Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Humr on July 15, 2021, 04:59:09 PM
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Hi. Couple days ago i tried to make styrene from 1-phenylethanol. I heated phenylethanol to 100 °C and than added 2 equivalents of 95% sulfuric acid. Only thing i got was black dense mud in manner of minutes. Can this reaction be done by using sulfuric or meybe phosphoric acid? And if answer is yes, what conditions would you suggest?
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Why do you want to make something that you can easily buy?
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Why did you give 2 moles of H2SO4 for 1 mole of C6H5-CH2-CH2OH ?
Even a few drops of H2SO4 can completely carbonize a piece of paper.
Concentrated H2SO4 dehydrates phenylethanol not only to styrene, but to pure carbon overall.
It is just too strong for this reaction.
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Where is fun in buying that? I am just a student and i would like to try some basic reactions like this and explore science on my own. I am in research group surrounded by people using "fancy" chemicals worth kidney, yet i am unable to do simple dehydration.
Orcio_Dojek: I read in literature it is needed excess of acid.
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Humr,
When I need conditions for a reaction, I usually use SciFinder. For relatively simple reactions I consult Tietze and Eicher's book, or sometimes Organic Syntheses.
Do you think that the acid acts catalytically or stoichiometrically in this reaction?
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You could try catalytic p-TSA, reflux in toluene. I dont think you should do it neat. You can use a Dean-Stark trap. Its problematic to separate toluene and styrene, thats a drawback.
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@Humr Be careful as the styrene can polymerize in the presence of strong acid (H2SO4).
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Thanks for suggestions. I can try the idea with p-TSA or try to modify http://www.orgsyn.org/demo.aspx?prep=CV3P0204 (http://www.orgsyn.org/Result.aspx?ga=pa) .
Also i found some reactions on reaxys for decarboxylation of cinnamic acid
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Styrene can do cationic polymerization initiated by a strong acid like pTSA or sulfuric acid, though it will be a mess.
Decarboxylation of cinnamic acid seems a little nicer... but what about doing the classic markonikov addition of an OH if you're trying to spread your wings? Mercuric acetate and water followed by NaBH4 is right out of sophmore organic.
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I have done this type of elimination with p-TSA, this was 1-phenyl-1-isopropyl methanol so its very similar, it worked fine. H2SO4 is probably to strong, I agree with you on that wildfyr. One problem with this synthesis is that styrene is volatile, distillation will be the only way of purification.
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Its not that volatile, it will make it through your column just fine. BP is 145C so most of it will stick around if you don't rotovap it too hard.
Fractional distillation is probably easier than a column anyways though.
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Yes, 145°C is not to bad, aspirator vacuum maybe? If distilling a mixture with toluene I think you will always get contamination.
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Thanks for continuing debate about my problem, but i found solution how to avoid styrene. My goal is to make phenylacetylene. With this path i found conditions for every step. So it is not my own black mud making freestyle.
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Is the first step Hunsdiecker? Thats a low-yield reaction.
Ok, found this, seems as there is improved procedure:
https://en.wikipedia.org/wiki/Hunsdiecker_reaction
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As a lover of music, I like to this of the decarboxylation to make a halogenated compound as the Borodin reaction, but that is just an aside.
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Interesting Babcock!
https://www.omegaensemble.com.au/news/the-borodin-reaction
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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.
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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?
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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.
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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.
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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.
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You need strong heat, ethanol no good.