Sulfuric Acid → 4-[4-(2,5-Dichlorobenzoyl)phenoxy]benzene sulfonic acid sodium salt

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Reaction Steps

2,5-dichloro-4′-phenoxybenzophenone (A, 137.3 g, 400 mmol) was put in a 3 L three-necked flask equipped with a stirring device and cooling tube, and 500 mL of 1,2-dichloroethane (1,2-DCE) was added and dissolved. Furthermore, 2 M of acetyl sulfuric acid solution prepared by mixing 56 mL of concentrated sulfuric acid, 152 mL of acetic anhydride, and 400 mL of 1,2-DCE, was added to the flask while stirring, and the reaction was performed in an oil bath at 60° C. After the predetermined period, 300 mL of 1-propanol was added to stop the reaction. Next, the reaction liquid was concentrated to a volume of 400 mL, and NaOH aqueous solution (120 g (3 mol)/water 400 mL) was added. The remaining 1,2-DCE in the reaction liquid was removed by azeotropic distillation, and a transparent light yellow solution was obtained. The light yellow solution was cooled, and deposition was filtered. The deposition was dried in a vacuum at 70° C. to obtain a white fine powder of 4-[4-(2,5-dichlorobenzoyl)phenoxy]benzene sulfonic acid sodium salt (A—SO3Na) shown in Chemical Formula 3. The crude crystal was used in the next process without being purified.

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