Junk_Enginerd
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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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njl
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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 
edit: I stand corrected, the active nitrating agent is N2O5, not NO2
[Edited on 11-5-2020 by njl]
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Junk_Enginerd
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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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Herr Haber
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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.
The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
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Tsjerk
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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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Herr Haber
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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.
The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
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Laboratory of Liptakov
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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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caterpillar
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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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caterpillar
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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.
Women are more perilous sometimes, than any hi explosive.
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Laboratory of Liptakov
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RDX is basically university level for anyone from amateur. In any way method. Its intersting Ca(NO3)2 + H2SO4. Useful info...
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caterpillar
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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.
Women are more perilous sometimes, than any hi explosive.
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clearly_not_atara
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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?
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It produces carbon dioxide, heat, and a messed up desk. Making nitroglycerin under agitation?!
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Laboratory of Liptakov
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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...
[Edited on 1-12-2020 by Laboratory of Liptakov]
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caterpillar
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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.
Women are more perilous sometimes, than any hi explosive.
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Laboratory of Liptakov
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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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caterpillar
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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.
Women are more perilous sometimes, than any hi explosive.
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