Concept:Aldehydes and ketones react with 2,4-dinitrophenylhydrazine (2,4-DNPH) via a condensation reaction (nucleophilic addition followed by elimination of water) to form 2,4-dinitrophenylhydrazones.
Formula:$$ (CH_3)_2C=O + H_2N-NH-Ar \longrightarrow (CH_3)_2C=N-NH-Ar + H_2O $$
Solution:- Acetone has the formula \( (CH_3)_2C=O \).
- During the reaction, the oxygen atom from the carbonyl group of acetone and the two hydrogen atoms from the primary amine group of 2,4-DNPH are removed as a water molecule.
- A new double bond forms between the carbonyl carbon and the nitrogen, giving the hydrazone structure \( (CH_3)_2C=N-NH-C_6H_3(NO_2)_2 \).
Why other options are incorrect:Option B is the hydrazone of acetaldehyde. Option C is the hydrazone of 3-pentanone (diethyl ketone). Option A lacks the carbon-nitrogen double bond completely.
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