Question

Benzaldehyde differs from acetaldehyde in that:

Options

• Benzaldehyde does not react with Tollens reagent.

• Benzaldehyde does not react with NaHSO₃.

• Benzaldehyde does not react with Fehling's solution.

• Benzaldehyde does not react with HCN.

Answer 1

Benzaldehyde does not react with Fehling's solution.

Explanation:

Fehling's Solution Test: When acetaldehyde is heated with a Fehling solution, the red ppt. of cuprous oxide is formed. But benzaldehyde does not give red ppt. with Fehling solution.

The reaction is as follows:

\[\ce{CH3CHO + 2Cu^{2+} + 5OH^- -> CH3COO^- + Cu2O + 3H2O}\]

\[\ce{C6H5CHO + 2Cu^{2+} + 5OH^- -> No red ppt.}\]