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Author: Subject: Preparation of Mononitrotoluenes (o-, p-)
UnintentionalChaos
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[*] posted on 5-11-2014 at 11:55


Quote: Originally posted by CuReUS  
DJF90
so nitration on sulphonated ring is possible .but while sulphonating wont the sulpho group go to ortho as well as para position because the methyl group is not such a bulky molecule?


o-toluenesulfonic acid is unfavorable due to sterics. Importantly, though, is that the reaction is readily reversible and at the high temps used for sulfonation of toluene with concentrated sulfuric acid, the less stable ortho-product desulfonates/resulfonates into the more stable p-isomer readily. Nitration is not, to my knowledge, readily reversible.

You might see considerable o-toluenesulfonic acid if you used oleum at low temperatures where the reaction is not so readily reversible and the much greater sulfonating power of oleum makes up for the lack of heat.

The nitration of the p-toluenesulfonic acid would require moderate conditions, because it is possible for a nitro group to displace the sulfonic acid moiety on the ring. This is the case for TNT, where some preps specify treatment of dinitrotoluene with oleum before adding the final amount of nitric acid.

[Edited on 11-5-14 by UnintentionalChaos]




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CuReUS
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[*] posted on 5-11-2014 at 19:27


Quote: Originally posted by UnintentionalChaos  


o-toluenesulfonic acid is unfavorable due to sterics. Importantly, though, is that the reaction is readily reversible and at the high temps used for sulfonation of toluene with concentrated sulfuric acid, the less stable ortho-product desulfonates/resulfonates into the more stable p-isomer readily. Nitration is not, to my knowledge, readily reversible.


that's great ,if even a small group like methyl can cause the sulpho group to go to para ,think of how many reaction could be controlled by this method


Quote:
The nitration of the p-toluenesulfonic acid would require moderate conditions, because it is possible for a nitro group to displace the sulfonic acid moiety on the ring. This is the case for TNT, where some preps specify treatment of dinitrotoluene with oleum before adding the final amount of nitric acid


iirc ,moderate conditions of nitration is conc nitric acid/sulphuric acid at 100'c but then you say that the nitro group will replace the sulpho group at high temp(that's also the method to make picric acid;) ) .so what should we do.
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[*] posted on 4-4-2015 at 09:26


so, I attempted this procedure a while ago and it went pretty well. During the nitration process, which I did by following a friend's advice by adding the toluene to the mixed acids, after each addition, the toluene turned dark, and then turned yellowish in a minute or two. I had to take water out of the ice bath a few times and add fresh ice to maintain a cold enough temp. It turned out well.
Recently, I tried this again. This time, anticipating having to keep adding ice to the water bath, the night before I froze a few inches of water in the bottom of the water bath vessel. When I added the reaction flask and some water, it maintained a cold (18C) temp easily. It seemed like maybe it was too cold, I would add toluene to the reaction, and it never turned dark at all, and it didnt heat up at all. I was able to add all the toluene without it ever really heating up.
I figured it was all done, so I stepped away for less than 10 minutes. When I returned, there was brown gas evolving from the reaction, I put in a thermometer and it was still climbing at 60C when I yanked it out, and put a whole lot of ice and cold water around the RBF this was happening in. I was prepared to run, but it cooled down. Later, I thought it was done but when I poured it into a sep funnel, there was still nitrogen dioxide coming off it, so I put it back in the RBF and let it react another hour. In the end, the finished product looked ok, maybe a little darker than the first time. I thought perhaps there was some NO2 dissolved in it causing the darker color, like the way it does in Nitric acid.
Now, a few days later, the nitrotoluene has separated in the storage bottle, with the top third appearing as the normal , yellow, thick liquid and the bottom two thirds being a darker, thinner liquid. Whats the deal? Id like to make o-toluidine from this. Is it usable?
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S.C. Wack
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[*] posted on 4-4-2015 at 09:54


Quote: Originally posted by S.C. Wack  
...maybe no dinitrotoluene is formed using excess nitric acid if the temperature is low enough and there is enough sulfuric acid to compensate for the water...maybe that isn't how it goes. AFAIK it isn't recommended.


Surprised that no one mentioned COPAE:

A mixture of 294 grams of concentrated sulfuric acid {d. 1.84) and 147 grams of nitric acid (d. 1.42) is added slowly from a dropping funnel to 100 grams of toluene in a tall 600-cc. beaker, while the liquid is stirred vigorously with an electric stirrer and its temperature is maintained at 30° to 40° by running cold water in the vessel in which the beaker is standing. The addition of acid will require from an hour to an hour and a half. The stirring is then continued for half an hour longer without cooling; the mixture is allowed to stand over night in a separatory funnel...




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[*] posted on 17-4-2015 at 11:20


Did you see the procedure in Science and Technology of Explosives-Urbanski?They say that this procedure gives o- and p- free of m-.The nitrating composition is 68% acetic anhydride and 32% nitric acid with an exces of 10% acid,made at 10 degrees Celsius over a period of 2 hours.It also says that you can reduce the m- quantity by adding sodium nitrite....Here's a SS:

http://i.imgur.com/yP6gxT2.jpg

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[*] posted on 16-11-2015 at 20:23


I'm planning on attempting this synthesis soon, but I just wanted to clarify- what concentrations are the nitric and sulfuric acids that you used? I'd guess ~63% and 98% respectively, but I wanted to make sure before I go throwing stuff together so I'll know to do stoichiometric corrections as needed.

Sorry if I missed something, but I didn't see exact concentrations mentioned anywhere in the thread.




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Magpie
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[*] posted on 17-11-2015 at 09:23


There are many contributions to this thread, but I'm assuming you are asking me.

My con H2SO4 is whatever Rooto supplies: probably about 96%.
My con nitric acid is the azeotrope which IIRC is about 68%.

Good luck.

edit: I see that in my procedure I specify nitric acid of density 1.44, which corresponds to a 77wt% acid. I likely took this from Cumming. Normally I don't have this so likely used an equivalent amount of 68%. Unfortunately I didn't say anything about this in my notebook.

[Edited on 18-11-2015 by Magpie]




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[*] posted on 18-11-2015 at 07:22


Alright, thank you! I may try this synthesis today if I have time.



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