Al Koholic
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o-Phthalic acid
Allll right. I've been thinking about production of 3-nitrophthalic acid for some time now and I finally started doing some experimenting.
First I did a nitration of naphthalene to a-nitronaphthalene by H2SO4, KNO3, and naphthalene. I ended up not using enough H2SO4 so yield was kinda
bad and product impure but I got it...I ended up with some 230 grams of impure product from 240 grams naphthalene. I let this sublime for a week in
the garage and it lost about 30 grams but still smelled strongly of naphthalene.
I used 20 grams of this impure product in my next experiment which consisted of adding 36g KMnO4 to 350 cc water and 20 ml 28% HCl. I heated this
mixture to 50C and noticed a strong pungent smell (I think HCl), a small amount of oil on the surface (Mn2O7!??), and slight bubbling (effervescence).
I started magnetic stirring and over the course of 5 minutes added the impure nitronaphthalene. The mix began to bubble more vigorously but nothing
out of control and bubbled for about 20 minutes all the while getting more and more viscous (MnO2 forming). I kept heating and stirring until the
viscosity broke and I thought the color of the liquid had become nearly purple free. The smell of naphthalene had also diminished from the mix.
I now vacuum filtered it while hot and to my dismay, the filtrate was still quite purple. However, I did filter out a whole lot of MnO2. I set the
filtrate aside to cool and I then washed the MnO2 with ether. The ether took on a yellow color and I evaporated the solvent leaving a bright orange
crystal mass weighing 5.7 grams and smelling STRONGlY of naphthalene (damn). So I set this outside and went to bed dissapointed.
Two days later I went to check on the flask of purple filtrate and noticed that it had become completely clear with a nice layer of MnO2 on the
bottom. I put some ether into the flask and swirreled it around but didn't notice much of a yellow color. Today it is a little more yellow but
not much (I think I'll take the ether off tomorrow and concentrate the solution after filtration).
Anyway, I was expecting that naphthalene impurity wouldn't matter because I thought it would be oxidized by the KMnO4.
Now I'm beginning to think that I may be able to get o-phthalic acid straight from naphthalene and then convert to the anhydride then nitrate.
THis route might be less problem prone I don't know. The only thing I need some help with here is
a) can naphthalene be oxidized by hot, acidic KMnO4?
b) what sort of molar ratio do I need? I discovered that I might not have used enough KMnO4 in my initial experiment. 4 KMnO4 are going to be
required to break one of the rings because it will have 2 double bonds. This will leave me with oxalic acid which will also get oxidized correct?
Should it be a 4 :1 oxidizer to naphthalene ratio as I suspect or is the oxalic oxidation interfering?
Anyway sorry for the long post but 3-nitrophthalic acid would be great (for luminol)...hope you all think so too!!
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vulture
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I used 20 grams of this impure product in my next experiment which consisted of adding 36g KMnO4 to 350 cc water and 20 ml 28% HCl. I heated this
mixture to 50C and noticed a strong pungent smell (I think HCl), a small amount of oil on the surface (Mn2O7!??)
Strong pungent smell ---> chlorine!
KMnO4 + HCl will liberate chlorine gas, so you probably got a chlorinated product that wasn't water soluble.
HCl is not strong enough to form Mn2O7.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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Marvin
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Ive posted most of this info before I'm sure for a luminol synthesis.
There is an alpha nitronapthalene synthesis in Vogel that would be perfect for this, and since its online its no trouble and better than the version I
wrote initially.
Oxidation in the synth was with strongly *alkaline* permanganate. That way the 3-nitropthallic acid ends up in aq solution and doesnt get in the way
of furthur nitronapthalene oxidation. Acidic oxidation does not seem to work well as youd have probably found if youd had used sulphuric acid.
As vulture pointed out, HCl is a reducing agent, so you got chlorine.
Becuase its a reducing agent, it doesnt matter how strong the HCl is as an acid, Mn2O7 wouldnt form anyway.
Alternative steps. Oxidation of napthalene to pthallic acid. This can be done the same way, or with conc sulphuric acid. This reaction can be
catalysed with mercury sulphate, but I dont like mercury compounds so I stayed away from this. Rumor has it this can be done without mercury on a
much longer timescale, but I'm unsure if it will just sulphonate instead.
If you get to pthallic acid, dont dehydrate, nitrite. It nitrates very readuly, so like for phenol you need to take precautions to prevent
destruction of the product (primarily decarboxylation, I think), which will then yeild the 3-nitro as majority product. I dont know the exact method,
becuase I went the other way.
I had to stop my actual praxtical, becuase the method I had for making hydrazine was waaay too toxic in its byproducts.
We have versions on the net that will do hydrazine sulphate, and information to go from that to the hydrate hydrate without distillation. If you can
make an 8% solution or therabouts you can make luminol in a furthur 2 steps, which I'll post if you get that far, though if youve worked all this
out from napthalene as I did, you probably have this worked out. If you were thinking of trying the huntress et al synth from the hydrazine salt, you
might prefer that dispite having to bake the salt, than to make the hydrate first.
Incidentally, steam distillation will seperate alpha and beta nitronapthalene becuase the latter is not steam volitile. Unfortunatly unreacted
napthalene is steam volitile, so this doesnt easily get rid of the major contaminant, but follow vogel and all will be well.
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Al Koholic
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Good points...
Thanks a lot for your input guys!
I understand what you mean about permanganate and HCl...
The reason I was messed up by it before was because I was under the impression that any possible HMnO4 would be higher pKa than HCl and would then
form Mn2O7...ah well.
Anyway marvin, I actually have read most of vogel and would have followed his synth (which I will next attempt) except for not having any HNO3 around
at the time and not wanting to spend the day making it when I could just use KNO3...turns out the KNO3 method is quite poor.
As for beta-nitronaphthalene...that should form the 4-nitro derivative and Microtek posted the results of a nice purification of 3-nitro based on
recrystallization.
Anyway, once I get to this (which won't be long) I have everything planned out for hydrazine (to form sulfate salt) and using that directly in
luminol. Turns out there are umpteen million luminol synths available on the web (orgsyn and lots of college chem procdures of which mine is an
adaptation of both). I'll be sure to post the results of my experimenting (which should take place this weekend).
Marvin, I just cruised through a post I made on E&W about forming 3-nitroaniline...
I noticed that I made some mistakes in my post and some clarification is in order since it pertains to what I would like to try with the 3-nitro
phthalic acid...
I want to make nitrophthalimide by bubbling NH3 into a solution of ethanol (not ethanoic acid as I wrote before) and 3-nitrophthalic...I'm not
100% certain this will work because I haven't actually read a synth for this; I've only seen this step referrenced on Bielstien chemical
database. I can get the journals these steps are printed in but some of them I can't read unfortunately...
Anyway, from the nitrophthalimide I thought it would be possible to do a hoffman rearangement yes. So I checked the great Bielstien and yes they had
a method involving NaOH and CaCl2...Now that I think about it though...doesn't the Hoffman rearrangment only apply to primary amides?!
DAMN...perhaps I would be best with trying to form a diamide derivative....this is getting confusing.
Sorry for the confusing post after the first bit everyone. The rest is more than open for feedback but I think marvin may get more clarification from
that considering he asked me about it in another thread.
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