Thionyl chloride is a chemical compound with the formula SOCl2. It is a colorless liquid that has a pungent odor and is commonly used in organic synthesis. Thionyl chloride is known for its ability to convert alcohols into chlorides, making it a valuable reagent in the production of various chemicals. In addition to its use in organic chemistry, thionyl chloride can also serve as a chlorinating agent and is involved in the preparation of sulfur dichloride and other sulfur-containing compounds. Due to its reactivity, it must be handled with care, as it can release toxic gases when it reacts with water.