Chapter 17: Aldehydes and Ketones. Nucleophilic Addition to C=O

Cyanohydrin Formation

• Cyanide adds to aldehydes and ketones to give a cyanohydrin.
• The reaction is usually carried out using NaCN or KCN with HCl.
• HCN is a fairly weak acid, but very toxic.
• The reaction is useful since the cyano group can be converted into other useful functional groups (-CO₂H or -CH₂NH₂)

NUCLEOPHILIC ADDITION OF CYANIDE TO AN ALDEHYDE
Step 1: The nucleophilic C in the cyanide adds to the electrophilic C in the polar carbonyl group, electrons from the C=O move to the electronegative O creating an intermediate alkoxide
Step 2: An acid/base reaction. Protonation of the alkoxide oxygen creates the cyanohydrin product.

© Dr. Ian Hunt, Department of Chemistry