DennyDevHE77
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Synthesis of picric acid from nitric acid 70% without sulfuric acid
There is such a way to obtain picric acid:
To a mixture of 100 parts
nitric acid (p = 1.4) and 30 parts of ethyl alcohol are added with good
stirring 20 parts of phenol. Instead of ethyl alcohol, you can take methyl alcohol
or glycerin. The reaction mixture is then poured into hot water. By cooling
crystalline picric acid is released. Yield 95% of theory (based on
anhydrous phenol)
Has anyone prepared picric acid this way? And what is the mechanism of nitration? As I understand it, phenol is easily nitrated with nitrogen dioxide,
which is released here during oxidation with nitric acid, for example, glycerin.
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Texium
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Cite your source
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DennyDevHE77
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Certainly. The information is taken from the book "Houben-Weyl Methods of Organic Chemistry Vol. IV". I'll attach a screenshot, but you can check it
out here: https://books.google.de/books?id=pI2ZAwAAQBAJ&pg=PA152&a...
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OneEyedPyro
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Something tells me this wouldn't work at all. I've been wrong before but if yields were 95% this would be the standard method of making TNP and I've
never heard of such a synthesis.
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Texium
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It may very well work, but there's a good chance that it is avoided for safety reasons: https://en.wikipedia.org/wiki/Nital
Relevant source from that wiki page: https://web.archive.org/web/20160305084621/http://www.ab.ust...
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B(a)P
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I have read about the nitration of phenol without sulfuric acid, but only with the use of a catalyst.
If the phenol is not first sulfonated or no catalyst is present, what stops the nitric acid from oxidising the phenol?
While you may get some picric acid, I find it very hard to believe that a yield of 95% is obtainable. It would also require a huge excess of nitric
acid to get the last nitro group on.
The final issue is that of what happens if you heat a mixture nitric acid with ethanol?
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DennyDevHE77
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What if you use glycerin? He doesn't seem to be that dangerous. Of course, if nitroglycerin is not formed there, but I don’t think that it will be
synthesized with 70% nitric acid. Personally, I thought that the mixture would boil, emit a lot of NOx, which would need to be diverted somewhere.
But if this mixture is really explosive, then maybe it's worth trying to carry out the reaction in a Teflon cup? In the event of an explosion, at
least plastic fragments will be
Acetic acid is also a good solvent, and does not react with nitric acid
[Edited on 25-7-2023 by DennyDevHE77]
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B(a)P
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Quote: Originally posted by DennyDevHE77  |
What if you use glycerin? He doesn't seem to be that dangerous. Of course, if nitroglycerin is not formed there, but I don’t think that it will be
synthesized with 70% nitric acid. Personally, I thought that the mixture would boil, emit a lot of NOx, which would need to be diverted somewhere.
But if this mixture is really explosive, then maybe it's worth trying to carry out the reaction in a Teflon cup? In the event of an explosion, at
least plastic fragments will be
Acetic acid is also a good solvent, and does not react with nitric acid
[Edited on 25-7-2023 by DennyDevHE77] |
The reaction will still require a large excess of nitric acid. Acetic acid will likely work to form mono, di and potentially some trinitrophenol as it
will cause the formation of the nitronium ion.
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DennyDevHE77
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| Quote: Originally posted by B(a)P | | Quote: Originally posted by DennyDevHE77 |
What if you use glycerin? He doesn't seem to be that dangerous. Of course, if nitroglycerin is not formed there, but I don’t think that it will be
synthesized with 70% nitric acid. Personally, I thought that the mixture would boil, emit a lot of NOx, which would need to be diverted somewhere.
But if this mixture is really explosive, then maybe it's worth trying to carry out the reaction in a Teflon cup? In the event of an explosion, at
least plastic fragments will be
Acetic acid is also a good solvent, and does not react with nitric acid
[Edited on 25-7-2023 by DennyDevHE77] |
The reaction will still require a large excess of nitric acid. Acetic acid will likely work to form mono, di and potentially some trinitrophenol as it
will cause the formation of the nitronium ion. |
I don't think much nitronium ion can form there. But the peculiarity of phenol is that, due to the presence of a hydroxyl group, the aromatic nucleus
is strongly activated in electrophilic substitution reactions. Well, that is, in the ortho and para positions, the electron density greatly increases.
Therefore, nitration can be carried out with the nitrosonium cation NO+. which then oxidizes. In short, a typical catalytic nitration (catalyst -
nitrogen oxides).
I hope to do a test synthesis when the phenol arrives. I'm much more worried about the danger of an explosion (if it exists of course). Although it
will not be difficult to establish whether picric acid has come out, or just dnintrophenol, I think.
But besides this, there is a safe way through sulfanilic acid. There is also no need for conc. sulfuric acid. And precursors like sodium nitrite and
sulfanilic acid are generally legal.
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