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Author: Subject: Help me identify an organic compound
m1tanker78
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[*] posted on 1-8-2012 at 18:34
Help me identify an organic compound


I was going to post this in the Organic section but anticipate it would have been moved so..

Background:
I was attempting to speed up the polymerization of styrene with sodium metal as cited by several sources on the net. The styrene I used was the raw liquid that distills over from polystyrene pyrolisis. It isn't pure and it isn't exclusively the monomer. The distillate sat in my hot garage for a couple of days before I was able to experiment with it.

Procedure:
I filled a test tube about 1/3 with this raw styrene and dropped a small piece of crusty sodium in it. To my surprise, the sodium looked as if it was slowly becoming cleaner (at ambient temp). Some yellow/orange patches began to form in certain places on the metal's surface. I became impatient and heated the test tube with a small butane torch. A very deep red substance began to spontaneously form on the surface of the metal while hot. If too hot, the red substance would whisp upward. As the whole thing cooled, the red substance would redissolve in the warm raw styrene leaving perfectly clean sodium except where the sodium bead contacted the test tube. Even this would eventually dissolve away. I repeated this heating to boiling and cooling cycle several times and the sodium bead didn't seem to be consumed by the reaction. After a few cycles, a yellowish precipitate would persist. At some point, the red color would persist in the solvent.

This one's had me scratching my head and scouring the net. I hope one of you knows or can point me in the right direction.

Here are some images I took:







Note that the sodium bead is completely clean except where the red substance hides it. I wasn't quick enough with the camera to capture it completely covered in red.

What substance can this be and what are some proposed chemical reactions taking place? It appears that the sodium catalyzes the reaction.

The only reference I was able to find is from wikipedia:
Quote:
Styrene reacts in toluene with sodium to 1,3-diphenylpropane [2] through the intermediate carbanion:


Your help in identifying this compound would be greatly appreciated,

Tank




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blogfast25
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[*] posted on 2-8-2012 at 05:16


I'd advise to repeat the experiment with pure styrene. Model airoplane outfits often sell it. G-d only knows what kind of crap might be in your depolymerised PS...



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Endimion17
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[*] posted on 2-8-2012 at 07:16


This is probably impossible to solve. These things are simply called "tar" in organic chemistry. It's obvious by the color. There's orange, yellow, red... It screams "polymerization".



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m1tanker78
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[*] posted on 2-8-2012 at 16:12


Thanks. I guess I was over-thinking this. :D

I didn't expect the red color during the polymerization. And it makes sense that this step is self-limiting due to the limited surface contact area of the metal.

Tank




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[*] posted on 4-8-2012 at 11:17


I have no idea what it is but maybe it could be used as a dye. Try it on cotton.
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kristofvagyok
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[*] posted on 4-8-2012 at 12:15


As far I remember BuLi is used as an initiator for this polymerization and it is called living polymerization, but if you use simply sodium as an initiator it will probably won't do much (it is a metal, it is heterogenous and it is not a strong base enough to remove a proton from the styrene). Prepare some Na-naphthalenide, what will probably initiate the polymerization.

Just add a little naphthalene and boil it, it will start immediately.

And don't use this much sodium, traces are enough for this.

For the yellow participate it could be sodium oxide/superoxide what could be formed from the traces of oxygen and water in the styrene, filter it out and check it with water and a pH indicator paper.

And for last: the reaction what you have mentioned requires some toluene what is deprotonated from the sodium, and what reaction conditions you have posted, there is no toluene in it, so it won't be this.




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Pyro
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[*] posted on 4-8-2012 at 13:11


try reacting your styrene with sodium oxide, sodium hydroxide, sodium azide... your styrene might not attack the sodium, but the rubbish surrounding it.



all above information is intellectual property of Pyro. :D
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kristofvagyok
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[*] posted on 4-8-2012 at 13:23


Quote: Originally posted by Pyro  
try reacting your styrene with sodium oxide, sodium hydroxide, sodium azide... your styrene might not attack the sodium, but the rubbish surrounding it.


Sodium oxide? Sodium hydroxide? Sodium azide? WHY?

They are all useless, especially the NaOH what always contain some water and this water will react with the metallic sodium. Or try to make water free NaOH, it is simple, just melt it in a silver pot and heat it until it stops boiling.

And the NaN3 what would that do? I have no ideas about this, could you please tell a but more from this idea?

Just an idea, but try to distill the styrene at reduced pressure with a polymerisation "stopper" - I don't know the proper name for that, but 2,6-Di-tert-butylphenol, sulfur and a lot else reagents could be used.

[Edited on 4-8-2012 by kristofvagyok]




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Pyro
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[*] posted on 4-8-2012 at 13:54


because maybe his styrene isnt reacting with the sodium



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m1tanker78
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[*] posted on 7-8-2012 at 12:23


Quote: Originally posted by kristofvagyok  

[...]And for last: the reaction what you have mentioned requires some toluene what is deprotonated from the sodium, and what reaction conditions you have posted, there is no toluene in it, so it won't be this.


Actually, according to several sources (sorry, don't have them on hand), toluene is a significant product of polystyrene pyrolisis. This satisfies the requirements of the last reaction I posted from Wiki. It's the only reference I found that involves the reaction between styrene, toluene and sodium metal. I would have to repeat this on a much larger scale in order to weigh the sodium before and after to figure how much of it reacts. I could reflux some sodium under this stuff but I'd hate for it to go 'goo' in one of my flasks.

Unfortunately, I don't have a good vac pump to properly distill the raw styrene.

Tank




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