Cyanoethylation

Cyanethylation is a nucleophilic addition reaction. A molecule of acrylonitrile is added to a nucleophile, for example an alcohol, thiol or an amine.

Due to the mesomeric stabilization of acrylonitrile and the electron withdrawing nitrile group, the β-carbon atom (the carbon atom that is furthest from the nitrile group) is positively polarized and therefore acts as a Michael acceptor. This leads to an approaching of the nucleophile to the β-carbon atom, which initiates the reaction. The reaction is terminated by absorption of a proton from the solvent by the intermediate product. In industrial applications, the reaction is normally catalyzed by a base that polarizes or (negatively) charges the nucleophile and thus accelerates the reaction.[1]

Cyanethylation is used especially in the industrial pharmaceutical and dye sector, since this reaction extends the nucleophile bearing molecule by three carbon atoms plus the -C≡N bond can afterwards be removed or modified by (for example) reduction. Cyanethylation is also used in technical polymerization. If cyanethylation takes place in a medium that cannot release a proton to the product at the end of the reaction, an anionic polymerization occurs. Due to the lack of protonation, the α-carbon atom remains negatively charged, causing the individual cyanethylation products to polymerise.

Literature
  • Jerry March: Advanced Organic Chemistry. Reactions, Mechanisms, and Structure. 3. Edition. Wiley-Interscience, New York 1985, ISBN 0-471-85472-7, S. 665.
  • https://en.wiktionary.org/wiki/cyanoethylation
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References
  1. Hajime Kabashima, Hideshi Hattori: Cyanoethylation of alcohols over solid base catalysts, in: Catalysis Today, Volume 44, Issues 1–4, 30. September 1998, S. 277–283, doi:10.1016/S0920-5861(98)00200-4.
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