Fosforioksikloridia

Fosforioksikloridia, known in English as phosphorus oxychloride (POCl3), is an inorganic phosphorus(III) compound widely used as a chlorinating and dehydrating agent in organic synthesis. It is a colorless to pale yellow, fuming liquid with a strong, acrid odor. It hydrolyzes readily in moisture to phosphoric acid and hydrogen chloride, and is highly corrosive to skin, eyes, and mucous membranes.

Production and occurrence

Phosphorus oxychloride is typically produced on an industrial scale by controlled oxidation of phosphorus trichloride (PCl3) with oxygen. Alternative routes include chlorination of phosphoryl compounds or dehydration of phosphoric acid derivatives under suitable conditions. Because POCl3 reacts with water, it is handled under strictly anhydrous conditions and stored in moisture-free containers.

Properties

POCl3 is a reactive chlorinating and dehydrating agent. It reacts with water, alcohols, and amines to form corresponding phosphate esters or acid chlorides, releasing hydrogen chloride. It is commonly used in stirred, dry reactors and in the presence of catalysts or bases that facilitate chlorination or phosphorylation reactions.

Uses

In organic synthesis, POCl3 serves as a versatile reagent for chlorination and activation steps. It is employed to convert carboxylic acids to acid chlorides in conjunction with catalytic DMF, and to prepare phosphate esters by reacting with alcohols or phenols. It is a key component in the Vilsmeier-Haack formylation system when combined with dimethylformamide (DMF). Phosphorus oxychloride is also used as an intermediate in the production of flame retardants, plasticizers, and various organophosphorus compounds.

Safety and handling

POCl3 is highly corrosive and toxic. It fumes in air and its vapors irritate the eyes, skin, and respiratory tract. It reacts violently with water, releasing HCl and phosphoric acid. Handling requires a fume hood, appropriate PPE, and moisture-controlled equipment. It should be stored in tightly closed, dry containers, typically under inert atmosphere, away from moisture and incompatible materials. Environmental release should be avoided; spills require immediate containment and neutralization.