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Author: Subject: Can you make p-TSA in situ without too much residual H2SO4?
stoichiometric_steve
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[*] posted on 5-10-2020 at 11:14
Can you make p-TSA in situ without too much residual H2SO4?


If one were to make p-TSA in situ from Toluene/H2SO4 using a Dean-Stark trap, how much unreacted H2SO4 would possibly remain?

[Edited on 5-10-2020 by stoichiometric_steve]
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SaccharinSlayer157
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[*] posted on 5-10-2020 at 11:40


Not sure exactly what you're asking but these might help if you haven't seen them

https://www.youtube.com/watch?v=1GosyO-W-1o&ab_channel=N...

https://www.youtube.com/watch?v=VBOvq6Lr1Zk&ab_channel=D...

Edit: Wait you're an international hazard I probably misunderstood the question

[Edited on 5-10-2020 by SaccharinSlayer157]
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stoichiometric_steve
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[*] posted on 5-10-2020 at 11:54


Sorry i'll try to make it more precise:

I have a reaction that needs p-TSA as a catalyst and can use Toluene as the solvent, but doesn't tolerate H2SO4 very well.

I want to make p-TSA since it's more economical than buying it.

Also since i'm a lazy fucker, i don't want to isolate the p-TSA and even prefer its anhydrous form.

I've never made p-TSA before so i need to know if the H2SO4 fully reacts or not.

If not, can i distill Toluene from the mixture first, then distill out p-TSA under vacuum, leaving H2SO4 behind?



[Edited on 5-10-2020 by stoichiometric_steve]
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Tsjerk
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[*] posted on 5-10-2020 at 14:05


I reacted ethylene glycol with cyclopentanone in toluene after refluxing the toluene with sulfuric acid and catching some water in a Dean Stark.

As far as I could tell sulfuric acid is not very soluble in toluene and the reaction is driven towards p-TSA completely in a Dean Stark.

The reaction is also a nice test to see whether your toluene is pure, it darkens technical grade toluene.
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clearly_not_atara
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[*] posted on 5-10-2020 at 19:21


The formation of TsOH is an equilibrium reaction and is reversed in sulfuric acid containing sufficient water (but not enough to inhibit the reaction). As such it will not proceed to completion in situ. Sorry.



[Edited on 04-20-1969 by clearly_not_atara]
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[*] posted on 6-10-2020 at 01:30


It is not obligately necessary to use Dean Stark trap when making p-TSA, but I strongly recommend to use a magnetic stirrer to make reaction mass as homogeneus as possible. When reaction is complete, a whole reaction mass will solidify upon cooling and standing. To check is reaction completed or not, just simply stop magnetic stirrer and take a look at toluene layer consumption, but it is not really necessary to wait when it will be consumed completely, I actually have about 20% of initial toluene amount unreacted, because in my country (EU) we have cheap toluene and sufuric acid too.

So, you simply have to take magnetic stirrer hotplate, toluol, H2SO4, heat a whole reaction mass while stirring, and you will end up with an amber coloured liquid when about 80-90% of toluene is consumed, then you turn off heating and cool down your solution, and it will solidify then.
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stoichiometric_steve
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[*] posted on 6-10-2020 at 01:36


Quote: Originally posted by Tsjerk  

As far as I could tell sulfuric acid is not very soluble in toluene and the reaction is driven towards p-TSA completely in a Dean Stark


Is there a bottom layer of sulfuric acid after the reaction that can be pipetted out?

Atara, but what's the DS trap for then if it doesn't go to completion? That was exactly my question, how much H2SO4 remains when removing all water produced with a DS trap?
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Tsjerk
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[*] posted on 6-10-2020 at 02:36


I indeed meant the reaction going to completion when using a DS.

The sulfuric acid indeed forms a bottom layer which can be pipetted, but I don't know how much sulfuric acid dissolves in toluene. I would use the dean stark and wait for it to go to completion. You probably don't need much p-TSA anyway.
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stoichiometric_steve
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[*] posted on 6-10-2020 at 02:50


Quote: Originally posted by Tsjerk  
You probably don't need much p-TSA anyway.


