BRAINCAKETollens' Reagent
Tollens' reagent is a mild oxidising agent used to distinguish aldehydes from ketones. It is also called ammoniacal silver nitrate, because it contains the complex ion [Ag(NH3)2]+, the diamminesilver(I) ion.
Preparing Tollens' reagent (it must be made fresh):
1. Add a few drops of sodium hydroxide solution to aqueous silver nitrate. A brown precipitate of silver(I) oxide forms.
2. Add dilute aqueous ammonia drop by drop until the precipitate just dissolves, giving a colourless solution.
The test: add a few drops of the compound to the Tollens' reagent in a clean test tube and warm it in a hot water bath. A water bath is used rather than a naked flame because many carbonyl compounds are flammable.
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More in Carbonyl Compounds
- Aldehydes and Ketones
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- Physical Properties of Carbonyls
- Oxidation of Aldehydes
- Fehling's and Benedict's Solutions
- Iodoform Reaction
- 2,4-DNPH Test
- Reduction with LiAlH4
All 11 lessons in Carbonyl Compounds · All Edexcel A-level Chemistry topics