Conversion of 1,4-diphenyl-1,3-butadiene to Terphenyl
The first step is simple enough, the procedure calls for reacting 1.5 g 1,4-diphenyl-1,3-butadiene with 1 ml dimethyl actylenedicarboxylate in
triglyme (I used tiethyleneglycol dimethylether) at reflux for 30 min. Cool, wash out the vessel with tert-butyl methyl ether and wash the organic
phase with water.
One time this worked great, the washings went well and such, the second time I got a 'skin' between the organic and aqueous layer, upon
filtering this skin it looks quite crystalline, I think maybe the reaction may have messed up, but most other people got this 'skin'.
Anyway, the resulting (dried with calcium chloride) organic layer was evaporated in a flask under nitrogen with magnetic stirring and mild heating to
give a gunk at the bottom of the reaction vessel.
Now, to this I was supposed to add .5 g KOH in 10 ml water and heat. But the mixture formed clumps in it and I added some methanol which broke up the
clumps the first time I didn't and they were solid at the end and hard, this time I got a powdery precipitate. Supposedly this is the ester, I
have yet to characterize the small sample I have so this may be where I messed up.
Next up was adding the ester to solid KOH with triethylene glycol, now here is one point open for interpretation, everyone up till now has been using
the glyme that I mentioned before, triethylene glycol dimethyl ether, and I did the same the first time, the solution turned blue/purple then brown,
with just triethylene glycol I got a light brown solution when it was heated to 140C and held for 10 minutes as stated.
Here is where things really go to crap. Pouring the resulting mixture into a flask and rinsing the tube with water, 50 ml, then heating to dissolve,
anything undissolved should be filtered. Problem is it always looks like nothing is dissolved. I always end up filtering off a ton of stuff. To the
resulting solution I am supposed to add 3.4 g K3Fe(CN)6 and heat for 5 minutes, upon cooling white crystals of the terphenyl are supposed to separate.
I have tried this twice and never got any crystals (supposedly I am supposed to get about .75 g).
So, my questions, what does this actual step do with the potassium ferrocyanide, up till then I follow the procedure pretty good. Also, any ideas
what may be going wrong anywhere or IF something is going wrong? Maybe there are better solvents to use. I am moving on to the next experiment
because no one in the class has got this one to work yet and people have spent around 50 hours in the lab working on it, failing again and again.
The teacher encourages us to find help from outside sources, well, hopefully someone here can help.
BTW, the procedure comes from “Macroscale and Microscale Organic Experiments”, 3E, by Willamson, K.L., Houghton-Mifflin Co., Boston, 1998
And yes, someone did look up this original reference to compare it with the lab procedure we got, there was only one minor difference regarding the
step involving adding the KOH solution to make the ester, it was an alcoholic KOH solution, people have tried this with no success.
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