Sciencemadness Discussion Board

3,5-Dinitrosalicylic acid

guy - 9-7-2007 at 19:38

Can this be made by carefully nitrating salicylic acid?

not_important - 9-7-2007 at 20:04

Yes, here's one method

Attachment: Dinitrosalicylic_acid_as_a_reagent_for_the_estimation_of_sugar.pdf (344kB)
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guy - 9-7-2007 at 20:21

I can always count on you. :D

I suppose nitric acid can be formed in situ by adding KNO3 into H2SO4? Is there any specific way I should do this step?

not_important - 9-7-2007 at 20:34

Sorry, would know for sure but it does sound possible. The K2SO4 might be a problem, given its low solubility. But I've not done enough such nitrations to be an expert, when concentrated acids were required I bought or made HNO3.

Bolt - 9-7-2007 at 22:18

I can't imagine that the yields are very good from that preparation. Obviously, the carboxylic acid is delicate, but you've got two ring deacitvators (COOH and NO2) meta to the carbon on which you want to put the final nitro group. It seems odd to me that the final nitro group can be attached if the reaction is kept cold and the reaction time is short.

Another reference for the synthesis of dinitrosalicylic acid is in Beilstein's 'Lehrbuch der Organischen Chemie,' 4th Edition, Vol. 10, page 122.

When using HNO3/H2SO4 as your nitrating mixture for an aromatic nitration, it is standard procedure to use 2-3% theoretical excess HNO3. The sulfuric acid content is decided on an individual basis. I'm not sure how that translates into xNO3/H2SO4 mixtures. Damn, how many times have I wished someone had intelligently started a thread about that? BTW I read somewhere that, if added to a nitrating mixture, the K+ and HSO4- ions can actually increase the reaction rate. Maybe you'll have some luck with that.

Why do you want the dinitrosalicylic acid? Picric Acid is the only thing I've ever dreamt about that used salicylic acid. (You might want to take some pointers from the nitration of acetylsalicylic acid to Picric Acid using xNO3/H2SO4. But I'm sure you knew that.)

[Edited on 10-7-2007 by Bolt]

not_important - 9-7-2007 at 22:49

It looks as if it was the preferred method back in that decade. Here's another article from a few years later, it uses the same method but changes the workup a little. No yield given. I suppose if you wanted a lot of it you could run fairly small batches, recover the mono-nitrated acids, and recycle them into the next batch. No ideas as to how bad oxidation of the substrate may be.

Attachment: COLORIMETRIC METHOD FOR ESTIMATION OF SUGAR BLOOD.pdf (616kB)
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Sauron - 9-7-2007 at 23:45

I would not expect any difficulty introducing the second nitro group. The phenolic -OH is a powerful activator and as such has more influence than the two deactivators. The position that is ortho to the hydroxyl is metal to the carboxyl, and also metal to the first nitro (that will be mainly para to the hydroxyl) and that looks like smooth sailing to me.

If oxidation of the carboxyl group proves a problem, you can esterify it first and then saponify it after the nitration(s).

Sorry for the somewhat dated jargon.

Bolt - 10-7-2007 at 00:41

Forgive me if I seem as though I'm trying to be contrary.
Quote:
Originally posted by Sauron
I would not expect any difficulty introducing the second nitro group. [....]


The reason I'm a little hesitant about the 'smooth sailing' is that I've dreamt of Picric Acid from SA. With even moderate heating (40*C), I got no appreciable yield. Yes, the phenolic hydroxyl group is one of the strongest O/P activators (outside of O-), but the final nitro group in DNSA is battling the same odds as TNP. (Two M deactivators, although admittedly -NO2 is a stronger M deactivator than -COOH and in order to reach TNP decarboxylation then nitration must occur.) Take that for what you will...

I guess if it's in literature it works right? :P

[Edited on 10-7-2007 by Bolt]

IPN - 10-7-2007 at 02:23

No wonder you get low yeilds of picric acid if you only heat to 40C. :o

I have recently made picric acid with the procedure found at lambdasyn.org (http://www.lambdasyn.org/synfiles/pikrinsaeure.htm preparation B, use babelfish if you can't read german). The final heating is done at 120C, and although it may seem a bit much this ensures complete nitration & decarboxylation of the salicylic acid/phenolsulphonic acids and a good yeild of picric acid. :)

not_important - 10-7-2007 at 03:47

There's 3 deactivators when going from DNSA to TNSA, and the CO2H is sitting in the spot for the 3rd NO2, which is also one of the three activated by the OH. So you must decarboxylate for that, while for DNSA it's just ordinary nitration which looks to proceed fairly well on nitrophenol. And the prep explicitly says that there's mono-nitroSAs as byproducts; I doubt they were looking for absolute highest yields given that the starting material was fairly cheap.

Sauron - 10-7-2007 at 05:48

So PA is the target of this prep? I thought Vulture was closing down new picris acid threads and directing anyone interested to one or more of the multitude of existing threads on this topic.

No skin off my nose, though. Enjoy!

I think the thread starter said that the decarboxylation had to happen before the third nitro group - at least he implied it, and I think he explicitly stated so.

