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.
Choose the correct answer from the options given below :
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (B) and (D) only
In the Cannizzaro reaction, an aldehyde that has no α-hydrogen atom undergoes self oxidation and reduction (disproportionation) on heating with concentrated alkali: one molecule is reduced to the alcohol and another is oxidised to the salt of the carboxylic acid.
\( \displaystyle \ce{2HCHO + NaOH} \xrightarrow[\Delta]{\text{conc.}} \ce{CH3OH + HCOONa} \)
(A) It has alpha-hydrogen atom. — Incorrect. Formaldehyde, HCHO, has no α-carbon at all, so it has no α-hydrogen. Aldehydes with α-hydrogen give aldol condensation instead.
(B) It does not have alpha-hydrogen atom. — Correct. This is the condition for the Cannizzaro reaction.
(C) It does not undergo self-oxidation and reduction on heating with concentrated alkali. — Incorrect. Self oxidation and reduction is what happens: methanol and sodium formate are formed.
(D) It undergoes self-oxidation and reduction on heating with concentrated alkali. — Correct. One molecule is reduced to \( \ce{CH3OH} \) and the other is oxidised to \( \ce{HCOO-} \).
NCERT (2026-27 edition):
Other Reactions
