The preparation of p-nitroaniline from aniline and nitric acid involves a nitration reaction. Here is a step-by-step procedure for the synthesis:1. Preparation of the nitrating mixture: In a round-bottom flask, carefully mix concentrated sulfuric acid H2SO4 with an equal volume of concentrated nitric acid HNO3 in an ice bath. The mixture should be cooled to 0-5C. The ice bath is essential to prevent the formation of dinitroaniline, which is a side product at higher temperatures.2. Dissolving aniline: In a separate flask, dissolve aniline in an equal volume of concentrated sulfuric acid. The mixture should be cooled to 0-5C as well.3. Slow addition of aniline solution: Slowly add the aniline solution to the nitrating mixture, drop by drop, while maintaining the temperature at 0-5C. Stir the mixture continuously to ensure proper mixing.4. Completion of the reaction: After the addition of the aniline solution, let the reaction mixture sit for an additional 30 minutes to 1 hour, maintaining the temperature at 0-5C.5. Pouring the reaction mixture: Pour the reaction mixture onto crushed ice and let it stand for a few minutes. The p-nitroaniline will precipitate as a yellow solid.6. Filtration: Filter the precipitate using vacuum filtration and wash it with cold water to remove any remaining acid.7. Recrystallization: To purify the p-nitroaniline, dissolve it in hot ethanol or a mixture of ethanol and water. Filter the hot solution to remove any insoluble impurities. Allow the solution to cool slowly, and p-nitroaniline will crystallize out. Filter the crystals and let them dry.Precautions:1. Wear appropriate personal protective equipment, including gloves, safety goggles, and a lab coat, as both aniline and the nitrating mixture are corrosive and toxic.2. Perform the reaction in a well-ventilated area or under a fume hood, as the reaction produces toxic fumes.3. Maintain the temperature at 0-5C throughout the reaction to avoid the formation of unwanted side products and to minimize the risk of a runaway reaction.4. Add the aniline solution slowly to the nitrating mixture to prevent a sudden increase in temperature and to ensure proper mixing.5. Be cautious when handling concentrated acids, as they can cause severe burns and damage to surfaces. In case of contact with skin or eyes, rinse immediately with plenty of water and seek medical attention if necessary.