Aldehydes, Ketones and Carboxylic Acids

About this unit

This unit deals with compounds containing the carbonyl group, C=O. In aldehydes the carbonyl carbon carries at least one hydrogen, in ketones it is bonded to two carbon groups, and in carboxylic acids it is part of the –COOH group. These compounds are found in flavours, perfumes, medicines, plastics and in the chemistry of living cells, so the unit links organic theory with everyday materials.

Key ideas

• Structure and polarity of the carbonyl group and the IUPAC names of carbonyl compounds.
• Methods of preparing aldehydes and ketones, including several named reactions.
• Nucleophilic addition, the central reaction type of aldehydes and ketones.
• Tests that distinguish aldehydes from ketones (Tollens', Fehling's) and the iodoform test.
• Reactions due to α-hydrogen: aldol condensation; and the Cannizzaro reaction of aldehydes without α-hydrogen.
• Acidity of carboxylic acids and the effect of substituents on it.
• Reactions of the –COOH group and of the hydrocarbon part (HVZ reaction, ring substitution).

How to prepare

• Make a one-page chart of named reactions with reagent, reactant and product: Rosenmund, Stephen, Etard, Gattermann–Koch, Clemmensen, Wolff–Kishner, Cannizzaro, aldol, HVZ and Kolbe electrolysis.
• Practise conversion problems (for example ethanal → butanal, toluene → benzoic acid) and ordering questions on reactivity and acidity.
• Expect questions that ask which compound gives a particular test or which reagent achieves a given change.