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Author: Subject: Substitute for dioxane
maxidastier
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[*] posted on 25-8-2011 at 02:30


Thank you!
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blogfast25
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[*] posted on 25-8-2011 at 08:28


No probs. Let us know how you get on. I'm really interested in making some dioxane but had never heard of the toluene sulphate method...



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maxidastier
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[*] posted on 25-8-2011 at 09:36


AFAIK you don't use the sulphate but the p-TsOH monohydrate.
I've one last question before I try it again: Since the p-TsOH is a catalyst, it doesn't get consumed right? So can I use the same amount of TsOH for even more ethylene glycol if I continuously add fresh ethylene glycol?
By this way I also don't get that much waste at the end.
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[*] posted on 25-8-2011 at 10:21


Quote: Originally posted by maxidastier  
Since the p-TsOH is a catalyst, it doesn't get consumed right? So can I use the same amount of TsOH for even more ethylene glycol if I continuously add fresh ethylene glycol?


Catalysts, chemically speaking, don't get consumed, that's correct. But catalyst recovery can be quite a kerfuffle, as I suspect will be the case here. Just adding more and more glycol won't cut it, I'm fairly sure.




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maxidastier
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[*] posted on 26-8-2011 at 00:28


I didn't want to recover the catalyst, but if you say a continuous process isn't possible, ok then.

[Edited on 26-8-2011 by maxidastier]
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[*] posted on 8-9-2011 at 01:27


Can HCl destroy the p-TsOH if it isn't removed immediately?
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[*] posted on 8-9-2011 at 03:19


No.



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maxidastier
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[*] posted on 9-9-2011 at 08:38


This is now my second attempt to make p-TsOH from H2SO4 and Toluene.
I've with the help of two literature instructions. One is from Gattermann-Wieland and Experiments in Organic Chemistry by Fieser.

So, then: I've used 40ml 96% H2SO4 and 200ml Toluene and a Dean-Stark-Trap as Gatterman-Wieland suggests.
Everything went fine. I've got around 13ml of H2O after 4 hours, so should it be complete reaction, which means there still were aroung 115ml unreacted Toluene left. I decided to collect this with the same apparatus, and collected aroung 100ml through the Dean-Stark-Trap.
Then I did something, which MIGHT be the reason for the failed attempt: I went upstairs to go to the toilet and drink something.
When I came back, the residue in the flask had become dark brown- I immediately removed the flask from the heating mantle.
I transferred the mixture in a beaker glass to cool down. I added around 1 ml of water to test, if there was some TsOH. Where the drops touched the water, instantly became white and solid.
So I let it cool down and added 100ml conc. HCl. I heated until boiling and cool again to recrystallize and get mainly the para isomere.
But I didn't get white crystals. I only got a brown slurry, when I vacuum-filtrated it.
I thought okay, then another recrystallization, added another 50ml HCl, heated, cooled and still having brow-white slurry.

Is the dark brown colour after the reaction normal? Here, I can't see any brown: http://www.sciencemadness.org/talk/viewthread.php?tid=15522

Does that mean, the TsOH became completely desulfonated while I was upstairs and the heat was to high?

When I cleaned my flask and other stuff with water, there were white solid pieces swimming in it. This can't be TsOH, since it is soluble in water and I couldn't dissolve by shaking or anything. What is it?

[Edited on 9-9-2011 by maxidastier]
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[*] posted on 10-9-2011 at 00:52


Quote: Originally posted by garage chemist  
When no more water is collecting in the trap (all H2SO4 has reacted), one adds a small, carefully measured amount of water to the mix after cooling which makes the p-TsOH crystallize from the excess toluene as the monohydrate. The byproduct o-TsOH does not form such a hydrate and stays in solution.
The filtered crude p-TsOH*H2O is then purified by dissolving it in half its own weight of water and saturating the solution with HCl gas.

For your needs you can skip the tedious recrystallization step. Impurities don't make much of a difference in your application.

Given you appear to be doing this out of practice/fun rather than the need for dioxane (or else you would just use the H2SO4 based procedures), you might as well try using NaHSO4 as the catalyst (instead TsOH). It is available in any shop selling pool chemicals.
The idea of using a continuous process is a good one (reactive distillation of products as they form and feeding in fresh ethylene glycol), but I think you should optimize the batch process first to get an understanding of the critical reaction parameters. Though with a continuous process you would still end up doing a batch isolation process.
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[*] posted on 10-9-2011 at 01:17


Thanks for your input!
But I still don't know what has happened to my TsOH...
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[*] posted on 11-9-2011 at 08:23


It's really a mess. The problem is, after adding the water to make the p-TsOH crystallize as the monohydrate, it does not crystallize as long as the solution is to hot, but if it's cool enough, after adding water, everything solidifies, the o-TsOH does not stay in solution. How can I get rid of it then and moreover, how can I get rid of the toluene?
I didn't use HCl this time as you suggested. Now I have some clumpy, pink, wet crystals which dissolve in the air and there are little droplets where the solid used to be.
What am I doing wrong?
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[*] posted on 19-9-2011 at 01:57


Is there another way aside from potassium carbonate to create an organic layer containing mainly Dioxane and another layer containing the water, since after the synthesis there would be a 1:1 mix of Dioxane/water?
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[*] posted on 19-9-2011 at 05:09


I'm not sure why specifically it calls for (the more expensive) K2CO3, when I believe Na2CO3 should do just as well (my guess). But the principle of 'salting' cannot be avoided, AFAIK...



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[*] posted on 19-9-2011 at 11:32


Yes, that is exactly my question: Could I use Na2CO3 instead?
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[*] posted on 19-9-2011 at 11:51


Quote: Originally posted by maxidastier  
It's really a mess. The problem is, after adding the water to make the p-TsOH crystallize as the monohydrate, it does not crystallize as long as the solution is to hot, but if it's cool enough, after adding water, everything solidifies, the o-TsOH does not stay in solution. How can I get rid of it then and moreover, how can I get rid of the toluene?

What kind of analysis gave you the confirmation that ortho-toluenesulfonic acid also precipitated? Why don't you nevertheless follow up with the isolation, do the vacuum filtration, wash the product, etc.? Why do you want to remove all the ortho isomer when it is obvious you need the product as an acid catalyst?




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[*] posted on 19-9-2011 at 12:34


Quote: Originally posted by maxidastier  
Yes, that is exactly my question: Could I use Na2CO3 instead?


I see no good reason why not.




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[*] posted on 29-10-2011 at 22:51


Quote: Originally posted by blogfast25  
Quote: Originally posted by maxidastier  
Yes, that is exactly my question: Could I use Na2CO3 instead?


I see no good reason why not.


Could you use sodium bicarbonate instead of the carbonate?
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[*] posted on 30-10-2011 at 03:50


Quote: Originally posted by Takron  
Quote: Originally posted by blogfast25  
Quote: Originally posted by maxidastier  
Yes, that is exactly my question: Could I use Na2CO3 instead?


I see no good reason why not.


Could you use sodium bicarbonate instead of the carbonate?


No. It doesn't have any dehydrating power whatsoever.




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[*] posted on 30-10-2011 at 05:56


And Na2CO3 is a pretty poor dehydrating agent compared to K2CO3.
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[*] posted on 30-10-2011 at 12:50


I've never understood whether that is true or not: it seems counter-intuitive that a substance that froms no hydrates would be a better dessicant than a substance that forms a relativly stable decahydrate.



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