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Author: Subject: Cathodic reduction of amino acids
Adas
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[*] posted on 9-5-2015 at 11:27
Cathodic reduction of amino acids


Hello, DF!

It's been a long time of my inactivity here, and now I come to you with a question.

Basically, I would like to know if one could reduce an alpha-amino acid at cathode. With the addition of H2SO4, the amino acid would move to the cathode where it would discharge and release hydrogen which could, after multiple steps, reduce the carboxylic acid. The close proximity of these two groups could make it possible.

So that's the theory. But one thing that worries me is that I can't find any reference to such reaction. Maybe it needs higher voltage, or a different cathode material, or something else. I've actually tried it and could smell some amine after alkalizing the solution, but extraction with ethyl acetate yielded nothing except the amine smell. Maybe I need a different cathode material (Cu was used). I ran the cell at 20V so voltage should not be a problem. Maybe it just has a low efficiency and I would have to leave the cell running for hours and hours, but I'm not sure.

Any info is appreciated. Everybody talks about some Kolbe electrolysis, but that's an entirely different mechanism which yields dirty byproducts. Also when you look at Wikipedia ("Electrosynthesis"), you can see the crazy compounds that can be reduced on the cathode, even compounds that are not even polar. When I saw that I asked myself: Why not amino acids?

And please don't say that it can not work just because there is no reference on the Internet. Because ascorbic acid can reduce ketones to alcohols and you won't find that on the Internet, either.

Thanks for your time.




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smaerd
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[*] posted on 10-5-2015 at 03:36


Okay, Adas. It's never been published, you don't know the conditions, your theory isn't very sound. I'm not sure what anyone can say other then do some experiments and report back. Amino acid's are very cheap to experiment with, I'd love to see your results.

edit - also "amino acids" is very vague believe it or not. I mean every essential amino acid is pretty different from one another.

[Edited on 10-5-2015 by smaerd]




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Mesa
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[*] posted on 10-5-2015 at 05:24


He's probably using the term coz the methodology is developed and predominately used in biochemistry, where amines are rare and obscure artefacts nobody really cares about.

Given the procedure requires a 3 compartment cell with and careful voltage adjustment I'd say he's a long way from practical attempts.
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WGTR
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[*] posted on 10-5-2015 at 12:12


I've found this to be an older, yet interesting book:

http://books.google.com/books/about/Electrochemistry_of_orga...

It compiles a great deal of information about organic electrode processes, and was useful enough to me that I bought a copy.

Typically, cathode processes vary depending on the substrate and its type of interaction with various organic materials. Some processes are catalytic, others are a straightforward reduction at the cathode. Some need acid or base conditions, etc. High hydrogen overvoltage cathodes such as mercury or cadmium can be used to reduce alcohols all the way to alkanes.

One thing I vaguely remember reading (because this interested me as well), was that carboxylic acids are very difficult (or impossible) to reduce this way. If I remember later I can try and find this reference from the book.
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[*] posted on 10-5-2015 at 20:58


Quote: Originally posted by WGTR  
I've found this to be an older, yet interesting book:

http://books.google.com/books/about/Electrochemistry_of_orga...

It compiles a great deal of information about organic electrode processes, and was useful enough to me that I bought a copy.

Typically, cathode processes vary depending on the substrate and its type of interaction with various organic materials. Some processes are catalytic, others are a straightforward reduction at the cathode. Some need acid or base conditions, etc. High hydrogen overvoltage cathodes such as mercury or cadmium can be used to reduce alcohols all the way to alkanes.

One thing I vaguely remember reading (because this interested me as well), was that carboxylic acids are very difficult (or impossible) to reduce this way. If I remember later I can try and find this reference from the book.


The issue is more in other groups present that would be susceptible to anodic/cathodic redox, as well as the reversibility of the reaction. Technically it can be done in a 2 cell system but they have their own complications.

Wouldn't there be a definite difference between the reactivity of a carboxylic acid and a carboxylate? Just as protonated amines have very different properties to the deprotonated base.
Is that relevant or overthinking it?
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WGTR
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[*] posted on 11-5-2015 at 17:17


Quote: Originally posted by Mesa  
The issue is more in other groups present that would be susceptible to anodic/cathodic redox, as well as the reversibility of the reaction. Technically it can be done in a 2 cell system but they have their own complications.

Wouldn't there be a definite difference between the reactivity of a carboxylic acid and a carboxylate? Just as protonated amines have very different properties to the deprotonated base.
Is that relevant or overthinking it?


I'm afraid you have confused me with someone who knows what he's talking about. Don't worry, it's a common mistake.
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