BRAINCAKEDistinguishing Aldehydes and Ketones
Aldehydes can be oxidised further to carboxylic acids, but ketones cannot. Two tests use this difference. In each, the aldehyde acts as a reducing agent and is itself oxidised:
RCHO + [O] → RCOOH
Tollens' reagent
Tollens' reagent is a colourless solution containing the complex ion [Ag(NH3)2]+. Warm the sample with it in a water bath (not over a flame, as organic compounds are flammable).
Aldehyde: a silver mirror forms on the inside of the test tube, as silver(I) ions are reduced to silver atoms:
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Key terms in this lesson
- aldehyde
- An organic compound containing the -CHO functional group at the end of a carbon chain.
- ketone
- An organic compound containing a C=O group bonded to two carbon atoms within the chain.
- carboxylic acid
- An organic compound containing the -COOH functional group.
More in Alcohols
- Ethanol by Hydration of Ethene
- Biofuels and Carbon Neutrality
- Oxidation of Alcohols
- Oxidation of Primary Alcohols to Aldehydes and Carboxylic Acids
- Oxidation of Secondary Alcohols
- Dehydration of Alcohols
- Mechanism of Dehydration
- Reflux and Distillation
All 13 lessons in Alcohols · All AQA AS-level Chemistry topics