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not_important
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hmmm ... nitration of salicylic acid might do. If it didn't decarboxylate during the nitration won't pass the dinitro stage, and it might give a bit
less tar than using phenol. I remember it can be done with "fuming" nitric acid, or standard mixed acid after just plain nitric to get to the
mono-nitro stage. The question is then can the dinitrosalicylic acid be reasonably decarboxylated?
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Sauron
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Especially in the hands of a tyro. Given that the dinitro compound is likely to be somewhat explosive, and the most likely decaroxylation technique is
heat...I would be hesitant to go this way.
On the other hand Rosco_B. likes this route to picric acid so maybe he has some thoughts?
I'm sure I made mononitrophenols in teaching lab as an undergrad, I remember the tar and I am sure we only used conc nitric and sulfuric. Going in two
steps and limiting the amount of acid in second step (both steps) ought to give a mix of 2,4 and 2,6- DNPs. Purifification ought not to be too much of
a hassle. ??
Org Syn is not helpful re dinitrophenols or dinitrochlorobenzene.
Vogel has prep of mixed mononitrophenols and seperation of these. Dilute nitric acid.
And he has prep of picric acid from mixed ortho and para pehnolsulphonic acids.
I think I will check PATR and see if they offer any help.
[Edited on 23-12-2007 by Sauron]
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not_important
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Well, tri-nitro benzoic acid decarboxylates in boiling water, so there's a chance di-NO2 salicylic acid might do the same with perhaps a boost from
copper salts. But I can't find anything giving examples with that or related compounds so it's just speculation.
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Sauron
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The lit. says 2,4-dinitrochlorobenzene can be obtained by nitration of o-nitrochlorobenzene, and that the seperation of the resulting mixture of 2,4
and 2,6 isomers is accomplished by alkaline ethanol-water solution. See Merck Index 12th. entry on 1-chloro-2,4-dinitrobenzene.
Direct nitration of anisole turns out to be hazardous and it is usually prepared through the picryl chloride, itself from 2,4-dinitrochlorobenzene. So
no help here.
Back to the books.
(later) I went out for a dinner and now am back but too bloated to get anything done so will tackle this afresh tomorrow.
Looks like o-nitrochlorobenzene -> 2,4-dinitrochlorobenzene -> 2,4-DNP and a pair of references from Ann. and J.Chem.Soc.
Also Davis talks about a French process from phenol and sulphonation that allows seperation out of the 2,4-DNP (insol in the reaction mix)
So there may be some hope.
[Edited on 23-12-2007 by Sauron]
[Edited on 23-12-2007 by Sauron]
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chloric1
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My deepest apologies
Hey guys! I am really sorry about those posts. Someone really had a good time at my expense. I will make sure I close this website if I leave my
computer even for a second.
To stay genuine with this topic, the first time I discovered Science Lab I did not like there prices and I did not feel comfortable with there website
at all. I have not purchased any chems from a lab dealer in more than a year. I either have been synthesizing stuff from my stockpile or bought some
chems from pottery suppliers and garden shops. There is enough to keep a working married guy with a child more than busy.
Fellow molecular manipulator
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Sauron
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Okay, now I have this nailed.
Start with chlorobenzene.
Nitrate with mixed acid consisting of 30% conc HNO3, 56% conc H2SO4 and 14% water. Temperature 40-70 C. The usual conditions for aromatic nitration
apply, i.e., vigorous stirring and reflux.
This will produce a 95% yield of nitrochlorobenzenes consisting of about 35% 2-nitrochlorobenzene, which is low melting, and 65% 4-nitrochlorobenzene,
much higher melting. These are readily seperated by repeated fractional crystallizations in a procedure described in Ullmann.
Further nitration of the purified 4-nitrochlorobenzene produces only the desired 2,4-dinitrochlorobenzene. This is done at 60 C with mixed acids
consisting of 35% conc nitric acid and 65% conc sulfuric acid.
This contrasts with nitration of 2-nitrochlorobenzene which is said to give 90% of the desired isomer plus 10% of the 2,6-dinitrochlorobenzene.
Fortunately, as the para mononitro isomer predominates, this is not inconvenient.
