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JEE Main 2025 Jan 22 Shift 2, Chemistry Q18: Properties and Important Reactions of Aldehydes & Ketones

JEE Main2025Jan 22, Shift 2Chemistry
Q.

Residue (A) + HCl (dil.) Compound (B)

Structure of residue (A) and compound (B) formed respectively is :

  1. A

    1

  2. B

    2

  3. C

    3

  4. D

    4

Solution

Step (i) and (ii): Etard's reaction. Toluene with in followed by acidic hydrolysis () converts the methyl group to a group, giving benzaldehyde.

Step (iii): Benzaldehyde reacts with to form a water-soluble crystalline bisulphite addition product, . This adduct precipitates and can be separated by filtration. This is residue (A).

Treatment of (A) with dilute HCl is the standard procedure to regenerate the parent aldehyde: the bisulphite adduct is hydrolysed back to benzaldehyde (B).

(A) is the bisulphite adduct of benzaldehyde and (B) is benzaldehyde, matching option (4).

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