Aldehydes and ketones
Aldehydes (RCHO) and ketones (RCOR') contain the polar C=O group; the carbon is δ+ and attacked by nucleophiles. Nucleophilic addition: HCN (from KCN + acid) adds to give hydroxynitriles; NaBH₄ (source of H⁻) reduces aldehydes to primary alcohols and ketones to secondary alcohols. Tests: 2,4-DNPH gives an orange precipitate with any carbonyl. Only aldehydes reduce Tollens' reagent (silver mirror) and Fehling's (blue → brick-red), because aldehydes can be oxidised. The iodoform test (yellow CHI₃) detects CH₃CO–. Because C=O is planar, CN⁻ attacks from either side, so a chiral product forms as a racemic mixture.
≈ 50 min