11/11/11 - Claisen Condensation

    So first off as an introduction I have decided that I will be using this blog to increase my knowledge of Chemistry by posting a reaction everyday on here (well at least attempting, we all know how good I am at not keeping up with blogs), and to educate other people in a clear way.
    In this first post I would like to look at a reaction that I have learnt in my Advanced organic Chemistry course; a reaction in which will further my understanding of the topics being taught in class.  I am not an avid organic chemist, but I do appreciate the complex notions that drives the model.  I feel that it is appropriate to attempt in explaining the reaction in a molecular model so that there can be a greater understanding of the reaction.
    This first reaction, being that of a Claisen Condensation, is one that I was studying back in September extensively in my organic chemistry class while we were analyzing carbonyl condensation reactions.  This historical reaction was published by Rainer Ludwig Claisen in 1881.
 This here is the combination of two ester molecules (where there is a central carbon with a double bond to an oxygen and single bond to an oxygen which has a single bond attached to an alkyl group) yielding a β keto ester.  There are certain requirements brought up by the mechanism stating that one of the esters must contain two deprotonable alpha hydrogens in order for one of the esters to become an ester enolate ion.  Which then in turn performs a nucleophilic attack onto the ester of the other molecule yielding a tetrahedral intermediate, which kicks out the ethoxide causing the ethoxide to deprotonate the beta keto ester.  Finally the reaction is finished with a simple acid workup to reprotonate that position.  This is just a simple case seen below, but in these synthetic mechanisms, they can be used to carry out elaborate reactions to make molecules of biological significance.

Ref:
Claisen, L., and A. Claparede. Ber. Deut. Chem. Ges., 1881, 14, 2460.