Aldehyde Reactions: Cyanohydrin Formation from Aldehyde, Ketone using CN

Cyanohydrins can be formed from aldehydes and ketones using sodium cyanide (NaCN), potassium cyanide (KCN), or hydrogen cyanide (HCN):

The reaction mechanism is depicted below:

In the first step, the sodium-carbon bond breaks forming cyanide (cyano ion), which attacks the carbon atom that is part of the aldehyde/ketone functional group. This breaks the double bond between carbon and oxygen, sending the electrons to the oxygen atom.

In the second step, the newly acquired lone pair electrons on the oxygen atom attack a nearby acid molecule (illustrated here with HCN), stripping away its proton, finishing the reaction.

The reagents used for this reaction are NaCN, KCN, HCN, and usually some sort of acid workup (H+, H3O+, H2SO4).