Phosphorus oxychloride

Chemical properties

Phosphorus oxychloride is a clear, colorless to yellow, fuming, oily liquid with a pungent and musty odor.

Physical properties

Colorless fuming liquid with a pungent odor; density 1.645 g/mL; freezes at 1°C; boils at 105.5°C; reacts with water and ethanol.

The Uses of Phosphorus oxychloride

Phosphorus oxychloride is an important intermediate in the production of triarylphosphate esters (e.g., triphenyl phosphate and tricresyl phosphate), which have been used as flame retardants and plasticizers for PVC. It is acutely toxic to the eyes, throat, and respiratory tract. Phosphorus oxychloride is also used in nuclear reprocessing, as chlorinating agent, especially to replace oxygen in organic compounds, as solvent in cryoscopy and the semiconductor industry.

The Uses of Phosphorus oxychloride

A solution of the SM (6.5 g, 18.3 mmol) in POCl3 (21 mL) was heated to reflux for 2 h, after which time it was cooled to RT and poured carefully into a stirring mixture of ice (200 mL) and saturated aq NaHCO3 (20 mL). The resulting mixture was extracted with EtOAc (2 x 250 mL). The combined org layers were washed with H2O, brine, dried (Na2SO4), and concentrated in vacuo. The residue was purified by silica gel column chromatography (3% EtOAc/hexane) to provide the product. [5.1 g, 15 mmol]

The Uses of Phosphorus oxychloride

Phosphorus oxychloride is used to produce hydraulic fluids, plasticizers, and fireretarding agents; as a chlorinating agent; and as a solvent in cryoscopy.

The Uses of Phosphorus oxychloride

In the manufacture of pesticides, pharmaceuticals, plasticizers, gasoline additives, and hydraulic fluid.

Definition

A white crystalline solid. It is a monobasic acid forming the anion H₂PO₂ – in water. The sodium salt, and hence the acid, can be prepared by heating yellow phosphorus with sodium hydroxide solution. The free acid and its salts are powerful reducing agents.

Preparation

Phosphorus oxychloride can be prepared from phosphorus trichloride or phosphorus pentachloride. It can be obtained from phosphorus trichloride by cautious addition of potassium chlorate:
3PCl₃ + KClO₃ → 3POCl₃ + KCl
The oxychloride also is obtained by the action of boric acid or oxalic acid with phosphorus pentachloride:
3PCl₅ + 2B(OH）₃ → 3POCl₃ + B₂O₃ + 6HCl
PCl₅ + (COOH）₂ → POCl₃ + CO + CO₂ + 2HCl
Phosphorus oxychloride also is made by heating calcium phosphate in a current of chlorine and carbon monoxide at 350°C:
2Ca₃(PO₄）₂ + 9Cl₂ + 6CO → 4POCl₃ + 6CaCO₃
Alternatively, heating a mixture of calcium phosphate and carbon in a current of chlorine at 750°C yields the oxychloride.

General Description

A colorless fuming liquid with a pungent odor. Density 14.0 lb / gal. Very toxic by inhalation and corrosive to metals and tissue. Used in gasoline additives and hydraulic fluids.

Reactivity Profile

Phosphorus oxychloride is water reactive. Incompatible with strong oxidizing agents, alcohols, bases (including amines). May react vigorously or explosively if mixed with diisopropyl ether or other ethers in the presence of trace amounts of metal salts [J. Haz. Mat., 1981, 4, 291]. Combining the chloride with zinc dust caused immediate ignition, due to the formation of phosphine gas which ignites, [Mellor, 1940, Vol. 8, 1025]. An exotherm starting with the mixing of Phosphorus oxychloride with acetone (a ketone) lead to an explosion, may behave similarly with other ketones, [Organic Process Research and Development, Vol.4, No. 6,200, "Phosphorus oxychloride and Acetone: An Incompatibility Investigation Using ARC."]

Hazard

The compound is highly irritating to skin, eyes and mucous membranes. Inhaling its vapors can cause pulmonary edema.

