 15:42


Quote: Originally posted by happyfooddance  
I'm sure you would get more help if you specified what "compound" is... Because the answer depends on what "compound" is. This doesn't seem like a typical soxhlet extraction, and this seems like you are running a reaction with a soxhlet to help with the reaction, but unless you specify what "compound" is, you are not likely to any help, because nobody know's what "compound" could be if you don't say.


My bad, of course.
I`m trying to convert β-unsaturated nitro compound into saturated amine.
β-nitro stryrene to be precise.

I`m completely unfamiliar with Pd/C approach, nor do i have the equipment.
Other sources suggest iron as possibility. Never researched such options. I have a nice Allihn condenser and Sohxlet to match.

The reflux is supposed to last for 48 hours - i guess the idea here is to slowly add the styrene to LAH with use os sohxlet. But i don`t get the modification of thimble - why use thimble at all? I understand the styrene must dissolve bad in ether, so why not fill sohxlet with saturated solution of styrene (no thimble) and let the refluxed ether dilute the styrene and add it dropwise to th RBF, where LAH awaits. Am I reading this wrong?

[Edited on 12-1-2018 by A.Fleming]

[Edited on 12-1-2018 by A.Fleming]

[Edited on 12-1-2018 by A.Fleming]
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[*] posted on 12-1-2018 at 16:38


You ought to watch a YouTube video showing how a Soxhlet extractor works.



This is my YouTube channel: Extreme Red Cabbage. I don't have much posted, but I try to do nice writeups once in a while.
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[*] posted on 12-1-2018 at 18:01


You might get a more friendly and helpful response if you were to dispel lingering concerns of cookery.

Going from beta-nitro styrene to the corresponding fully saturated amine would be VERY close to amphetamine. Perhaps you already knew this, as this is what you are trying to make? Or maybe you aren't trying to make this. LiAlH4 is hard to get, and not necessary for this reduction - a good cook would know this. On the other hand, you have a post history of two, and signed up the same day.

The point is that we don't know. Convince us, and some of the more knowledgeable members might be able to offer some assistance.

Edit:

I was wrong - it wouldn't be very close to an amphetamine. It would be an amphetamine. (Took me a minute to visualize that.) If I recall correctly, this method (Substituted nitrostyrene reduced using LiAlH4)is identical to the one provided in Alexander Shulgin's: "PIHKAL".
Correct me?

[Edited on 13-1-2018 by Vosoryx]
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[*] posted on 12-1-2018 at 18:45


Did I mention i smelled onions frying?

Actually i got to be honest and say i think i get this now.

I think i was spot on. As mentioned if you watch a soxhlet it fills up completely then empties entirely. The compound is dissolved in ether and put into a thimble in the soxhlet. So you got a soxhlet with a thimble of liquid in.... Whats going to happen as soon as it fills?

Its going to dump the lot in one go into the pot. If you were doing certain naughty things, you wouldnt want this if doing it this way would you? NO.

So as i said the modification is to block part of the return in the soxhlet, this way it just drips non stop. So your solvent reaches the condenser and drops on the compound, the exact same amount from the thimble is then returned to the pot.

This is why its 48 hours, you reflux really slow. the rate should match the soxhlet volume. I am going to guess and say this was done with a 250ml soxhlet, if i got the sums right then it would take roughly 42 hours for the thimble to have had delivered 250ml of solvent at a very slow rate.

So the reaction actually takes place in the soxhlet, if that makes sense. If it dosnt then go search certain books on interesting compounds that are closer than precursors to stuff that might get you in trouble.

EDIT LOL the post above was posted as i was doing mine! SNAP

Yeah i saw the same book reference, hence the reference to it being closer than a precursor!

BUT funny how i am crap at chemistry but that kind of chemistry is easy to understand!

[Edited on 13-1-2018 by NEMO-Chemistry]
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[*] posted on 12-1-2018 at 18:50


So yes use your condesor on top of a soxhlet, dont bother with the mod and a thimble, keep a fire blanket handy though.

