The preparation of p-nitroaniline from aniline and nitric acid involves a nitration reaction. The specific steps and optimal reaction conditions are as follows:1. Preparation of the nitrating agent: To carry out the nitration reaction, a nitrating agent is required. This is typically a mixture of concentrated nitric acid HNO3 and concentrated sulfuric acid H2SO4 . The concentrated sulfuric acid acts as a catalyst and dehydrating agent, promoting the formation of the nitronium ion NO2+ , which is the active electrophile in the reaction.2. Cooling the reaction mixture: The nitration reaction is highly exothermic, and controlling the temperature is crucial to obtain a high yield of the desired product. The reaction mixture should be cooled to around 0-5C using an ice bath before adding the aniline.3. Protection of the amino group: Aniline is a strong activating group and can undergo multiple nitration reactions, leading to undesired products. To prevent this, the amino group -NH2 in aniline is protected by converting it into an acetanilide derivative. This is done by reacting aniline with acetic anhydride CH3CO 2O to form acetanilide C6H5NHCOCH3 . This step reduces the reactivity of the amino group and directs the nitration to the para position.4. Nitration of acetanilide: Add the acetanilide to the cooled nitrating agent mixture slowly, with continuous stirring. The temperature should be maintained between 0-5C to prevent the formation of undesired products. The nitration reaction will occur, and p-nitroacetanilide will be formed.5. Isolation and purification of the product: After the reaction is complete, the mixture is poured into cold water to precipitate the p-nitroacetanilide. The solid product is collected by filtration and washed with water to remove any remaining acids. The crude product can be purified by recrystallization using a suitable solvent, such as ethanol or water.6. Hydrolysis of p-nitroacetanilide: To obtain the final product, p-nitroaniline, the p-nitroacetanilide is hydrolyzed by heating it with a dilute acid, such as hydrochloric acid HCl . This step cleaves the amide bond, releasing p-nitroaniline and acetic acid.7. Isolation and purification of p-nitroaniline: The p-nitroaniline can be isolated by filtration and washed with water to remove any remaining acid. The product can be further purified by recrystallization using a suitable solvent, such as hot water or ethanol.Optimal reaction conditions for a high yield of p-nitroaniline include:- Maintaining a low temperature 0-5C during the nitration reaction to prevent the formation of undesired products.- Using a suitable protecting group for the amino group, such as acetyl, to direct the nitration to the para position and prevent multiple nitration reactions.- Careful control of reaction times and concentrations of reactants to ensure a high yield of the desired product.