Phosphorus oxychloride (chemical formula: POCl3), is a type of industrial raw material. It is a colorless and transparent liquid, and it has an unpleasant irritating odor. It will smoke intensely in humid air. Its relative density is 1.68, melting point is 1.25℃, boiling point is 105.1℃. It breaks down into phosphoric acid and hydrogen chloride in water and ethanol. When suddenly combined with a large amount of water, an intense reaction may occur. POCl3 reacts with water and alcohol to create phosphoric acid or phosphate. If alcohol replaces the water in the reaction, the end product will be trialkyl phosphate. This type of reaction often occurs in pyridine or ammonia, as it absorbs the produced HCl to stimulate the reaction. When catalyzed by a Lewis acid such as manganese chloride, POCl3 and a large amount of phenol (ArOH) heats to produce triaryl phosphate, such as in the reaction below: 3 C6H5OH + O=PCl3 → O=P(OC6H5)3 + 3 HCl. Phosphorus oxychloride is a Lewis base, and it produces compounds with many Lewis acids, such as in its reaction with titanium tetrachloride: Cl3P5+O− + TiCl4 → Cl3P5+O-−TiCl4. Its adduct with aluminum chloride (POCl3•AlCl3) is very stable, and thus POCl3 is used to remove the AlCl3 in the end products of Friedel-Crafts reactions. In the presence of AlCl3, POCl3 reacts with hydrogen bromide to create POBr3.
Phosphorus oxychloride can be used as a semiconductor dopant, and it is a raw material for light-conducting fibers. It is widely used in pesticides, pharmaceuticals, dyes, phosphates and flame retardant production. It is a raw material for producing organic phosphorus herbicide and chlordimeform, and it is a plasticizer in plastic production. Phosphorus oxychloride is also used in the chlorination of long-acting sulfa drugs, is an intermediate in dye production and a catalyst in organic synthesis of chlorinating agents, and it is an extracting agent in uranium mining. It is also used in producing pharmaceuticals.
Toxicity is similar to phosphorus trichloride, phosphorus pentachloride and phosgene. Large mice, oral, LD50: 380 mg/kg; inhaled, LC50: 32 ppm/4H. Acute poisoning in small mice results in restlessness, upper respiratory tract and conjunctival irritation, depression, convulsions, unsteady walking, lying on the side, and eventually, death. For large mice, in addition to the symptoms above, also exhibited tearing, cornea clouding, and pulmonary edema. Subacute and chronic toxicity: large mice, inhaled for 60 days at a concentration of 33.5mg/m3, exhibited slowed weight gain, skin ulcers, decreases survival rates in lung macrophages, no liver and kidney functions, and organ characteristic changes.
This product has a strong oxidizing and liposoluble effects; besides burning the digestive tract, it can also cause acute necrosis and autolysis in the liver when absorbed through the digestive tracts. Additionally, besides burning the skin, when completely absorbed through the skin, 3% can cause death in animals. When phosphorus oxychloride is inhaled and comes in contact with the moist respiratory tract mucosa, it will break down into phosphoric acid and hydrogen chloride, and it will irritate and corrode the mucosa. When humans contact at a concentration of 70mg/m3, they will usually exhibit symptoms after a 2-6h latency period, including respiratory tract mucosa irritation and eye pain. Serious cases include a choking sensation, cyanosis, pulmonary edema, heart failure, anemia, liver damage, and proteinuria. When the temperature in the car is high and the humidity is relatively low, there is a high risk of inhalation and poisoning.
The highest permitted concentration is 0.05 mg/m3. Handlers should wear protective equipment, and production equipment must be tightly sealed. Processors can also wear filtering gas masks. Take care to protect skin and eyes.
After inhalation, emergency response and treatment is similar to chlorine, hydrogen chloride and other irritating gases. If contacted with skin, first use paper or cotton to absorb the liquid, then rinse with water for at least 15 minutes; if directly rinsed with water, it may produce phosphoric acid and continue to burn the skin. Treat injury as an acid burn.
Danger regulations GB8.1 type 81040. Iron regulation: Level one inorganic acidic corrosive product, 91022. UN No. 1810. IMDG CODE page 8197, type 8.
As chlorinating agent, especially to replace oxygen in organic compounds; as solvent in cryoscopy.
Health Hazards : This poison is toxic by inhalation and ingestion and is strongly irritating to skin and tissues. It causes burns of the mucous membranes of the mouth and digestive tractand may be fatal.
Hazards & Safety Information
Category Corrosive items
Toxicity grading highly toxic
Acute Toxicity Oral-Rat LD50: 380 mg/kg
Flammability and Hazardous characteristics being explosive upon coming across water with release of toxic chloride, phosphorus oxide gas
Storage and transportation characteristics Ventilated, low temperature and dry; and store it separately from alkali
Fire Extinguishing agent dry sand, dry stone powder; prohibit the usage of water
Occupational Standard TLV-TWA 0.1 PPM (0.6 mg/m3); STEL 0.5 PPM (3 mg/m3)
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.
Warnings and Precautions
Phosphorus oxychloride is often used in industrial production; there are many details to take note of when using phosphorus oxychloride to prevent safety concerns and accidents:
1. Phosphorus oxychloride preparation: As many factories use water jet vacuums to store phosphorus oxychloride, great attention must be paid to the switch order to prevent accidents. The buffer vacuum tank must be frequently inspected to prevent the water from being sucked into storage containers and causing accidents.
2. Phosphorus oxychloride with hydrogen chloride: take care to not add an excess of phosphorus chloride. If there is an excess, slowly drop in water to hydrolyze the phosphorus chloride, and then remove the produced phosphoric acid.
3. Slowly place any materials containing phosphorus oxychloride into a hydrolysis kettle containing cold water and mix continuously. Avoid adding water to the material.
4. Whenever using systems containing phosphorus oxychloride, take care to measure the water content in all the components to prevent an excess of water from causing an explosion.
5. Frequently inspect reactors for cracks and imperfections to prevent water from leaking in and coming in contact with the phosphorus oxychloride.
6. When adding phosphorus oxychloride to a reactor, remain observant and stop adding material immediately if there are any abnormal occurrences. Only continue adding material after investigating the cause of these occurrences.
7. Phosphorus oxychloride reacts slowly with water when at a lower temperature. Thus, drop in slowly to prevent sudden intense reactions.
8. Phosphorus oxychloride can be used in combination with dichloroethane and toluene solutions, but not with alcohol and ammonia solutions.
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.
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.
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."]