The Krapcho decarboxylation is the
chemical reaction
A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...
of
ester
In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...
s with
halide
In chemistry, a halide (rarely halogenide) is a binary chemical compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative (or more electropositive) than the halogen, to make a fluor ...
anion
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
s. The ester must contain an
electron-withdrawing group
In chemistry, an electron-withdrawing group (EWG) is a substituent that has some of the following kinetic and thermodynamic implications:
*with regards to electron transfer, electron-withdrawing groups enhance the oxidizing power tendency of the ...
in the beta position, such as β-ketoesters, malonic esters, α-cyanoesters, or α-sulfonylesters. It works best with
methyl
In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in many ...
esters, since methyl groups are more susceptible to S
N2-reaction than are, say, ethyl groups. The byproducts of this decarbomethoxylation are
chloromethane
Chloromethane, also called methyl chloride, Refrigerant-40, R-40 or HCC 40, is an organic compound with the chemical formula . One of the haloalkanes, it is a colorless, odorless, flammable gas. Methyl chloride is a crucial reagent in industrial ...
and
CO2. They are lost as gases, which helps drive the reaction.
The Krapcho decarboxylation is a useful way to manipulate
malonic esters because it cleaves only one of the two ester groups. The apparent alternative, base hydrolysis followed by decarboxylation, requires a subsequent step to regenerate the ester.
:
References
{{reaction-stub
Elimination reactions
Substitution reactions
Name reactions