Nucleophilic addition — cyanide (hydroxynitriles)

Year 2

AQA 3.3.8

Carbonyl & aromatic chemistry · KCN, then dilute acid (H₂SO₄) · room temperature

Reagents: KCN, then dilute acid (H₂SO₄) · Conditions: room temperature

Step 1 of 2

1.The lone pair on the CARBON of ⁻:C≡N attacks the δ+ carbonyl carbon — this forms the new C–C bond (attack through C, not N).
2.The C=O π bond breaks; both electrons move onto the more electronegative oxygen, giving an alkoxide.

CN⁻ adds to the carbonyl carbon and the π electrons move to O, giving a negatively charged alkoxide.

Step 2 of 2

1.A lone pair on the alkoxide O⁻ takes a proton (from HCN or the dilute acid), forming the –OH group.

The alkoxide is protonated: 2-hydroxypropanenitrile.

Product: 2-hydroxypropanenitrile

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