BRAINCAKEReaction with HCN
Aldehydes and ketones react with hydrogen cyanide, HCN, to form hydroxynitriles. HCN adds across the C=O double bond: the CN group bonds to the carbonyl carbon and the H bonds to the oxygen, forming an OH group.
Conditions: HCN in the presence of potassium cyanide, KCN, at room temperature. HCN is a weak acid and only slightly ionised, so KCN is added to provide a high concentration of cyanide ions, CN−, which are the attacking nucleophile. HCN is extremely toxic, so the reaction is carried out in a fume cupboard.
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Key terms in this lesson
- hydroxynitrile
- A compound containing both a hydroxyl (OH) group and a nitrile (CN) group, formed when hydrogen cyanide adds to a carbonyl compound.
More in Carbonyl Compounds
- Physical Properties of Carbonyls
- Oxidation of Aldehydes
- Tollens' Reagent
- Fehling's and Benedict's Solutions
- Iodoform Reaction
- 2,4-DNPH Test
- Reduction with LiAlH4
- Nucleophilic Addition Mechanism
All 11 lessons in Carbonyl Compounds · All Edexcel A-level Chemistry topics