Phosphorus trichloride

Phosphorus (III ) chloride

Colorless, fuming in moist air, liquid with a pungent odor

Liquid

1.57 g · cm -3 ( 21 ° C)

-112 ° C

76.1 ° C

12700 Pa ( 20 ° C)

• Hydrolysis in water
• Soluble in diethyl ether, chloroform, and carbon disulfide

1.5122 (21 ° C)

Risk

2.8 mg · m-3

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Phosphorus trichloride or phosphorus (III ) chloride is a colorless, toxic and highly corrosive liquid having a pungent odor, which fumes in moist air due to hydrolysis.

Representation

It is formed in the direct reaction of chlorine with white phosphorus, P4, in addition to small amounts of phosphorus pentachloride, PCl5. The latter reacts with excess phosphorus also to phosphorus.

Properties

Phosphorus trichloride is the acid chloride of phosphorous acid, a tautomer of the dyadischem phosphonic acid. As a result, the hydrolysis is carried out with water and hydrogen chloride to this:

Hydrolysis of the phosphorus (III ) chloride to phosphoric acid / phosphorous acid

In an analogous manner to form alcohols with phosphorous. The chlorine atoms are substituted step by step:

Reaction of phosphorus trichloride with methanol - progressive substitution

Analogously, the reactions with amines, thiols or (pseudo) halide.

Phosphorus is a fairly strong reducing agent and is used as an oxygen acceptor. Serves it as the latter, so formed as an oxidation product of phosphoryl chloride, phosphorus chloride as an impurity which accompanied, if this comes in contact with air.

Phosphorus can be further chlorinated to phosphorus pentachloride:

Use

Phosphorus trichloride is a raw material in the chemical industry, which finds various use. You need it for the preparation of other phosphorus derivatives as insecticides, pharmaceuticals, di-and trialkyl phosphites, phosphoryl, thiophosphorylchloride and esp. m.

On the laboratory scale can be represented by means of phosphorus carboxylic acid chlorides, a method that compared with the representation by means of thionyl chloride or oxalyl chloride, however, does not present any advantages.