Diethyl carbonate, ester interchange with

Another reasonable step that can take place under the reaction conditions is removal of one of the protons on the carbon a to the carbonyl groups in diethyl malonate. However, this reaction does not lead to the product and is an example of an unproductive step. Another unproductive reaction is ester interchange in diethyl malonate. In this case, sodium methoxide would react with the ethyl ester to produce a methyl ester. However, this reaction is inconsequential because methyl and ethyl esters have similar reactivity and the alkyl oxygens with their substituents are lost in the course of the reaction. 

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