The preparation of 2,4-dinitrobenzoic acid from benzoic acid and nitric acid is an electrophilic aromatic substitution reaction, specifically a nitration reaction. To achieve the highest yield and purity, it is important to optimize the reaction conditions, including reaction time and temperature.The optimal reaction time and temperature for the nitration of benzoic acid to form 2,4-dinitrobenzoic acid can vary depending on the specific procedure and reagents used. However, a general guideline for this reaction is as follows:1. Dissolve benzoic acid in a mixture of concentrated sulfuric acid and nitric acid. The use of sulfuric acid helps to generate the nitronium ion NO2+ , which is the active electrophile in the reaction.2. The reaction temperature should be kept low, typically around 0-5C. This can be achieved by cooling the reaction mixture in an ice bath. Maintaining a low temperature helps to minimize the formation of undesired side products, such as the formation of trinitrobenzoic acid or decomposition of the reactants.3. The reaction time can vary depending on the scale of the reaction and the concentration of the reactants. Generally, the reaction should be allowed to proceed for 1-3 hours, with periodic monitoring of the reaction progress using thin-layer chromatography TLC or another analytical technique.4. After the reaction is complete, the product can be isolated by pouring the reaction mixture into an ice-water mixture, followed by filtration and washing of the solid product. The crude product can then be purified by recrystallization from a suitable solvent, such as ethanol or water.It is important to note that these conditions are general guidelines and may need to be adjusted depending on the specific procedure and reagents used. Always consult the literature or a reliable protocol for the exact conditions required for a particular nitration reaction.