HeinzBeans
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N2O4 as a nitration/nitrolysis agent?
Before we start I just wanted to say this is a repost of a question I asked in the energetic materials section, the reason for a repost being extra
opinions and info.
“Hello, I have a few questions about dinitrogen tetroxide and its uses since I recently found a cheap and accessible way to make fairly large
amounts.
1)
Can N2O4 be directly used as a nitration/nitrolysis agent? As in a direct replacement for HNO3? I am aware that dinitrogen pentoxide can but have
heard very little about the tetroxide which is far easier to make in bulk (condensation of 2 NO2 groups at low temps). Unless I am missing something I
don’t see why it wouldn’t work, but I have found very little info on this.
2)
If it can indeed nitrate things would it be feasible to use it whilst dissolved in a solvent such as dichloromethane for lower temperature reactions?
My thinking behind this is that since N2O4 freezes at -11c dissolving it in a solvent with a much lower freezing point (DCM -96c) would lower the
overall freezing temp. The reason I ask this is cause I’m interested in producing potassium dinitramide and other dinitramide salts in the future
which require very cold conditions (-30 to -40c) and using N2O4 (if it works) would be cheaper than fuming HNO3 it seems.
3)
From what I have heard when reacted with water N2O4 forms nitric/nitrous acid, along with some nitric oxide, the nitrous acid then presumably oxidises
into nitric acid after a while. If this is so could N2O4 potentially be used as a kind of desiccant? For example if pure N2O4 was added to azeotropic
nitric acid would the N2O4 react with the excess water forming more nitric acid and therefor concentrating the nitric acid? Perhaps fuming nitric acid
could be easily produced from azeotropic nitric acid this way.
4)
And finally if N2O4 does not indeed work as I had hoped, does anyone know of an effective way of converting it to the pentoxide? I know that N2O5 can
be formed by reacting ozone and nitrogen dioxide and I assume that dinitrogen tetroxide would react with ozone to form the pentoxide too, but could
some other method that doesn’t use ozone work?
Anyway, I know I have asked a lot but these questions have really been bugging me for a while, and I have found little info about it. So if any
reaction savvy people want to help please do, thank you  “
That was the whole reposted question. Now, from responses I have already received it seems that NO2 alone acts differently to the nitronium ion (NO2
+) which is normally made from a nitric + Sulfuric acid nitration mix.
Since N2O4 is made from 2 condensed NO2 molecules perhaps the same is true for that as well, but maybe not, I really don’t know. If so, perhaps the
addition of H2SO4 to N2O4 would work well as a nitration mix?
Also a bit of a random one but what about using singlet oxygen to oxidise N2O4 to N2O5 instead of ozone?
Anyway thank you
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clearly_not_atara
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Dinitrogen tetroxide tends to react as (NO+)(NO3-) or as NO2* in radical processes. So it usually gives nitrosation first, or it acts as a radical,
giving different regioselectivity. Often the nitroso products are then oxidized in situ by the N2O4 to give nitro compounds. But the existence of
multiple reaction pathways and intermediates makes it less preferable for selective nitrations, and of course all the toxic gases don't help. N2O4
will also dehydrate sodium acetate to acetic anhydride, but this process is not preferred because of the toxicity of the chemical.
Dinitrogen pentoxide is also very dangerous but it has certain advantages (namely being very reactive and IIRC soluble in nonpolar solvents) that
recommend its use in some cases. Unlike N2O4, the pentoxide always reacts like "NO2+".
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HeinzBeans
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I see, thank you for the response
I wonder if the addition of either H2SO4 or HNO3 to Dinitrogen tetroxide could potentially help it not to form nitroso groups so easily? I know at
this point it may be wise to just use a normal nitration mix (HNO3 + H2SO4) but I am curious, and just like the sound of N2O4.
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chornedsnorkack
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Quote: Originally posted by HeinzBeans  |
“Hello, I have a few questions about dinitrogen tetroxide and its uses since I recently found a cheap and accessible way to make fairly large
amounts.
1)
Can N2O4 be directly used as a nitration/nitrolysis agent? As in a direct replacement for HNO3? I am aware that dinitrogen pentoxide can but have
heard very little about the tetroxide which is far easier to make in bulk (condensation of 2 NO2 groups at low temps). Unless I am missing something I
don’t see why it wouldn’t work, but I have found very little info on this.
2)
If it can indeed nitrate things would it be feasible to use it whilst dissolved in a solvent such as dichloromethane for lower temperature reactions?
My thinking behind this is that since N2O4 freezes at -11c dissolving it in a solvent with a much lower freezing point (DCM -96c) would lower the
overall freezing temp. The reason I ask this is cause I’m interested in producing potassium dinitramide and other dinitramide salts in the future
which require very cold conditions (-30 to -40c) and using N2O4 (if it works) would be cheaper than fuming HNO3 it seems.
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Note that pure HNO3 itself, called "White Fuming Nitric Acid" (WFNA), freezes at -41 C. Solution of N2O4 in
HNO3 is well known, it is called "Red Fuming Nitric Acid" (RFNA) and on the end closer to WFNA where the solid is HNO3, should
freeze below -41 C.
| Quote: Originally posted by HeinzBeans |
3)
From what I have heard when reacted with water N2O4 forms nitric/nitrous acid, along with some nitric oxide, the nitrous acid then presumably oxidises
into nitric acid after a while. |
The reactions include dismutation of nitrous acid
3HNO2=HNO3+2NO+H2O
| Quote: Originally posted by HeinzBeans |
If this is so could N2O4 potentially be used as a kind of desiccant? For example if pure N2O4 was added to azeotropic nitric acid would the N2O4 react
with the excess water forming more nitric acid and therefor concentrating the nitric acid? Perhaps fuming nitric acid could be easily produced from
azeotropic nitric acid this way. |
Depends - white fuming nitric acid or red fuming nitric acid?
Nitric acid decomposition and formation reaction goes:
4HNO3<>2N2O4+2H2O+O2
This goes on already in azeotropic HNO3. Pure HNO3 and its mixtures with only water are colourless - well, blue in large
amounts. Any yellowish colour is NO2 impurities, whether left at production or formed later. If you purify nitric acid so it is colourless
then even at azeotropic concentrations, it will turn yellow and build up oxygen pressures over time.
Driving this reaction towards HNO3 under pressure of O2 is industrial production of WFNA. But what do you get when you have
excess of N2O4 but cannot apply pressure?
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chornedsnorkack
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Some physical and chemical properties:
https://apps.dtic.mil/sti/tr/pdf/ADA036741.pdf
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