Romain
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Benzoyl peroxide extraction - polymerization of the solvent?
Hi everybody,
A few months ago, I dissolved about 100 g of benzoyl peroxide "radical initiator" in about 250 ml of solvent, whose exact composition is not known.
The bottle says "Universal paint cleaner" and states it contains xylene, possibly among other things. I tried water before but benzoyl peroxide was
insoluble in it apparently. I didn't try acetone because I feared that it would make acetone peroxide. I don't know if that's even possible...
The goal was to recrystallize the benzoyl peroxide to purify it. At first I decided to let the solvent dry at room temperature but the process was
very slow. I managed to get a few crystals (colourless, monoclinic, the biggest were 10 mm long). I tested them to be sure they were benzoyl peroxide;
I ignited one and it burned very rapidly with black smoke.
Anyway, I tried to speed things up and heated the solvent a bit. Yes, very unwise to heat peroxide and solvent together...
The solution, previously yellow transparent turned cloudy orange and then darkened more and more until it was a brown black thick liquid (like oil).
My bet is that the solvent somehow polymerized into a longer molecule, hence the increased viscosity, the darker colour, etc...
What are your thoughts?
P.S. I don't have much experience in organic chemistry at all, I'm just starting.
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Metacelsus
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To my knowledge, xylene doesn't polymerize. Polymerization of alkenes can proceed by a radical mechanism, so if the solvent had alkenes, it might have
polymerized. Do you have any of the solvent left? If you do, and want to find out what happened, I recommend two things:
1) Heat the solvent to boiling without adding anything, and see what happens. This will determine if the peroxide was to blame.
2) Test for alkenes by adding some bromine (or bromine water) and see if the bromine color disappears.
[Edited on 23-11-2014 by Cheddite Cheese]
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Dr.Bob
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I would not heat any real amount of it, it likely still has some oxidant left, and might detonate. Be very careful and store it away from people. I
know at least one person who burned their family house down with some old mix of oxidants and solvent they made and stored inside until the house
burned down.
Benzoyl peroxide is some bad stuff, and can be very dangerous, I avoid using it other then in tiny amounts. i would much rather handle black powder
in lather quanties than benzoyl peroxide. I had a lab mate injured when they concentrated a peroxide reaction down and it blew up in the hood. They
were injured from glass blowing off of the hood sash, even with the sash down.
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Etaoin Shrdlu
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What's the brand of the thinner? It would be nice to try to track down an MSDS. I am also inclined to say it sounds like there might have been alkenes
in there.
EDIT: Does it smell like citrus? Limonene polymerizes and is also a popular paint stripper.
[Edited on 11-24-2014 by Etaoin Shrdlu]
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Romain
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I put some of the black liquid in a test tube and heated it to it's boiling point. It didn't seem to change much but at the time, I was most concerned
about cleaning the beaker that contained the rest of the black liquid, fearing that it would be hard to get off the glass.
I don't have bromine or bromine water to test for alkenes, unfortunately.
I disposed of the black liquid in the solvent waste bottle I normally use, but I think I'll get rid of that bottle now, because as you pointed out,
Dr.Bob, there may be some peroxide left and I certainly don't want it randomly catching on fire in my basement. I guess burning the solvents waste in
a metal can is OK? There's about 100 ml of ethanol + the black liquid in the bottle.
The brand of the cleaner is Kluthe, it's the Lösin 100 thinner. Here's the msds: MSDS. It says it contains
- Xylene, n-Butyl Acetate, Hydrocarbons, C6-C7, N-alkane, Iso-alkane, aromatic hydrocarbons, <5% n-hexane, n-butanol, toluene, and ethylbenzene.
Maybe the alkenes are included in "hydrocarbons" but I'd have to test to be sure.
One thing is for sure, I won't work with organic peroxides again. They are scary and I really don't want to burn my house down.
[Edited on 24-11-2014 by Romain]
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