Sulfonic Acids & Anhydrides
Sulfonic Acids & Anhydrides
Sulfonic acid forms a class of organosulfur compounds which can be thought of as sulfuric acid with one hydroxyl being substituted by an organo substituent. Thus, they are compounds bearing sulfonyl hydroxide group with the general formula RS(=O)2ûOH. Due to their strongly acidic nature, they are employed as catalysts. p-Toluenesulfonic acid is as an “organic-soluble” acid catalyst that is routinely employed in organic synthesis. Polymeric sulfonic acids like Dowex resin which are derivative of polystyrene are used as catalysts and for water softening through ion-exchange. Another polymeric sulfonic acid Nafion is used in fuel cells as proton exchange membranes. Their salts are used in detergent industry as anionic surfactant. As supporting electrolytes, salts of methanesulfonic acid are extensively used in zinc-cerium and lead-acid (methanesulfonate) flow batteries.
Sulfonic anhydrides are the acid anhydrides of sulfonic acid. This may be used to generate the corresponding sulfonate esters. Methanesulfonic anhydride is employed as a reagent for aromatic alkylation. It is also known for its powerful sulfonylating ability. Methanesulfonic anhydride in DMSO is used to oxidize primary and secondary alcohols. Triflic anhydride finds use an important reagent for ester formation.