BTW do more reading, there is a trip up with the phenethylamines

sorry but when i google this look what pops up
http://onlinelibrary.wiley.com/doi/10.1002/0471264180.os023....
[Edited on 13-1-2018 by NEMO-Chemistry]

[Edited on 13-1-2018 by NEMO-Chemistry]
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[*] posted on 13-1-2018 at 03:53


I know how it looks like - random guy pops here with 0 post and asks very fishy questions :D I`ve been moderator and administrator to different forums (not chem related, but still) and i know the idea.
I`ll come up with better response probably in the evening as i`m in the hurry right know, but to sum up :
- i have 10 years of lab experience (including PhD) but it was a molecular biology lab, not pure organic chemistry. I have some experience, but organic chem is a field i want to improve right know.
- i have no problems with getting equipment and chemicals as i run my own chem-related company so i can order anything i want as long as it fits with my company profile
- i do understand the idea behind Soxhlet extraction but this is a different use of it, so i decided i`d ask you guys. I THINK that the idea here is to have a very slow addition of the reagent to the hydride, but the modification puzzles me.
- if you REALLY need to know, i`m trying to explore my very own pet project that resolves around alternative pathways of diaminopyrimidine chemotherapeutics, hence the aromatic aldehydes
- i KNOW what can be made out of substituted aromatic compounds, trust me, i had to fill out the forms while ordering it. I`ve no interest in amphetamine synthesis or any other illicit use of those compounds.

This is a technical challenge for me. I sequenced genome of some god forsaken plant but nobody ever told me how to properly recrystallize stuff, i learned it all for my self.

Last edit - it took me a while to get the "onions frying" metaphor :)

[Edited on 13-1-2018 by A.Fleming]

[Edited on 13-1-2018 by A.Fleming]

[Edited on 13-1-2018 by A.Fleming]
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[*] posted on 13-1-2018 at 04:28


Quote: Originally posted by A.Fleming  
I know how it looks like - random guy pops here with 0 post and asks very fishy questions :D I`ve been moderator and administrator to different forums (not chem related, but still) and i know the idea.
I`ll come up with better response probably in the evening as i`m in the hurry right know, but to sum up :
- i have 10 years of lab experience (including PhD) but it was a molecular biology lab, not pure organic chemistry. I have some experience, but organic chem is a field i want to improve right know.
- i have no problems with getting equipment and chemicals as i run my own chem-related company so i can order anything i want as long as it fits with my company profile
- i do understand the idea behind Soxhlet extraction but this is a different use of it, so i decided i`d ask you guys. I THINK that the idea here is to have a very slow addition of the reagent to the hydride, but the modification puzzles me.
- if you REALLY need to know, i`m trying to explore my very own pet project that resolves around alternative pathways of diaminopyrimidine chemotherapeutics, hence the aromatic aldehydes
- i KNOW what can be made out of substituted aromatic compounds, trust me, i had to fill out the forms while ordering it. I`ve no interest in amphetamine synthesis or any other illicit use of those compounds.

This is a technical challenge for me. I sequenced genome of some god forsaken plant but nobody ever told me how to properly recrystallize stuff, i learned it all for my self.

Last edit - it took me a while to get the "onions frying" metaphor :)

[Edited on 13-1-2018 by A.Fleming]

[Edited on 13-1-2018 by A.Fleming]

[Edited on 13-1-2018 by A.Fleming]


The soxhlet adaptation is as I mentioned, ironically the best information is on the cook sites! Personally I think I would try a different approach. But if you want to try the soxhlet then the idea is to lift the bottom hole up.

I can think of a couple of ways to do this, most would ruin the soxhlet. So I think the bigger clue is in the thimble part, most thimbles are of two types, one type is porous and the other has a hole in the bottom.

If you watch a soxhlet, you see it empties the entire thing each time, this is because the outlet is at the bottom. So the adaptation has to be something that raises the outlet so the soxhlet only empties a little each time.

I looked at my Thimbles and I think you got two realistic choices that are easy to do. Use a thimble that is non porous and block the bottom hole of it, then put a small hole near to the top level of the Soxhlet point where it triggers the siphon.

This way the thimble fills up and leaks into the main body of the soxhlet, eventually it will reach the siphon point and empty the Soxhlet.

However most the contents of the thimble will not empty as it can only empty down to the thimble hole.

The other way need a smaller thimble, same idea but you put a tube from the bottom hole in the thimble, terminate this tube just below siphon point.

Its slightly harder to do, but it means you will be taking solution from the bottom of thimble each time and not the top. I think this will also speed things up. No idea if I can bodge a pic to explain, but I will try.

My skills at computer art really suck!

Might be a good idea to fully explain next time, as this method is mentioned in the litrature almost exclusively for meth making.
I will be back with a rough pic
EDIT

I just figured an easier way, using two thimbles BRB

Can you see what I mean now? The inner thimble is porous at bottom so solvent goes through all product. Comes out of bottom and into the outer thimble, the outer thimble is shorter than inner, but higher than siphon point.

