Target Exam

CUET

Subject

Chemistry

Chapter

Organic: Aldehydes, Ketones and Carboxylic Acids

Question:

The following reaction is an example of

Options:

Cannizzaro reaction

Hell-Volhard Zelinsky reaction

Friedel-Craft reaction

Gatterman-Koch reaction

Correct Answer:

Cannizzaro reaction

Explanation:

The correct answer is Option (1) → Cannizzaro reaction

Complete statement:

The given reaction is an example of the Cannizzaro reaction.

Reasoning:

Benzaldehyde (an aldehyde without an α-hydrogen atom) reacts with concentrated NaOH and undergoes disproportionation. In this process:

  • One molecule of benzaldehyde is reduced to benzyl alcohol (–CH₂OH).
  • Another molecule is oxidized to sodium benzoate (–COONa).

This simultaneous oxidation and reduction of the same aldehyde in a strong base is characteristic of the Cannizzaro reaction.

  • Reactant: Benzaldehyde ($C_6H_5CHO$) is used. The carbon atom adjacent to the aldehyde group (the $\alpha$-carbon) is part of the benzene ring and has no attached hydrogens.
  • Conditions: It reacts in the presence of a strong base, specifically Conc. NaOH, and heat ($\Delta$).
  • Products: One molecule of benzaldehyde is reduced to an alcohol (Benzyl alcohol, $C_6H_5CH_2OH$), while the second molecule is oxidized to a carboxylic acid salt (Sodium benzoate, $C_6H_5COONa$).