[mayorquin9]

After running the reaction to completion, I obtained a small yield 30mg (theoretical 210mg) and took the melting point which I found to be over 300 degrees C. Are there any by-products formed in this reaction or any hints as to what went wrong with my reaction?

[ARGOS++]

Dear Mayorquin9;

It sounds like you may have isolated some “Salts” (of less soluble kind).

Data and Spectrum you can inspect on NIST:

"Diphenylethyne”

Which method of preparation (elimination) you used?


Good Luck!
                   ARGOS⁺⁺

[mayorquin9]

i used an E2 elimination with KOH and triethylene glycol....im really bad at this chem stuff

[ARGOS++]

Dear Mayorquin9;

Maybe the product did not survive such conditions, but I don’t know at which max. Temperature you were keeping the reaction.
Quite all “short” Acetylenes are very instable, and yours will not be a real exception.
Also all have a high partial vapour pressure, check NIST for sublimation too.

Good Luck!
                   ARGOS⁺⁺

[mayorquin9]

the max temp was 190 degrees C. aahhhh...this is difficult. thanks for your help so far!

[ARGOS++]

Dear Mayorquin9;

How did you the isolation?
Because the high partial vapour pressure I had always the biggest lost during isolation till I finally did my Lots of different Acetylenes by preparative GC.
And even that can some times be tricky too.

If I had to do it I would try to start from the Di-Brom-Di-Phenyl-Ethane and do Elimination at -78°C in liquid ammonia with Na-metal.
But isolation will still be a little tricky (I have some procedures – I have to search.).
Also some other Intermediates may work this way.

Good Luck!
                   ARGOS⁺⁺

[mayorquin9]

to isolate the product i cooled to 40-50 degrees C and then added water to the mixture. then i placed the flask in an ice bath for about 15 mins. and then collected the solid in a hirsch funnel

[ARGOS++]

Dear Mayorquin9;

So I can imagine where your product had gone, if it were “build”.
Maybe you can check the condenser for it, if used.

Additional Hint:
I know it is of more work, but do an Extraction of your aqueous mixture next time with an adequate solvent could be of more success.

Good Luck!
                   ARGOS⁺⁺

[agrobert]

I have done this reaction before with the same procedure and it works fine.  Do you know if your meso stilben dibromide is pure?

[mayorquin9]

it was as pure as i could get it   probably 85% pure