Question

Identify the product when a ketone reacts with hydrazine $(NH_2-NH_2)$

• A. Oxime
• B. Hydrazone
• C. Semicarbazone
• D. Phenylhydrazone

Hint:

Important carbonyl derivatives formed with ammonia derivatives:

• Hydroxylamine \(\rightarrow\) Oxime
• Hydrazine \(\rightarrow\) Hydrazone
• Semicarbazide \(\rightarrow\) Semicarbazone
• 2,4-DNP \(\rightarrow\) 2,4-DNP derivative (orange precipitate)

Answer 1

The Correct Option is B

Concept:
Aldehydes and ketones undergo nucleophilic addition–elimination reactions with ammonia derivatives of the type \(NH_2-G\). In these reactions, the nucleophile attacks the carbonyl carbon, followed by the elimination of a water molecule, forming a compound containing a \(C=N-G\) linkage.
Step 1: {Identify the reacting reagent.} The given reagent is hydrazine \((H_2N-NH_2)\), which is an ammonia derivative.
Step 2: {Write the general reaction.} Ketones react with hydrazine in the presence of acid catalyst to form hydrazone: \[ R_2C=O + H_2N-NH_2 \xrightarrow{H^+} R_2C=N-NH_2 + H_2O \] In this reaction:

• The nucleophile \(H_2N-NH_2\) attacks the carbonyl carbon.
• A molecule of water is eliminated.
• A double bond \(C=N\) is formed.

Step 3: {Name the product.} When the group \(G = -NH_2\) (from hydrazine), the product formed is called a hydrazone.
Step 4: {Conclusion.} Therefore, the product formed in this reaction is: \[ \text{Hydrazone} \]