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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Silden on March 25, 2011, 12:34:28 PM

Title: Hydrolysis of ester with sat. K2CO3 in MeOH
Post by: Silden on March 25, 2011, 12:34:28 PM
How does the hydrolysis of an ester with saturated K2CO3 in MeOH work? Will it produce KOH that works in a basic hydrolysis or is it CO3(2-) that starts the reaction. If it is KOH I know the mechanism, but if it is the carbonate ion can someone please tell me how it works?
Title: Re: Hydrolysis of ester with sat. K2CO3 in MeOH
Post by: adianadiadi on March 25, 2011, 01:36:54 PM
carbonate undergoes anionic hydrolysis and hence basic.
Title: Re: Hydrolysis of ester with sat. K2CO3 in MeOH
Post by: Silden on March 25, 2011, 05:24:05 PM
I am still not sure that I understand. So K2CO3 will be hydrolysed and OH- is formed which will be used in the hydrolysis of the ester? Is that right?
Title: Re: Hydrolysis of ester with sat. K2CO3 in MeOH
Post by: orgopete on March 26, 2011, 02:06:28 AM
If K2CO3 generated methoxide from methanol, what would the product(s) be?
Title: Re: Hydrolysis of ester with sat. K2CO3 in MeOH
Post by: adianadiadi on March 26, 2011, 07:33:06 AM
Quote from: Silden on March 25, 2011, 05:24:05 PM
I am still not sure that I understand. So K2CO3 will be hydrolysed and OH- is formed which will be used in the hydrolysis of the ester? Is that right?

Yes  :)
Title: Re: Hydrolysis of ester with sat. K2CO3 in MeOH
Post by: Camus023 on March 26, 2011, 07:43:09 AM
you can use LiOH to hydrolyse ester
Title: Re: Hydrolysis of ester with sat. K2CO3 in MeOH
Post by: Honclbrif on March 26, 2011, 09:48:00 AM
You may be misleading yourself because hydrolysis means "to split with water", but in this reaction there is no water present, so it can not be a hydrolysis reaction. However, the reaction is still similar to hydrolysis but since the reactants are slightly different, the products will be slightly different. Think of how water and MeOH are different, but also how they are similar.

Since you seem to be familiar with the basic hydrolysis of water: how is the nucleophile that attacks the ester generated when the solvent is water (what's the acid and what's the base)? Now, what happens if instead of water, you substitute MeOH? What nucleophile gets generated? Run through the reaction mechanism with that nucleophile and see what comes out the other side.
Title: Re: Hydrolysis of ester with sat. K2CO3 in MeOH
Post by: nox on March 26, 2011, 11:51:05 PM
You will NOT hydrolyze your ester, but instead you will get a transesterification product.
Quote from: adianadiadi on March 25, 2011, 01:36:54 PM
carbonate undergoes anionic hydrolysis and hence basic.

I call BS on this.
Title: Re: Hydrolysis of ester with sat. K2CO3 in MeOH
Post by: adianadiadi on March 27, 2011, 01:36:42 AM
transesterfication requires acidic medium and not basic. You will get salt of carboxylic acid which do not undergo esterification.
Title: Re: Hydrolysis of ester with sat. K2CO3 in MeOH
Post by: Honclbrif on March 27, 2011, 08:05:00 AM
This violates my earlier attempts to utilize the Soccratic Method, but things in this thread are getting a little weird.
Quote from: adianadiadi on March 27, 2011, 01:36:42 AM
transesterfication requires acidic medium and not basic. You will get salt of carboxylic acid which do not undergo esterification.

No. Transesterification will work under acidic or basic conditions. Under basic conditions, an alkoxide is initially formed which attacks the ester to form a tetrahedral intermediate. Upon collapse this intermediate ejects another equivalent of alkoxide, forming a new ester. No carboxylate required. Use mass action to favor a particular product.

RCOOR' + R''O-  ::equil:: RCOOR'' + R'O-
 
Basic methanolysis of triacylglycerols is a common method for people to make biodiesel.

Title: Re: Hydrolysis of ester with sat. K2CO3 in MeOH
Post by: adianadiadi on March 27, 2011, 08:33:21 AM
so either no water or less water. You call it methanolysis. right?  :D