Sciencemadness Discussion Board

Picric acid synth idea from ASA w/o sulfonation

niertap - 14-3-2012 at 02:07

Some theory::

When synthesizing picric acid the phenol is first sulfonated. This is to prevent oxidation and polymerization. Heating phenol and sulfuric acid sulfonates in the para position because of it's bulk, it cannot therefore be directed to the ortho position.

I'm unsure if it stops oxidation because it deactivates the ring or because it deactivates it some. If it's because of the deactivation this should work.


A paper on microwave assisted nitration that is fairly interesting. Acetic acid seems to be a good solvent during nitration.

HIGHLY ACCELERATED MICROWAVE ASSISTED AROMATIC NITRATION WITH
DILUTE NITRIC ACID
http://envirofacs.org/Pre-prints/Vol%2039%20No%201/Papers/Wi...






Synthesis::

Treat Acetasalycylic acid(ASA) with dilute ~20% nitric acid. This should produce nitrosalycylic acid and acetic acid(from ester hydrolysis). Then nitrate it under stronger conditions to create picric acid. This would also remove the carboxylate.

I prefer not to use nitric acid, so I would put the ASA, 1.2eq of sodium nitrate, and maybe enough water to make a slightly liquid paste to a flask. Then add sulfuric acid drop wise until the nitration to picric acid. I would keep it a little below room temp. Quench with cold water to extricate the product.






quicksilver - 14-3-2012 at 09:37

.
QUOTE from paper:

"The theoretical explanation for these remarkable accelarations is not yet
clear. It is possible that the effect is purely a thermal one, with the rapid attainment of
very high local temperatures due to the efficient absorption of microwave energy."


This is also an interesting discussion topic. BUT make VERY sure that people KNOW that it is NOT to be attempted by a youngster in his parent's kitchen!

We could discuss the microwave design issues (a carousel of table turning which complicates maintenance of consistent temp) or MW beam focus. But remember one cannot use a droplet technique in a closed MW commercial product, nor manage temp as effectively as with proper lab equipment. That being said we are forced to wonder why this is not used professionally. It's not becasue of the product (many other nitrobenzenes are in current demand).

When examining a potentially (extremely) dangerous concept: always look for why it has not been implemented on a plant-level. That DOESN'T mean we shouldn't discuss the concept; but remember this is a public Forum and with the public we have a great many levels of maturity.

VERY dangerous concept? Horrifyingly so. But it is interesting. Note that the authors do everything they can to make this a query of possibilities with many unanswered issues

niertap - 14-3-2012 at 10:47

ha ha, I didn't quite mean carry out the proposed synthesis in a microwave, though that would be interesting to see someone try to figure out how.


The topic of microwave assisted synthesis is indeed very could be interesting. From the article it appears nitric acid absorbs microwave radiation significantly better than water. The effects could be to that or it's possible it has something to do with transition states. I think there is a tiny delay between absorption and heat generation/releasing the energy by some other means. The energized state could be what's reacting.

It's also interesting how salicylic acid nitration only gave the 5/para isomer, while the normal nitration produces some of the 3. It might be that the microwaves enhance the directing ability of the salicylic acid, creating a very positive para position.


Dilute HNO3 as an effective nitrating agent may not be a dream anymore.

killswitch - 14-3-2012 at 11:10

I know this is kind of the opposite of the topic of the thread, but how exactly does the standard aspirin synthesis work? I'm still unclear on how sulfuric acid turns 2-acetoxybenzoic acid into phenylsulfonic acid, and how the hydroxyl group causes such a large difference in behavior from the other aromatic nitrations such as TNB and TNT.

497 - 14-3-2012 at 11:22

Like I posted in the huge existing picric acid thread, simply boiling salicylic acid, among other things, in below azeotropic HNO3 does get decent yields of nitro compounds including picric acid. This was discovered many many years ago.

As for the microwave nitration, it is very interesting indeed. Why not add an inert immiscible solvent to dilute any precipitated nitrobenzene to safe levels?

caterpillar - 14-3-2012 at 14:40

Quote: Originally posted by niertap  
Some theory::

When synthesizing picric acid the phenol is first sulfonated. This is to prevent oxidation and polymerization. Heating phenol and sulfuric acid sulfonates in the para position because of it's bulk, it cannot therefore be directed to the ortho position.

I'm unsure if it stops oxidation because it deactivates the ring or because it deactivates it some. If it's because of the deactivation this should work.


A paper on microwave assisted nitration that is fairly interesting. Acetic acid seems to be a good solvent during nitration.

HIGHLY ACCELERATED MICROWAVE ASSISTED AROMATIC NITRATION WITH
DILUTE NITRIC ACID
http://envirofacs.org/Pre-prints/Vol%2039%20No%201/Papers/Wi...






Synthesis::

Treat Acetasalycylic acid(ASA) with dilute ~20% nitric acid. This should produce nitrosalycylic acid and acetic acid(from ester hydrolysis). Then nitrate it under stronger conditions to create picric acid. This would also remove the carboxylate.

