The most efficient and optimal method for the preparation of 2,4-dinitrophenylhydrazine from hydrazine and 2,4-dinitrochlorobenzene is the nucleophilic aromatic substitution reaction. This method provides a good yield, high purity, and can be carried out with appropriate safety measures.Here's a step-by-step procedure for the synthesis:1. Preparation of hydrazine solution: Dissolve an appropriate amount of hydrazine hydrate N2H4H2O in a solvent like ethanol or methanol. This will be used as the nucleophile in the reaction.2. Cooling: Cool the hydrazine solution to 0-5C using an ice bath. This is important to control the reaction rate and minimize the risk of side reactions.3. Addition of 2,4-dinitrochlorobenzene: Slowly add the 2,4-dinitrochlorobenzene to the cooled hydrazine solution with constant stirring. The reaction is exothermic, so it is essential to maintain the temperature below 10C during the addition. This can be achieved by adding the 2,4-dinitrochlorobenzene in small portions and waiting for the temperature to stabilize before adding more.4. Stirring and completion of the reaction: After the addition of 2,4-dinitrochlorobenzene, continue stirring the reaction mixture for an additional 1-2 hours at 0-5C. This ensures the completion of the reaction and formation of the desired product, 2,4-dinitrophenylhydrazine.5. Precipitation and filtration: The 2,4-dinitrophenylhydrazine product will precipitate as an orange-red solid. Filter the solid using vacuum filtration and wash it with a cold solvent e.g., ethanol or methanol to remove any unreacted starting materials and byproducts.6. Drying and purification: Dry the obtained solid under vacuum or in a desiccator to remove any residual solvent. If necessary, recrystallize the product from a suitable solvent e.g., ethanol or methanol to improve its purity.7. Characterization: Analyze the synthesized 2,4-dinitrophenylhydrazine using techniques such as melting point determination, infrared spectroscopy IR , and nuclear magnetic resonance NMR to confirm its identity and purity.Safety measures:- Hydrazine is toxic and corrosive, so handle it with care and use appropriate personal protective equipment gloves, goggles, lab coat .- Perform the reaction in a well-ventilated area or under a fume hood to avoid inhalation of harmful vapors.- Monitor the temperature during the reaction to prevent overheating and side reactions.- Dispose of waste materials according to local regulations and guidelines.