Question

Which of the following compounds gives a positive Tollen's test but negative Fehling's test?

Options

• Acetaldehyde

• Benzaldehyde

• Acetophenone

• Acetone

Answer 1

Benzaldehyde

Explanation:

Benzaldehyde is an aromatic aldehyde that reduces Tollen's reagent to silver and thus gives a positive Tollen's test, but it does not respond to the Fehling reagent test due to the lack of alpha hydrogen.

\[\ce{C6H5CHO + 2[Ag(NH3)2]^{+} + 2OH^{-} -> C6H5COOH + 2Ag ↓ 4NH3 + H2O}\]

\[\ce{C6H5CHO ->[Fehling soultion] No cuprous oxide formed}\].