2,4-dinitrophenol synthesis by electrophilic aromatic nitration of phenol

[scalpere]

i asked AI for a complete synthesis of this substance, i want to know if this synthesis is reliable?

1. Preparation of the Reaction Mixture

- Place 5 g of phenol in a 100 mL beaker.

- Slowly add 10 mL of concentrated sulfuric acid while stirring. The phenol will dissolve and form a reddish solution.

- Cool the mixture to 0–5 °C using an ice bath.


2. Preparation of the Nitrating Agent

- In a separate container, carefully mix 10 mL of concentrated nitric acid with 10 mL of concentrated sulfuric acid. This mixture generates the nitronium ion (NO₂⁺), the electrophile in this reaction.

3. Nitration Reaction

- Slowly add the nitrating mixture dropwise to the cold phenol/sulfuric acid solution under constant stirring.
- Maintain the temperature below 15 °C during addition to control the reaction rate and prevent over-nitration.

Once the addition is complete, allow the mixture to warm to room temperature and stir for 30–60 minutes to complete the reaction.

4. Isolation of the Product

- Pour the reaction mixture into 300 mL of crushed ice water in a large beaker. A yellow precipitate of 2,4-dinitrophenol should form.

Collect the solid by vacuum filtration using a Büchner funnel.

Wash the crude product with cold distilled water to remove acid residues.

5. Purification

- Recrystallize the crude solid from hot ethanol or a mixture of ethanol and water to obtain pure yellow crystals of 2,4-dinitrophenol.

Dry the product at room temperature or under vacuum. Avoid high heat due to potential thermal instability.


i know there is no all details but do u think AI gave a reliable synthesis or this is not accurate enough to be copied?

 

[dnBQByvHb8Zkawbjpx]

I'll preface by saying that my knowledge and experience is limited, but I've been interested in DNP for 20 years now and I'm scrambling to perform a synthesis myself in the coming months. Also, DNP is outside of the scope of the forum since DNP is not a psychoactive substance, so don't be surprised if this gets removed at some point.

In general the synthesis by nitration of phenol is well known and repeatedly performed by many, as well as documented in various patents. The process that you've posted is generally the same as shown in this video by Pyrotechnical. He starts by extracting phenol from aspirin and from there the remaining steps are the same (nitration, extraction, purification). In the video 95 % ethanol is used as the medium for the reaction which can be found in Russian patents describing the synthesis, but I've seen other documents that use H2SO4 instead.

To brush up on general knowledge related to the nitration of phenol I have this video in my notes. It covers the topic quite well in my opinion, and it matches your process well (no ethanol, only H2SO4 as medium).

While the process in your post is generally correct (I can't confirm the exact quantities and other numbers), I would not rely on AI beyond some basic research on a given topic. It is known to provide bogus or outright incorrect claims at times and this stuff is no joking matter with serious real life implications if mistakes are made. I recommend you watch the linked video and read few patents regarding the synthesis of DNP to use as a starting point. That's what I do, anyway.

Finally, think twice regarding the last step of drying. DNP is usually kept moist/wet to limit the risk of explosion, although it is not as serious as popular sources make it to be.

edit: HEISENBERG almighty, I plead to you that DNP is tolerated on the forum. Thank you for your consideration.

 

[scalpere]

DNP has nootropic effects if i read correctly. so for me DNP deserves to be accepted here !! but yeah thats not a « drug » like stims, opi…

thx for the vid !

 

[GhostChemist]

2,4-Dinitrophenol has very big biological activity as a fat burner and metabolic accelerator
Your method for synth of 2,4-Dinitrophenol not selective and danger because can be formed Picric acid

In the big scale for commercial using the method of alkaly hydrolizing of 2,4-Dinitrochlorobenzene (DNCB) cas 97007
The method is very simple and not danger
DNCB is heated by the alkali in water solution for several hours and then 2,4-Dinitrophenol is cedimented by hydrochloric acid
2,4-Dinitrophenol is filtered, washed and dried
2,4-Dinitrophenol is not explosive and stable up to 100С. But note dinitrophenol penetrates through protective gloves - hands will be painted yellow!

 

[dnBQByvHb8Zkawbjpx]

I've gone a long way in the prep for my own synthesis of DNP since I made the comment above. Here's what I've learned:

You are right about the selectivity. OP should study the article titled "Synthesis of 2,4-Dinitrophenol" published in the Russian Journal of Applied Chemistry in 2012. Instead of H2SO4 it uses 95% ethanol as the medium for the nitration because of it's higher selectivity for dinitration instead of nitrating the substrate fully into the picric acid. With proper temperature control and heating to 60-70 °C (below ethanol BP) the nitration stops at DNP as the third nitration requires a higher temperature.

The nitration route is quite affordable in terms of reagents. Phenol, HNO3 and ethanol are not too hard to come by for a chemist qualified to attempt the nitration in the first place. Looking at DNCB I can already see how much more difficult it would be to obtain for someone like me. The cost and effectivity of the process is of no concern to someone like me, the availability of reagents, the selectivity and safety are way more important.

For OP's benefit, the paper suggests to use activated carbon (coal) for purification. My research says to use cold water for washing (same as you) and hot water for recrystallization (not water/ethanol solution). If you are still preparing we can compare notes in detail. I'm about 1 month away from doing the synthesis myself and I've completed 90 % of all prep.

 

[GhostChemist]

Direct method for nitration phenol was given only by the technical product which is not suitable for biological application. It is difficult to obtain 1 kg of product by nitration in one synthesis

DNCB can be easy obtained by nitration of chloro- or bromobenzene (This compound is more stable in terms of detonation)

 

[dnBQByvHb8Zkawbjpx]

OP's scale is 5 g of phenol (=9.8 g of DNP), mine is the same or a half of it. 1 kg of product is a totally different debate.

Why do you think the product of dinitration of phenol in ethanol medium (following the article/paper I mentioned) at 5 g to 10 g scale would not be suitable for biological application? Is it a low selectivity for dinitration? Other by-products that it would be impossible to remove by using activated carbon, washing and recrystallization? Something else?

 

[GhostChemist]

Maybe for 5-10 g of starting phenol method is suitable according to the article

But the classical nitration process of phenol give the different products include 2,4,6-tnp

By hydrolizing of dncb only 2,4-dnp is the main product

 

[dnBQByvHb8Zkawbjpx]

Per my research, with ethanol as medium and reflux the temperature is kept at 78 °C which favors dinitration and is insufficient for over-nitration. This is an advantage over using H2SO4 as medium which would be more reactive and favor over-nitration.

The suggested route from DNCB sounds good but a quick search confirmed how painfully difficult it would be to source for me. Might as well get DNP at that point. So I'll stick to the nitration of phenol.

 

[GhostChemist]

The choice of method is yours!