Used primarily as a sulfonating agent in organic synthesis, enabling the introduction of butanesulfonyl groups to alcohols, amines, and other nucleophiles. Commonly employed in the preparation of sulfonate esters and sulfonamides, which serve as intermediates in pharmaceuticals and agrochemicals. Its reactivity makes it suitable for activating functional groups in peptide coupling and other condensation reactions. Also utilized in the synthesis of dyes and functional polymers where sulfonyl chloride groups enhance chemical stability or modify solubility. Requires careful handling due to high reactivity with moisture and potential for exothermic reactions.