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 step forms a sigma bond between the nitrogen atom of hydrazine and the carbon atom of 2,4-dinitrochlorobenzene.2. Formation of a Meisenheimer complex: The nucleophilic attack results in the formation of a Meisenheimer complex, which is an intermediate species in the reaction. This complex is stabilized by the electron-withdrawing nitro groups present on the benzene ring.3. Loss of chloride ion: In the next step, the chloride ion leaves the Meisenheimer complex, resulting in the formation of a new aromatic ring.4. Proton transfer: Finally, a proton from the hydrazine molecule is transferred to the nitrogen atom that was initially bonded to the carbon atom in the 2,4-dinitrochlorobenzene. This step leads to the formation of 2,4-dinitrophenylhydrazine as the final product.Overall, the reaction can be summarized as follows:N2H4 + C6H3Cl NO2 2 C6H3N2 NO2 2 + HClIn the synthesis process, hydrazine is usually used in the form of its hydrate N2H4H2O and the reaction is carried out in a polar solvent, such as ethanol or methanol, under reflux conditions. The 2,4-dinitrophenylhydrazine product can be isolated by filtration and recrystallization from a suitable solvent, such as ethanol or ethyl acetate.