If you dinitrate the mixture of ortho and para nitrochlorobenzenes, therefore, it would be expected that 10% of the 35% ortho isomer present would be
converted to 2,6-dinitrochlorobenzene.
The French procedure for seperation of the two isomeric dinitrochlorobenzenes could then be applied. This procedure is referenced in the Merck section
above. (Alkaline ethanol-water soln.)
Once pure 2,4-dinitrochlorobenzene is on hand, use the Vogel procedure to convert it yo 2,4-dinitrophenol.
So you have your choice of nitrating pure 4-nitrochlorobenzene, or of using the crude mixed isomers and then removing the 3-4% of the 2,6-isomer from
your 2,4-DNCB.
My advice would be to go the more elegant and seperate the mononitrochloro isomers, then nitrate only the 4-nitrochlorobenzene. You will then have
pure 2,4-isomer and thus, after hydrolysis, pure 2,4-dinitrophenol.
After all the details of the French procedure may be hard to come by, and even if you can get them they will need translation.
This is as simple as it gets. No fuming acid required. No nitration of phenol. You should note that the nitrochlorobenzenes are toxic and you need to
guard against skin contact, inhalation of fumes, etc. Do this outdoors or in a fume hood, wear gloves and goggles, a lab coat, etc.
[
[Edited on 24-12-2007 by Sauron]
Attachment: 24DNCB.txt (3kB)
This file has been downloaded 1271 times
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Sauron
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Being concerned that the Ullman definition of mixed acids for nitration was a trifle vague as to concentration of the HNO3, I delved a little deeper.
Unfortunately PATR was not much help.
I found a prep of monochloronitrobenzene in Fundamental Processes of Dye Chemistry (forum library) but it employed fuming nitric acid d.1.52. Likewise
the direct dinitration of chlorobenzene in same volume employed the same fuming nitric acid. Not so convenient for the thread author.
Merck Index 12th ed. references J.Chem.Soc 1006(1948) for prep of mixed isomers of DNCH from nitration of o-nitrochlorobenzene. The acids used in
nitrating mixture are ordinary concentrated reagents, nitric acid d 1.4 and sulfuric acid d.1.84. I will modify this convenient and simple procedure
by replacing the ortho compound with p-nitrochlorobenzene so that we will obtain pure 2,4-dinitrochlorobenzene rather than the isomer mix that the
ortho compound gives.
Dissolve 315 g 1-chloro-4-nitrobenzene in 1300 ml conc sulfuric acid in a 3-neck round bottom 3-Liter flask. Slowly and with stirring add 315 g conc
nitric acid dropwise. After addition reflux the mixture, with continued stirring, on boiling water bath (100 C). Let the mixture cool, then pour onto
2 Kg cracked ice. The product seperates as a yellow oil that will crystallize to a yellow cake. Filter, remelt under water to remove traces of acid,
cool, let solidify, filter again and wash. 2,4-dinitrochlorobenzene is insoluble in water. Once dry, mp 51 C.
So now all we need is a nitration of chlorobenzene to the mononitro products, I believe Vogel gave us that in the form of prep of the
p-nitrobromobenzene, which we can simply used by analogy.using standard acids. Ullmann and Vogel both have direction for seperation of the o- and
p-isomers. This page from Vogel is attached.
As long as the thread author can obtain (or prepare) chlorobenzene, he now has all the information needed to get to 2,4-dinitrophenol without needing
anything exotic.
Chlorobenzene
Conc sulfuric acid
conc Nitric acid
sodium carbonate
Three steps. Mononitration, and isolation of the p-isomer. Dinitration and workup. Alkali hydrolysis to the phenol.
[Edited on 24-12-2007 by Sauron]
Attachment: Pages from vogel_practical_ochem_3.pdf (284kB)
This file has been downloaded 706 times
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Axt
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I've posted the preparation of dinitrochlorobenzene starting from sodium benzoate in the pre pub section:
http://www.sciencemadness.org/talk/viewthread.php?tid=8027
Which gives a convenient chlorination of benzene, though as sauron noted above, in my case the 2,4-DNCB contained some byproduct 2,6-DNCB (which
doesn't matter if its to be further nitrated, but will matter in your case).
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Sauron
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I probably ought to rewrite that Vogel prep specifically for chlorobenzene. Let's scale it up 10x at same time.
