Kapitan
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Accidental acetone peroxide synthesis?
Hi guys.
The other day I was oxidizing an aryl aldehyde to the corresponding acid with nitric acid. After the workup, the product was dissolved in about a
liter of dilute nitric acid solution, so I spent a couple hours rotovapping it off. When the solvent was almost gone, I realized that some product was
left in the reaction vessel, and so (like an idiot) I rinsed it into the rotovap flask with acetone. Of course, a very vigorous exothermic reaction
resulted, evolving a lot of brown NO2 gas and scaring the shit out of me. Luckily, this all happened in a fume hood. When the reaction was finished, I
noticed the formation of some kind of crystalline solid in the flask.
My question is this: Is there a chance that I accidentally synthesized acetone peroxide? I know they usually make that with acetone, an acid catalyst,
and an oxidant. However, hot nitric acid could conceivably act as both an oxidant and an acid catalyst, right?
I tested the resulting solution with a peroxide test. Unfortunately, the positive result for the test strips is yellow, and my solution is also
yellow, so the result was indeterminate. I couldn't find any reports online of acetone peroxide resulting from a procedure like this, but there are
reports of explosions after combining acetone and nitric acid in eg. waste containers.
If this made acetone peroxide, surely there would be reports or warnings online ... right? I mean, these are both very common laboratory chemicals.
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Metacelsus
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No, it wouldn't form a peroxide. However, the residue could still contain nitro compounds, and be potentially dangerous. Next time, you should
neutralize excess acid before workup.
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Kapitan
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Thanks for the quick reply! I know better for next time 
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Praxichys
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No, you do not have acetone peroxide. Acetone and nitric acid are always a bad combo. Mixing the two together results in a vigorous exothermic
reaction with NO2 release.
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PHILOU Zrealone
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Aceton may only form aceton peroxyde if you have a source of peroxyde (H2O2, percarbonate, persulfate, urea-peroxyde complex, ...) and a strong acid
(HCl, H2SO4, ...)
Aceton and HNO3 are uncompatible chemicals...whitin seconds or minutes, depending on the ratio of reactants, initial temperature, and % concentration,
the mix starts to runnaway-boil evolving heat and NxOy. If entrapped, the pressure may build up to rupture the container and spread hot flamable and
explosiove NxOy/aceton vapours... 
This is part of the process of making nitroform (trinitromethane) from isopropanol or aceton and concentrated HNO3 in excess...the aceton exist as an
enol form that adds HNO3 easily to form a nitrocompound...then whith oxydoredox reactions the reactions and products becomes more complex
(nitrosation, oxydation to nitro, decarboxylation, hydrolysis, ...) and you end up with acetic acid and TNM.
If you don't use exces concentrated HNO3, you get intermediary complex products that polymerises by condensations (nitroacetons are selfcondensing
reactive stuffs....)
HNO3 even diluted allows for nitration of aromatic aldehydes so probably into your aryl acid, you have nitrobenzaldehyd and nitrobenzoic acid...this
must explain the yellow color!
When working in a lab, it is always good to study the 2 or 3 pages of uncompatibles chemicals 
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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Kapitan
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Yeah, it's totally my fault. I don't know how I missed that part of my safety training! I haven't worked with concentrated nitric acid much before
this. I'll know for next time, though.
Thanks for the advice, everybody.
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Bert
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Thread Moved
28-6-2016 at 19:52 |
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