What is formed when acetone reacts with hydrazine?

The correct answer is Option (3) → Acetone hydrazone

Hydrazine (\( \ce{H2N-NH2} \), Z = –NH₂) adds to the carbonyl group of acetone, and the intermediate loses water to give a >C=N–NH₂ product, a hydrazone:

    \( \displaystyle \ce{(CH3)2C=O + H2N-NH2} \xrightarrow{\ce{H^+}} \ce{(CH3)2C=N-NH2 + H2O} \)

NCERT (2026-27 edition):
8.4 Chemical Reactions – “(e) Addition of ammonia and its derivatives: Nucleophiles, such as ammonia and its derivatives H₂N-Z add to the carbonyl group of aldehydes and ketones. The reaction is reversible and catalysed by acid.”

Table 8.2: Some N-Substituted Derivatives of Aldehydes and Ketones (>C=N-Z)