Sciencemadness Discussion Board

Other dehydrating agents for nitration

WD40_enjoyer - 9-9-2025 at 04:28

To make a common nitration bath one would add nitric acid and sulfuric acid in a beaker. But with the current political situation in the EU sulfuric acid is harder and harder to get a hold of and that goes for nitric too.

I would make nitric acid cheap via the Birkeland eyde process from air so that is not really a problem. But sulfuric acid is still hard to come by in high concetrations.

Is it possible to get a good nitration to make for example NG with a dehydrating agent like P2O5 or some other agent that is easier (though hopefully cheaper then P2O5) that wont contaminate the product or destroy it (this goes for more then NG that is)?

bariumbromate - 9-9-2025 at 19:33

look here: https://youtu.be/0zcqeaJfY-8?si=cfwQsRg6KrzoRVXL&t=245

Fery - 9-9-2025 at 20:41

Some nitrations with anhydrous HNO3 (without H2SO4) use acetic anhydride (I saw it in one explosive synthesis).

jackchem2001 - 10-9-2025 at 04:11

That seems a bit hazardous. Can't that produce nitroform and tetranitromethane? (Through enol chemistry if you draw an ionic mechanism for it)

teodor - 10-9-2025 at 05:55

I think the role of H2SO4 (probably SO3) is not dehydration but stabilization of the nitronium anion.

Reaction between HNO3 and H3PO4 produces free N2O5 which is decomposing under light to NO2 and O2 especially in the presence of organic substances, so you really don't need the the dehydrating power of P2O5 to do the nitric acid dehydration. Only addition of water can stabilize N2O5 but you will not get what you are looking for. Using P2O5 probably will decompose HNO3 at the first step forming nitrosyl phosphates of different level of condensation becuase in this case you have even less water which works as a stabilizer in the P2O5 - N2O5 system. So, the way is not to dehydrate HNO3 by to stabilize the nitronium anion. Well, there is NO2BF4 and othere nitronium salts, but concentrating H2SO4 I think is easier.

Fuming nitric acid can be relatively easily distilled from a mixture of diluted nitric acid, sodium hexametaphosphate and (optionally, not sure it is required) sodium nitrate. According to my experimets the optimal temperature is around 290C but destillation is very slow because HNO3 has a great affinity to phosphate, not so much as water though (the actual reaction mechanism consumes the water but not N2O5, that's why). Also you need a very effisient condenser, fuming acid is quite volatile (well, that's why it's fuming). So, using this fuming NA (the color of it is straw-yellow) you can probably use less sulfuric acid. But I didn't do any experiment with nitration using this product. If you will try this procedure I would recommend put concentrated H2SO4 in the receiving flask because it will consume the byproduct - NO2/N2O4 partially converting it to NO2+, the anion you try to use from the nitric acid.
You can also think on modifying this procedure distilling the mixture of (diluted) sulfuric and nitric acid together from NaPO3, but I didn't experimenting with that, so I can only recommend the temperature when you can expect the distillation to happen (was already mentioned).

As you guess, you can probably start with diluted H2SO4, NaPO3 and NaNO3 mixture forming HNO3 in situ and get the nitration mixture in the receiving flask after spending some time in refining the conditions.


[Edited on 10-9-2025 by teodor]

chempyre235 - 10-9-2025 at 08:01

Quote: Originally posted by teodor  
I think the role of H2SO4 (probably SO3) is not dehydration but stabilization of the nitronium anion.

I'm fairly certain sulfuric acid performs both of these roles. It is also used as a catalyst for the formation of esters and ethers: aiding the dehydration of acids and alcohols. I could be wrong, though.

teodor - 10-9-2025 at 08:11

HNO3 + 2H2SO4 = NO2+ + H3O+ + 2HSO4-

The goal here is not H3O+, the goal is NO2+.

