Claisen-Schmidt condensation

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The Claisen-Schmidt condensation , named after the discoverers Ludwig Claisen and J. Gustav Schmidt , is a name reaction from the field of organic chemistry that was first described in 1881. The Claisen-Schmidt condensation is a special form of the crossed aldol reaction , in which aldehydes without an α- hydrogen atom, with aliphatic aldehydes or ketones , can be selectively converted to α, β- unsaturated carbonyl compounds .

Overview reaction

In the case of the crossed aldol reaction , a mixture of more than four different products can result from deprotonation of the α- hydrogen atoms of two different carbonyl compounds . By using a mostly aromatic aldehyde without an α-hydrogen atom and aldehydes or ketones as starting materials, the number of products can be halved by the Claisen-Schmidt condensation. Since aldehydes are more reactive than ketones, a reaction between the deprotonated ketone and the aldehyde occurs primarily, whereby α, β- unsaturated carbonyl compounds are formed. The reaction can be carried out either in a basic or in an acidic medium.

In the following, the reaction is exemplified with benzaldehyde and a ketone with an alkyl radical, which are selectively converted to an α, β- unsaturated carbonyl compound .

Claisen-Schmidt condensation overview reaction

Reaction mechanism

The reaction takes place via the aldol condensation.

Individual evidence

  1. ↑ L. Claisen and A. Claparède: Condensations of ketones with aldehydes In: Ber. German Chem. Ges. 14, 1881, pp. 2460-2468, doi: 10.1002 / cber.188101402192 .
  2. ↑ J. Gustav Schmidt: About the action of acetone on furfural and on bitter almond oil in the presence of alkali In: Ber. German Chem. Ges. 14, 1881, pp. 1459-1461, doi: 10.1002 / cber.188101401306 .
  3. ↑ W. Uhl and A. Kyriatsoulis: Name and Keyword reactions in organic chemistry , Vieweg + Teubner Verlag, 1984, ISBN 978-3-663-02003-5 , pp 30-32, doi: 10.1007 / 978-3- 663-02002-8_18 .
  4. ^ Albert Wollrab: Organic Chemistry - An Introduction for Teacher Training and Minor Subject Students , 4th Edition, Springer Spectrum, 2014, ISBN 978-3-642-45143-0 , p. 502.
  5. ^ Zerong Wang: Comprehensive Organic Name Reactions and Reagents , Wiley, 2009, ISBN 978-0-471-70450-8 , pp. 660-664.