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Author: Subject: Nitration with NO2 instead of H2SO4?
Junk_Enginerd
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[*] posted on 5-11-2020 at 02:02
Nitration with NO2 instead of H2SO4?


Note: I'm not making this thread with an intent to perform this experiment, just as a way of testing my understanding of the chemistry. That also means that other "simpler" methods are irrelevant.

For the sake of discussion, let's say it's about nitration of glycerine.

The H2SO4 used in nitration of for example glycerine is not a direct requirement for the reaction as I understand it; it is only needed to prevent water from disrupting the nitration reaction.

I also understand that the reaction works just fine, at least initally, if one simply uses 100% nitric acid and 100% glycerine. It will however stop quite soon, when water is formed in the reaction, unless there's a large excess of HNO3 to just dilute the water.

Now I'm starting to get a little unsure, but as I've understood it the HNO3 becomes oxidizing when the concentration drops, and this oxidizes any new nitroglycerin trying to form. Is this correct?

One way of increasing the strength of HNO3 is to dissolve NO2 in it, just as nitric acid can be made by dissolving NO2 in water.

So, let's say we do a nitration starting with 100% HNO3 and glycerin in stoichiometric amounts. The reaction stops well before completion due to water being formed. Now we start to bubble NO2 into the mix. What effect would this have?

I'm thinking:

The NO2 combines with the water to make more acid while removing water in the process, thereby allowing the reaction to go ahead.

But there's also the fact that when making nitric acid from NO2 and H2O, oxygen is needed. Typically I've seen that it's recommended(not not necessary?) to add H2O2 to the water to provide this. But if oxidation(due to dilution of the HNO3) is what's stopping the glycerin nitration from proceeding, and we're not adding H2O2, shouldn't the NO2 then "deplete" any possibilty of oxidation, thereby enabling the ntiration to proceed not only by the synthesis of new acid, but also by this... "antioxidant" effect? So, effectively providing two simultaneous mechanisms to drive the reaction forward?

Please excuse the lack of proper technical terms, I'm not a chemist. :)

I'm thinking it's a pretty solid method. Are there any obvious flaws that I've missed?

Also, I'm not sure about the effects of possible "going above 100% reaction", meaning once the nitration is finished, what are the effects of supplying more NO2? Nothing? Wrong products(dinitroglycerine?)? Runaway?


[Edited on 5-11-2020 by Junk_Enginerd]
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[*] posted on 5-11-2020 at 04:30


I believe that sulfuric acid does in fact play a role other than dehydrating agent, this is a common misconception that I was also guilty of carrying. The active nitrating agent is not HNO3, it is the NO2 synthon, created when H2SO4 reacts with HNO3 to form the unstable intermediate. In a way it is just a dehydrating agent, but it does more than push the reaction forward by pulling away water. I do like your idea though. When NO2 is dissolved in water it gives nitric as well as nitrous acid, the latter being oxidized to nitric acid by oxygen as you mentioned. On the other hand, nitrous acid is unstable and could decompose into various products, maybe one decomposition pathway is able to oxidize a second molecule of HNO2 to HNO3, making H2O2 or other external oxidizers unnecessary.

I hope that made sense :P

edit: I stand corrected, the active nitrating agent is N2O5, not NO2

[Edited on 11-5-2020 by njl]
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[*] posted on 5-11-2020 at 07:10


I'm not convinced... Theres a book about nitroglycerin hosted here on sciencemadness, where alternatives to h2so4 are discussed. Among these is using an excess of HNO3 as well as stuff like CaCl2 instead of h2so4. None are as convenient and effective as h2so4, but it does seem to work.
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[*] posted on 5-11-2020 at 11:34


N205, not NO2.

You'll find in mentioned in most modern publications. It may be Unobtainium for hobby chemists but solves a few problems that were harder with mixed acids.

If you dissolve NO2 in HNO3 you get red acid, not "more acid". It doesnt mean it's more concentrated. It can be 80% acid, some water and NO2. It'll happily oxydize things you put it into contact with.




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[*] posted on 5-11-2020 at 13:43


There is a difference between nitrations and nitrations. When nitrating alcohols, like glycerine you create a nitrate ester, RONO2. In this reaction pathway there is no need for a "NO2 synthon", it is a Fischer esterfication. Sulfuric acid dehydrates and drives the reaction to the right.

When nitrating for example toluene you do a electrophilic substitution with NO2+

I think the reaction between NO2 and H2O only works with arelatively high concentration of water.

[Edited on 5-11-2020 by Tsjerk]
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[*] posted on 5-11-2020 at 15:44


In addition, in a few nitrations some water must be present. Cant recall the specifics but I once needed a certain type of NC.
Cant remember if it needed around 11 or 12% of water at the end but the nitration mixture was by no means anhydrous at the beginning either.




