January 29, 2022, 01:48:49 AM
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### Topic: Trans vs cis stillbene  (Read 969 times)

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#### sharbeldam

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##### Re: Trans vs cis stillbene
« Reply #15 on: May 08, 2021, 07:21:21 AM »
So I get the fact now that cis is more polar, but my inquiry that remains in this synthesis.
if you allow me though, in a specific step of this lab, we get trans/cis isomers and the side product TPPO, so basically two solids and a liquid (cis isomer), to get the cis isomer, can we just used filtration to get the liquid which is the cis isomer, and then we are left with two solids, one is polar and the second is not which is easy to seperate because of the difference in polarity?
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#### rolnor

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##### Re: Trans vs cis stillbene
« Reply #16 on: May 08, 2021, 10:21:25 AM »
Its not that easy, the liquid stilbene is a good solvent for the solid stilbene so you get mixture. If you use benzylmagnesium chloride and react this with benzaldehyde, then heat with mild acid I think you get pure trans. If you use Wittig you will always get mixture I think. The TPPO can be removed by crystalization if Wittigis used. You can use modifications of Wittig to get pure E-stilbene:
https://en.wikipedia.org/wiki/Wittig_reaction

Also if you have a solution of the cis and add some Pd(0) you will probably get pure trans in time.
« Last Edit: May 08, 2021, 11:46:47 AM by rolnor »

#### Youyin Bai

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##### Re: Trans vs cis stillbene
« Reply #17 on: May 10, 2021, 10:22:53 AM »
It is difficult to separate in TLC or HPLC, you can try SFC separation