2,4-DNP is_________

The correct answer is Option (2) → 2,4-Dinitrophenylhydrazine

2,4-DNP (Brady’s reagent) is 2,4-dinitrophenylhydrazine, a derivative of ammonia, \( \ce{H2N-NH-C6H3(NO2)2} \). It adds to the C=O group of aldehydes and ketones and loses water (addition-elimination), giving a 2,4-dinitrophenylhydrazone:

    \( \displaystyle \ce{R2C=O + H2N-NH-C6H3(NO2)2 -> R2C=N-NH-C6H3(NO2)2 + H2O} \)

NCERT (2026-27 edition):
Addition of Ammonia and Its Derivatives