The preparation of 2,4-dinitrophenylhydrazine from hydrazine and 2,4-dinitrochlorobenzene involves a nucleophilic aromatic substitution reaction. The chemical reaction can be represented as follows:CHCl NO + NH CH NNH NO + HClIn this reaction, hydrazine NH acts as a nucleophile and attacks the electrophilic carbon in 2,4-dinitrochlorobenzene CHCl NO , replacing the chlorine atom and forming 2,4-dinitrophenylhydrazine CH NNH NO and hydrochloric acid HCl as byproduct.For this reaction to proceed efficiently, the following conditions are typically required:1. A polar aprotic solvent, such as dimethylformamide DMF or dimethyl sulfoxide DMSO , is used to dissolve the reactants and facilitate the nucleophilic attack.2. The reaction is usually carried out at an elevated temperature, typically around 60-80C, to increase the reaction rate.3. An acid scavenger or a base, such as sodium acetate or potassium carbonate, can be added to the reaction mixture to neutralize the HCl formed during the reaction. This helps to prevent the protonation of hydrazine, which would reduce its nucleophilicity and slow down the reaction.4. The reaction is often carried out under an inert atmosphere, such as nitrogen or argon, to prevent the oxidation of hydrazine.5. The reaction is usually allowed to proceed for several hours to ensure complete conversion of the starting materials to the desired product.