Used primarily as a sulfonating agent in organic synthesis, enabling the introduction of sulfonyl functional groups into molecules. Commonly applied in the preparation of sulfonamides, which are key structural motifs in pharmaceuticals and agrochemicals. Also utilized in the development of dyes, polymers, and specialty chemicals where sulfonyl chloride reactivity is required. Its ability to form stable covalent bonds with nucleophiles makes it valuable in modifying biomolecules and creating intermediates for drug discovery.