thionyl chloride

…of a carboxylic acid with thionyl chloride, SOCl₂ (often in the presence of an amine such as pyridine, C₅H₅N), converts the carboxyl group to the corresponding acyl chloride (RCOOH → RCOCl).

Thionyl chloride, SOCl₂, is a dense, toxic, volatile liquid used in organic chemistry to convert carboxylic acids and alcohols into chlorine-containing compounds. Sulfuryl chloride, SO₂Cl₂, is a liquid of similar physical properties utilized in the preparation of certain compounds that contain sulfur, chlorine, or both.

Thionyl chloride, a very corrosive and toxic chemical, serves not only as the electrolyte solvent but also as the cathode material. Formation of a film of lithium chloride salt on the lithium prevents a runaway reaction between the lithium anode and the adjacent liquid cathode…