Question

Explain Cannizzaro reaction with suitable example.

Hint:

Aldehydes WITH $\alpha$-H (like Acetaldehyde) undergo Aldol Condensation. Aldehydes WITHOUT $\alpha$-H (like Benzaldehyde or Formaldehyde) undergo Cannizzaro reaction.

Answer 1

Step 1: Understanding the Concept:
The Cannizzaro reaction is a redox (disproportionation) reaction where two molecules of an aldehyde react to produce one molecule of an alcohol and one molecule of a carboxylic acid salt.
Step 3: Detailed Explanation:
This reaction is characteristic of aldehydes that do not have any \(\alpha\)-hydrogen atoms (e.g., Formaldehyde, Benzaldehyde).
When such aldehydes are treated with concentrated alkali (50% \(NaOH\) or \(KOH\)), one molecule is reduced to an alcohol, and the other is simultaneously oxidized to a salt of carboxylic acid.
Example: Reaction of Formaldehyde (\(HCHO\)):
\[ 2HCHO + \text{conc. } NaOH \rightarrow CH_3OH \text{ (Methanol)} + HCOONa \text{ (Sodium formate)} \]
Step 4: Final Answer: The Cannizzaro reaction involves the disproportionation of non-enolizable aldehydes into alcohols and carboxylates.