So eventually outer thimble spills into soxhlet, after a while the spill over will reach siphon and empty the soxhlet, but it will only empty the contents of soxhlet which is all spill over.

This is why it takes so long, inner thimble only leaks from bottom so all product in contact with solvent.

sox5.png - 147kB

[Edited on 13-1-2018 by NEMO-Chemistry]

[Edited on 13-1-2018 by NEMO-Chemistry]

sox6.png - 149kB
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[*] posted on 13-1-2018 at 05:33


Quote: Originally posted by JJay  
You ought to watch a YouTube video showing how a Soxhlet extractor works.

Why?
The OP explicitly says that the Soxhlet has been modified so it doesn't work the way it would in a TY video.
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[*] posted on 13-1-2018 at 06:30


Quote: Originally posted by Vosoryx  
You might get a more friendly and helpful response if you were to dispel lingering concerns of cookery.

Going from beta-nitro styrene to the corresponding fully saturated amine would be VERY close to amphetamine. Perhaps you already knew this, as this is what you are trying to make? Or maybe you aren't trying to make this. LiAlH4 is hard to get, and not necessary for this reduction - a good cook would know this. On the other hand, you have a post history of two, and signed up the same day.

The point is that we don't know. Convince us, and some of the more knowledgeable members might be able to offer some assistance.

Edit:

I was wrong - it wouldn't be very close to an amphetamine. It would be an amphetamine. (Took me a minute to visualize that.) If I recall correctly, this method (Substituted nitrostyrene reduced using LiAlH4)is identical to the one provided in Alexander Shulgin's: "PIHKAL".
Correct me?

[Edited on 13-1-2018 by Vosoryx]


If it’s just beta nitrostyrene then the corresponding amine would be phenylethylamine, amphetamine would require another methyl group (for simplicity sake, isopropyl as opposed to 1,2-ethyl). Completely legal to possess, I usually buy a couple of hundred grams at a time for personal use over a few months. However, the amounts produced here wouldn’t even be enough for a single dose, so I don’t see the concern unless it’s a substituted nitrostyrene.. Not enough to warrant cookery claims IMO, considering the knowledge of chemistry shown.

[Edited on 13-1-2018 by LearnedAmateur]




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[*] posted on 13-1-2018 at 07:06


Quote: Originally posted by unionised  
Quote: Originally posted by JJay  
You ought to watch a YouTube video showing how a Soxhlet extractor works.

Why?
The OP explicitly says that the Soxhlet has been modified so it doesn't work the way it would in a TY video.


The type of extraction a Soxhlet does is referred to as "continuous solvent extraction." Where exactly are you seeing that the Soxhlet wouldn't work the way it would in a YT video?

More to the point, the OP said he had never used a Soxhlet before and was having trouble understanding how one works.




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[*] posted on 13-1-2018 at 12:49


Quote: Originally posted by NEMO-Chemistry  

Can you see what I mean now?
[Edited on 13-1-2018 by NEMO-Chemistry]

[Edited on 13-1-2018 by NEMO-Chemistry]


YES! Thank you so much for your hard work here. I need to think on this with clear head but for now your idea involves the least glass molding and the addition of compound should be slow enough. I just need some decent thimbles now, nice :)

Quote: Originally posted by Vosoryx  
Not enough to warrant cookery claims IMO, considering the knowledge of chemistry shown.
[Edited on 13-1-2018 by LearnedAmateur]

Thank you.
Quote: Originally posted by JJay  
Quote: Originally posted by unionised  
Quote: Originally posted by JJay  
You ought to watch a YouTube video showing how a Soxhlet extractor works.

Why?
The OP explicitly says that the Soxhlet has been modified so it doesn't work the way it would in a TY video.

The type of extraction a Soxhlet does is referred to as "continuous solvent extraction." Where exactly are you seeing that the Soxhlet wouldn't work the way it would in a YT video?
More to the point, the OP said he had never used a Soxhlet before and was having trouble understanding how one works.


I have no trouble understanding the soxhlet extraction, quite the opposite - i admire the idea, its simplicity and efficiency. What i couldn`t understand was how to modify said soxhlet so it goes more into continuous and less "batchy" system of work. More drop-wise, less "down-goes-the-full-volume-of-soxhlet-into-RBF" mode ;) Also - this is a synthesis use of soxhlet, not the usual extraction.
Now i have some idea to work with, thanks to NEMO.


[Edited on 13-1-2018 by A.Fleming]
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[*] posted on 13-1-2018 at 13:55


What exactly makes you think that this isn't the full-volume-of-soxhlet-into-rbf style? I know it says "modified" Soxhlet, but it doesn't say "simple reflux extractor" (which I guess would be called a Payen extractor and predates the Soxhlet).





