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Author: Subject: Facile, Efficient nitration of Phenol to 2,4-dinitrophenol
Nickdul
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[*] posted on 6-12-2015 at 14:54
Facile, Efficient nitration of Phenol to 2,4-dinitrophenol


Hi all,
I recently came upon the following paper (attached):
Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 10, pp. 1577−1580
"Synthesis of 2,4-Dinitrophenol"
DOI: 10.1134/S1070427212100163

Abstract—New highly selective method is suggested for synthesis of 2,4-dinitrophenol by nitration of phenol with nitric acid in an aqueous-alcoholic medium at the boiling point of the reaction mixture. The yield of 2,4-dinitrophenol is as high as 80%.

EXPERIMENTAL
We used for synthesis freshly distilled crystalline
phenol, concentrated nitric acid of chemically pure grade
(concentration 65%), and rectified ethanol (ethanol
content 95.3%).

2,4-Dinitrophenol. A 2.5-g portion of phenol and
an aqueous-ethanolic solution of nitric acid, prepared
from 12.5 mL of concentrated nitric acid and 50 mL of
ethanol, was mixed in a round-bottomed flask.
The reaction mixture was heated in an installation
with a reflux for 0.5–2 h. Then, approximately 50 mL
of a liquid was obtained by vacuum distillation. The
residue was transferred to a cup. The product crystallized
as yellow crystals. The crystals were washed with cold
water and dried in a vacuum-desiccator.
Yield: 4.7-8 g (>95%)
Disregarding the "transferred to a cup" nonsense, the procedure seems straightforward and as soon as I get back to my lab, I'd try to do it (with the overarching goal of salicylic acid - phenol - 2,4-DNP - 2,4-diaminophenol HCL).
Until then, if someone could come up with a precedent synthesis or mechanism (EtNO3, nitronium ion? seems too little acid)
Thanks, looking forward to ideas :D


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mnick12
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[*] posted on 6-12-2015 at 15:33


Uhhhhhh, there must be something wrong here or the article is complete bs.

Using a mixture of ethanol and nitric acid as a nitrating mixture, especially with heating, seems like a great way to have a nice lab fire/explosion.
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careysub
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[*] posted on 6-12-2015 at 18:14


That's what the paper claims. Does look like dubious reaction conditions - maybe you do get your product if explosion does not result? And the experimental is awfully sketchy for what is supposed to be the sole breakthrough of their paper. Nothing on nitric oxide evolution, safety considerations, variations, etc. It even makes it seem like you might be keeping nitric acid-ethanol mixture on hand.

Oh yeah, check out this YouTube video:
https://www.youtube.com/watch?v=uFwiZYfEsuY

This is 2 mL ethanol/4 mL conc. nitric acid simply added together and look at what happens at about 2:30.

If instead of adding 2 mL of ethanol they had added 15 mL, they would have had the recommended nitration mixture from this paper (but only 1/3 that described in the experimental). Think about how you would like to try refluxing that for a few hours.




[Edited on 7-12-2015 by careysub]
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AvBaeyer
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[*] posted on 6-12-2015 at 19:27


I have to agree with Careysub. This paper is very suspect. I sure would not try it.

AvB
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macckone
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[*] posted on 6-12-2015 at 20:13


Given the 65% nitric and the large amount of ethanol, this is probably not going to explode. Given the large amount of ethanol, a runaway is equally unlikely. One thing to keep in mind is that countries differ in regard to safety. Russia tends to shrug off safety concerns. Now back to the reaction, at the end point there should be most of the ethanol evaporated off with about a 50:50 mix of water and product. This is the most likely point for an accident as you have a heated solution of dinitrophenol. I would guess a water bath is used. And the ethanol should evaporate off with most of the water remaining. It is an interesting reaction if it works. I would guess it actually does and the primary danger is overheating the dinitrophenol if a water bath is not used. The transfer to a cup would be to encourage evaporation, ie. An evaporating dish. This compound is reasonably safe when wet but dangerous when dry. Don't overheat or heat to dryness.

Ps. The concentration of nitric acid is 16% of solution with the added water, it should be less dangerous than 10% nital.

