Used as a key reagent in organic synthesis, particularly for introducing sulfonyl functional groups into molecules. It serves in the preparation of sulfonamides, which are important in pharmaceuticals and agrochemicals due to their biological activity. Also employed in the synthesis of dyes and polymers, where it acts as a cross-linking or chain-extending agent. Its high reactivity with nucleophiles like amines and alcohols makes it valuable in constructing complex molecular frameworks. Handle with care due to its moisture sensitivity and corrosive nature.