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Topic: Soapification reaction with KOH  (Read 266 times)

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Offline lewisdonner

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Soapification reaction with KOH
« on: April 27, 2021, 04:19:25 AM »
Hello Chemichal Forums
I have a question regarding the following reaction:

As I see it, the strong base OH- destoys the esterbonds in the triglyceride. The hydrogenatom of KOH goes to the "skeleton" of the triglyceridemolecule seperated by the broken esterbonds to form the glycerol, and the O- ion and K+ ion goes to the carboxylate-ion to form the potassium salt. This is how I make it work in the reaction, but I find it very odd that an o- ion exist like this.
It this the correct interpretation?

Thank you very much for any help

Offline Ben111

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Re: Soapification reaction with KOH
« Reply #1 on: April 27, 2021, 04:36:23 AM »
It is opposit. OH- goes to the Glycerine and only K+ goes to the carboxyl rest.

Offline lewisdonner

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Re: Soapification reaction with KOH
« Reply #2 on: April 27, 2021, 05:00:59 AM »
Oh so really the reaction is like this?

Offline rolnor

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Re: Soapification reaction with KOH
« Reply #3 on: April 27, 2021, 05:40:30 AM »
The OH- attacks the carbonyl, acetate is not a leaving group.

Offline lewisdonner

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Re: Soapification reaction with KOH
« Reply #4 on: April 27, 2021, 05:55:39 AM »
Thank you @Rolnor
So I can't illustrate it or describe it as simply as I have attempted to?
If the OH- attacks the carbonyl group, what is the result of this?

Offline kriggy

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Re: Soapification reaction with KOH
« Reply #5 on: April 27, 2021, 06:07:42 AM »
@lewisdonner: Not really. The OH from the hydroxide ends up in the carboxylic acid. There might be some rather special cases when this is not true but I think they mostly deal with acidic hydrolysis not basic.

After addition of the OH- to the carbonyl, you get tetrahedral intermediate which then collapes and gives you the products. Wikipedia has a saponification page including the ilustration how the reaction works. I suggest you start there

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