Consider the reaction: RCHO + NH2NH2 → RCH=N-NH2. What sort of reaction is it?

The reaction RCHO + NH2NH2 → RCH=N-NH2 is a nucleophilic addition-elimination reaction. First, a molecule of hydrazine is added to the carbonyl group. This is a nucleophilic addition reaction. RCHO + NH2NH2 → RCH(OH)-NH-NH2 Then a molecule of water is eliminated. This is an elimination reaction. RCH(OH)-NH-NH2 → RCH=N-NH2 + H2O