If I had to make PA I think I'd either use the mercuric nitrate catalytic process, or the more interesting route via 2,4-dinitrochlorobenzene. That way with picryl chloride in hand you can end up with picramide as well as PA and you are sitting pretty to make a number of useful analytical reagents, or some nice energetics if that is your thing. Picric acid of course is both of those.

I think chlorobenzene is just as cheap as salicylic acid. Next time I am rooting around in Acros catalog I will have to take a look.

guy - 10-7-2007 at 07:11

I'm not trying to make picric acid. I just wanted to play around with DNS.

Bolt - 10-7-2007 at 07:42

Quote:
Originally posted by IPN
No wonder you get low yeilds of picric acid if you only heat to 40C. :o

*laughs* Of course, I use Rosco's good ol' country recipe. That was one of my own experiments using varying temperatures. :D
Quote:
Originally posted by Sauron
I think the thread starter said that the decarboxylation had to happen before the third nitro group - at least he implied it, and I think he explicitly stated so.

First, I'm not the thread starter. I'd never start a new thread as a new poster, and certainly not about TNP. :o I was comparing the HUGE difference in reaction time and temperature between rather similar reactions.

@guy: Check out US2021497 Lead Salts of Dinitrosalicylic Acid.

===

For a little OT discussion:
Quote:
Originally posted by Sauron
If I had to make PA I think I'd use [...] the more interesting route via 2,4-dinitrochlorobenzene.

Yes! I once thought about performing extensive experiments on that, but unfortunately, IIRC, the nitration requires oleum for good yields.
Quote:
Originally posted by Sauron
I think chlorobenzene is just as cheap as salicylic acid. Next time I am rooting around in Acros catalog I will have to take a look.

It's not quite as cheap, but it's still pretty cheap. Monochlorobenzene pops up on eBay every once in a while as well.

[Edited on 10-7-2007 by Bolt]

Ozone - 10-7-2007 at 15:01

DNS reagent (prepared with Rochelle salt) is a nice, sensitive indicator for reducing sugar (sucrose does nothing). Just take 1 mL reagent + sample, heat in boiling water for 10 min (goes dark red-brown), and examine with a spec (or comparison chart).

It does go to crap after a while (and is light sensitive, so wrap your reagent bottle with Al° foil).

It is not too specific. All it needs is a reducing end.

Cheers,

O3

guy - 11-7-2007 at 11:36

I put 28g of KNO3 in 25mL water and added slowly ~85mL conc. H2SO4. This was in an ice bath. Then I added 15g of salicylic acid. The solution turned brown-yellow due to some NO2. After about 15minutes I added the stuff to 500mL of cold water and light yellow crystals precipitated. I filtered it and got light yellow precipitate and the filtrate was orange.

The precipitate (probably DNS) dissolves in water to form a light yellow-green solution and turns into a very intense red-orange color when NaOH was added.

Is this DNS?

[Edited on 7/11/2007 by guy]

Bolt - 11-7-2007 at 13:16

I don't believe you can tell what you have by simply looking at the compound. How you know you don't have mononitrosalicylic acid? or MNP or DNP? Many possibilities exist.

Did you notice any effervescence? (The effervescence could be from decarboxylation.)

Also, what was the max temperature that the reaction reached? I find it hard to believe that the reaction is emitting NOx if it's kept cold.

PHILOU Z has this to say about the red crystals.
Quote:
Answer is nitronic acid rearangement!

CH3-C(OH)=C(CH3)-NO2 <--> CH3-CO-CH(CH3)-NO2
CH3-CO-CH(CH3)-NO2 <-OH(-)-> CH3-CO-C(CH3)=N(O)-OH
Thus beta nitro enols undergo enol-ceton [ketone] equilibrium to provide a alfa hydrogenated nitro derivative in tiny % that gives the yellow colour; the later upon the action of a base undergo the nitronic rearangement
cf NM:
CH3-NO2 + NaOH --> CH2-NO2(-) + Na(+) --> CH2=N(O)-ONa
The later compound is deep orange to deep red-brown!


Did you check out that patent I pointed you too? (I dunno what you mean by 'playing around' with DNSA.)

guy - 11-7-2007 at 13:24

I don't think the temperature was more than room temperature. It was cold the whole time. It was barely forming NO2 because I could not see the gas above the solution; only the solution turned orange. I don't think there was decarboxylation since you need a high temperature.

guy - 11-7-2007 at 21:14

Does anyone know what DNSA is supposed to look like? And the sodium salt?

sparkgap - 11-7-2007 at 21:22

My copy of CRC says that your DNSA comes out of recrystallization from water as white needles or plates.

sparky (~_~)

guy - 11-7-2007 at 21:58

Quote:
Originally posted by sparkgap
My copy of CRC says that your DNSA comes out of recrystallization from water as white needles or plates.

sparky (~_~)


Mine are pale yellow and give a yellow solution on dissolving. The sodium salt is orange-red. I don't think this is right.

Should I give my nitration more time?

garage chemist - 12-7-2007 at 00:45

Have you stirred in the salicylic acid well? I'd think that would be very important with inhomogenous reactions like this.

Also, measure the melting point! That is the first thing to do when unsure about the purity of a substance!