19.2.2—Preparation of hydroxynitriles

Cyanide attacks the carbonyl carbon and protonation gives a molecule containing both –OH and –C≡N: a hydroxynitrile. KCN helps generate CN⁻ and heat supports the reaction.

The product has one more carbon than the carbonyl compound because the nitrile carbon is added. Aldehyde and ketone starting structures lead to different substitution patterns.

CH₃CHO + HCN → CH₃CH(OH)CN. The new carbon bears OH, CN, H and CH₃.

Hydroxynitrile formation is not nitrile hydrolysis and does not remove the carbonyl carbon.