[Humr]

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?

[Babcock_Hall]

Why do you want to make something that you can easily buy?

[Orcio_87]

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.

[Humr]

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.

[Babcock_Hall]

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?

[rolnor]

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.

[Orcio_87]

@Humr Be careful as the styrene can polymerize in the presence of strong acid (H₂SO₄).

[Humr]

Thanks for suggestions. I can try the idea with p-TSA or try to modify http://www.orgsyn.org/demo.aspx?prep=CV3P0204 .

Also i found some reactions on reaxys for decarboxylation of cinnamic acid

[wildfyr]

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.

[rolnor]

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.

[wildfyr]

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.

[rolnor]

Yes, 145°C is not to bad, aspirator vacuum maybe? If distilling a mixture with toluene I think you will always get contamination.

[Humr]

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.

[rolnor]

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

[Babcock_Hall]

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.