Question

Give one chemical test to distinguish between the following pair of compounds:

Acetaldehyde and benzaldehyde

Answer 1

Acetaldehyde and benzaldehyde:

Acetaldehyde gives a red precipitate with Fehling's solution but benzaldehyde does not.

\[\ce{CH3CHO + \underset{(Fehling's solution)}{2Cu^{2+} + 5OH^-} ->[\Delta] CH3COO^- + \underset{red ppt}{Cu2O ↓} + 3H2O}\]

\[\ce{C6H5CHO + \underset{(Fehling's solution)}{2Cu^{2+} + 5OH^-} ->[\Delta] No reaction}\]