Statement I: Aromatic aldehydes do not respond to Fehling’s test.
Statement II: Ketones are oxidised by mild oxidising agents such as Tollens’ reagent.
In the light of the above statements, choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Only Statement I is correct.
Aldehydes and ketones differ in their oxidation. Aldehydes are oxidised easily, even by mild oxidising agents, so Tollens’ and Fehling’s tests are used to tell aldehydes from ketones.
Statement I: Aromatic aldehydes do not respond to Fehling’s test. — True. Aliphatic aldehydes give a reddish brown precipitate with Fehling’s reagent, but aromatic aldehydes such as benzaldehyde do not.
Statement II: Ketones are oxidised by mild oxidising agents such as Tollens’ reagent. — False. It is aldehydes that mild oxidising agents oxidise. Ketones are oxidised only under vigorous conditions — strong oxidising agents at high temperature — with breaking of a carbon-carbon bond.
NCERT (2026-27 edition):
8.4 Chemical Reactions – “…Even mild oxidising agents, mainly Tollens’ reagent and Fehlings’ reagent also oxidise aldehydes.”
“Ketones are generally oxidised under vigorous conditions, i.e., strong oxidising agents and at elevated temperatures. Their oxidation involves carbon-carbon bond cleavage to afford a mixture of carboxylic acids having lesser number of carbon atoms than the parent ketone.”
“(ii) Fehling’s test: …On heating an aldehyde with Fehling’s reagent, a reddish brown precipitate is obtained. Aldehydes are oxidised to corresponding carboxylate anion. Aromatic aldehydes do not respond to this test.”