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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: xshadow on October 20, 2020, 08:28:18 AM

Title: cis-trans 1,4-diphenyl-1,3-butadiene
Post by: xshadow on October 20, 2020, 08:28:18 AM

Someone can tell me the boiling point of the cis trans isomer

Checking online I found that the trans-trans isomer has  350°C as boiling point
Thanks

Title: Re: cis-trans 1,4-diphenyl-1,3-butadiene
Post by: chenbeier on October 20, 2020, 08:45:55 AM

367 +- 12°C at 760 mmHg

http://www.chemspider.com/Chemical-Structure.1267740.html

Title: Re: cis-trans 1,4-diphenyl-1,3-butadiene
Post by: AWK on October 20, 2020, 09:34:39 AM

This is the value calculated by ACD/Labs.
I cannot believe that at this temperature the compound will not isomerize to the (E, E) isomer with the known boiling point of 353°C.

Title: Re: cis-trans 1,4-diphenyl-1,3-butadiene
Post by: chenbeier on October 20, 2020, 09:47:44 AM

Probably this happens 12 K is a big Delta already. 367 °C - 12 °C = 355 °C but it could also be 379°C

Title: Re: cis-trans 1,4-diphenyl-1,3-butadiene
Post by: xshadow on October 20, 2020, 12:24:50 PM

....Because I made the trans-trans  1,4-diphenyl -1,3 -butadiene with WIttig.
But I also get some impuritiy of the cis-trans isomer and some of the triphenyl phosphine oxide.

Using gascromatografy the main peak (trans-trans) arrives after 12.8min

But I also get two very small peak:
one at  11.5min
the other at 14min

I think the peak at 14min is the triphenyl phosphine oxide (more polar)
Don't know why the trans-trans has a higher B.P/ polarity than the cis-trans