Question

What product is formed when a ketone reacts with hydrazine \( (\mathrm{NH_2-NH_2}) \)?

• A. Alcohol
• B. Hydrazone
• C. Amide
• D. Ester

Hint:

Reactions of aldehydes and ketones with nitrogen nucleophiles:

• \(NH_2OH\) → Oxime
• \(NH_2NH_2\) → Hydrazone
• \(NH_2NHCONH_2\) → Semicarbazone

Answer 1

The Correct Option is B

Concept: Ketones react with hydrazine \( (\mathrm{NH_2-NH_2}) \) in a condensation reaction to form hydrazones. This reaction involves nucleophilic attack of hydrazine on the carbonyl carbon followed by elimination of water. General reaction: \[ R_2C=O + NH_2NH_2 \rightarrow R_2C=NNH_2 + H_2O \] The product \(R_2C=NNH_2\) is called a hydrazone.
Step 1: {Identify the functional group in ketones.} Ketones contain the carbonyl group: \[ R_2C=O \]
Step 2: {Reaction with hydrazine.} Hydrazine acts as a nucleophile and attacks the carbonyl carbon, forming an intermediate which eliminates water.
Step 3: {Formation of final product.} The final product contains the functional group \[ C=NNH_2 \] which is known as a hydrazone. Hence, the correct option is (B).