Question

Formaldehyde undergoes Cannizzaro reaction because
(A) It has alpha-hydrogen atom.
(B) It does not have alpha-hydrogen atom.
(C) It does not undergo self-oxidation and reduction on heating with concentrated alkali.
(D) It undergoes self-oxidation and reduction on heating with concentrated alkali.

• A. It does not have alpha-hydrogen atom
• B. It has alpha-hydrogen atom
• C. It does not undergo self-oxidation and reduction on heating with concentrated alkali
• D. It undergoes self-oxidation and reduction on heating with concentrated alkali

Answer 1

The Correct Option is A

The Cannizzaro reaction, a redox process, occurs when an aldehyde lacking an alpha-hydrogen atom reacts with a concentrated strong base, typically an alkali. The reaction proceeds as follows:

• The aldehyde substrate must be devoid of an alpha-hydrogen atom.
• Upon treatment with concentrated alkali, one aldehyde molecule is reduced to an alcohol, and another is oxidized to a carboxylate ion.
• This reaction is exclusively applicable to aldehydes without alpha-hydrogen atoms; the presence of an alpha-hydrogen atom promotes enolization, leading to alternative reactions like aldol condensation.

Formaldehyde (HCHO) exemplifies an aldehyde that undergoes the Cannizzaro reaction due to its absence of an alpha-hydrogen atom, rendering it amenable to this specific reaction pathway.

Consequently, the rationale for this reaction is accurately stated as (A) It does not have an alpha-hydrogen atom.