Question

Consider the reaction:
$RCHO+N{H}_{2}N{H}_2\to RCH=N—N{H}_2+H_{2}O$
This reaction is

• A. electrophilic substitution-elimination reaction
• B. free radical addition-elimination reaction
• C. Electrophilic addition-elimination reaction
• D. Nucleophilic addition-elimination reaction

Answer 1

Answer: (D)

The reaction $RCHO+N{H}_{2}N{H}_2\to RCH=N-N{H}_2$ is a nucleophilic addition-elimination reaction.
First a molecule of hydrazine is added to the carbonyl group.
This is a nucleophilic addition reaction.
$RCHO+N{H}_{2}N{H}_2\to RCH(OH)-NH-N{H}_2$
Then a molecule of water is eliminated. This is an elimination reaction.
$RCH(OH)-NH-N{H}_2\to RCH=N-N{H}_2+H_{2}O$