Sciencemadness Discussion Board

Leuckart reaction with oxalic acid

njl - 30-3-2020 at 07:27

Would oxalic acid work as a substitution for formic acid as a reducing agent in the leuckart reaction? Formic acid has the advantage of being oxidized to CO2 but apparently oxalic acid is a stronger reducing agent.

P.S. Searched for this question but didn't find naything, sorry if it's a repeat

unionised - 30-3-2020 at 08:09

No.
There's no hydride to transfer.

clearly_not_atara - 30-3-2020 at 09:41

However, there is apparently an oxalic acid Eschweiler-Clarke:

https://www.researchgate.net/profile/Paul_Kosma/publication/...

Corrosive Joeseph - 30-3-2020 at 09:51

https://chemistry.mdma.ch/hiveboard/novel/000497428.html


/CJ

unionised - 30-3-2020 at 10:39

"Primary and secondary amines are N-methylated by a mixture of paraformaldehyde..."

Just for a start, if you have paraformaldehyde, you can make formic acid.

clearly_not_atara - 30-3-2020 at 11:47

You can also make formic acid from oxalic acid, which I was going to recommend but I thought it was too obvious. But what's the best way to make formic acid from paraformaldehyde?

njl - 31-3-2020 at 07:22

@All thank you for responses.

@Atara depends on where you are/what you have but basically hydrolyze paraformaldehyde to get a concentrated aqueous solution and then oxidize over KMnO4. Using KMnO4 has the advantage of leaving you with the formate salt after oxidation, so you can easily purify and then recover the acid with HCl. The reason I didn't mention the oxalic acid --> formic acid prep is because I don't have any glycerin at the moment.

unionised - 31-3-2020 at 08:27

Quote: Originally posted by clearly_not_atara  
You can also make formic acid from oxalic acid, which I was going to recommend but I thought it was too obvious. But what's the best way to make formic acid from paraformaldehyde?

Hydrolysis to formaldehyde by dissolution in hot water, then this

https://en.wikipedia.org/wiki/Cannizzaro_reaction

to get formate.

unionised - 31-3-2020 at 08:29

I'd avoid the oxidation by permanganate since it also attacks formic acid.

njl - 31-3-2020 at 09:09

I agree the Cannizzaro reaction looks better. I don't have any experience with it which is why I didn't mention it.

@unionised wouldn't the potassium salt be less prone to oxidation to oxidation?

unionised - 31-3-2020 at 09:44

Probably, but paraformaldehyde is cheaper than permanganate.

S.C. Wack - 31-3-2020 at 11:02

One would add peroxide first, unless small amounts of methanol are needed.