fosforoxychlorider

Fosforoxychlorider, also known as phosphorus oxychloride (POCl3), is an inorganic compound widely used as a chlorinating and dehydrating agent in organic synthesis. Its molecular structure features a phosphorus atom double-bonded to oxygen and single bonds to three chlorine atoms, giving a trigonal pyramidal geometry around phosphorus. It is typically a colorless to pale yellow liquid with a strong, irritating odor, and it hydrolyzes readily in the presence of water.

Chemical properties and handling

POCl3 is highly reactive with moisture, releasing heat and forming phosphoric acid and hydrogen chloride: POCl3 + 3 H2O → H3PO4 + 3 HCl. It is hygroscopic and fumes in air, and it can react with many materials, including metals and amines. It is not considered flammable, but contact with water or humid air can generate corrosive HCl fumes. Safe handling requires use in a dry, well-ventilated fume hood, with appropriate personal protective equipment (gloves, goggles, and protective clothing). Containers should be tightly closed and protected from moisture; it should be stored away from bases, oxidizers, and water sources.

Uses

In organic synthesis, POCl3 serves as a versatile chlorinating and dehydrating agent. It converts alcohols to alkyl chlorides, activates carboxylic acids to acid chlorides, and enables formation of phosphate esters through reaction with alcohols. It is employed in the preparation of organophosphorus compounds, certain pesticides, plasticizers, flame retardants, and various pharmaceutical intermediates. It is also used to facilitate dehydration steps in esterifications and to generate reactive phosphorus intermediates for further transformation.

Safety and disposal

Due to its corrosivity and reactive hydrolysis products, POCl3 must be handled with care and disposed of following institutional and regulatory guidelines for hazardous reagents. Spills should be contained, and exposed skin or eyes should receive immediate decontamination. Proper ventilation and avoidance of moisture are essential in all operations involving this chemical.