The best method for preparing 2-chloro-4-nitroaniline from aniline and chlorine gas is a two-step process involving nitration followed by chlorination. Here's the step-by-step process:Step 1: Nitration of anilineFirst, you need to protect the amino group of aniline by acetylation to prevent it from reacting during the nitration step. To do this, react aniline with acetic anhydride to form N-acetylaniline.Aniline + CH3CO 2O N-acetylaniline + CH3COOHNext, nitrate the N-acetylaniline using a mixture of concentrated sulfuric acid H2SO4 and concentrated nitric acid HNO3 . This will form 4-nitro-N-acetylaniline.N-acetylaniline + HNO3 4-nitro-N-acetylaniline + H2OStep 2: ChlorinationNow, you can chlorinate the 4-nitro-N-acetylaniline using chlorine gas Cl2 in the presence of a catalyst, such as ferric chloride FeCl3 , to form 2-chloro-4-nitro-N-acetylaniline.4-nitro-N-acetylaniline + Cl2 2-chloro-4-nitro-N-acetylanilineFinally, hydrolyze the 2-chloro-4-nitro-N-acetylaniline using hydrochloric acid HCl and water to remove the acetyl protecting group and obtain the desired product, 2-chloro-4-nitroaniline.2-chloro-4-nitro-N-acetylaniline + H2O + HCl 2-chloro-4-nitroaniline + CH3COOHOptimal reaction conditions:1. Nitration:- Temperature: 0-5C cooling the reaction mixture in an ice bath - Reaction time: 30-60 minutes- Concentration of H2SO4 and HNO3: concentrated approximately 98% H2SO4 and 65% HNO3 2. Chlorination:- Temperature: room temperature 20-25C - Reaction time: 2-4 hours- Catalyst: Ferric chloride FeCl3 3. Hydrolysis:- Temperature: reflux conditions around 100C for water - Reaction time: 1-2 hours- Concentration of HCl: 6MPlease note that these reactions involve hazardous chemicals and should be performed in a well-ventilated area with proper safety precautions, such as wearing gloves, goggles, and a lab coat.