Claisen condensation clarification

[monsieurwise]

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I am reviewing my reactions, and I noticed this on wikipedia:
http://en.wikipedia.org/wiki/Claisen_condensation
The reaction shown did not remove the O-R on the right and replace it with OH. Why is this? I thought that anytime ester + H3O+ ---> carboxylic acid?
Thanks guys!

 

[J777]

The Claisen Condensation typically combines two esters together. This is accomplished by first deprotonaring a hydrogen (with base) from one of the alpha carbons of one of the esters to form an enolate. The enolate then attacks the carbonyl carbon of the other ester to form the beta keto ester. This is not like a normal ester. Since there is a very acidic proton between the two carbonyl groups, the base will readily deprotonate it. The acid is simply there to reprotonate to give us that desired beta keto ester. But you are correct. If the ester were treated with acid, it would form a carboxylic acid. The key is to recognize that it is first treated with strong base and that we are condensing two esters. The acid comes during the final step of the rxn