Answer the question on the basis of passage given below:
Aldehydes are generally more reactive than ketones in nucleophilic addition reactions due to steric and electronic reasons. Sterically, the presence of two relatively large substituents in ketones hinders the approach of nucleophile to carbonyl carbon more than aldehydes having only one such substituent. Electronically, aldehydes are more reactive than ketones because two alkyl groups reduce the electrophilicity of the carbonyl more effectively than in former.
Formaldehyde on reaction with benzaldehyde in basic medium gets converted to:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Formic acid
Neither formaldehyde nor benzaldehyde has an α-hydrogen, so with concentrated alkali they undergo the Cannizzaro reaction instead of aldol condensation. When two such aldehydes are mixed (cross Cannizzaro reaction), formaldehyde, the more reactive of the two, is the one that is oxidised; the other aldehyde is reduced to its alcohol:
\( \displaystyle \ce{HCHO + C6H5CHO + NaOH} \xrightarrow{\text{conc.}} \ce{HCOONa + C6H5CH2OH} \)
\( \displaystyle \ce{HCOONa + H+ -> HCOOH + Na+} \)
So formaldehyde ends up as sodium formate, that is, formic acid after acidification, while benzaldehyde gives benzyl alcohol.
Option (1) Methanol — Incorrect. Methanol forms from HCHO only when HCHO reacts with itself (2HCHO → HCOO− + CH3OH). In the crossed reaction HCHO is oxidised, and the reduction product is benzyl alcohol.
Option (3) o/p-hydroxymethylbenzaldehyde — Incorrect. This is a ring-hydroxymethylated compound, with a –CH2OH group on the ring. Such a product forms when HCHO attacks a strongly activated ring, as in phenol; the –CHO group deactivates the ring of benzaldehyde, so HCHO/OH− does not attack it.
Option (4) o/p-hydroxymethyl benzoic acid — Incorrect. This too is a ring-substituted compound. The Cannizzaro reaction takes place only at the –CHO groups and puts no –CH2OH group on the ring.
NCERT (2026-27 edition):
Cannizzaro Reaction – “Aldehydes which do not have an α-hydrogen atom, undergo self oxidation and reduction (disproportionation) reaction on heating with concentrated alkali. In this reaction, one molecule of the aldehyde is reduced to alcohol while another is oxidised to carboxylic acid salt.”
Note: The same/similar question has been asked in different years by NTA as per the details given below:
| 2026 | 2025 | 2024 | 2023 | 2022 |
|---|---|---|---|---|
| – | – | – | 12-06 S3 08-06 S3 | – |