To prepare p-nitroaniline from aniline and nitric acid, you can follow the nitration process. Here's a specific procedure, required materials and conditions, and the mechanism of the reaction:Materials:1. Aniline C6H5NH2 2. Concentrated sulfuric acid H2SO4 3. Concentrated nitric acid HNO3 4. Ice bath5. Sodium bicarbonate NaHCO3 6. Distilled water7. Separatory funnel8. Round-bottom flask9. Vacuum filtration apparatusProcedure:1. Dissolve a specific amount of aniline in a minimal amount of concentrated sulfuric acid in a round-bottom flask. This will form an anilinium ion C6H5NH3+ , which is a better substrate for nitration.2. Cool the reaction mixture in an ice bath to maintain a low temperature 0-5C throughout the reaction. This is crucial to control the reaction rate and minimize the formation of by-products.3. Slowly add a mixture of concentrated nitric acid and concentrated sulfuric acid dropwise to the cooled aniline solution, while stirring continuously. The nitrating mixture should be prepared in a 1:1 ratio by volume.4. After the addition is complete, let the reaction mixture stir for an additional 30 minutes in the ice bath.5. Slowly pour the reaction mixture into a large volume of crushed ice and water. This will cause the p-nitroaniline to precipitate out of the solution.6. Neutralize the acidic solution by adding sodium bicarbonate until effervescence stops. This will ensure that the p-nitroaniline is fully precipitated.7. Collect the precipitate by vacuum filtration and wash it with cold distilled water to remove any remaining acid or impurities.8. Dry the product and, if necessary, recrystallize it from a suitable solvent e.g., ethanol or water to obtain pure p-nitroaniline.Mechanism:The reaction proceeds via electrophilic aromatic substitution. The anilinium ion C6H5NH3+ reacts with the nitronium ion NO2+ , which is generated in situ from the reaction between nitric acid and sulfuric acid. The nitronium ion acts as an electrophile and attacks the aromatic ring of the anilinium ion, leading to the formation of p-nitroaniline.Determining and optimizing purity and yield:1. Determine the purity of the product by melting point analysis. Compare the obtained melting point with the literature value 147C . A narrow melting point range close to the literature value indicates high purity.2. Analyze the product using thin-layer chromatography TLC or high-performance liquid chromatography HPLC to confirm the presence of p-nitroaniline and check for impurities.3. Calculate the yield by weighing the obtained product and comparing it to the theoretical yield based on the initial amount of aniline used.4. Optimize the reaction conditions, such as temperature, reaction time, and the ratio of reactants, to improve the yield and purity of the product. Perform multiple trials with varying conditions to determine the best combination for the highest yield and purity.