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Author: Subject: Double bond ox. cleavage to aldehyde with CuO
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[*] posted on 17-1-2025 at 03:02
Double bond ox. cleavage to aldehyde with CuO


From the patent US2516412A

https://patentimages.storage.googleapis.com/23/db/8f/1e3b03d...

Quote:
EXAMPLE VII: Syringaldehyde from the isolated intermediate

Syringaldehyde may also be prepared by oxidizing the isolated 3,5-dimethoxy-4-hydroxypropenylbenzene of Example V with nitrobenzene in alkali or other low potential oxidizing agents.

Thus 195 parts 3,5-dimethoxy-4-hydroxypropenylbenzene are added to a cupric oxide mixture freshly prepared from 1000 parts hydrated copper sulfate, 660 parts sodium hydroxide, and 8000 parts of water and the resulting mixture is heated to boiling under reflux for eight hours. The separated red cuprous oxide is filtered and washed with water. The alkaline filtrate and washings are acidified and extracted with ether. Bisulfite purification of the ether extract should yield approximately 155 parts or 90% syringaldehyde.

Other alkaline copper oxidizing agents such as Fehling's Solution, Benedict’s Solution, may be used with the same results.

An alkaline copper oxidizing agent is particularly advantageous for replacing the propenyl group with the aldehyde group because the strength of its action in changing from a cupric to a cuprous compound is definitely adequate to oxidize to the aldehyde, and at the same time insufficient to continue the oxidation to the acid further or to destruction.

However, in large scale operation, it will be obvious that oxidizing agents having no such automatic action may be employed for reasons of economy, and the extent of the reaction controlled by controlling the amount of the reagent.


So if Cuo is able to ox. cleavage 3,5-dimethoxy-4-hydroxypropenylbenzene to syringaldehyde, i do not see the reason why it wont work with other propenyl group. For example:

styrene-->benzaldehyde
cinnamic acid-->benzaldehyde
piperic acid-->piperonal
3bromocinnamic acid-->3bromobenzaldehyde
2hydroxy cinnamic acid-->salicylaldehyde

and so on

The procedure looks super simple and high yielding

[Edited on 17-1-2025 by underground]
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[*] posted on 17-1-2025 at 06:54


Sounds nice, but patents can sometimes be complete bunk, so you’ll have to try it out to see if it actually works. I’d suspect that freshly prepared CuO is essential, so if you try it, prepare it the way they described, don’t just use CuO off the shelf, as it probably won’t have the same activity, just as freshly prepared MnO2 can do a lot more than junk from a pottery store.

There’s a couple other reasons the reaction may not be so general, though. The electron donating groups on the syringaldehyde precursor might also help to activate the alkene for oxidation, so it may be that it will work on electron rich aromatics only. The propenyl double bond is also going to be easier to oxidize than the one in a cinnamic acid. So while the molecules you list are superficially similar in structure, there’s a decent chance they won’t react the same way. Still, it wouldn’t hurt to try.




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[*] posted on 17-1-2025 at 08:15


Quote: Originally posted by Texium  
Sounds nice, but patents can sometimes be complete bunk, so you’ll have to try it out to see if it actually works. I’d suspect that freshly prepared CuO is essential, so if you try it, prepare it the way they described, don’t just use CuO off the shelf, as it probably won’t have the same activity, just as freshly prepared MnO2 can do a lot more than junk from a pottery store.

There’s a couple other reasons the reaction may not be so general, though. The electron donating groups on the syringaldehyde precursor might also help to activate the alkene for oxidation, so it may be that it will work on electron rich aromatics only. The propenyl double bond is also going to be easier to oxidize than the one in a cinnamic acid. So while the molecules you list are superficially similar in structure, there’s a decent chance they won’t react the same way. Still, it wouldn’t hurt to try.


What could underlie the activity present in freshly prepared CuO?
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