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[*] posted on 13-1-2018 at 17:42


Quote: Originally posted by LearnedAmateur  

If it’s just beta nitrostyrene then the corresponding amine would be phenylethylamine, amphetamine would require another methyl group...


Alas, I was wrong. You're right - whoops.

I apologize for this.




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[*] posted on 14-1-2018 at 13:51


Quote: Originally posted by JJay  
What exactly makes you think that this isn't the full-volume-of-soxhlet-into-rbf style? I know it says "modified" Soxhlet, but it doesn't say "simple reflux extractor" (which I guess would be called a Payen extractor and predates the Soxhlet).


What makes me think that is the quote in the OP which says it isn't.
i.e. " a Soxhlet extraction condenser which is modified allowing the continuous return of condensed solvent (through the thimble).".
A Soxhlet doesn't do continuous extraction it's intermittent.
What the synthesis needs is a continuous, slow, addition of the material. A Soxhlet which adds none for ages and then a whole lot at once is the equivalent of trying to titrate using a tomato ketchup bottle.
It may well mean something more like Payen's idea.
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[*] posted on 14-1-2018 at 14:26


Quote: Originally posted by unionised  
A Soxhlet doesn't do continuous extraction it's intermittent.


Whatever, dude. The only part that isn't continuous is the addition of the solvent to the flask below. I'm getting tired of your incessant and pointless questions, unionized.

http://oleoresins.melbia.com/principle-of-soxhlet-extraction...

"Soxhlet extraction is a continuous solid/liquid extraction."





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[*] posted on 14-1-2018 at 14:47


Taking "modified" Soxhlet and "continuous" return of solvent too literally isn't necessarily the writer's intent.

See https://books.google.com/books?id=Vz39BAAAQBAJ&pg=PA523#... for example, which describes a similar use of a Soxhlet. Do you really think the author intended that a distillation flask containing LiAlH4 be placed below the Soxhlet?






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[*] posted on 14-1-2018 at 15:34


The actual answer, guys.

This is a question only somebody who was in O-chem a few decades ago is likely to know the answer to.

Soxhlet extractors are not designed the way they were when Schulgin posted that recipe.

There was no external siphon tube. The siphon tube was an integral part of the thimble. This means you could just break the siphon tube off the thimble and the liquid would continuously drip through the thimble.

The extractor body was just open inside top to bottom, and the thimble was hung in there on a wire through holes at the top of the thimble.

This means even if you've got old-time extraction thimbles (I do) you can't use them as Schulgin did without the old style Soxhlet body.

I'm not saying there aren't some clever ways around this as suggested above, but the Schulgin ref is about breaking the integral siphon off the old-style thimble. Seriously, check out the original paper and I believe he makes it explicit. If not, he did elsewhere in his writings.

EDIT: Somebody posted here recently that they have a 1980s Aldrich, or Sigma, or some such catalogue.
That catalogue may be old enough to have old style Soxhlets listed in it.

[Edited on 14-1-2018 by SWIM]




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[*] posted on 14-1-2018 at 15:48


Quote: Originally posted by SWIM  
The actual answer, guys.

This is a question only somebody who was in O-chem a few decades ago is likely to know the answer to.

Soxhlet extractors are not designed the way they were when Schulgin posted that recipe.

There was no external siphon tube. The siphon tube was an integral part of the thimble. This means you could just break the siphon tube off the thimble and the liquid would continuously drip through the thimble.

The extractor body was just open inside top to bottom, and the thimble was hung in there on a wire through holes at the top of the thimble.

This means even if you've got old-time extraction thimbles (I do) you can't use them as Schulgin did without the old style Soxhlet body.

I'm not saying there aren't some clever ways around this as suggested above, but the Schulgin ref is about breaking the integral siphon off the old-style thimble. Seriously, check out the original paper and I believe he makes it explicit. If not, he did elsewhere in his writings.

EDIT: Somebody posted here recently that they have a 1980s Aldrich, or Sigma, or some such catalogue.
That catalogue may be old enough to have old style Soxhlets listed in it.

[Edited on 14-1-2018 by SWIM]


According to the information that is available on this topic, that does not seem to be the case. This paper has a copy of Soxhlet's original drawing of his extractor, which was considered a "modification" of Payen's extractor. What is the Shulgin reference here?

Nm... this is clearly Shulgin's mescaline synthesis... why the heck would you use a Soxhlet for that?

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[Edited on 15-1-2018 by JJay]




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