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Claisen condensation[′klās·ən känd·ən′sā·shən]
a method of obtaining β–ketoesters (or β-aldehyde esters) by the interaction of identical or different esters in the presence of alkaline agents. A typical example of Claisen condensation is the production of acetoacetic ester (ethyl acetoacetate) from ethyl acetate in the presence of alcoholates of sodium, metallic sodium, sodium hydride, or sodium amide:
CH3COOC2H5 + HCH2COOC2H5
→CH3COCH2COOC2H5 + C2H5OH
With the use of esters of formic acid, derivatives of aldehyde acids are formed:
HCOOC2H5 + C6H5CH2COOC2H5
→C6H5CH(COOC2H5)CHO + C2 H5 OH
The Claisen condensation is also used to obtain other β–carbonyl compounds. Thus, the reaction of esters with nitriles leads to β-ketonitriles; for example,
CH3COOC2H5 + C6 H5 CH2 CN
→CH3COCH(C6H5)CN + C2H5OH
β-diketones, such as acetylacetone, are formed with the ketones:
CH3COOC2H5 + CH3COCH3
→CH3COCH2COCH3 + C2 H5 OH
The Claisen condensation is widely used in industry to obtain various organic compounds, such as acetoacetic ester and acetylacetone and their homologues. The reaction was studied in detail in 1887 by the German chemist L. Claisen.
REFERENCESOrganicheskie reaktsii collection 1. Moscow, 1948. Page 345. (Translated from English.)
Nesmeianov, A. N., and N. A. Nesmeianov. Nachala organicheskoi khimii, book 1. Moscow, 1969. Page 411.
IA. F. KOMISSAROV