Cyanoethylation

The cyanoethylation is a nucleophilic addition reaction . A molecule of acrylonitrile is added to a nucleophile , for example alcohols , thiols and amines .

${\displaystyle \mathrm {YH+H_{2}C{=}CH{-}CN\longrightarrow Y{-}CH_{2}{-}CH_{2}{-}CN} }$

Due to the mesomerism stabilization of the acrylonitrile and the electron-withdrawing nitrile group, the β- carbon atom , the carbon atom that is furthest away from the nitrile group , is positively polarized and therefore functions as a Michael acceptor . This results in an approach of the nucleophile to the β-carbon atom, which initiates the reaction. The reaction is terminated by the intermediate product taking up a proton from the solvent . In industrial applications, the reaction is usually catalyzed by a base that polarizes or (negatively) charges the nucleophile and thus accelerates the reaction.

Since this reaction expands the converted molecule by three carbon atoms, whereby the –C≡N bond can be removed or changed by (for example) reduction , cyanoethylation is particularly used in the industrial pharmaceutical and dye sector. Cyanoethylation is also used in technical polymerization. If the cyanoethylation takes place in a medium that cannot release a proton to the product at the end of the reaction, an anionic polymerization takes place. The α-carbon atom remains negatively charged due to the lack of protonation , as a result of which the individual products of the cyanoethylation polymerize.

literature

• Jerry March: Advanced Organic Chemistry. Reactions, Mechanisms, and Structure . 3rd ed. Wiley-Interscience, New York 1985, ISBN 0-471-85472-7 , p. 665.

Individual evidence

1. ↑ Hajime Kabashima, Hideshi Hattori: Cyanoethylation of alcohols over solid base catalysts , in: Catalysis Today , Volume 44, Issues 1-4, September 30, 1998, pp. 277-283, doi : 10.1016 / S0920-5861 (98) 00200 -4 .