DNP Synthesis

[Thrawn]

2.5-g portion of phenol and an aqueous-ethanolic solution of nitric acid, prepared from 12.5 mL of concentrated nitric acid and 50 mL of ethanol, was mixed in a RB flask. The reaction mixture was heated in an installation with a reflux for 0.5–2 h. Then, approximately 50 mL of a liquid was obtained by vacuum distillation. The residue was transferred to a cup. The product crystallized as yellow crystals. The crystals were washed with cold water and dried in a vacuum-desiccator. It was found that the yield of the product depends on the reaction duration. It was 4.8, 4.8, 4.7, and 4.8 g at reaction duration of 0.5, 1, 1.5, and 2 h, respectively, which is close to the theoretical value (4.89 g). To be purified, 2,4-dinitrophenol was dissolved in a hot 1 M solution of NaOH and 16% activated carbon was added. In 5–10 min, the activated carbon was separated by filtration. The filtrate was cooled and acidified with hydrochloric acid to pH 2–3. The precipitated light yellow crystals were separated from the solution by vacuum-filtration and dried. The yield upon the purification was 80% relative to the mass of the product taken for recrystallization.