Thionyl chloride is a colorless to pale yellow transparent liquid with a strong pungent and suffocating odor. It emits fumes in moist air. It is chemically reactive and serves as a highly effective chlorinating agent and acyl chlorinating agent. It reacts violently with water, alcohols, amines, etc., releasing hydrogen chloride and sulfur dioxide gases.

1. Organic Synthesis:Converts carboxylic acids to acyl chlorides and alcohols to alkyl chlorides. It is a key chlorinating reagent for the synthesis of pharmaceutical, pesticide and dye intermediates.
2. Lithium Battery Industry:Used in the preparation of lithium salts (e.g. LiFSI, LiPF₆) and electrolyte additives.
3. Others:Used as a dehydrating agent and chlorinating agent in polymers, fragrances, metal surface treatment and other fields.