Used primarily as a sulfonating agent in organic synthesis, enabling the introduction of sulfonic acid groups into molecules. Commonly employed in the production of surfactants and detergents due to its ability to enhance water solubility and surface activity. Plays a key role in synthesizing betaine-type compounds, which are used as zwitterionic surfactants in personal care products and industrial cleaners. Also utilized in the preparation of functional monomers for specialty polymers with ion-exchange properties. Its reactivity makes it valuable in pharmaceutical intermediates where sulfonate groups are required for biological activity or solubility.