Question

Draw structure of the 2, 4-dinitrophenyl hydrazone derivative of benzaldehyde.

Hint:

This reaction is a standard test for the presence of a carbonyl group (\(C=O\)) in an unknown organic compound.

Answer 1

Step 1: Understanding the Concept:
Aldehydes react with 2,4-dinitrophenylhydrazine (Brady's reagent) to form orange/yellow crystalline solids called 2,4-dinitrophenylhydrazones via a nucleophilic addition-elimination reaction.
Step 2: Detailed Explanation:
The reaction involves the loss of a water molecule from the carbonyl oxygen of benzaldehyde and the two hydrogens of the \(-NH_2\) group of the hydrazine.
Reaction:
\[ C_6H_5-CHO + H_2N-NH-C_6H_3(NO_2)_2 \rightarrow C_6H_5-CH=N-NH-C_6H_3(NO_2)_2 + H_2O \]
The structure consists of a benzaldehyde skeleton linked by a double bond to the nitrogen of the substituted phenylhydrazine.
Step 3: Final Answer:
The structure is Benzaldehyde 2,4-dinitrophenylhydrazone.