MDCAT Aldehydes & Ketones 2026

Distinguishing Tests

• Tollens reagent — positive for aldehydes (silver mirror); negative for ketones
• Fehling solution — positive for aliphatic aldehydes (red-brown ppt); negative for aromatic aldehydes & ketones
• Iodoform test — positive for CH₃CO− group (acetaldehyde, methyl ketones, ethanol)

Reactions

• Reduction (LiAlH₄) → alcohol
• Oxidation (KMnO₄): aldehyde → carboxylic acid; ketone resists
• Aldol condensation (base, α-H needed) → β-hydroxy aldehyde

Pair with our Organic cheat sheet.