Used primarily as an intermediate in organic synthesis, especially in the pharmaceutical industry. It plays a key role in the preparation of active pharmaceutical ingredients (APIs) by enabling the introduction of acyl groups to amines or alcohols. Its reactivity makes it valuable for constructing amide and ester bonds in complex molecules. Commonly applied in the synthesis of anti-inflammatory agents and analgesics, including derivatives related to paracetamol. Also utilized in the development of dyes and functionalized polymers due to its ability to modify aromatic structures. Requires careful handling due to moisture sensitivity and potential for exothermic reactions.