The reaction between hydrazine N2H4 and 2,4-dinitrochlorobenzene C6H3Cl NO2 2 in the preparation of 2,4-dinitrophenylhydrazine C6H3N2 NO2 2 is a nucleophilic aromatic substitution reaction. The mechanism involves the following steps:1. Nucleophilic attack: Hydrazine, which acts as a nucleophile, attacks the electrophilic carbon atom of the 2,4-dinitrochlorobenzene that is bonded to the chlorine atom. This is because the electron-withdrawing nitro groups -NO2 on the benzene ring make the carbon atom more electrophilic, and the chlorine atom is a good leaving group. The nucleophilic attack results in the formation of a sigma complex, with a negative charge on the nitrogen atom of the hydrazine.2. Proton transfer: A proton H+ is transferred from the nitrogen atom with a negative charge to the adjacent nitrogen atom in the hydrazine molecule. This results in the formation of a resonance-stabilized intermediate, where the negative charge is delocalized over the nitrogen atoms.3. Loss of the leaving group: The negatively charged nitrogen atom in the intermediate pushes out the chlorine atom as a chloride ion Cl- , forming a new C-N bond between the benzene ring and the hydrazine molecule.4. Tautomerization: The 2,4-dinitrophenylhydrazine product is initially formed as an imine tautomer, with a double bond between the nitrogen atoms. A proton transfer occurs within the molecule, moving the double bond to the carbon-nitrogen bond and forming the more stable 2,4-dinitrophenylhydrazine product.Overall, the reaction mechanism involves a nucleophilic attack, proton transfer, loss of the leaving group, and tautomerization to form the final 2,4-dinitrophenylhydrazine product.