Sadly i need 2:1 PTSA:Substrate (1.2:1 w/w) , but it should absolutely be worth it :)
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stoichiometric_steve
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[*] posted on 6-10-2020 at 05:32


Check this out:

Screenshot 2020-10-06 at 15.30.41.jpg - 44kB

Screenshot 2020-10-06 at 15.31.05.jpg - 53kB

Attachment: 10.1021@acs.jnatprod.0c00436.pdf (1.9MB)
This file has been downloaded 44 times

also:
Screenshot 2020-10-06 at 15.36.16.jpg - 8kB

[Edited on 6-10-2020 by stoichiometric_steve]
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karlos³
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[*] posted on 6-10-2020 at 08:33


But its just lousy delta-8.
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Tsjerk
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[*] posted on 6-10-2020 at 09:20


Why do you want to use anhydrous p-TSA? In the article they get excellent yields (delta-9) with the monohydrate.
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stoichiometric_steve
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[*] posted on 6-10-2020 at 09:36


Quote: Originally posted by karlos³  
But its just lousy delta-8.


read again ;)

Quote:

Why do you want to use anhydrous p-TSA? In the article they get excellent yields (delta-9) with the monohydrate.


so i don't have to add water to the p-TSA made in situ on a DS trap.


[Edited on 6-10-2020 by stoichiometric_steve]
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clearly_not_atara
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[*] posted on 6-10-2020 at 10:03


Quote: Originally posted by stoichiometric_steve  

Atara, but what's the DS trap for then if it doesn't go to completion? That was exactly my question, how much H2SO4 remains when removing all water produced with a DS trap?

It shifts the equilibrium. You have:

H2SO4 + PhMe <> TsOH + H2O

[H2SO4] = a
[PhMe] = b
[TsOH] = c
[H2O] = d

The forward reaction rate is k1*a*b and the reverse reaction rate is k2*c*d. A Dean-Stark trap will reduce the reverse reaction rate and increase the yield while also making it easier to recover the product, but the forward reaction rate will always approach zero as [H2SO4] goes to zero.

In fact this is not the actual reaction, it is this:

H3SO4+ + PhMe <> TsOH + H3O+

but H3SO4+ has to be generated by the rxn of two molecules of H2SO4:

2 H2SO4 + PhMe <> TsOH + H3O+ + HSO4-

In the above mechanism we instead find a forward reaction rate of k1*b*a^2 and a reverse rate of k2*a*c*d. Of course you can also do this:

H2SO4 + PhMe + TsOH <> TsOH + H3O+ + TsO-

In the second mechanism TsOH rather than H2SO4 supplies the proton. But TsOH is substantially weaker (about 1000 times weaker) than H2SO4! So the reaction rate is much slower.

Really the forward reaction rate is then: k1*b*a^2 + k3*a*b*c, k1 >> k3.

In all cases, though, we find that the reaction is very slow, perhaps not quite second-order slow but close, in the absence of sufficient sulfuric acid.

Now if you could pipette it out as Tsjerk suggests you might have yourself a method.




[Edited on 04-20-1969 by clearly_not_atara]
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karlos³
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[*] posted on 6-10-2020 at 12:09


Ok thats really interesting.
I need some more CBD to try this out, although I thought that the delta nine produced from CBD just acts like a heavy hammer, when I made predominantly this with the diluted HCl method in ethanol.
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Corrosive Joeseph
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[*] posted on 6-10-2020 at 14:48


Attaching Purification of p-TsOH from Armarego and Chai.



/CJ

Purification of p-Toluenesulfonic Acid - Armarego and Chai.PNG - 71kB




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stoichiometric_steve
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[*] posted on 7-10-2020 at 03:18


karlos, HCl in Ethanol apparently isn't a reliable method since it also produces variable amounts of impurities like ethoxylated compounds. There have been so many claims made about HCl, Phosphoric and other acids for delta9 THC production, it has become hard to tell what influence the respective reaction conditions have on the distribution of the resulting products and impurities.
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Tsjerk
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[*] posted on 7-10-2020 at 04:54


Quote: Originally posted by stoichiometric_steve  


Quote:

Why do you want to use anhydrous p-TSA? In the article they get excellent yields (delta-9) with the monohydrate.


so i don't have to add water to the p-TSA made in situ on a DS trap.

[Edited on 6-10-2020 by stoichiometric_steve]


You could just reflux, cool down to crystallize the monohydrate and filter. That way you also know there is no sulfuric acid left.
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stoichiometric_steve
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[*] posted on 7-10-2020 at 05:02


Thats what i want to avoid, the monohydrate doesn't form when using a DS trap.

If going that route, i could just as well buy PTSA, it's quite cheap and not worth messing around with isolating it. But i would prefer to design a one-pot process or at least one as streamlined as possible, just for the fun of it.

I guess i will have to find out the solubility of Sulfuric acid in Toluene somehow, or maybe it is even so low that it doesn't matter.
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