Phosphorus trichloride, or PCl3, is a chemical compound made up of one phosphorus atom and three chlorine atoms. It is a colorless, oily liquid at room temperature and has a pungent odor. PCl3 is commonly used in the production of various chemicals, including pesticides and pharmaceuticals, due to its reactivity. In addition to its industrial applications, PCl3 is also used as a reagent in organic synthesis. It can react with alcohols to form phosphites and is involved in the chlorination of organic compounds. Proper safety measures are essential when handling PCl3, as it is toxic and can cause irritation to the skin and respiratory system.