Health Hazard

Inhalation of vapors of phosphorus oxychloride produced acute and chronic toxicity in test subjects. In humans, exposure to its vapors may cause headache, dizziness, weakness, nausea, vomiting, coughing, chest pain, bronchitis, and pulmonary edema. Most of these symptoms are manifested from chronic exposure to its vapors.
LC50 value, inhalation (rats): 48 ppm (301 mg/m³)/4 h
Vapors of this compound are an irritant to the eyes and mucous membranes. The liquidis corrosive and can cause skin burns. An oral LD50 value for rats is documented to be 380 mg/kg (NIOSH 1986)..

Fire Hazard

Poisonous, corrosive, and irritating gases are generated when Phosphorus oxychloride is heated or is in contact with water. Phosphorus oxychloride may ignite other combustible materials (wood, paper, oil, etc.). Phosphorus oxychloride reacts violently with water. When heated to decomposition, Phosphorus oxychloride emits toxic fumes of chlorides and oxides of phosphorus; Phosphorus oxychloride will react with water or steam to produce heat and toxic and corrosive fumes. Incompatible with carbon disulfide; N,N-dimethylformamide; 2,5-dimethylpyrrole; 2,6-dimethyl- pyridine N-oxide; dimethylsulfoxide; Ferrocene-1,1-dicarboxylic acid; water; and zinc. Do not store with combustible materials, particularly fibrous organic materials, or with electrical or other equipment that can be corroded. Reacts violently with moisture.

Safety Profile

Poison by inhalation and ingestion. A corrosive eye, skin, and mucous membrane irritant. Potentially explosive reaction with water evolves hydrogen chloride and phosphine, which then ignites. Explosive reaction with 2,6dimethylpyridine N-oxide, dimethyl sulfoxide, ferrocene1 ,l'-dicarboxylic acid, pyridne N-oxide (above bO'C), sodmm + heat. Violent reaction or ignition with BI3, carbon disulfide, 2,5-dimethyl pyrrole + dimethyl formamide, organic matter, zinc powder. Reacts with water or steam to produce heat and toxic and corrosive fumes. Incompatible with carbon disulfide, N,Ndimethyl-formamide, 2,5-dunethylpyrrole, 2,6-dimethylpyridine N-oxide, dimethylsulfoxide, ferrocene1 ,I-dicarboxylic acid, water, zinc. When heated to decomposition it emits highly toxic fumes of Cland POx

Potential Exposure

Phosphorus oxychloride is used in the manufacture of pesticides, pharmaceuticals, plasticizers, gasoline additives; and hydraulic fluids.

Shipping

UN1810 Phosphorus oxychloride, Hazard class: 6.1; Labels: 6.1-Poisonous materials, 8-Corrosive material, Hazard Zone B.

Purification Methods

Distil the liquid under reduced pressure to separate it from the bulk of the HCl and the phosphoric acid (from hydrolysis); the middle fraction is re-distilled into ampoules containing a little purified mercury. These ampoules are sealed and stored in the dark for 4-6weeks with occasional shaking to facilitate reaction of any free chloride with the mercury. The POCl3 is then again fractionally distilled and stored in sealed ampoules in the dark until required [Herber J Am Chem Soc 82 792 1960]. Lewis and Sowerby [J Chem Soc 336 1957] refluxed their distilled POCl3 with Na wire for 4hours, then removed the Na and again distilled. Use Na only with almost pure POCl3 to avoid explosions. HARMFUL VAPOURS; work in an efficient fume cupboard.

Incompatibilities

A powerful oxidizer. Violently decomposes in water, forming heat and hydrochloric and phosphoric acids. Violent reaction with alcohols, phenols, amines, reducing agents; combustible materials; carbon disulfide; dimethylformamide, and many other many materials. Rapid corrosion of metals, except nickel and lead.

Waste Disposal

Pour onto sodium bicarbonate. Spray with aqueous ammonia and add crushed ice. Neutralize and pour into drain with running water. In accordance with 40CFR165, follow recommendations for the disposal of pesticides and pesticide containers. Must be disposed properly by following package label directions or by contacting your local or federal environmental control agency, or by contacting your regional EPA office.