I prefer not to use nitric acid, so I would put the ASA, 1.2eq of sodium nitrate, and maybe enough water to make a slightly liquid paste to a flask. Then add sulfuric acid drop wise until the nitration to picric acid. I would keep it a little below room temp. Quench with cold water to extricate the product.


Sulfonation of phenole is very simple proces and according to literature that I've read it gives orto, para mono and disulphophenole disulphophenoles. Dissolve phenole in conc H2SO4 and treat it by means of boilng water bath for one our. That's all. There is another way to prevent oxidation- two-step nitration, something like that you described. Once I made experiment: I added H2SO4 (drop wise!) to phenole + KNO3. Aforementioned mixture was ignited. Diluted mixed acide is not good for final nitration. The best way that I found is something like this: solution of phenolesulphoacides in H2SO4 is to be slowly added to mixtute of KNO3 (or NaNO3) and H2SO4. Temperature must be kept below, let's say, 30 C. Wait for one night and heat mixture by means of boilng water bath for 1 our. Finally put reaction mixture into large volume of cold water (may be, with some crushed ice). Picric acide precipitates. Wash it with some cold water. That's all. I met no visible oxidation- reaction mixture, been heated, produced very small amount of NO2. But do not use NH4NO3 !!! I used 250 gr of phenole and 1 kg of KNO3. Amount of H2SO4 I do not remember- something like 800 gr for sulphonation of phenole and 2 kg to mix with KNO3. May be, amount of H@SO4 could be decreased a little.

niertap - 14-3-2012 at 14:53

@497

It wouldn't be boiling ASA in 70% HNO3. If slowly acidified the ester would have time to hydrolyze and release acetic acid into the solution. The HOAc with dilute HNO3 appears to be a little better at nitrating salicylic acid than H2SO4/HNO3 and significantly better than 70% HNO3. I'm not going to site, but there's plenty on the web. I think the HOAc changes the solvent characteristics to stabilize the nitronium and prevent oxidation. I will edit in an estimate of how it stabilizes it.



On a side note I found a very intriguing paper on science direct. If anyone has an account for it i'm sure everyone would appreciate more than the abstract.

Microwave promoted rapid nitration of phenolic compounds with calcium nitrate


Tetrahedron Letters, Volume 47, Issue 12, 20 March 2006, Pages 1885-1888
Ajay K. Bose, Subhendu N. Ganguly, Maghar S. Manhas, Sheetal Rao, Jeffrey Speck, Uri Pekelny, Esteban Pombo-Villars

It involves an acetic acid calcium nitrate solution. Their example of nitrating phenol gave reaction conditions of 1min at 400watts to produce nitrophenol(mono nitrate).

http://www.sciencedirect.com/science/article/pii/S0040403906...


[Edited on 14-3-2012 by niertap]

quicksilver - 14-3-2012 at 17:52

Quote: Originally posted by niertap  


Dilute HNO3 as an effective nitrating agent may not be a dream anymore.



I am going to see if this had ever been undertaken on a plant-level. It may have been successful in a lab. However most all the nitrate towers also make nitric for plants: so I am not sure if cost on the acid side is a heavy out-put of capital. This is a damn interesting issue.

caterpillar - 14-3-2012 at 21:49

Well, assume mono nitrophenol can be obtained in such way. But what do you plan to do with it? Further nitration will require mixed acid or mixture of nitate and sulphuric acide anyway.

niertap - 15-3-2012 at 03:56

@caterpillar

If you read the line below what you're talking about I describe the actual procedure I would follow.

niertap - 2-4-2012 at 04:38

I ran the proposed reaction(mostly), but got lazy and intolerant of red fumes. It appears that dinitrosalicylic acid is REALLY easy to make. I plan on renitrating this under harsher conditions to ipso substitute a nitro for a carboxylic acid.


I added 40g ASA, 60g NaNO3 to a graduated mason jar. Then added about 20ml distilled white vinegar(krogers brand). It formed kind of a thick paste. Then I added about 30ml rooto brand H2SO4(93%). I added it dropwise at first, but soon began adding it several ml at a time. Temperature doesn't appear to be a problem at all and I estimate the reaction took place at 50C. The only problem until now was the acetic acid vapor. After adding another 10ml sulphuric acid, a red miasma began to emanate from the flask. heeding to caution i stopped the addition. The flask was then allowed to digest for 30m and promptly drowned in cold water. The white precipitate was quite voluminous, though deceptively pale. It did however turn paper yellow after prolonged contact.

To elucidate the identity of the product, it was heated to melting. It almost immediately turned black after crossing the melting point and released an odor of phenol. Next I combined 5g of the powder with 10ml h20. It was yellow in solution, but when heated to around 85-90C it formed a red liquid under the aq layer. The flask also began to smell of acetic acid. Upon cooling, it reluctantly crystallized into a solid white mass on the bottom of the flask. I believe The formed product was a mixture of dinitrosalicylic acetate and the free acid. When combined with KClO4, it reluctantly detonates upon action of silver azide(what doesn't?).


It always cheers me up to sprinkle several grains of silver azide slightly smaller than sand, on a soda can. I'm always impressed by the clean holes they leave, exactly their size.