Used as an intermediate in the synthesis of sulfa drugs and other pharmaceuticals. It plays a key role in creating sulfonamide derivatives by reacting with amines, forming compounds with antibacterial properties. Also utilized in the production of dyes and pigments due to its ability to introduce sulfonyl chloride functional groups into aromatic systems. Its reactivity makes it valuable in organic synthesis for building complex molecules, especially in agrochemicals and specialty polymers. Requires careful handling due to high reactivity with moisture and potential corrosiveness.