Pentafluorosulfanyl-3-Sultones and Sulfonic Acids

The family of fluoroalkyl sulfonic acids are some of the strongest protonic acids known. These acids or their derivatives are known to have wide chemical applications. There are several methods available for their preparation (254-258). The utility of any of these methods in producing an SF5-containing sulfonic acid or its derivatives has not been demonstrated. 

Sulfur trioxide reacts with fluoroolefins, producing /3-sultones (256). At least two /3-sultones containing the SF5 group are well characterized and will be described here, along with their utility in preparing the desired sulfonic acids or their derivatives. The reader is referred to a review by Gard (259) on /3-fluorosultones. 

The pentafluorosulfur /3-sultone, 2-hydroxyl-l-(pentafluoro- 6-sulf-anyl)-l,2,2-trifluoroethanesulfonic acid sultone (I), is prepared in 58% yield by reacting SF6CF=CF2 with distilled S03 at 100°C (260). 

It is a colorless, stable liquid that boils at 88°C. On treatment with a base, either Ca(OH)2 or NaOH, the corresponding calcium or sodium hydryl(pentafluoro-X6-sulfanyl)fluoromethanesulfonate is produced. 

The calcium or sodium salt with 100% H2S04 gives over a 60% yield of a SF5-containing sulfonic acid, hydryl(pentafluorosulfur-X6-sulfanyl)-trifluoromethanesulfonic acid, SF5CFHS03H. It is a colorless, stable liquid, boiling at 89-90°C. 

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