Question

The Cannizzaro’s reaction is not given by

• A. formaldehyde
• B. Acetaldehyde
• C. benzaldehyde

Answer 1

The correct option is B

Acetaldehyde

Explanation for correct answer:-

Option (B) Acetaldehyde:

Cannizzaro reaction:-

• Cannizzaro reaction is a type of reaction that involves the base-induced disproportionation of two molecules of a non-enolizable aldehyde that lacks $\mathrm{\alpha }$-hydrogen.
• The base mainly used in this reaction is Sodium hydroxide$\left(\mathrm{NaOH}\right)$
• The product yielded during this reaction is a carboxylic acid and a primary alcohol.
• The general reaction is:

Acetaldehyde:-

• Acetaldehyde$\left({\mathrm{CH}}_3\mathrm{CHO}\right)$ have 3 $\mathrm{\alpha }$-hydrogen atoms, as a result, it does not undergo Cannizzaro reaction.
• But instead in the presence of the base, it undergoes Aldol condensation.
• The product formed in this reaction is 3-hydroxy butanal:

Explanation for incorrect answer:-

Option (A) formaldehyde:

• Formaldehyde$(\mathrm{H}-\mathrm{CHO})$ has no presence of $\mathrm{\alpha }$-hydrogen, and thus it undergoes Cannizzaro reaction.
• The products formed due to this reaction are Sodium formate and Methanol.
• The reaction is as follows:

Option (C) benzaldehyde:

• Benzaldehyde$\left({\mathrm{C}}_6{\mathrm{H}}_5\mathrm{CHO}\right)$ has no presence of $\mathrm{\alpha }$-hydrogen, and thus it undergoes Cannizzaro reaction.
• The products formed due to this reaction are Sodium benzoate and Benzyl alcohol.
• The reaction is as follows:

Therefore, The Cannizzaro’s reaction is not given by option (B) Acetaldehyde$\left({\mathrm{CH}}_3\mathrm{CHO}\right)$