In the case of H3PO4 I think it would be more or less

H3PO4 + 2 HNO3 = H3PO4 * H2O + N2O5

H3PO4 wants to dilute itself to 85%. This is a pure dehydration. That's why it doesn't work for nitration

( 100% H3PO4 is not a single compound but a mixture having also polyacids, they are driving force in this dehydration )

Strictly speaking N2O5 <-> [NO2]NO3, so you get NO2+ , but N2O5 -> 2 NO2 + 1/2 O2 is a practical problem. It goes left only in presence of O3.


N2O4 is much nicer compound, even solution in ethyl acetate is more or less stable and can be used to produce inorganic nitrates. But N2O4 is not a nitrating agent for most of organic.



[Edited on 10-9-2025 by teodor]

[Edited on 10-9-2025 by teodor]

[Edited on 10-9-2025 by teodor]

Radiums Lab - 10-9-2025 at 10:49

Quote: Originally posted by WD40_enjoyer  
To make a common nitration bath one would add nitric acid and sulfuric acid in a beaker. But with the current political situation in the EU sulfuric acid is harder and harder to get a hold of and that goes for nitric too.

I would make nitric acid cheap via the Birkeland eyde process from air so that is not really a problem. But sulfuric acid is still hard to come by in high concetrations.

Is it possible to get a good nitration to make for example NG with a dehydrating agent like P2O5 or some other agent that is easier (though hopefully cheaper then P2O5) that wont contaminate the product or destroy it (this goes for more then NG that is)?


That is a problem in many places here in India too but after lot of searching I have contacted a supplier and another newly formed chem company to supply reagents for me, 5L of Sulfuric acid 98% lab grade costs around 25-30 USD for me.

Go check out the latest video of Lab Coatz, he made super strong phirana solution, He used oleum produced by heating NaHSO4 in a furnace, and yields were pretty good, you can technically stop distillation or add some water slowly to get your sulphuric acid.
Be careful because it's Oleum.

teodor - 10-9-2025 at 11:22

You know, "just add water" in some cases is a way to check how many people are reading this thread.

Radiums Lab - 10-9-2025 at 11:41

Quote: Originally posted by teodor  
You know, "just add water" in some cases is a way to check how many people are reading this thread.


Yea that's true too. They do the same thing in contact process,
But an amature won't have the apparatus to do that and many end up damaging the stuff around them or just hurting themselves in the process.
Adding Oleum to cold water to dilute and make sulphuric acid is a bit less risky compared to adding water to oleum.
Oleum if made should be treated with respect(doesn't mean make a room for it and start praying).


[Edited on 10-9-2025 by Radiums Lab]

teodor - 10-9-2025 at 11:54

Well, oleum dilution topic is covered in SM wiki. Just to save this thread for discussion of alternative nitration mixture. Also there is a nice thread about drying H2SO4 with pyrosulfate created recently, even with some math in it.

P.S. Well, I added water to the organic sulfonation result which was made with oleum, because it was more economical way (the sulfate has to be removed with BaOH after dilution), but it shouldn't be recommended as a general procedure.

... and you can make Oleum with P2O5 which was proposed by OP as an available matherial ...

... and you probably don't actually need a furnance just to concentrate H2SO4 ...
Quote: Originally posted by WD40_enjoyer  

I would make nitric acid cheap via the Birkeland eyde process from air so that is not really a problem. But sulfuric acid is still hard to come by in high concetrations.


WD40_enjoyer, of course it is just imagination (making a nitric acid from air) but to make it complete, you can imagine how to use nitrogen dioxide to concentrate H2SO4.

[Edited on 10-9-2025 by teodor]

[Edited on 10-9-2025 by teodor]

teodor - 10-9-2025 at 13:45

Just noticed the topic was discussed here before and people said for nitration of some compounds (like nitrocellulose) the mixture of HNO3 + H3PO4 + P2O5 works pretty well.

OK, probably the stability of N2O5 is not a problem there.

[Edited on 10-9-2025 by teodor]