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Author: Subject: Oxidation of styrene to phenylacetaldehyde
gravityzero
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[*] posted on 2-11-2016 at 15:39


After reading the thread in full, it is still unclear if anyone is able to get to Styrene Oxide simply using a peracid, such as performic acid or peracetic acid.
It is assumed it would work, but OrgSyn uses perbenzoic acid which I had never heard of until today. Not really a miracle or anything.

If anyone can confirm a success using a more convenient peracid or oxone that would be helpful.

Then it is stated using silica gel to isomerize the oxirane to the aldehyde.
Sorry for any spoonfeeding. Just want to make sure I'm understanding all this.
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NitreRat
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[*] posted on 2-11-2016 at 18:35


Quote: Originally posted by gravityzero  
After reading the thread in full, it is still unclear if anyone is able to get to Styrene Oxide simply using a peracid, such as performic acid or peracetic acid.


I have performed a few epoxidations of alkenes with peracids (including in-situ peracetic acid), albeit in a formal lab setting. Peracids are strong oxidising agents so the actually reaction occurs quite readily, the real difficulty is trying to isolate the epoxide before any nasty nucleophiles can attack the poor epoxide and break open its ring with their electrons...

Because of the inherent acid present with peracid epoxidations, any water, amines or alcohols present in the reaction mixture can react with the epoxide after it's formed - creating alcohols and vicinal diols. These alcohols and diols/glycols can then be oxidized and cleaved by the peracid forming aldehydes, ketones, hydroxy-ketones, diketones and carboxylic acids.

If you're using anhydrous peracetic, performic or (m-chloro)perbenzoic acid the hydrolysis can be avoided. If you're doing a one-pot in-situ peracid epoxidation with H2O2(aq) + acid + alkene, you will inevitably end up with the hydrolysis and oxidation products. With styrene, I would expect phenylacetic acid, phenylglyoxylic acid and benzoic acid to be the main products of this reacation.

[Edited on 11/3/2016 by NitreRat]
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purplephanta
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[*] posted on 5-1-2017 at 05:00


Hello Phendrol, or anyone else for that matter,

Have you had success using the method referenced by Nicodem and TheCatalyst?

DO.108/00397919508011817 (http://dx.doi.org/10.1080/00397919508011817)

If so, what were the pitfalls;

Is the reaction not scalable?
Is very pure, anhydrous styrene oxide required?
Can the ethyl acetate be recycled or is it consumed?

Thanks
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madcedar
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[*] posted on 17-6-2017 at 23:14
styrene oxide to phenylacetaldehyde via the pinacol rearrangement?


In theory, mixing styrene oxide and a non-halo acid (H2SO4) should give styrene glycol. A halo acid such as HCl will give a halohydrin instead.

styrene glycol.png - 3kB

On further mixing and heating phenylactaldehyde should be the product (see this Youtube video on the Pinacol Rearrangement).

phenylacetaldehyde.png - 3kB

I'm assuming roughly following this procedure in the attached pdf (Organic Syntheses, Coll. Vol. 1, p.462 (1941); Vol. 5, p.91 (1925)) and substituting an equal molar amount of styrene oxide for pinacol will give the desired results.

I don't have any glassware to try this out myself but any comments on the theory are welcome.

Attachment: Pinacol Rearrangement cv1p0462.pdf (298kB)
This file has been downloaded 242 times

[Edited on 18-6-2017 by madcedar]
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JJay
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[*] posted on 18-6-2017 at 00:02


I ran across this paper a while back. I can't read most of it, but according to the authors, it's possible to do the rearrangement from styrene oxide to phenylacetaldehyde using a catalyst consisting of nitric acid on activated carbon in ethyl acetate at 75 C:

Preparation of Phenylacetaldehyde and 1, 3-Dioxolanes from Styrene Oxide with Mineral Acid-Treated Activated Carbon Catalyst




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Chemi Pharma
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[*] posted on 22-6-2017 at 09:08


Better produce phenylacetaldehyde from the isomerization of styrene oxide with silica gel in acetone, at room time for an hour, like said in the paper i bring below.

I think the better route to phenylacetaldehyde is dissolving styrofoam in acetone, mix with MgSO4 as a cataliser and distill at 250-300ÂȘC the styrene monomer with the acetone all onto the same flask.

The styrene in acetone obtained react with TCCA to form the chloridrine and further with KOH to form the epoxide.

Finally, proceed with the epoxide isomerization with silica gel as I said above.

Here's the papers:

Attachment: styrene oxide to phenyl acetaldehyde with silica gel.pdf (981kB)
This file has been downloaded 384 times

Attachment: styrene from polystyrene.pdf (1MB)
This file has been downloaded 206 times

Attachment: styrene to styrene oxide with TCCA and KOH.pdf (234kB)
This file has been downloaded 310 times
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JJay
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[*] posted on 14-7-2018 at 20:57


I've read a number of interesting papers about isomerization of styrene oxide with exotic catalysts, and there is a U.S. patent regarding the use of silica gel in the vapor phase, but doing it with silica gel in half an hour at room temperature... is that really possible?

Apparently, it is pretty easy to isomerize styrene oxide to phenylacetaldehyde in a bomb reactor with heat:

US3860614A - Thermolysis of Styrene Oxide

Attachment: Thermal Rearrangement of 1,2-Epoxyethylbenzene.pdf (252kB)
This file has been downloaded 97 times

I'm not terribly familiar with sealed tube reaction protocols, but I think the thermolysis could be performed using the ol' toaster oven with a long extension cord trick and some sandbags. I'm not seeing why you couldn't use an unlined iron pipe sealed with plumber's tape to contain the reaction, although I would advise extreme caution of course.

If you wanted to get really fancy, you could use an autoclave or a Parr reactor.




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notoxicshit
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[*] posted on 15-7-2018 at 10:17


Works in acetone over silica gel in high yield. Forgot the name of the paper though it should be easy to find.
However they dont mention how dry the acetone has to be. That may be the reason I failed once but I got too confident and didnt check before the follow-up reaction.
But it seemed legit.
Report back please.
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JJay
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[*] posted on 15-7-2018 at 11:18


Chemi Pharma posted the paper directly above. Silica gel 60 is pretty expensive... I'd be more inclined to try heat/pressure... the temperatures required are nothing ridiculous, and no fancy apparatus is required.

Nicodem mentioned an expired Dow Chemical patent on a continuous vapor phase process for isomerizing styrene oxide to phenylacetaldehyde. It uses silica gel and water. The process looks a little involved, but it might be useful if you want to produce more than a liter or so of phenylacetaldehyde.




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