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The Krapcho decarboxylation is the chemical reaction of esters with halide anions. The ester must contain an electron-withdrawing group in the beta position. Examples include: β-ketoesters, malonic esters, α-cyanoesters, or α-sulfonylesters. It works best with methyl esters, since methyl groups are more susceptible to SN2 reaction than larger alkane chains. The byproducts of the decarbomethoxylation shown below are chloromethane and CO2. Both byproducts are lost as gases, which helps drive the reaction as entropy increases.

The Krapcho decarboxylation is a useful way to manipulate malonic esters because it cleaves only one of the two ester groups. The alternative to the Krapcho decarboxylation is base catalyzed ester hydrolysis followed by decarboxylation, requires a subsequent step to regenerate the ester.


 * [[Image:Krapcho reaction.svg|left|500px]]