Used as a mild and stable sulfonating agent in organic synthesis, particularly for introducing sulfonic acid groups into aromatic compounds and alcohols. It is preferred in pharmaceutical manufacturing due to its controlled reactivity and reduced corrosiveness compared to free sulfur trioxide. Commonly employed in the production of surfactants, dyes, and sulfonamide drugs. Its complexation with pyridine enhances handling safety and solubility in organic solvents, making it suitable for laboratory-scale and industrial applications requiring precise sulfonation.