In a 3 liter round bottom three-necked flask fitted with a mechanical stirrer, a reflux condenser and a dropping funnel, place 200 ml (285 g) of
concentrated nitric acid. Slowly in a thin stream from the dropping funnel add 200 ml (370 g) conc sulfuric acid. Cool the mixture to room
temperature.
Charge the addition funnel with 102 ml (113 g) of chlorobenzene. Add this dropwise with vigorous stirring to the mixed acids, not allowing the
temperature to rise above 50-60 C. Once the addition is complete and exothermic reaction has subsided (no more rise in temperature), heat the reaction
mixture on a boiling water bath for 1 hr. Continue the mechanical stirring throughout the heating period.
Remove from bath, discontinue stirring and allow to cool to ambient.
Pour into 2 Kg cracked ice. If the nitrochlorobenzene does not immediately srystallize, stir until the oil solidifies. Filter, wash with water, and
drain as well as possible. Recrystallize from 1 to 1.2 L 95% ethanol heated on a water bath to just under boiling (75-78 C). Let cool. Filter the
precipitated p-nitrochlorobenzene. The mother liquor contains the ortho isomer contaminated with some p-isomer.
Yield about half a mol of pure p-isomer. (70-75 g)
-----------------
Thanks, Axt. If the thread author can't get benzene or chlorobenzene, he still might have a better chance of getting sodium benzoate, and TCCA
(swimming pool chemical) ought to be a snap. That's a very nice series of preps you have there. I had not looked at them before.
[Edited on 24-12-2007 by Sauron]
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Ozone
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Sauron is not kidding!
Some brief notes on the toxicity of dinitrophenols:
1. Look up electron transport, then imagine it running out of control (then imagine uncontrolled anorexia). Nitrophenols have a tendency to eliminate
via urine and have been demonstrated to increase the risk of bladder cancer.
2. From elsewhere on this site (quoting myself):
"...sec-butyl-2,4-dinitrophenol (Used at the time as a polymerization inhibitor) goes straight through nitrile gloves. I developed a migraine, fast
irregular heartbeat, I was *hot*, sweating profusely. I removed my gloves to find that I had yellow fingers. Not good. I went outside, (it was cold,
thank goodness) sat down and had a smoke (tasted like DNP and metal). Fortunately, this went away, but the dose was small and *transdermal*. yikes..."
Remember that your intermediate products are toxic as well!
Take care and merry Christmas,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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Sauron
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Damned right they are toxic. 2,4-DNCB is not an obscure compound, it has been mass manufactured for a very long time because of its vast strategic
importance in the explosives and even moreso, the dyestuffs industries. So its toxicity has been amply documented and well studied. It is a notorious
itching powder, producing eczema and unbearable itching upon contact with the skin, especially when in solution. The French actually used it as an
explosives additive in shells (or left it in as an impurity) precisely because they liked this harassing effect on enemy troops.
Incidentally, pure 2,4-DNCB is regarded as somewhat less toxic than mixtures of 2,4- and 2,6-DNCB which implies that 2,6 isomer is far more toxic than
the other. As mentioned, the ortho to para ratio for mononitrochlorobenzene is about 33/66 with balance traces of m-isomer. And further nitration
produces c.97% 2,4-DNCB and 3% 2,6-DNCB because all of the p-isomer gives only the 2,4-isomer while the o-NCB gives 90% 2,4 and 10% 2,6. So 10% of 33%
is 3.3%.
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Alan
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I would not recommend buying ANY thing from there. I know way to many people that got dicked around for a couple MONTHS or they NEVER even received
what they sent money for.
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anotheronebitesthedust
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Sciencelab = Science Alliance
http://www.chemindustry.com/apps/search?category_id=11&s...
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quicksilver
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| Quote: | Originally posted by chloric1
.....the first time I discovered Science Lab I did not like there prices and I did not feel comfortable with there website at all. I have not
purchased any chems from a lab dealer in more than a year..... |
I'm not in the habit of bashing a company but that one really gets me going. I placed a rather large order with them which was not delivered, etc,
etc. They charged my card, bla, bla. They gave me the run-a-round like I have not had in quite awhile ...They are extremely haphazard in their
business practices. Never again.
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