26.2 Identifying Aldehydes & Ketones
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What is the test for the presence of a carbonyl group?
Brady’s reagent/2,4-DNP (dinitrophenylhydrazine) positive result = forms yellow/orange precipitate
How can you distinguish between an aldehyde & a ketone?
Tollen’s reagent forms silver mirror in presence of aldehyde (acts as oxidising agent - uses property that aldehydes can be oxidised whereas ketones cannot)
What is Tollens reagent made from?
solution of silver nitrate in aqueous ammonia
How can you differentiate between an ester & an aldehyde?
Add Brady’s reagent, esters are too stable to react
Why do ketones not react with Tollen’s reagent?
Tollen’s reagent is an oxidising agent forms silver mirror when reduced. Ketones cannot be oxidised, therefore no change occurs with Tollen’s.