[Edited on 7-12-2015 by macckone]
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Nickdul
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[*] posted on 6-12-2015 at 21:32


Heh, I've known not to heat nitric acid and ethanol, and I did see that youtube video once I recognized it is a safety hazard.
I tried to find the Russian original of the paper and compare it to the translation, but the closest I found was that the authors submitted a patent (attached). Thе procedure is the same, although it is unclear whether they only strip the ethanol/acid mixture by vacuum distillation, or if they also distill the 2,4-dinitrophenol over. Funny thing, they outline a bunch other synthetic routes and find faults in them, so if they are to be believed, their method is the best :D


[Edited on 7-12-2015 by Nickdul]

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[Edited on 7-12-2015 by Nickdul]
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Boffis
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[*] posted on 7-12-2015 at 07:49


Actually, when you think about the proposed method it's not as bad as if sounds initially. This is probably a nitrosation-oxidation process and these are well established as a means of nitrating phenols. In essence the partial reduction of some of the nitric acid to lower N oxides brings about nitrosation to 2,4 dinitrosophenol which is then oxidized by the excess nitric acid to the nitro compound.

[Edited on 7-12-2015 by Boffis]
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Nickdul
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[*] posted on 8-12-2015 at 13:24


Boffis, thanks for chiming in on this. Indeed, I have seen several preparative methods involving a nitroso- intermediate. Also, a "conventional" mixed acid nitration synthesis from a Russian synthetic manual claims 65% yield after purification (acid-base recrystallization)
see attached


[Edited on 8-12-2015 by Nickdul]

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[Edited on 8-12-2015 by Nickdul]

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CuReUS
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[*] posted on 9-12-2015 at 08:56


I can't comment on the mechanism in the russian paper,but see this paper, they claim a 98% yield
https://www.thieme-connect.com/products/ejournals/abstract/1...
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Nickdul
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[*] posted on 9-12-2015 at 10:43


Zolfigol, M. A., Madrakian, E., & Ghaemi, E. (2003). Trichloroisocyanuric Acid/NaNO 2 /wet SiO 2 as an Efficient System for the ­Selective Dinitration of Phenols under Solvent-free Conditions. Synlett, (14), 2222–2224. http://doi.org/10.1055/s-2003-42063

Another one on my list then :D

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Antiswat
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[*] posted on 4-3-2018 at 04:54


so the article suggests lower than actual 65% HNO3 to be used? i have long ago succesfully made benzyl nitrite using catalytic amount of NaNO2 along with 5% HNO3 and benzyl alcohol, the benzyl nitrate broke down forming benzaldehyde. the alcohol could be playing a role in forming NOx which would then efficiently react with the phenol, the TCCA + NaNO2 i'd say suggests that there is something about NOx being useful for making DNP
of what i find its suggested that DNP is a "powerful explosive", relative to TNP how much would that be? it leaves 3 carbon atoms after complete decomposition, 80% yield is quite great for something that doesnt even require sulfuric acid and has doable stability
what im more interested in is - what are the alkali salts like? sodium picrate is a weak primary, so what about diphenolates? with such great yields i think were missing out on some very potent compounds
maybe the heavymetal diphenolates would be interesting, and if this all turns out mundane maybe DNP would serve as high yield precursor for TNP? phenol is as easy as salicylic acid destructively distilled, and possibly this can be catalyzed with an mixture of copper salts





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Chemi Pharma
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[*] posted on 4-3-2018 at 22:52


All these papers @Nickdul brought to the thread have been already discussed here at the 2,4 DNP thread. See: http://www.sciencemadness.org/talk/viewthread.php?tid=15006&...

The same concern expressed here about mixing ethanol and 65% HNO3, were discussed at that thread. Something needed to think about is the fact the presence of phenol in the reaction mix as a substrate will atenuate every possible runway. The NOx will react in situ with phenol and we will not see the large brown fumes of NO2 escaping from the vessel as we can see in the you tube video @careysub indicated to us, but just ethanol, water and a little NO2 vapors evoluting instead.

Nobody here didn't ever try to make mercury fulminate from mercury as substrate, 95% ethanol and 65% nitric acid? I did. Several times. It's the same thing. No runaway at all, just a mild reaction, even heating the mix to kick off .
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[*] posted on 23-3-2018 at 18:58


You should theoretically be able to use n-butanol instead of ethanol, which seems like it'd be a lot safer. The problem with ethanol is that it's oxidized into acetaldehyde, which can undergo a haloform-like reaction with nitrous acid (which forms after nitric acid oxidizes something). Since the runaway only seems to occur with alpha-methyl carbonyl groups (similar to the haloform reaction) you should theoretically be able to avoid it by using a longer-chain alcohol that isn't oxidized into an alpha-methyl carbonyl compound.

This is just a theory I've had, but woelen said something about similarities between hypochlorous and nitrous acids and it got me thinking about other similarities.




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