October 23, 2021, 04:16:40 PM
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Topic: Styrene  (Read 1563 times)

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Offline rolnor

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Re: Styrene
« Reply #15 on: July 22, 2021, 01:16:17 AM »

Offline Humr

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Re: Styrene
« Reply #16 on: July 26, 2021, 02:49:07 PM »
I tried 2 variants of Hunsdicker. One with NBS/TEA and one with HBr/NaNO2/air. NBS metod was looking promising. I saw a low of fizzing n flask during the reaction. Reaction mixture had yellow-brown color as it should have. I tried to extract it to NH4Cl/EtOAc, but than i just got clear solution and there was not change on TLC. HBr/NaNO2/air in ACN is something i found on reaxys. Autors of article claimed 90% yield. Only thing i got from it were exploding balons with air and bad mood.

So i changed strategy. Today i tried to react cinnamic acid with bromine. We did proof reaction of double bond with bromine in practicals, so i thought it has to work. Well it did. From NMR spectrum i would say, there was 85-90% conversion. With 2,3-dibromo-3-phenylpropanoic acid should be decarboxylation easier. I found article, where autors used for dehydrohalogenation + decarboxylation conditions bellow. I already started this reaction, so i hope tomorrow analysis will be success.

Offline rolnor

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Re: Styrene
« Reply #17 on: July 26, 2021, 03:14:42 PM »
You are doing a lot of experiments, thats good! One question, do you have an actuall reference on this exact compound you are trying to make? If not, you should probably get one, it can be a lot of time, money and effort wasted to try to make this compound, there is probably a very good method available. I am thinking about the last method, how do you isolate the product from DMSO-solvent? Do you plan to distill this or wash the DMSO out with water?

Offline Humr

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Re: Styrene
« Reply #18 on: July 26, 2021, 03:40:00 PM »
What do you mean with "actuall reference"?

with last step i am following this protocol:

A mixture of anti-3-aryl-2,3-dibromopropanoic acid 1 (0.5 mmol) and K2CO3 (207 mg, 1.5 mmol) in 5
mL of DMSO was stirred at 115 ℃ for 12 h. The mixture was then extracted using Et2O/H2O (15
mL/20 mL×3) after being cooled down to r.t. The organic layers were combined, rinsed with brine,
and dried over anhydrous Na2SO4. The mixture was then evaporated to remove the solvent.

If i get this phenylacetylene, i will distill it. I found in literature conditions 55 °C vapour temperature when pressure 20 Torr is used. We have well maintained rotavap in lab capable of pressure 1 mBar, so that should do it.

Offline rolnor

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Re: Styrene
« Reply #19 on: July 27, 2021, 04:13:23 AM »
Sorry, I mean a reference to this exact compound. I see you have this, good. It seems like a nice procedure, it will be fine.

Offline Humr

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Re: Styrene
« Reply #20 on: July 27, 2021, 11:38:53 AM »
After 16 hours i did work up. It worked and i saw only traces of another things in NMR spectrum. But i want to try change base and solvent. I was thinking about KOH and some alcohol. Probably ethanol, or better 2-methoxyethanol.

Offline rolnor

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Re: Styrene
« Reply #21 on: July 27, 2021, 12:33:09 PM »
You need strong heat, ethanol no good.

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