The preparation of p-nitroaniline from aniline and nitric acid can be carried out through a nitration reaction. Here is a step-by-step procedure for this reaction:1. Safety precautions: Wear appropriate personal protective equipment PPE such as gloves, goggles, and a lab coat. Work in a well-ventilated area or fume hood, as the reaction involves corrosive and toxic chemicals.2. Prepare the nitrating mixture: Slowly add concentrated nitric acid HNO3 to concentrated sulfuric acid H2SO4 with constant stirring. The mixture should be cooled in an ice bath to maintain a low temperature around 0-5C to prevent the formation of undesired by-products.3. Dissolve aniline: Dissolve aniline C6H5NH2 in a minimal amount of glacial acetic acid CH3COOH to form an acetanilide derivative. This step is crucial to prevent the formation of meta- and ortho-nitroaniline isomers.4. Nitration reaction: Slowly add the cold nitrating mixture to the aniline solution with constant stirring. Maintain the temperature below 10C to ensure selective para-nitration.5. Quench the reaction: After the addition is complete, slowly pour the reaction mixture into crushed ice and water to quench the reaction. The p-nitroaniline will precipitate as a solid.6. Isolation and purification: Filter the solid p-nitroaniline using vacuum filtration. Wash the solid with cold water to remove any remaining acid. Recrystallize the product from a suitable solvent e.g., hot water or ethanol to obtain pure p-nitroaniline crystals.7. Drying: Dry the purified p-nitroaniline crystals in a vacuum desiccator or an oven at a low temperature 40-50C .To confirm the purity of the final product, various analytical techniques can be employed:1. Melting point determination: Compare the melting point of the synthesized p-nitroaniline with the literature value 147-149C . A sharp melting point close to the literature value indicates high purity.2. Thin-layer chromatography TLC : Perform TLC analysis to check for the presence of any impurities or unreacted starting materials. A single spot on the TLC plate indicates a pure product.3. Infrared IR spectroscopy: Analyze the IR spectrum of the synthesized p-nitroaniline and compare it with the reference spectrum. The presence of characteristic peaks e.g., nitro group peak around 1530-1350 cm-1 and the absence of starting material peaks confirm the purity of the product.4. Nuclear magnetic resonance NMR spectroscopy: Obtain 1H-NMR and 13C-NMR spectra of the synthesized p-nitroaniline and compare them with reference spectra. The presence of characteristic signals and the absence of impurity signals confirm the purity of the product.5. Elemental analysis: Perform elemental analysis CHN analysis to determine the percentage of carbon, hydrogen, and nitrogen in the synthesized p-nitroaniline. Compare the obtained values with the theoretical values for p-nitroaniline to confirm the purity of the product.