The preparation of 2,4-dinitrophenol from phenol and nitric acid is typically carried out through a nitration reaction. The optimum temperature for this reaction is around 0-5C, as it minimizes the formation of undesired by-products. The reaction time can vary depending on the specific conditions, but it usually takes around 2-4 hours for the reaction to reach completion.The yield of the reaction depends on several factors, such as the purity of the starting materials, the reaction conditions, and the efficiency of the purification process. In general, the yield of 2,4-dinitrophenol from this reaction can range from 60-80%.It is important to note that 2,4-dinitrophenol is a hazardous substance and should be handled with caution. Always follow proper safety protocols and consult the material safety data sheet MSDS for information on handling and disposal.