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[*] posted on 6-11-2020 at 09:29


The original idea sounds good and creative. But. Maybe only one particular nitration - esterification - will work accordingly. I don't know which one. On the contrary, there are more used esterifications - nitrations, where 98% H2SO4 + dry NH4NO3 are used. Thanks to which there is (at the start) the absence of water from HNO3 65%. For example, esterification of cellulose gives better results by this method.
PS: In amateur conditions

[Edited on 6-11-2020 by Laboratory of Liptakov]




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[*] posted on 10-11-2020 at 04:01


NO2 is not a good idea- usually, it makes nitro and nitroso components. An excellent nitrating agent is N2O5, pure or dissolved in HNO3- read Jai_Prakash_Agrawal,_Robert_Hodgson-Organic_Chemistry_of_Explosives-Wiley(2007)



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[*] posted on 10-11-2020 at 04:09


Quote: Originally posted by Laboratory of Liptakov  
The original idea sounds good and creative. But. Maybe only one particular nitration - esterification - will work accordingly. I don't know which one. On the contrary, there are more used esterifications - nitrations, where 98% H2SO4 + dry NH4NO3 are used. Thanks to which there is (at the start) the absence of water from HNO3 65%. For example, esterification of cellulose gives better results by this method.
PS: In amateur conditions

[Edited on 6-11-2020 by Laboratory of Liptakov]


I used four nitrates- Na, K, NH4 and Ca correspondingly. The mix of NH4NO3 with H2SO4 made a runaway reaction when I was making TNP. The reaction mix turned into foam, full of NO2. I had to stop the process. In this particular case KNO3 works fine. The reaction of dry Ca(NO3)2 with H2SO4 is a very efficient way to make mixed acid. it requires some time, however- day and night usually. I made mixed acid and made gun cotton and NG. Unfortunately, I didn't know at that time that this mixed acid can be used to make keto-RDX, mixed with RDX. What a pity.




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[*] posted on 24-11-2020 at 07:17


RDX is basically university level for anyone from amateur. In any way method. Its intersting Ca(NO3)2 + H2SO4. Useful info...:cool:



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[*] posted on 30-11-2020 at 19:09


Quote: Originally posted by Laboratory of Liptakov  
RDX is basically university level for anyone from amateur. In any way method. Its intersting Ca(NO3)2 + H2SO4. Useful info...:cool:

At the first, you have to get rid of water- usually, you can get Ca(NO3)2*4H2O. Heat it- this salt will boil and then becomes solid. You need small pieces, not dust. Calculate the necessary amount of H2SO4- assume, you wanna get normal mixed acid 60:40 H2SO4:HNO3. The reaction is going slowly- you'll need one day and night approximately. During the reaction period, once in two hours you should turn the reaction vessel bottom up, let pieces of salt move through acid, and then turn the vessel in its normal position. Well, I describe all details. Finally, filter the liquid through some filter that is resistant to mixed acid.




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[*] posted on 30-11-2020 at 19:49


NO2 is a nitrosating agent, not a nitrating agent. It generally reacts as NO+*NO3-. But because it's so reactive it can oxidize the formed nitroso compounds to the nitro compounds.

The problem with it is simple: it's a gas!
Quote:
So, let's say we do a nitration starting with 100% HNO3 and glycerin in stoichiometric amounts. The reaction stops well before completion due to water being formed. Now we start to bubble NO2 into the mix. What effect would this have? Now we start to bubble NO2 into the mix. What effect would this have?

It produces carbon dioxide, heat, and a messed up desk. Making nitroglycerin under agitation?!




[Edited on 04-20-1969 by clearly_not_atara]
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[*] posted on 1-12-2020 at 01:39


caterpillar: It it some similar, what I developed before years. H2SO4 + NH4NO3 + heating in closed reflux.
https://www.youtube.com/watch?v=UGGaC0YA2yM
Here is prepare HNO3 done during a 3 hours. But is it pretty mad method...:D

[Edited on 1-12-2020 by Laboratory of Liptakov]




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[*] posted on 1-12-2020 at 03:50


Quote: Originally posted by Laboratory of Liptakov  
caterpillar: It it some similar, what I developed before years. H2SO4 + NH4NO3 + heating in closed reflux.
https://www.youtube.com/watch?v=UGGaC0YA2yM
Here is prepare HNO3 done during a 3 hours. But is it pretty mad method...:D

[Edited on 1-12-2020 by Laboratory of Liptakov]


Look, I'm a little bit afraid to use AN mixed with sulfur acid. I made TNP many times, using KNO3, but once I made an experiment- I used AN + H2SO4. I got a runaway reaction- the reaction vessel had been fulfilled with red foam and I had to stop the preocess.




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[*] posted on 1-12-2020 at 09:26


Maybe impurities in AN. I my attempt it was without any reaction at mixing AN + SA. However at - 10C for SA. AN simply strewed into SA.



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[*] posted on 1-12-2020 at 12:44


Quote: Originally posted by Laboratory of Liptakov  
Maybe impurities in AN. I my attempt it was without any reaction at mixing AN + SA. However at - 10C for SA. AN simply strewed into SA.

Not sure. Of course, I didn't make such an experiment (heating only AN + SA without some organic). I described the result of one experiment. Oh, BTW, slightly off-topic. AN may contain some trace amount of HNO3. And this may cause some unpleasant surprises. The mix of AN with red phosphorus may self-ignite after a while. Same situation with the nitroso-analog of RDX. I made once such a mix and get a violent reaction after ten days (!) approximately.




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