Cyanhydrinbildung

Cyanhydrinbildung is a chemical reaction where a cyanide ion attacks a carbonyl group, forming a cyano compound with a hydroxyl group attached to the same carbon. This reaction is characteristic of aldehydes and ketones. The cyanide ion, a nucleophile, attacks the electrophilic carbon of the carbonyl group. The subsequent protonation of the alkoxide intermediate by a proton source, often water or an acid, yields the final cyano alcohol, known as a cyanhydrin.

This reaction is reversible, and the equilibrium position depends on factors such as pH and the specific carbonyl compound. Cyanhydrinbildung is generally favored under slightly alkaline conditions, which increase the concentration of the nucleophilic cyanide ion. However, strongly alkaline conditions can lead to side reactions.

Cyanhydrins are important intermediates in organic synthesis. They can be hydrolyzed to alpha-hydroxy acids, reduced to beta-amino alcohols, or dehydrated to alpha,beta-unsaturated nitriles. The addition of hydrogen cyanide (HCN) to carbonyl compounds is a common method for cyanhydrin formation. Due to the toxicity of hydrogen cyanide, alternative cyanide sources like sodium cyanide or potassium cyanide in the presence of an acid are often employed. The formation of cyanhydrins is a classic example of nucleophilic addition to a carbonyl group.