Acetic Acid → 1,4-Butanedisulfonic acid, 1,1,2,2,3,3,4,4-octafluoro-

To a mixture of 25 mL of acetonitrile and 15 mL of water were added 8.44 g (18.6 mmol) of diiodoperfluorobutane, 8.50 g (48.8 mmol) of sodium hydrosulfite, and 4.60 g (55 mmol) of sodium hydrogen carbonate. The resultant mixture was stirred at room temperature for 1 hour. This reaction mixture solution was filtered and the filtrate was cooled with ice. As a result, a white solid precipitated. This precipitate was taken out by filtration and dried to obtain sodium perfluorobutane-1,4-disulfinate in an amount of 6.8 g (98%). Subsequently, 7.2 g (19.2 mmol) of the sodium perfluorobutane-1,4-disulfinate was added to a mixture of 80 mL of aqueous hydrogen peroxide solution (30%) and 8 mL of acetic acid, and the resultant mixture was stirred at 60° C. for 4 hours. A reaction proceeded stoichiometrically. After completion of the reaction was ascertained by 19F-NMR spectroscopy, the reaction mixture was neutralized by adding 30 mL of 1-N NaOH solution thereto. Thus, an aqueous solution of perfluorobutane-1,4-disulfonic acid ((I)-44) was obtained.